Permian Brachiopods of West Texas, IV (PART 1 - TEXT) NUMBER G. ARTHUR COOPER and RICHARD E. GRANT SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY SERIAL PUBLICATIONS OF THE SMITHSONIAN INSTITUTION The emphasis upon publications as a means of diffusing knowledge was expressed by the first Secretary of the Smithsonian Institution. In his formal plan for the Insti- tution, Joseph Henry articulated a program that included the following statement: "It is proposed to publish a series of reports, giving an account of the new discoveries in science, and of the changes made from year to year in all branches of knowledge." This keynote of basic research has been adhered to over the years in the issuance of thousands of titles in serial publications under the Smithsonian imprint, com- mencing with Smithsonian Contributions to Knowledge'W;lBi8 and continuing with the following active series: ^ Smithsonian Annals of Flight Smithsonian Contributions to Anthropology Smithsonian Contributions to Astrophysics Smithsonian Contributions to Botany Smithsonian Contributions to the Earth Sciences Smithsonian Contributions to Paleobiology Smithsonian Contributions to Zoology Smithsonian Studies in History and Technology In these series, the Institution publishes original articles and monographs dealing with the research and collections of its several museums and offices and of professional colleagues at other institutions of learning. These papers report newly acquired facts, synoptic interpretations of data, or original theory in specialized fields. These pub- lications are distributed by mailing lists to libraries, laboratories, and other interested institutions and specialists throughout the world. Individual copies may be obtained from the Smithsonian Institution Press as long as stocks are available. S. DILLON RIPLEY Secretary Smithsonian Institution SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY • NUMBER 21 Permian Brachiopods of West Texas, IV (PART l-TEXT) G. Arthur Cooper and Richard E. Grant ISSUED FEB 12^76 SMITHSONIAN INSTITUTION PRESS City of Washington 1976 ABSTRACT Cooper, G. Arthur, and Richard E. Grant. Permian Brachiopods of West Texas, IV. Smithsonian Contributions to Paleobiology, number 21 (part 1: text; part 2: plates), pages 1923-2607, figure 41, plates 503-662, 1976.—The fourth of a six-part monograph on the Permian brachiopods from several mountain ranges in western Texas, especially the Glass Mountains of Brewster County, this volume contains descriptions of genera and species in the orders Rhynchonellida and Spiriferida. The Rhynchonellida contain 30 genera in the superfamily Rhynchonellacea and 3 genera in the superfamily Stenoscismatacea. The Spiriferida contain 2 genera of Cyrtiacea, 4 of Athyridacea, 9 of Spiriferacea, and 6 of Reticulariacea. Permian Brachiopods of West Texas, I. Smithsonian Contributions to Paleobiology, number 14, 231 pages, 39 figures, 23 plates. Issued 29 December 1972. Permian Brachiopods of West Texas, II. Smithsonian Contributions to Paleobiology, number 15, pages 233-793, figure 40, plates 24-191. Issued 16 April 1974. Permian Brachiopods of West Texas, III. Smithsonian Contributions to Paleobiology, number 19 (part 1: text; part 2: plates), pages 795-1921, plates 192-502. Issued December 1975. OFFICIAL PUBLICATION DATE is handstamped in a limited number of initial copies and is recorded in the Institution's annual report, Smithsonian Year. SI PRESS NUMBER 5094. SERIES COVER DESIGN: The trilobite Phacops rana Green. Library of Congress Cataloging in Publication Data Cooper, Gustav Arthur, 1902- Permian brachiopods of West Texas. (Smithsonian contributions to paleobiology, no. 14-15, 19, 21) Supt. of Docs: SI 1.30: 21 Includes bibliographies. 1. Brachiopoda, Fossil. 2. Paleontology—Permian. 3. Paleontology—Texas. I. Grant, Richard E., joint author. II. Title. III. Series: Smithsonian Institution. Smithsonian contributions to paleobiology, no. 14 [etc.] QE701.S56 no. 14, etc. [QE796] 5G0'.8s [564'.8'097649] 72-4218 Contents Page Order Rhynchonellida 1923 Superfamily Rhynchoncllacea 1928 Family Petasmatheridae 1928 Genus Petasmalherus 1928 Genus Elassonia 1935 Genus Ptygmaclrum 1939 Genus Iotina 1944 Family Trigonirhynchiidae 1945 Subfamily Tricoriinae 1945 Genus Tricoria 1945 Family Amphipellidae 1947 Genus Amphipella 1947 Family Wellerellidae 1950 Subfamily Wellerellinae 1950 Genus Wellerella 1950 Genus Phrenophoria 1955 Genus Holosia 1971 Genus Tautosia 1973 Genus Cenorhynchia 1986 Subfamily Strigirhynchiinae 1996 Genus Strigirhynchia . 1996 Genus Chaeniorhynchus 1999 Genus Madarosia 2002 Family Allorhynchidae 2003 Genus A llorhynchus 2003 Genus Ptilotorhynchus 2010 Genus Deltarina 2012 Genus Fascicosta 2014 Genus Hemileurus 2017 Family Pontisiidae 2019 Genus Pontisia 2019 Genus Lirellaria 2031 Genus Divaricosta 2033 Genus Antronaria 2036 Genus Aphaurosia 2048 Genus Acolosia 2050 Genus Anteridocus 2054 Family Camarotoechiidae 2063 Subfamily Camarotoechiinae 2063 Genus Bryorhynchus 2063 Genus Leiorhynchoidea 2068 Subfamily Paranorellinae 2073 Genus Paranorella 2073 Subfamily Trophisininae 2077 Genus Trophisina 2078 Superfamily Stenoscismatacea 2080 Family Stenoscismatidae 2080 Subfamily Stenoscismatinae 2080 Genus Stenoscisma 2081 Subfamily Torynechinae 2116 Genus Torynechus 2116 IV SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY Page Family Atriboniidae 2119 Subfamily Psilocamarinae 2119 Genus Psilocamara 2119 Order Spiriferida 2120 Suborder Spiriferidina 2120 Superfamily Cyrtiacea 2120 Family Ambocoeliidae 2120 Genus Crurithyris 2120 Genus Attenuatella 2131 Suborder Athyrididina 2133 Superfamily Athyridacea 2133 Family Athyrididae 2133 Subfamily Athyridinae 2133 Genus Cleiothyridina 2133 Genus Composita 2140 Family Nucleospiridae 2168 Genus Nucleospira 2168 Family Xenosariidae 2170 Genus Xenosaria 2170 Superfamily Spiriferacea 2172 Family Spiriferidae 2172 Subfamily Neospiriferinae 2172 Genus Neospirifer 2172 Genus Cartorhium 2191 Genus Lepidospirifer 2203 Genus Gypospirifer 2209 Genus Spiriferinaella 2214 Family Brachythyrididae 2218 Genus Eridmatus 2219 Genus Spiriferella 2221 Genus Eliva 2237 Genus Elivina 2241 Superfamily Reticulariacea 2246 Family Elythidae 2246 Genus Neophricadothyris 2246 Genus Astegosia 2256 Family Anomaloriidae 2260 Genus Anomaloria 2260 Family Martiniidae 2263 Genus Martinia 2263 Genus Heteraria 2275 Genus Rallacosta 2277 Literature Cited 2283 FIGURE 41. Scatter diagram of length and width of Composita slalagmium, new species 2164 PLATES 503. Pelasmatherus and Tricoria 2289 504. Elassonia, Leiorhynchoidea, Aphaurosia, and Paranorella 2291 505. Ptygmaclrum and Fascicosta 2293 506. Trophisina 2295 507. Chaeniorhynchus, Deltarina, and Tricoria 2297 508. Pontisia, Strigirhynchia, Deltarina, Bryorhynchus, Phrenophoria, Chaeniorhynchus, Lirellaria, Ptilotorhynchus, and Cenorhynchia 2299 NUMBER 21 Page 509. Divaricosta, Fascicosta, and Allorhynchus 2301 510. Strigirhynchia, Paranorella, Pontisia, Cenorhynchia, Bryorhynchus, Anteridocus, and Cleiothyridina 2303 511. Lirellaria and Aphaurosia 2305 512. Amphipella and Acolosia 2307 513. Ptilotorhynchus, Iotina, Acolosia, and Madarosia 2309 514. Strigirhynchia and Phrenophoria 2311 515. Cenorhynchia, Acolosia?, Aphaurosia, Wellerella, Anteridocus, Phrenophoria, Pontisia, and Tautosia 2313 516. Pontisia and Phrenophoria 2315 517. Antronaria, Anteridocus, Cenorhynchia, Phrenophoria, Pontisia, and Madarosia .... 2317 518. Phrenophoria 2319 519. Phrenophoria, Tautosia, Cenorhynchia, and Holosia 2321 520. Cenorhynchia, Pontisia, Leiorhynchoidea, Anteridocus, Strigirhynchia, and Ptygmactrum 2323 521. Phrenophoria, Petasmatherus, Tautosia, Fascicosta, Anteridocus, Aphaurosia, Cenorhynchia, and Strigirhynchia 2325 522. Phrenophoria 2327 523. Phrenophoria, Holosia, and Tautosia 2329 524. Tautosia and Phrenophoria 2331 525. Tautosia, Phrenophoria, and Acolosia 2333 526. Tautosia 2335 527. Tautosia and Wellerella 2337 528. Wellerella 2339 529. Anteridocus, Pontisia, and Antronaria 2341 530. Antronaria and Pontisia 2343 531. Antronaria and Pontisia 2345 532. Antronaria 2347 533. Antronaria and Pontisia 2349 534. Anteridocus and Pontisia 2351 535. Anteridocus, Antronaria, and Pontisia 2353 536. Antronaria and Pontisia 2355 537. Antronaria 2357 538. Antronaria and Anteridocus 2359 539. Hemileurus and Anteridocus 2361 540. Anteridocus, Petasmatherus, and Allorhynchus 2363 541. Allorhynchus, Petasmatherus, and Phrenophoria 2365 542. Allorhynchus 2367 543. Allorhynchus and Cenorhynchia 2369 544. Cenorhynchia and Tautosia 2371 545. Cenorhynchia 2373 546. Cenorhynchia and Bryorhynchus 2375 547. Cenorhynchia and Bryorhynchus 2377 548. Bryorhynchus, Leiorhynchoidea, and Madarosia 2379 549. Leiorhynchoidea 2381 550. Leiorhynchoidea and Bryorhynchus 2383 551. Paranorella, Petasmatherus, and Anteridocus 2385 552. Aphaurosia, Divaricosta, Cenorhynchia, Pontisia, Ptilotorhynchus, Phrenophoria, Deltarina, Antronaria, Fascicosta, and Madarosia 2387 553. Phrenophoria, Stenoscisma, Wellerella, and Tautosia 2389 554. Stenoscisma 2391 555. Stenoscisma 2393 556. Stenoscisma 2395 557. Stenoscisma 2397 558. Stenoscisma 2399 559. Stenoscisma 2401 560. Stenoscisma 2403 561. Stenoscisma 2405 553. VI SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY Page 562. Stenoscisma 2407 563. Stenoscisma 2409 564. Stenoscisma 2411 565. Stenoscisma 2413 566. Stenoscisma 2415 567. Stenoscisma 2417 568. Stenoscisma 2419 569. Stenoscisma 2421 570. Stenoscisma 2423 571. Stenoscisma 2425 572. Stenoscisma 2427 573. Stenoscisma 2429 574. Stenoscisma 2431 575. Stenoscisma 2433 576. Stenoscisma 2435 577. Stenoscisma 2437 578. Stenoscisma 2439 579. Stenoscisma 2441 580. Stenoscisma 2443 581. Stenoscisma 2445 582. Stenoscisma 2447 583. Stenoscisma 2449 584. Torynechus 2451 585. Torynechus 2453 586. Psilocamara and Torynechus 2455 587. Xenosaria, Crurithyris, and Grandaurispina 2457 588. Crurithyris 2459 589. Crurithyris 2461 590. Crurithyris and Attenuatella 2463 591. Gypospirifer 2465 592. Gypospirifer and Neospirifer 2467 593. Neospirifer and Gypospirifer 2469 594. Neospirifer 2471 595. Neospirifer 2473 596. Neospirifer 2475 597. Neospirifer 2477 598. Neospirifer 2479 599. Neospirifer 2481 600. Neospirifer 2483 601. Neospirifer and Gypospirifer 2485 602. Neospirifer and Gypospirifer 2487 603. Neospirifer 2489 604. Neospirifer 2489 605. Neospirifer 2493 606. Neospirifer 2495 607. Neospirifer 2497 608. Neospirifer 2499 609. Neospirifer 2501 610. Neospirifer 2503 611. Neospirifer 2505 612. Neospirifer 2507 613. Cartorhium 2509 614. Cartorhium 2511 2513 615. Cartorhium 2517 2519 2521 616. Cartorhium 9515 617. Cartorhium 618. Cartorhium 619. Cartorhium 618. NUMBER 21 Vll Page 620. Cartorhium 2523 621. Lepidospirifer 2525 622. Lepidospirifer 2527 623. Lepidospirifer 2529 624. Cartorhium and Lepidospirifer 2531 625. Spiriferinaclla 2533 626. Spiriferinaclla, Eridmatus, and Spiriferella 2535 627. Spiriferella 2537 628. Spiriferella 2539 629. Spiriferella 2541 630. Spiriferella 2543 631. Spiriferella and Martinia 2545 632. Eliva 2547 633. Elivina, Rallacosta, and Eliva 2549 634. Elivina 2551 635. Neophricadothyris 2553 636. Neophricadothyris 2555 637. Neophricadothyris 2557 638. Neophricadothyris 2559 639. Neophricadothyris 2561 640. Anomaloria 2563 641. Astegosia 2565 642. Astegosia 2567 643. Martinia 2569 644. Martinia 2571 645. Martinia 2573 646. Rallacosta and Heteraria , 2575 647. Rallacosta . . 2577 648. Rallacosta 2579 649. Martinia, Neophricadothyris, Astegosia, and Anomaloria 2581 650. Cleiothyridina 2583 651. Cleiothyridina and Nucleospira 2585 652. Composita 2587 653. Composita 2589 654. Composita 2591 655. Composita 2593 656. Composita 2595 657. Composita 2597 658. Composita 2599 659. Composita 2601 660. Composita 2603 661. Composita 2605 662. Composita 2607 657. 657. Permian Brachiopods of West Texas, IV G. Arthur Cooper and Richard E. Grant Order RHYNCHONELLIDA Kiihn, 1949 Rostrate, narrow hinged, with functional pedicle; delthyrium open in some Paleozoic genera but more commonly partially closed by deltidial plates. Dental plates usually present, obsolescent in some genera; spondylia rare. Brachial valve with variable hinge plate having socket ridge; crura attached to outer hinge plates or directly to crural base; inner hinge plates variable, divided, or fused; crura var- iable in type; median septum, when present, com- monly supporting V-shaped chamber of variable proportions. Lophophore spirolophous with dorsad cones. "Mantle sinuses much branched with one pair in each mantle" (Ager in Williams et al., 1965: H552). Ornament commonly strongly costate, more rarely multicostate but with trends to costellation, multicostellation, and smoothness in late members of stocks. Impunctate. (Here it should be under- stood that in an effort to make the order more understandable we have excluded from this defini- tion the punctate members and reference to the metanephridea, which are usually two in modern genera but in the Cryptoporidae there is only one.) DISCUSSION.—Our study of the rhynchonellids of the Permian of West Texas has not been encum- bered by the necessity to prepare serial sections. One of the disadvantages of that method, when specimens are scarce, is that it is impossible to get a good idea of the variability of the interior of the rhynchonellid shell. This has been one of the diffi- culties in classification. We do not know intimately G. Arthur Cooper and Richard E. Grant, Department of Paleobiology, National Museum of Natural History, Smith- sonian Institution, Washington, D.C. 20560. how the interior of the rhynchonellid shell is devel- oped and how, after it reaches maturity, it may become modified by adventitious shell or by resorp- tion of previously deposited shell substance. These are matters that could not be brought out by the preparation of many serial sections and the destruc- tion of valuable material. Most of the West Texas rhynchonellids reveal the interiors in fair condition and in some of them we have been able to detect considerable variation in characters that are usually regarded as generic. For example, Trophisina, new genus, in the adult condition shows a development of the hinge plate from completely divided to completely bridged by fusion of the inner hinge plates. Phreno- phoria Cooper and Grant, as portrayed by P. per- plexa, new species, develops a minute chamber in the apex of the brachial valve, a structure not seen in other members of the genus. The septum is a structure not now well understood; it is strongly developed in some genera and seems to be a valid generic character, but in others such as Pontisia Cooper and Grant it is relict or absent. Some rhyn- chonellids that normally lack a median septum occasionally develop a minute one at the apex. Not much help in these matters has been obtained from recent rhynchonellids because there are too few of them. Hemithyris d'Orbigny and Notosaria Cooper are the only large ones that are fairly easily ob- tained, but we know of no studies on them along the lines mentioned above. The rhynchonellids of the Permian of West Texas offer a fair sample of the order. They have some members that seem primitive because they do not have any deltidial plates. These are either 1923 1924 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY not developed or completely absorbed. In others their development is spasmodic. Other genera show an advanced trend toward smoothness. Internally the West Texas shells are with or without median septa, and most of the possible changes in hinge plates are present. A trend toward obsolescence of the dental plates is detectable. The crura, on the other hand, seem to be fairly conservative, but in them, too, a developmental trend can be detected. Rhynchonellids are fairly common in the West Texas Permian. They are not abundant in the Wolfcamp Series but are fairly common in the Leonardian. In some parts of the Word Formation they are abundant. Our treatment of the genera may have lead to some repetition because we have not been able to identify certain of our material with genera prepared by serial sectioning. CRURA.—The crura are an important element in the interior of the rhynchonellid shell and there- fore deserve attention in classification. No attempt has been made to differentiate the types of crura in the Paleozoic rhynchonellids but an attempt has been made to define various types in the Mesozoic. Ager (1965) recognizes 11 different types. Dagis (1968) in a discussion of Mesozoic rhynchonellid genera differentiates 13 different kinds. Cooper (1959) identified 5 types of crura in the Tertiary and Recent rhynchonellids. Inasmuch as the treat- ment of the crura by the various authors is differ- ent, definition and understanding of the various types is not clear. Ager and Dagis distinguish the types mainly by study of serial sections. Cooper, on the other hand, based his descriptions on three- dimensional study of the whole structure. It is unnecessary to section Recent shells and the Ter- tiary ones are easily excavated. In our study of the Permian rhynchonellids we have not resorted to serial sections because all the genera have yielded material that can be studied directly. As a matter of fact, the silicified speci- mens obtained in residues would be very difficult to section serially because of their brittle and friable character. It would take special embedding techniques to make this possible. All this effort seems unnecessary when the actual structures can be obtained and observed for there is less ambi- guity in studying them. Orientation is extremely important in serial sectioning. Not all authors sec- tion in the same way and this leads to difficulties in interpretation. We recognize two definite types of crura in the West Texas rhynchonellids. The commonest type is the "falcifer," which also is common in the Mesozoic and is present in Recent brachiopods. The second type is in Bryorhynchus and is here termed "mucrifer." Another type is recognizable but we regard it as an aberration of the falcifer type and discuss it under that heading. FALCIFER TYPE.—The falcifer crus is best seen in modern shells in the Basiliolidae where it occurs in Basiliola, Eohemithryris, Neorhynchia, and Rhy- tirhynchia. It occurs in the Tertiary genera Probo- larina and Streptaria. It consists of a moderately to strongly curved blade, cresentic in cross section and the convex side out. The blade is so tilted that the concave sides face each other and the cross section of the blades is vertical. The blades in section may vary from vertical to moderately oblique, with the anterior or dorsal edge of the blade nearest to the side. Attachment to the socket ridge is usually accomplished by means of an outer hinge plate of variable width, wide in some genera but narrow to almost nonexistent in others. Neo- rhynchia has a wide hinge plate, but that of Probolarina is narrow. The small Permian genera, Petasmatherus, Iotina, Ptygmactrum, Acolosia, and Elassonia have short crura with fairly strong concavity facing me- dially, usually moderately curved and fairly wide apart. The distal end is not usually tapered but is obliquely truncated so that the free end of the crus nearest the pedicle valve is the more pointed. Shells of intermediate size—Allorhynchus, Ante- ridocus, Divaricosta, Deltarina, Cenorhynchia, Fascicosta, Lirellaria, Strigirhynchia, Tricoria, and Wellerella—usually are similar to the preceding but have a tendency toward a modification seen more commonly in the larger forms such as Antro- naria, Holosia, Phrenophoria, Tautosia, and Pon- tisia. This modification consists of an elongation of the crus and its slight rotation toward the interior, so that the concave part faces anteriorly or dorsally and the convex surface faces ventrally and toward the posterior. Two genera of smaller shells also have the crus so oriented: Hemileurus and Aphaurosia. The crus is definitely falciform but differs from the typical condition in having rotated medially about 90° Many intermediates exist in which the section of the crus is oblique. Inasmuch as many of the falciform crura (in cross NUMBER 21 1925 TABLE I.—Summary of generic characters of Rhynchonellacea (toticostate = costae extending from back to anterior margin) Genus Size Outline Development of fold, sulcus Interareas Ornament Acolosia minute to moderate small to medium small small fairly large small to medium medium small to medium medium small medium minute to small small to medium small large minute medium to large small to medium medium large small small to large small to medium medium small medium medium to large medium medium medium elongate-oval trigonal subpentagonal subpentagonal to rounded to trigonal transversely subelliptical to subpentagonal transversely elliptical to sub trigonal snbovatc to rotund-trigonal trigonal to pentagonal oval to subtrigonal trigonal subpentagonal to subtrigonal subtrigonal to subelliptical subelliptical to subtrigonal elongate-subtriangular elongate-oval pentagonal rounded trigonal subpentagonal to subcircular subpentagonal rounded to trigonal trigonal to subovate elongate-subtrigonal subpentagonal to trigonal triangular trigonal to elliptical subtrigonal to subcircular transversely triangular transversely triangular to pentagonal subcircular to longitudinally suboval subtriangular moderate moderate faint, shallow weak to moderate strong poor moderate moderate moderate moderate moderate to strong none moderate weak weak strong moderate moderate moderate moderate sulcate weak moderate moderate gentle none gentle strong fold sulcate weak strongly costate none none small or absent none none none none none none none none small none none none present none none none none present none none none present none none none none none smooth to incipiently costate toticostate direct smooth anterior incipiently costate strong costae, smooth umbo anterior weakly costate faint costae on fold, sulcus semicostate, flanks usually smooth toticostate Allorhynchus Amphipella Anteridocus Antronaria Aphaurosia Bryorhynchus Cenorhynchia Chaeniorhynchus Deltarina Divaricosta Elassonia Hemileurus Iotina few costae but toticostate Leiorhynchoidea Lirellaria costae irregular to strong costellate smooth, anteriorly lamellose smooth strongly toticostate semicostate costate, smooth umbo Ptilotorhynchus toti- and multicostate strongly toticostate, spines finely toticostate Tautosia strong costae, smooth umbo toticostate toti- and multicostate Wellerella semicostate 1926 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY TABLE 1.—Summary of generic characters of Rhynchonellacea (continued) Genus Profile Commissure Dental Plates Hinge Plate Median Septum Acolosia biconvex broadly uniplicate strong undivided, notched none Allorhynchus unequally biconvex uniplicate strong, vertical divided none, low myophragm Amphipella flatly biconvex broadly sulcate to uniplicate short, thin, partly to wholly fused notched or divided none Anteridocus strongly biconvex uniplicate strong, vertical undivided, notched deeply short septal brace Antronaria unequally biconvex strongly uniplicate strong to obsolescent undivided none, thick, low myophragm Aphaurosia subequally biconvex uniplicate short, stout undivided, notched none to apical rudiment Bryorhynchus branchial valve inflated uniplicate short, convergent, obsolescent divided septum thick, low Cenorhynchia unequally biconvex uniplicate strong, vertical undivided, notched septum high, thin Chaeniorhynchus subequally biconvex uniplicate strong undivided septum high, thin Deltarina narrowly biconvex uniplicate thin, convergent divided median ridge Divaricosta unequally biconvex uniplicate short, often fused to valve undivided thick, median ridge Elassonia flatly biconvex rectimarginate to weakly sulcate short, fused divided median ridge thick, low Fascicosta unequally biconvex uniplicate short, convergent divided low, slender, variable ridge Hemileurus biconvex broadly uniplicate thin, long, subparallel divided low myophragm Holosia unequally biconvex broadly uniplicate short, obsolescent broad, undi vided long, high, strong, thin none Iotina unequally biconvex narrowly uniplicate obsolescent divided Leiorhynchoidea unequally biconvex uniplicate short, usually obsolescent divided strong and thick Lirellaria unequally biconvex convexi-plane uniplicate uniplicate thin and short Madarosia short, ventrally undivided long, strong, and thin convergent Paranorella pedicle valve more convex sulcate receding, often obsolete undivided long and thin Petasmatherus flatly biconvex rectimarginate to uniplicate short, fused divided none, low myophragm Phrenophoria unequally biconvex uniplicate strong, vertical undivided strong and high unequally biconvex unequally biconvex uniplicate uniplicate strong undivided none, myophragm myophragm Ptilotorhynchus present in young, divided absent in old Ptygmactrum flatly biconvex rectimarginate to uniplicate short, vertical divided low ridge Strigirhynchia strongly biconvex gently uniplicate strong to fused undivided high, thin, long Tautosia unequally biconvex strongly uniplicate strong undivided strong, high unequally biconvex rectimarginate to thin to obsolescent divided high, thin, long uniplicate strongly biconvex uniplicate strong, convergent divided to short, anteriorly threadlike undivided (old) Wellerella unequally biconvex uniplicate strong, vertical undivided apical, rudimentaryNUMBER 21 1927 Beak Deltidial Plates Brachial Umbo Crura Tongue Special variable none swollen short falcifer moderately long nearly smooth straight to suberect rudimentary, disjunct convex falcifer long toticostate straight none convex short falcifer? very short apricatria present short, usually suberect straight to suberect short, nearly straight rudimentary, disjunct disjunct to conjunct conjunct convex to depressed convex swollen falcifer mod. falcifer mod. falcifer short to mod. long moderately long moderately long flanks weakly costate median costae of fold depressed semicostate erect-incurved rudimentary to swollen mucrifer short nearly smooth short to moderately long, suberect to erect suberect to erect conjunct none none convex convex falcifer falcifer moderately long moderately long usually smooth flanks completely costate long, straight straight to suberect rudimentary, disjunct conjunct convex convex short falcifer falcifer short moderately long divided costae multicostate straight none or rare sulcate falcifer none minute and multicostate straight to suberect absent convex falcifer moderately long bifurcated costae nearly straight small, disjunct convex mod. falcifer moderately long semicostate nearly straight, short disjunct convex to flattened mod. falcifer short to long completely costate long, nearly straight erect to slightly incurved suberect to erect none none to conjunct disjunct to conjunct convex swollen swollen falcifer mucrifer mod. falcifer moderately long short to long moderately long tiny exterior variable costellate, rounded contours suberect none or marginal flattened falcifer moderately long margin lamellose erect to incurved none? convex mucrifer? dorsal tongue short smooth, sulcate nearly straight nearly straight- suberect suberect small, disjunct disjunct to conjunct disjunct to conjunct variable, often flattened to sulcate variable convex falcifer mod. falcifer mod. falcifer short moderately long moderately long small, strong costae strong median septum septum absent short, straight conjunct, alate concave falcifer short alate deltidial plates nearly straight open or rudimentary convex falcifer absent or short small, often spiny costae straight to suberect nearly straight to suberect nearly straight open to conjunct conjunct none flattened to concave convex to indented convex falcifer mod. falcifer falcifer moderately long short to moder- ately long short dorsal umbo flat or concave strong costae anterior emarginate suberect small, disjunct swollen mucrifer moderately long obese, low fold, costellate nearly straight to suberect conjunct indented mod. falcifer moderately long apical septum1928 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY section) are not vertical but oblique, this is not a great change. Consequently, we record the genera with the horizontal cross section as "mod." (for modified) "falcifer" on the table. MUCRIFER TYPE.—-The mucrifer crus is charac- teristic of the rhynchonellids hitherto placed under Leiorhynchus but now regarded as Camarotoechia, sensu stricto, as revised by Sartenaer (1961b). As revealed by Bryorhynchus, which is the reference genus for this type of crus, the hinge plate is divided and the crus is narrow and solid, somewhat square in section, long, and curved moderately. Distally it expands slightly and is flattened antero- posteriorly. Distally it is gently concave on the anterior side but flattened on the posterior side. The extremity is pointed, with the sharp end on the inside. Generally the plates diverge at a low angle. This type occurs in Calvinaria as well as the genera named above. It also occurs in Leiorhyn- choidea and Paranorella. It is probably in all of the unquestioned Camarotoechiinae as listed in the Treatise on Invertebrate Paleontology (Williams et al., 1965). Amphipella is difficult to place in either of the above categories; it is placed here with the falcifer type, but with a query. The crura of Amphipella are long but not strongly curved; they are laterally compressed and not all of them show the inwardly facing concavity, but it is there in some of them. Superfamily RHYNCHONELLACEA Gray, 1848 PETASMATHERIDAE, new family Minute to small costate Rhynchonellacea having well developed interarea on pedicle valve, deltidial plates absent to rudimentary, disjunct when pres- ent. Short dental plates in pedicle valve; brachial valve with widely divided hinge plate, falcifer crura, no median septum. Genera in West Texas: Petasmatherus Cooper and Grant, 1969; Elassonia, new genus; Plygmac- trum, new genus; and Iotina, new genus. These minute genera probably would never have been detected by ordinary collecting methods. Petasmatherus characterizes the Word Formation of the Glass Mountains and is present in the Gua- dalupe Mountains in the Cherry Canyon Forma- tion. Elassonia is abundant in the Road Canyon Formation but Ptygmaclrum is one of the rarest genera in the Glass Mountains. Iotina is poorly known and occurs in the Sierra Diablo in the lower massive Bone Spring Formation. Genus Petasmatherus Cooper and Grant, 1969 Petasmatherus Cooper and Grant 1969:12. Small, rhynchonelliform, flatly biconvex; outline bluntly triangular to subovate; commissure slightly uniplicate or rectimarginate, with low fold and shallow sulcus; costae strong, beginning at beaks, becoming stronger anteriorly, crests sharp to rounded, no bifurcation or intercalation, inter- troughs sharp to broadly rounded. Pedicle valve beak sharp, nearly straight, apsa- cline interareas bounding delthyrium nearly flat transversely, longitudinally flat to slightly convex, orthocline to apsacline. Delthyrium triangular, wide, open, with small, disjunct deltidial plate; lateral pseudointerareas narrow, covered by slight overlap of valves. Brachial valve with wide, blunt beak, nearly straight across, forming definite hinge line; beak completely external, not curved, and extending into pedicle valve. Pedicle valve interior with sides abruptly widen- ing anterior to delthyrium; teeth small, elongate, parallel to and attached to sides of valve; dental plates short, supporting teeth, fused in some speci- mens to sides of valve. Muscle area obscurely marked; adductor scars on slight thickening of floor between dental plates; diductor scars slightly excavated, lying on each side of median line, widen- ing anteriorly. Median plication of exterior shell simulating median ridge. Brachial valve interior with short, wide hinge plate, slightly to deeply divided in middle; major part of sockets lateral to hinge plate, parallel to hinge line, rather deep, long, wide, minutely cor- rugated; socket ridge small, inclined over socket; outer hinge plate fairly wide; crural base narrow; crura short, falcifer, strong, projecting forward from lateral edges of hinge plate, slightly diverging anteriorly, straight to slightly curved ventrally, cross section nearly round near bases, laterally flattened at anterior ends; no inner hinge plates. Median septum absent, low, broad median ridge present or absent. Muscle area elongate oval; pos- terior adductor scars elongate, narrow, widely sep- NUMBER 21 1929 arated, nearly parallel to median ridge, diverging slightly anteriorly; anterior adductor scars larger, slightly widening anteriorly, lying along median line. TYPE-SPECIES.—Petasmatherus opulus Cooper and Grant (1969:12, pi. 2: figs. 8-14). DIAGNOSIS.—Small straight-hinged Rhynchonella- cea with well-developed interareas on pedicle valve and crura of the falcifer type. COMPARISON.—Petasmatherus is characterized by its strong costation, barely perceptible uniplication, well-marked interareas, blunt brachial beak that forms a straight hinge line, with resultant narrow- ing and compressing (antero-posteriorly) of the hinge plate and sockets, its short, nearly straight, stout crura, and lack of a median septum. The strong costae that begin at the beaks distinguish it from Wellerella; the absence of a median septum distinguishes it from Phrenophoria, Strigirhynchia, new genus, and its slightly to deeply divided hinge plate and interareas distinguish it from Allorhynchus. Two small species of different genera are sim- ilar to Petasmatherus and might be confused with it. Ptygmactrum, new genus, is small and trans- verse, has interareas, and is strongly plicated, but it differs from Petasmatherus in having broader angular ribs on the exterior. Small specimens of Allorhynchus resemble Petasmatherus but they lack interareas in the pedicle valve, have definite delti- dial plates, and usually have a well-formed fold and sulcus. Another small brachiopod that may be mistaken for Petasmatherus is Elassonia, new genus. This little shell has strong interareas like those of Petasmatherus but is sulcate and has a strong median ridge. DISCUSSION.—This genus combines many unusual features in one distinctive entity. The exterior is unusual because of the" broad and well-marked interareas bounding the delthyrium. These extend directly to the lateral margins. In the very young the interareas are strongly apsacline but they be- come more nearly orthocline in adults. The young pedicle valve is flatly convex in lateral profile but fairly strongly arched in anterior profile thus accommodating the nearly flat or concave brachial valve. The interarea bounds an elongate delthyrium which is open in the young and in young adults but is restricted by small deltidial plates at the anterolateral extremities. The deltidial plates take the form of small barbs or small triangles with the apex directed medially. They are small and restrict the delthyrium only to the extent of rounding the anterior side of the aperture and producing an elongated tear-shaped foramen. In detached valves the deltidial plates can be seen best at the lateral angles of the delthyrium well posterior to the teeth. A deep trough lies between them and the teeth. The exterior of the brachial valve is also dis- tinctive, because the young are flat to concave and have a strong median depression. The young are thus anteriorly sulcate but with advancing age the commissure reverts to a uniplicate condition. Gen- erally old shells retain the sulcate umbonal region, a fact that helps to separate this genus from many others. The hinge region of the brachial valve is unusually wide for a rhynchonellid and in old specimens produces small, poorly defined ears. In some old shells the posterior margin is gently concave because of the strong sulcation of the umbonal region. The unusual and distinctive features of the ex- terior of this genus are matched by correspond- ingly distinctive characters on the inside. Many specimens of the pedicle valve are considerably thickened and show some of the features to ad- vantage. The floor of the delthyrial cavity is usually much thickened and in some specimens produces a small platform with abrupt descent to the valve floor. This part probably lodged the pedicle cap- sule. Anterior to it the broad scar of the muscle field is subflabellate as usual in rhynchonellids, although individual scars are difficult to identify. In old specimens a low myophragm divides the field. This is partly produced by a median rib corresponding to the central interspace of the exte- rior. The height of this median rib is enhanced further by the development of a low myophragm on it. The teeth are large and nearly parallel to the hinge region of the brachial valve, thus lying nearly horizontal when observed from the inside, with the beak directed away from the observer. No corrugations were seen on any of the speci- mens. The teeth are buttressed by small receding dental plates that define short and narrow umbonal chambers. In old shells these slitlike cavities are filled by adventitious shell and the dental plates 1930 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY are thus rendered nearly unidentifiable. The cardinalia of the brachial valve are distinc- tive because of the straightness of the hinge region. The socket plates are elevated, strong, and hang over the sockets. The floor of the sockets is formed by a plate extended laterally far beyond the socket ridge. The sockets are thus wide, narrow, deep, and fairly strongly corrugated when preservation is favorable. The outer hinge plate is exceptionally large and attaches the bladelike crural base and short crus to the socket ridge. The crura are short, have somewhat expanded distal ends which are obliquely truncated, and the anterior end is some- what elongated. In cross section the crura are con- vex outward and of the falcifer type. No cardinal process in the form of a rounded boss is present nor does a pit at the beak serve as an adductor attachment. A ridge, continuous laterally with the socket ridge, appears along the posterior side of young specimens; adductor muscles attached to the median part of this ridge. With increase in size and age this ridge became greatly thickened, so much so that some specimens have a large flattened boss occupying the space between the crura. In some medium-grown specimens the cardinal process ridge takes the form of two bosses with a depres- sion between them. These are located on the poste- rior angle of the outer hinge plate. Anterior to the cardinalia the shell is often thickened to form a short broad ridge, that, in some specimens, has a short myophragm anterior to it. This indicates the location of the adductor field, although individual scars were not observed. Petasmatherus depressus, new species PLATE 503: FIGURE 23 Usual size for genus, subpentagonal in outline subequal in depth, wider than long, with rounded sides and anterior margin rounded but medially indented. Beak nearly straight, delthyrium open, no trace of marginal plates. Interareas narrow. Anterior commissure uniplicate. Surface costate, costae direct, straight. Both valves slightly sulcate, pedicle valve with 2 costae in sulcus but brachial valve with only 1. Flanks marked by 4 costae on pedicle valve and 5 on brachial valve. Pedicle valve gently convex in lateral profile but flatly domed in anterior profile; sulcus shallow and defined only from midvalve to anterior margin, flanks moderately convex. Brachial valve gently convex in both profiles and almost exactly like those of opposite valve. Sulcus defined from mid- valve to anterior margin, shallow. Interior not known. MEASUREMENTS (in mm).—Holotype USNM 154614: length 4.0, brachial valve length 3.8, maxi- mum width 4.4, thickness 2.5, apical angle 95° STRATIGRAPHIC OCCURRENCE.—Road Canyon For- mation. LOCALITY.—USNM 721j. DIAGNOSIS.—Petasmatherus with an indistinct fold on both valves. TYPES.—Holotype: USNM 154614. COMPARISON.—This species is intermediate be- tween P. recticardinatus, new species, and P. opu- lus Cooper and Grant. It is wider than the former and differently shaped; it is similar in outline to the latter but has definite sulci on both valves, whereas P. opulus has a poorly defined fold occu- pied by three costae in the brachial valve. This is a very rare species known only from the holotype. Petasmatherus mundus, new species PLATE 540: FIGURES 15-25 Small for genus, subtriangular in outline; length and width nearly equal; sides rounded and with maximum width anterior to midvalve. Anterior margin truncated; anterior commissure gently to moderately uniplicate. Beak short, suberect; del- thyrium mostly open but restricted in anterolateral extremities by vestigial deltidial plates. Surface completely costate, costae numbering 3 on fold, 2 in sulcus, and 5 or 6 on flanks. Pedicle valve gently convex in lateral profile; broadly and gently convex in anterior profile; median region gently swollen; sulcus shallow and poorly defined, originating near midvalve. Flanks gently convex and with moderately steep slopes. Brachial valve moderately convex in lateral pro- file and more convex than opposite valve; anterior profile broadly and moderately convex; umbonal and median regions moderately convex; fold incon- spicuous, scarcely visible except at front of valve; flanks gently swollen. Pedicle valve interior with strong dental plates convergent in ventral direction. Brachial valve in- NUMBER 21 1931 terior with divided hinge plate, outer hinge plates moderately wide; socket ridges strong; no inner hinge plates seen on single interior available; crura short, strongly curved, flattened laterally and con- cave inward and obliquely truncated distally. No septum, but low rounded median ridge. MEASUREMENTS (in mm).— brachial maxi- apical valve hinge mum thick- angle length length width width ness C) USNM 702-low 153472a 5.1 4.3 2.0 4.8 3.0 83 (holotype) 153472b 5.2 4.6 2.1 5.1 3.4 92 153572c 4.9 4.1 1.9 4.6 2.8 83 STRATIGRAPHIC OCCURRENCE.—Hess Formation; Cathedral Mountain Formation. LOCALITIES.—Hess: USNM 709h. Cathedral Moun- tain: 702-low. DIAGNOSIS.—Small, closely costate, triangular Petasmatherus with length and width nearly equal. TYPES.—Holotype: USNM 153472a. Figured par- atypes: USNM 153472c,d. Measured paratypes: USNM 153472b,c. Unfigured paratype: USNM 153472b. COMPARISON.—In general form and outline this species suggests P. nitidus and pumilus, both new, but it is smaller than they are, is more finely ribbed, is less convex, and has a less distinct fold and sulcus than the Road Canyon species. Allorhynchus venustulum, new species, although similar is not likely to be confused because it has much rounded and subdued costae and is a much rounder shell. Petasmatherus mundus is a very rare species. Petasmatherus nitidus, new species PLATE 540: FIGURES 26-55 Small, length and width about equal, outline subpentagonal to subtrigonal; sides rounded, ante- rior margin gently rounded; valves subequal in depth. Maximum width near midvalve. Anterior commissure gently uniplicate. Beak short, usually suberect; apical angle 80-90°. Surface costate, costae of both valves reaching beaks, narrowly rounded and with intertroughs of about equal width; fold with 5 costae, sulcus with 4, and flanks with 6. Pedicle valve moderately and evenly convex in lateral profile, and broadly but very gently convex in anterior profile; beak suberect; umbonal region narrow, gently convex; sulcus shallow, originating near midvalve, extended as short tongue. Flanks narrow, moderately steep. Foramen oval to nar- rowly elongate; deltidial plates small, anterior, disjunct. Brachial valve moderately convex in lateral pro- file, maximum curvature in umbonal region; ante- rior profile narrowly domed and with precipitous sides. Umbonal and median regions swollen; fold low, gently rounded, defined first at midvalve; lateral bounding costa on each side of fold slightly depressed below level of three median costae. Flanks rounded and steep. Pedicle valve interior with small teeth and deli- cate dental plates defining very narrow umbonal cavities. Muscle scars not clearly defined. Brachial valve with divided hinge plate; socket ridge strong, inclined laterally and overhanging smooth sockets. Outer hinge plates narrow; crural bases narrow; crura curved, laterally broad, convex laterally and distally serrate. Median septum ab- sent. Muscle marks not impressed. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (*> USNM 721j 154884h 6.8 5.6 6.8 4.8 88 (holotype) USNM 721x 154883a 7.4 6.3 6.7 5.6 85 154883b 6.8 5.9 6.8 4.7 75 154883c 7.3 6.1 6.8 4.6 85 154883d 6.7 5.8 6.3 4.2 85 154883e 5.9 5.1 5.5 4.0 80 154883f 5.2 4.3 4.8 2.7 85 154883g 4.9 4.1 4.5 2.2 85 154883h 4.0 3.3 3.2 1.8 85 154883i 3.5 2.8 3.0 1.6 80 154883J 8.0 7.0 8.1 5.4 90 STRATIGRAPHIC OCCURRENCE.—Road Canyon For- mation. LOCALITIES.—AMNH 507; USNM 702c, 703d, 706f, 720d, 721j, 721x, 721z, 723a, 724a, 726d, 726e, 736x. DIAGNOSIS.—Large, compact, elongate, finely ribbed Petasmatherus with short beak and low fold. TYPES.—Holotype: USNM 154884h. Figured par- atypes: USNM 154883a,b,j,k; I54884a-g; 154885a-c. 1932 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY Measured paratypes: USNM 154883a—j. Unfigured paratypes: USNM 154883c-h,l,m; 154884i,j. COMPARISON.—This species and P pumilus Cooper and Grant (1969) occur in the same forma- tion and may be confused as there is considerable resemblance between them. Petasmatherus nitidus can be distinguished by its better defined fold and sulcus, its shorter beak, generally less crowded costae, and usually less elongated outline. Although both species are equal in length and width or have the length slightly greater than the width, the longer beak of A. pumilus tends to give it a more elongated appearance. Petasmatherus opulus Cooper and Grant PLATE 503: FIGURES 1-20, 22 Petasmatherus opulus Cooper and Grant, 1969:12, pi. 2: figs. 8-14. Small, flatly biconvex; outline bluntly triangular to subovate or tear-shaped, sides diverging between 65° and 105°, averaging near 90°; commissure gently uniplicate, fold low, sulcus shallow; costae strong, beginning at beaks, becoming higher and wider anteriorly, without intercalation or bifurca- tion, crests sharp to blunt, intertroughs sharp or rounded, costae numbering 3 or 4 on fold, normally 3, one less in sulcus, 3 or 4 on each flank. Con- centric ornamentation absent; weak growth lines visible on some shells, especially near anterior margin. Pedicle valve gently convex, flanks not reflexed; beak sharp, nearly straight, not attenuate, inter- area adjacent to delthyrium transversely flat, longi- tudinally flat to slightly convex, projecting parallel to plane of commissure in some specimens, nor- mally slanting ventrally to plane. Delthyrium large, triangular base slightly constricted by small, dis- junct deltidial plates; lateral pseudointerareas nar- row, partly covered by slight overlap of brachial valve. Umbonal region convex; sulcus shallow, originating near midvale. Brachial valve slightly less convex, with barely perceptible fold originating posterior to midvalve, but umbonal region with shallow sulcus; beak blunt, normally nearly straight transversely, often slightly arched posteriorly, or slightly indented anteriorly on median line; apex of valve external, not curved into pedicle valve. Flanks narrow, rounded. Pedicle valve interior with sides abruptly widen- ing anterior to delthyrium, becoming nearly paral- lel to transverse line of shell, to accommodate straight hinge line of brachial valve; teeth small elongate knobs, parallel to and attached to sides of shell, supported by short dental plates slightly diverging to floor and either free or fused to sides of valve. Floor of beak area slightly built up, prob- ably for insertion of adductor muscles; diductor muscle scars slightly excavated, forming two lobes, one on each side of median line. Median plication built up in interior from sulcus, simulating median ridge. Brachial valve interior with short, wide hinge plate often thickened on underside and with mid: die slightly to deeply notched, not completely divided in old shells; sockets lateral to outer hinge plate, deep, wide, parallel to nearly straight hinge line, not denticulate; crura short, slightly diverg- ing from anterior lateral edges of hinge plate, sep- arated from socket ridge by fairly broad outer hinge plate; cural bases stout, rodlike, concave medially, anterior extremities flattened, somewhat concave proximally, curving slightly ventrally; me- dian septum absent; median ridge low when pres- ent. Muscle area elongate oval; posterior adductor scars long, narrow, widely separated, slightly di- verging anteriorly; anterior adductor scars larger, slightly widening anteriorly, lying on each side of median line of valve. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 706 148302a 1.7 1.5 1.9 1.0 . . 148302b 2.4 2.0 2.2 1.1 85? 148302c 3.1 2.5 2.7 1.4 84 148302d 3.7 2.9 2.9 1.9 90 148302e 4.2 3.4 3.8 2.4 90 148302f 5.0 4.1 5.0 2.8 99 USNM 706b 148305a 5.8 4.9 5.9 3.6 93 (holotype) 148305b 5.8 4.7 5.4 3.1 88 USNM 706c 148307a 3.1 2.3 3.0 1.4 90 148307b 4.9 3.9 4.8 2.3 97 148307c 5.0 4.1 4.8 3.0 99NUMBER 21 1933 STRATIGRAPHIC OCCURRENCE.—Word Formation (China Tank, Willis Ranch, and Appel Ranch members and lens between last two); Cherry Can- yon Formation (Getaway Member). LOCALITIES.—China Tank: USNM 706c, 706z, 726r. Willis Ranch: 706, 706e, 724u, 735c. Lens: 706b. Appel Ranch: 704, 726t. Getaway: AMNH 21, 496, 600; USNM 728, 730, 732. DIAGNOSIS.—Petasmatherus with broadly unipli- cate anterior commissure. TYPES.—Holotype: USNM 148305a. Figured paratypes: USNM 148305b,e,f. Unfigured paratypes: USNM 148305c,d. Figured hypotypes: USNM 148302L 148305g-m, 148307c, 154609. Measured paratype: USNM 148305b. Measured hypotypes: USNM 148302a-f, 148307a-c. Figured specimen: USNM 148310. COMPARISON.—This species is the largest and most abundant one known. It is characterized by broadly triangular form and straight hinge. It dif- fers from P. recticardinatus, new species, in its larger size, indistinct folds on both valves, and the rectimarginate anterior commissure. It differs from P. pusillus (Girty) in its more triangular outline, shorter beak, and more strongly developed fold and sulcus. DISCUSSION.—This species occurs commonly in the Willis Ranch, China Tank, and Appel Ranch members of the Word Formation. It also appears in excellently preserved specimens in the residues from the lens between the Willis Ranch and Appel Ranch members. Petasmatherus pumilus, new species PLATE 521: FIGURES 10-21; PLATE 541: FIGURES 31-58 Smaller than average for genus, flatly to mod- erately strongly biconvex; outline elongate sub- triangular, sides diverging between 60° and 100°; commissure gently uniplicate, fold low, flat to slightly arched in transverse section, gently convex in longitudinal profile; sulcus shallow, longitudi- nally uniformly convex. Costae strong, narrow, crowded, crests rounded, extending strongly to beaks, numbering 4 to 6 on fold, normally 4, one less in sulcus, 4 to 6, normally 5 on each flank; troughs about equal in width to costae, rounded, concentric striae closely spaced; growth lines not normally present. Pedicle valve moderately convex, with flanks not reflexed; beak acute, straight to slightly curved dorsally; beak ridges blunt; lateral pseudointer- areas narrow with slight overlap of valves. Del- thyrium triangular, open but slightly constricted by rudimentary deltidial plates at base. Brachial valve more strongly convex; umbonal area flattened in cross section; beak broad, blunt, apex within pedicle valve. Fold, strongest at ante- rior margin. Pedicle valve interior with delthyrium abruptly widened anterior to deltidial plates, forming recess for apex of brachial valve; each side with elongate, knoblike tooth supported by vertical plate reach- ing floor of valve. Muscle area triangular; shape and location of adductor scars not observed, prob- ably median and posterior in muscle area, as in other species of genus; diductor scars large, ante- riorly widening, longitudinally striate. Brachial valve interior with short, wide hinge plate divided by deep wedge-shaped median notch, bounded laterally by narrow, greatly elongate, anteriorly slightly widening, faintly denticulate sockets; each inner side of socket plate with crus projecting forward from anterior edge; crura strongly curved ventrally, may be twisted, dorsal edges carinate; some valves with low median ridge near apex. Muscle area elongate oval; posterior adductor scars elongate, narrow, diverging slightly toward anterior, their posterior ends widely sep- arate; anterior adductor scars on each side of midline, anteriorly widening, partly bisected by low myophragm. -Road Canyon For- USNM 703c, 703d, MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 707e 148061a 2.3 1.75 2.0 1.1 - 148061b 3.5 2.8 2.7 1.3 - 148061c 4.4 3.8 3.8 2.5 c.86 148061d 5.7 4.8 5.0 3.5 90 148061e 6.6 5.3 5.5 3.5 85 (holotype) USNM 706f 148063a 7.8 6.3 7.1 5.0 83 148063b 3.0 2.4 2.7 1.2 - STRATIGRAPHIC OCCURRENCE.- mation; Cibolo Formation. LOCALITIES.—Road Canyon: 1934 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY 706f, 707e, 710u, 710z, 712t, 721j, 721y, 721z, 722e, 722g, 724c, 732j, 736x. Cibolo: 738g, 738-1. DIAGNOSIS.—Elongate Petasmatherus with low, poorly defined fold and sulcus, with narrow, crowded costae and long beak. TYPES.—Holotype: USNM 148061e. Figured par- atypes: USNM 148061d,g-l; 148063a; 154766a,b; 154886. Unfigured paratypes: USNM 148061a-c,f,i; 148063b. Figured specimens: USNM 154887a,b. COMPARISON.—Petasmatherus pumilus is charac- terized by its small size, elongate triangular out- line with narrowly diverging sides, wide, blunt brachial beak, very low fold and shallow sulcus, and its strong costae with rounded crests, rounded intertroughs that extend strongly to the apexes. Its size is about the same as that of P. nitidus, new species, but that species has a short pedicle beak, and stronger fold and sulcus. This species differs from P. opulus Cooper and Grant of the Word Formation in being larger, more elongate, with more crowded costae, and more elongated beak. Petasmatherus pusillus (Girty) PLATE 551: FIGURES 35-42 Pugnax? pusilla Girty 1909:319, pi. 24: figs. 18-18b. Small size, strong costae extending from beak to anterior margin, sulcate brachial valve umbo and interareas bounding the delthyrium are definite characters that relate this small brachiopod to Petasmatherus. Compared to P. opulus, type species of the genus, Girty's form is more slender, has a narrower fold which is more strongly elevated, and it has 4 costae on the flanks, which is one more than usual for specimens of P. opulus of the same size. The beak of Girty's specimen is somewhat damaged but appears to have been shorter than that of P. opulus. STRATIGRAPHIC OCCURRENCE.—"Basal black lime- stone below Delaware Mountain sandstone." "Low hills, about 2 miles south of El Capitan" = USGS 2967 (green). Two miles south of El Capitan puts this locality in the Bone Spring Formation. DIAGNOSIS.—Small Petasmatherus with narrow, strongly elevated fold and thick valves. TYPES.—Holotype: USNM 118571. DISCUSSION.—R. E. King (1931:127) assigned Pugnax? pusilla Girty to the genus Hustedia. To this Girty objected strenuously (Girty in P. B. King 1948:22). Our examination of the type specimen fails to reveal beak characters, punctae, or orna- mentation features characteristic of Hustedia. All the characters of the shell are in harmony with assignment to Petasmatherus. Petasmatherus recticardinatus, new species PLATE 503: FIGURE 21 Usual size for genus, longer than wide, trape- zoidal in outline, widest part anterior to midvalve; sides moderately rounded; anterior broadly rounded. Apical angle 90°. Anterior commissure rectimargi- nate. Beak moderately long; delthyrium open, bounded by broad apsacline interareas. Costae narrowly angular, distant, 5 principal costae on brachial valve forming indistinct fold and middle 4 on opposite valve forming indistinct unit but not depressed; flanks marked by 2 costae on pecicle valve, 1 on brachial valve. Pedicle valve gently convex in lateral profile, most convex anteriorly; anterior profile broadly and moderately domed with steep sides; unbonal region somewhat concave but median and anterior parts swollen. Median 4 costae forming poorly defined fold fitting opposite to that of brachial valve; flanks very narrow and steep. Brachial valve with lateral and anterior profiles like those of pedicle valve; hinge wide and straight with prominent shoulders. Umbonal region flat- tened; costae subparallel on umbonal region; prin- cipal 5 costae forming broad low fold; flanks very narrow and steep. Interior not known. MEASUREMENTS (in mm). — Holotype USNM 152824: length 4.0, brachial valve length 3.5, maxi- mum width 3.7, thickness 2.8, apical angle 90°. STRATIGRAPHIC OCCURRENCE.—Cherry Canyon For- mation (Getaway Member). LOCALITY.—AMNH 512. TYPES.—Holotype: USNM 152824. DIAGNOSIS.—Petasmatherus with rectimarginate anterior commissure and obscure folds on both valves. COMPARISON.—The rectimarginate anterior com- missure and lack of well-marked fold and sulcus as well as the distant costae distinguish this species from all others of the genus. NUMBER 21 1935 Elassonia, new genus Small to minute, rhynchonelliform, flatly bicon- vex, anterior commissure rectimarginate to weakly sulcate; outline transversely subtrigonal to elongate subelliptical. Costae coarse, low or high, sharp or rounded, number increasing anteriorly by bifurca- tion, implantation or intercalation; concentric striae absent, growth lines weak. Pedicle valve with sharp beak, apsacline; beak ridges bordering interareas; delthyrium narrowly triangular or trapezoidal; deltidial plates normally absent, rarely present as narrow bands along sides of delthyrium; foramen often perforating apex. Lateral pseudo- interareas absent: no overlap of valves. Brachial valve with blunt beak; hinge line curved to nearly straight. Umbo sulcate; median sulcus shallow at midvalve and at anterior margin. Pedicle valve interior with small teeth, projecting forward, located on hinge margin just outside delthyrial edge; dental plates short, supporting hinge teeth, often fused to sides of valve. Muscle area tear-shaped; adductor scars small, median; diductor scars larger, anteriorly widening. Brachial valve interior with small, longitudinally compressed and deeply divided hinge plate; socket ridges short, strongly elevated; fulcral plates un- usually broad and flat, outer hinge plates narrow or nonexistent, sloping to crura, these strong, long, narrow, laterally compressed, slightly curved and obliquely terminated distally; inner edge of falcifer crura forming margin of notothyrial cavity; inner hinge plates not recognized; sockets small, with stout, wide fulcral plates. Median ridge moderately long, low. Muscle field narrowly elliptical; poste- rior adductor scars narrow, elongate and widely separated, slightly divergent and located at flanks of muscle field; anterior adductor scars larger, ante- riorly widening, and lying along midline of the valve, extending farther forward; diductor pit small, shallow and located at apex. TYPE-SPECIES.—Elassonia micraria, new species. DIAGNOSIS.—Small rhynchonellaceans with well- developed interareas and rectimarginate to sulcate anterior commissure. COMPARISON.—The small size of the members of this genus exclude it from comparison with most other forms having bifurcating costae. It is very unlike Divaricosta Cooper and Grant, which it resembles in shape, by having a much different interior; it differs from Deltarina, new genus, in the structure of the hinge plate and presence of prominent interareas. It is actually most like Petasmatherus in exterior form but it is generally smaller than even that small form. Elassonia is readily distinguished from Petasmatherus by exte- rior and interior features. The bifurcating and implanting costae of Elassonia are distinctive exte- rior differences, while the cardinalia are distinctive internally. DISCUSSION.—Elassonia is one of several minute rhynchonellids found in the residues. They are usually so small that they would be overlooked in the usual methods of collecting. This one, like the others, is characterized by having fairly broad inter- areas and a hinge wider than normal in rhyncho- nelloids. Deltidial plates, as usually understood, are not developed, although elongated, elevated plates appear along the delthyrial margin that are similar to those seen in Crytopora. among modern brachiopods. The exterior ornament is fairly dis- tinctive, consisting of direct costae radiating from the beak with intercalation of another generation near midvalve. Young specimens have fairly clear evidence of a fold and sulcus but these are lost or difficult to discern in the adult. The umbonal region of the young is narrowly convex and the median costa is larger than the rest. The opposite valve has a corresponding narrow groove at the apex. This does not constitute the fold and sulcus of more mature shells, because in young adults two strong costae bound the above-mentioned de- pression and widen rapidly anteriorly. Two costae are inserted between these two at about 0.25 mm anterior to the beak and these extend nearly paral- lel to the anterior margin. At the anterior, other costae are inserted on the outside of these two but within the two stronger costae mentioned above. The corresponding fold region on the pedicle valve is less clear. The median costa in all specimens is the strongest. The next strongest appear beside the median costa and diverge widely. The strongest costae and those that appear to define the most elevated part on the pedicle valve are the second pair of costae that appear anterior to the first. They appear at the anterior to be somewhat out- standing and thus form a visible fold but they correspond to only a part of the area bounded by the strongest ribs on the brachial valve, which bound a broadly sulcate region. 1936 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY The pedicle valve has the appearance of a minute "Orthis" with wide hinge and broad inter- areas. The teeth are in accordance with this im- pression because they lie at the anterior angles of the delthyrium and are parallel to the hinge line in their widest direction. They are also notched slightly on the end toward midvalve, where they have small points. The teeth are buttressed by stout, receding dental plates but details of the musculature could not be ascertained. The cardinalia of the brachial valve are dis- tinctive and much modified from the normal pat- tern seen in many of the Permian rhynchonellids. The socket ridges are high and erect but much narrowed or shortened in the lateral direction. They form, with the outer hinge plates which are difficult to individualize, a steep face descending to the crura. The sockets are small and are located at the distal end of the socket ridges. The unusual feature of the sockets is the broad and exposed fulcral plate which occurs laterally outside of the socket ridge. In some specimens this plate is broad and thin and must serve as a brace for the crura as well as a platform on which the broad part of the tooth rests, the narrow medial projection being inserted into the socket. The arrangement is sim- ilar to that of some orthid brachiopods. The crura form the margin of the notothyrial cavity and are long and slender. They are laterally compressed, bladelike, not concave toward mid- valve, slightly curved, and slightly convergent proximally. The distal end is somewhat expanded when completely exposed, obliquely truncated with the sharp end posteroventrad. The distal end ap- pears to have been ragged or serrated. The median ridge is basically formed by the infolding of the shell by the median groove repre- senting the initial sulcus of the young shell. This ridge is further thickened by shell substance de- posited in the notothyrial chamber about it and proximal ends of the hinge plate. No definite inner hinge plates were identified. In the adult the ridge is short but thick and widens to support the hinge plate. Elassonia micraria, new species PLATE 504: FICURES 1-16 Small, biconvex; outline transverse, subelliptical to subtrigonal, sides diverging between 90° and 135°; commissure variable from faintly uniplicate through rectimarginate to faintly sulcate. Costae coarse, round crested, beginning at beaks, increas- ing in number anteriorly by bifurcation, number- ing 12 to 18 along anterior margin. Concentric striae not observed; growth lines weak but present over most of surface, producing weak, crenulated effect on crests and in troughs of costae. Pedicle valve gently convex longitudinally and transversely; beak rather short, bluntly pointed, not attenuate, slanting ventrally, not curved dor- sally; beak ridges sharp, outlining broad interarea; delthyrium relatively narrow, sides only slightly diverging, perforating apex of beak, producing nearly rectangular elongate foramen; deltidial plates absent or rudimentary; lateral pseudointer- areas absent: no overlap of valves. Brachial valve faintly sulcate but more strongly convex than pedicle valve in profile; posterior margin of beak nearly straight, producing nearly straight hinge line, beak external, not curved into pedicle valve. Pedicle valve interior with sides of valve meeting sides of delthyrium nearly at right angles; teeth broad, flat, projecting forward, top continuous with interarea; dental plates nearly ventical, supporting hinge teeth. Muscle area broadly semiovate, occu- pying about one-half length of valve; details of pattern unknown. Brachial valve interior with divided hinge plate nearly reduced to merely crural bases and socket ridges, spread wide along nearly straight hinge line; sockets deep, wide, denticulate; crura strong, short, only slightly diverging, slightly curved ven- trally; crural bases extending as ridges from under- side of outer hinge plates and along undersides of crura; median elevation prominent, short, continu- ing forward in some specimens as low median ridge for about one-third valve length. Muscle area subcircular; posterior adductor scars elongate, rela- tively large, diverging anteriorly, lying at postero- lateral margins of muscle area; anterior adductor scars larger, median, anteriorly widening as two lobes along median line of valve. STRATIGRAPHIC OCCURRENCE.—Road Canyon For- mation. LOCALITIES.—USNM 702c, 703a, 706f, 709c, 719x, 720d, 721o, 723a, 724j. DIAGNOSIS.—Transverse Elassonia with strong costae. TYPES.—Holotype: USNM 154620d. Figured par- NUMBER 21 1937 MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 702c 148250a 1.1 0.8 1.1 0.6 c.95 148250b 1.3 1.1 1.4 0.8 c.92 148250c 1.6 1.3 1.7 1.0 102 148250d 1.9 1.7 1.9 1.1 97 148250e 2.0 1.7 2.2 1.1 110 148250f 2.3 2.0 2.5 1.3 105 148250g 2.6 2.3 2.8 1.6 116 154620d 2.9 2.6 3.1 1.5 100 (holotype) atypes: USNM 154620a-c,e-k. Measured paratypes: USNM 148250a-g. Unfigured paratypes: USNM 154620b,m-r. COMPARISON.—Elassonia micraria is characterized by its small size, transverse outline, nearly straight hinge line, straight margin, and strong rounded costae that increase in number anteriorly by bifur- cation, with the newly added costae weaker and sharper than the ones that begin at the beaks. It most closely resembles the other small new species of the genus, namely, E. petila, E. scitula, and E. sobrina, differing from them in its normally more transverse outline, stronger and more numerous costae with more frequent bifurcations and weaker secondary costae, and its dental plates that are not fused to the sides of the valve. It differs from Fascicosta longaeva (Girty) in its much smaller size, more transverse outline and lower convexity, and from Trophisina fenaria, new species, by its small size, stronger and fewer costae. This species resembles Petasmatherus opulus Cooper and Grant in its gross shape and outline, but is only about half the size, has more and weaker costae that are not simple but bifurcate, has a curved rather than straight hinge line, sim- pler and more proximally located hinge teeth, and much reduced fold, sulcus, and deltidial plates. DISCUSSION.—This species is very abundant at USNM 702c, where it is found in the fine screenings of the residues. It is found in lesser abundance in bioherms at the same level in the vicinity of the Hess Ranch. elongate, tear-shaped, sides diverging between 70° and 90°; commissure rectimarginate to subtly uni- plicate, fold and sulcus not apparent behind ante- rior margin but fold indicated by elevated median costa, sulcus by corresponding groove. Costae mod- erately strong, broadly rounded, beginning at beaks, increasing in number anteriorly by bifurca- tion, numbering 10 to 14 along anterior margin. Concentric striae not observed; growth lines weak, sporadically present, more frequent near anterior margins. Pedicle valve flatly convex longitudinally, some- what more convex transversely; beak elongate, bluntly pointed, not attenuate, normally slanting ventrally, not curved dorsally; beak ridges blunt, outlining interareas; delthyrium relatively narrow, sides only slightly diverging, without deltidial plates; foramen subrectangular, perforating apex of valve; lateral pseudointerareas absent; no over- lapping of valves. Brachial valve somewhat more convex, nearly circular in outline; beak bluntly pointed; hinge line curved. Pedicle valve interior with small hinge teeth projecting anteriorly; dental plates fused to sides of valve. Muscle area subovate, extending about half length of valve; details of pattern unknown. Brachial valve interior with moderately devel- oped outer hinge plates supported by broadly and deeply depressed lateral thickenings between crura and supported by low brace proceeding forward as low median ridge; sockets elongate, anteriorly widening; crura short, stout, not strongly curved; crural bases extending from underside of hinge plate along dorsal edges of crura. Muscle pattern unknown. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 702 148255a 1.4 1.1 1.3 0.6 86 (holotype) 148255b 1.6 1.2 1.3 0.9 74 148255c 1.7 1.3 1.6 0.8 85 148255d 1.9 1.6 1.7 1.0 85 Elassonia petila, new species PLATE 504: FIGURES 17-20 Small, moderately strongly biconvex; outline STRATIGRAPHIC OCCURRENCE.—Cathedral Moun- tain Formation. LOCALITIES.—USNM 702, 702a, 702un. TYPES.—Holotype: USNM 148255a. Figured par- 1938 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY atypes: USNM 148255b,e,f. Measured paratypes: USNM 148255b-d. Unfigured paratypes: USNM 148255c,d,g-k. DIAGNOSIS.—Elongate-oval Elassonia with fused dental plates and intercalated costae equal in size to the primary ones. COMPARISON.—Elassonia petila is characterized by its small size, tear-shaped outline, slightly folded margin, relatively coarse bifurcating costae that have the new or added costae just as strong as the ones that begin at the beak, its small hinge teeth, dental plates that fuse to the side of the valve, and its broadly depressed hinge plate. It most nearly resembles E. micraria, new species, differing in its outline, folding of the margin, uniformly strong but fewer costae, fused dental plates, depressed hinge plate, and more strongly curved hinge line. Its outline is different from that of E. scitula, new species, its beak less attenuate, and the bifurcations of its costae more consistent and frequent. Elassonia scitula, new species PLATE 504: FIGURES 21-28 Small, flatly biconvex; outline transversely sub- elliptical to subcircular, sides diverging between 100° and 150°; commissure rectimarginate to very slightly uniplicate: fold and sulcus not apparent on surface. Costae weak to moderately strong, broadly rounded, simple on some shells but nor- mally increasing anteriorly by bifurcation, number- ing 8 to 12 along anterior margins. Concentric ornamentation not observed; growth lines weak, irregularly spaced over surface of shell. Pedicle valve flatly convex; beak short, bluntly pointed, normally somewhat attenuate, slanting ventrally; beak ridges well defined, bordering inter- areas; delthyrium narrowly and bluntly triangular or subrectangular, open, without deltidial plates; lateral pseudointerareas absent; no overlap of valves. Brachial valve somewhat more convex; outline approaching semicircular, with greatest width just anterior to hinge; beak broadly rounded, with hinge line gently convex posteriorly. Pedicle valve interior with teeth projecting for- ward from platform of interarea; dental plates fused to sides of valve. Muscle area elongate sub- ovate; diductor scars central, elongate; adductor scars surrounding diductors, slightly widening an- teriorly, each terminating anteriorly as sharp wedge. Brachial valve interior with hinge plate widely divided, depressed, and with inner hinge plates fused to floor of umbo, thereby helping to support crura; median ridge low, extending forward short distance; sockets deep, anteriorly widening, finely denticulate; crura short stout, diverging, only slightly curved ventrally; crural bases strong, ex- tending from underside of hinge plate to ends of crura. Muscle area subovate, slightly depressed; posterior adductor scars narrow, elongate, widely separate from one another, lying at flanks of larger, median anterior adductor scars. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) 1.0 0.8 1.0 0.4 99 1.2 1.0 1.3 0.5 125 1.4 1.2 1.4 0.5 150 1.7 1.5 1.7 0.7 .113 1.9 1.6 1.8 . 0.1 102 USNM 708u 148261a 148261b (holotype) 148261c 18426Id 148261e STRATIGRAPHIC OCCURRENCE.—Cathedral Moun- tain Formation (base). LOCALITY.—USNM 708u. DIAGNOSIS.—Elassonia with widely elliptical out- line. TYPES.—Holotype: USNM 148261b. Figured par- atypes: USNM 148260a-c, 148261a. Measured para- types: USNM 148261a,c-e. Unfigured paratypes: USNM I48261c-e. COMPARISON.—Elassonia scitula is characterized by its small size, short but somewhat attenuate beak, rounded bifurcating costae with secondary costae just as strong as those beginning at the beaks, its widely divided hinge plate, low median ridge, and especially by its subelliptical outline with the greatest width at the midline, a form which makes the brachial valve widest anterior to its midline. It differs from E. micraria, new species, in its outline and its less frequently and consistently bifurcating costae that all are of nearly equal strength. It is distinguished from the other small species, namely E. petila, new species, and E. so- brina, new species, by its short attenuate beak and posteriorly wide brachial valve. NUMBER 21 1939 Elassonia sobrina, new species PLATE 504: FICURES 29-33 Small, unequally strongly biconvex, brachial valve more convex; outline subtrigonal to bluntly subpentagonal, sides widely divergent between 70° and 110°; anterior commissure faintly sulcate to rectimarginate. Costae strong, round crested, begin- ning at beaks, normally with few bifurcations just anterior to beaks and none farther forward, num- bering 8 to 10 along anterior margins. Growth lines weak, sporadically spaced. Pedicle valve slightly convex in lateral profile, broadly and gently convex in anterior profile, attenuate, not curved, strongly apsacline; beak ridges sharp, bordering broad interareas; del- thyrium triangular, open, without deltidial plates; foramen perforating apex of valve; lateral pseudo- interareas absent: no overlap of valve edges. Median costa prominent and elevated, forming a low fold. Brachial valve moderately convex, most convex in posterior half; anterior profile broadly convex; beak bluntly pointed producing slightly curved hinge line. Sulcus broad and shallow, occupied by two intercalated costae. Pedicle valve interior with small teeth; dental plates reduced, not extending forward as far as hinge teeth. Muscle area not observed. Brachial valve interior with divided hinge plate, delicate, slightly curved crura supported by keel-like crural bases, moderately high but short median ridge. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) 1.1 1.4 1.6 1.7 0.9 1.3 1.3 1.5 0.6 1.0 1.1 1.2 0.4 0.6 0.8 0.9 92 ? ? ? USNM 702d 148251a (holotype) 148251b 148251c 14825Id STRATIGRAPHIC OCCURRENCE.—Hess Formation (Taylor Ranch Member). LOCALITY.—USNM 702d. DIAGNOSIS.—Minute Elassonia with intercalation of costae near the beak in one generation only. TYPES.—Holotype: USNM 148251a. Figured par- atypes: USNM 148251b,d,e. Measured paratypes: USNM 148251b-d. Unfigured paratype: USNM 148251c. COMPARISON.—Elassonia sobrina is characterized by its small size and relatively few strong costae that intercalate or branch only near the beaks, then continue directly to the anterior margins. It is closest in most features to E. micraria, new species, differing in its smaller size, fewer costae with less frequent branching, which have the sec- ondary ones just as strong as the ones that start at the beak, its less transverse outline and less straight hinge line. Its outline is different from that of E. petila or E. scitula, both new species, its beak normally longer and its costae straighter. Ptygmactrum, new genus [Greek ptygmatos (folded) + maktron (napkin)] Small, rhynchonelliform, triangular to trans- versely elliptical, flatly biconvex, lenticular convexo- concave in profile, valves subequally deep, strongly costate; commissure normally without median fold or sulcus, slightly uniplicate in some species; out- line broadly triangular. Costae beginning at or near beaks, becoming very high anteriorly, without bifurcation or intercalation, angular to blunt, occa- sionally bearing spines; intertroughs similar in width. Pedicle valve beak sharp, nearly straight, apsa- cline; interareas adjacent to delthyrium nearly flat; delthyrium triangular, normally open but some constricted at base by rudimentary deltidial plates. Brachial valve beak blunt, not strongly curved, remaining on outside of pedicle valve; fold usually not developed. Pedicle valve interior with sides diverging widely anterior to delthyrium, teeth knoblike, supported by short, vertical dental plates reaching valve floor. Muscle area not clearly observed: probably triangu- lar, with apex between dental plates. Brachial valve interior with hinge plate com- pletely divided by wide, wedge-shaped notch, leav- ing only narrow socket ridges bounding deep sockets which are anteriorly widening and finely corrugated; no outer hinge plates; crural bases nar- row; falcifer crura short, stout, laterally compressed, slightly diverging anteriorly, slightly curved ven- trally, inner hinge plates rudimentary. No median septum, but a low median ridge may be present. TYPE-SPECIES.—Ptygmactrum extensum, new species. 1940 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY DIAGNOSIS.—Small Rhynchonellacea having a few strong costae, strong dental plates, no median sep- tum, and widely divided hinge plate. COMPARISON.—Ptygmactrum is characterized by its small size, strongly costate but gently uniplicate shell, divided hinge plate, and absence of a median septum. The attitude of its beak is similar to that of Petasmatherus Cooper and Grant, but Ptygmac- trum differs in its more strongly and less numer- ously costate shell without definite fold or sulcus, more transversely triangular outline, curved instead of straight posterior marginal outline, and its widely divided hinge plate. Some species of Tere- bratuloidea Waagen appear to be externally similar to Ptygmactrum, but they are much larger, more strongly convex, have the beak curved dorsally and with a circular foramen, and have no dental plates in the pedicle valve. No other genus of rhynchonel- lid closely resembles Ptygmactrum. DISCUSSION.—Rarity as well as small size is the characteristic that limits the size of the collection of this interesting genus, which is one of the rarest in the Glass Mountains. Its rarity also limits the number of interiors that are found or can be pre- pared, consequently much is still to be learned about its inner morphology. The exterior is characterized by the extremely strong and generally angular character of the costae. Another feature is the peculiarity of the costae ending anteriorly in short spinelike proc- esses. The costae are also direct from beak to margin and no bifurcation of them has been de- tected. The delthyrium is generally open but a few specimens exhibit rudimentary deltidial plates at the anterolateral angles. Broad interareas are another feature that lends distinction to this genus. Finally, the anterior commissure in most speci- mens is rectimarginate, but the margins are strongly serrated or toothed. The pedicle valve interior is characterized by small teeth that are buttressed by strong divergent dental lamellae bounding wide and deep umbonal cavities. The brachial valve is characterized by simplified cardinalia. The socket ridges are erect, strong, and define wide and deep sockets that appear to be corrugated. The crural bases are attached directly to the socket ridges without the aid of outer hinge plates. The crural bases are narrow and one specimen shows rudimentary inner hinge plates. These are so slightly developed that they might be easily overlooked. The crura are widely divergent, short, compressed laterally but concave toward midvalve. The distal extremity is frayed or serrate. No median septum is present in the brachial valve but a low ridge is developed just anterior to the notothyrial cavity in P. exten- sum, new species. Ptygmactrum acutum, new species PLATE 505: FIGURES 10, 11 Small, about usual size for genus, triangular, widest at anterior; wider than long; valves sub- equal in depth; sides straight, forming angle of 91°; interarea apsacline; anterolateral extremities narrowly rounded; anterior margin broadly rounded. Anterior commissure strongly zigzag but probably actually rectimarginate. Foramen large and oval, restricted anteriorly by minute, triangular deltidial plates. Surface strongly costate, 5 costae on brachial valve, 4 on pedicle valve, 2 on each side of deep, angular median depression. Each costa on both valves ending in blunt spine. Pedicle valve flatly convex in posterior part but gently concave in anterior part in lateral profile; anterior profile flatly convex but convexity obscure by flaring anterior. Sulcus deep and angular, bounded by strongly elevated angular costae, lat- eral costae angular but lower than median costae; all costae flared strongly in ventral direction. Brachial valve convex in umbonal region but concave anteriorly when viewed in lateral profile; anterior profile flat-topped, steep-sided, low dome; umbonal region swollen, marked by three costae rising anteriorly to flare in dorsal direction at front margin. Median costa more elevated than others, forming low keel. Flanks steep. MEASUREMENTS (in mm).—Holotype USNM 154623: length 3.0, brachial valve length 2.6, maxi- mum width 3.4, thickness at midvalve 1.4, apical angle 91°. STRATIGRAPHIC OCCURRENCE.—Road Canyon For- mation. LOCALITY.—USNM 720d. DIAGNOSIS.—Small triangular Ptygmactrum with four costae on the pedicle valve and five on the brachial valve, median costa of the brachial valve elevated above the others. TYPES.—Holotype: USNM 154623. NUMBER 21 1941 COMPARISON.—This species is most like Ptygmac- trum angulatum, new species, but has much more angular costae and the median costa strongly ele- vated. Further, the anterior spines are more prom- inent on P. acutum. It differs from P. depressum and spiculatum, both new, in the great angularity of the costae and their anterior flare. Neither of these species has the strongly elevated median costa of P. acutum. This is a very rare species and only the holotype is known. Ptygmactrum angulatum, new species PLATE 505: FIGURES 1-9, 21-25 Average size for genus, wider than long, broadly triangular in outline, posterolateral margins form- ing obtuse angle; greatest width anterior to mid- valve. Sides narrowly rounded. Anterior margin broadly rounded. Anterior commissure uniplicate; interarea strongly apsacline; interareas narrow; del- tidial plates rudimentary. Surface paucicostate, costae broad and angular, 6 on pedicle valve and 7 on brachial valve. Anterior extremity of costae with stubby spines; one specimen with rows of spines on costae at ends of growth lamellae. Pedicle valve gently concave in lateral profile and broadly concave in anterior profile. Umbonal region slightly convex; sulcus originating at umbo, widening and deepening anteriorly, angular and steep sided. Flanks triangular, gently concave. Brachial valve flat or nearly so in lateral profile, with moderate curvature on umbo; anterior profile broadly and slightly convex. Fold originating on the umbo, steep-sided, high, strongly angular. Flanks gently convex and broadly triangular. Pedicle valve interior with knoblike teeth sup- ported by strong and well-defined dental plates. Brachial valve with widely divided hinge plate, strong but narrow socket ridges; other details not preserved. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (') USNM 702b 148316a 2.6 2.2 3.4 1.9 105 148316b 3.1 2.8 3.8 1.5 92 USNM 703bs 148317 2.7 2.3 3.8 1.4 110 (holotype) STRATIGRAPHIC OCCURRENCE.—Cathedral Moun- tain Formation. LOCALITIES.—USNM 702b, 703bs, 708u. DIAGNOSIS.—Ptygmactrum with angular costae, distant and strong, and gently concave pedicle valve. TYPE:.—Holotype: USNM 148317. Figured para- types: USNM 148316a-d, 148318, 154622. Mea- sured paratypes: USNM 148316a,b. COMPARISON.—The costae of this species are much more angular and elevated than those of P. depressum and P. mordicum, new species. The species most like P- angulatum is P. spiculatum, new species, which also has a concave pedicle valve. The latter species is larger, with wider costae and stronger spines on the extremities. Its outermost costae are stronger than those of the Glass Moun- tains species and the beak is more strongly apsacline. DISCUSSION.—One specimen assigned to this spe- cies (USNM 148318) is unusual in having rows of spines along the crests of the costae near the ante- rior ends. These are produced at the tips and are progressively added with each addition of new growth lamellae. Ptygmactrum depressum, new species PLATE 505: FIGURES 16-18 Average size for genus, triangular in outline, width greater than length, maximum width slightly anterior to midvalve. Posterolateral margins form- ing angle of more than 90°. Sides narrowly rounded; anterior margin broadly rounded. Ante- rior commissure rectimarginate. Beak elongated, delthyrium long; bounded by narrow interareas and partially restricted by rudimentary deltidial plates; interareas apsacline. Surface costate, costae distant, narrowly rounded, 6 on pedicle valve, 5 on brachial valve. Pedicle valve gently convex in lateral profile but broadly and moderately convex in anterior pro- file, more convex in this view than brachial valve. Median region gently swollen; sulcus originating at beak, moderately wide and deep; flanks fairly widely triangular and moderately convex. Brachial valve flatly convex in lateral profile but very broadly and gently convex in anterior profile. Umbonal region and median area slightly convex. Umbonal region sulcate, sulcus occupied by me- 1942 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY dian costa or fold which is narrow, low and rounded, scarcely elevated above those on each side. Flanks widely triangular, moderately convex. Interior unknown. MEASUREMENTS (in mm).—From locality USNM 716xa specimen 148319 (holotype), and from USNM 721j, 152861, respectively: length 3.5, 2.7; brachial valve length 2.9, 2.0; width 4.0, 3.3; thick- ness 1.7, 1.0; apical angle 105°, 110°. STRATIGRAPHIC OCCURRENCE.—Road Canyon For- mation. LOCALITIES.—USNM 716xa, 721j. DIAGNOSIS.—Ptygmactrum with distant, narrowly rounded, fairly low costae. TYPES.—Holotype: USNM 148319. Figured and measured paratype: USNM 152861. COMPARISON.—This species is not so wide as P mordicum and P. externum and therefore need be compared only with P. spiculatum, new species, from which it differs in its less angular, narrower costae, lower costae and in the absence of thorn- like projections on the anterior ends of the costae. DISCUSSION.—This species is known from only two specimens, one of which is younger. The younger one retains the rudimentary deltidial plates and has a better preserved beak region. Ptygmactrum externum, new species PLATE 505: FIGURES 31-58; PLATE 520: FIGURES 40-44 About average size for genus, moderately bicon- vex; outline strongly transverse, length about half of width, widely elliptical; commissure broadly uniplicate, with low fold and shallow sulcus; costae strong, extending from beaks to anterior margins, numbering 3 on fold, 2 in sulcus, normally 3 on each flank, totaling 7 or 9 on brachial valve, 6 or 8 on pedicle valve, crests and troughs rounded, with- out intercalation or bifurcation. Growth lines strong, giving shell rough, corrugated surface, more closely crowded near anterior margins. Pedicle valve with beak blunt, but somewhat at- tenuated; in some specimens delthyrium wide, open, without deltidial plates; interareas flat, con- spicuous, extending nearly to lateral margins; hinge line nearly straight; lateral profile evenly convex, without reflexing of flanks. Brachial valve beak short, blunt; interarea slightly developed; convexity of valve low, even, slightly stronger longitudinally than laterally. Pedicle valve interior with sides forming nearly straight angle anterior to delthyrium; teeth form- ing small knobs supported by strong, divergent dental plates reaching valve floor. Muscle field broadly triangular, weakly marked, muscle pattern not observed. Brachial valve interior with hinge plate divided by wide median notch with narrow socket ridges; sockets deep, widening anteriorly, corrugated; crura not preserved on available specimens; myo- phragm short, low, rounded. Muscle marks not observed. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 703d 148321a 2.7 2.3 4.7 2.2 ca. 175 148321b 3.4 2.9 7.0 1.8 174 (holotype) USNM 703c 148320 3.0 2.5 5.9 2.1 ca. 170 STRATIGRAPHIC OCCURRENCE.—Road Canyon For- mation. LOCALITIES.—USNM 703c, 703d, 721 j. DIAGNOSIS.—Fairly large Ptygmactrum, with width twice the length. TYPES.—Holotype: USNM 148321b. Figured par- atypes: USNM 148321a,c-e; 148320. Measured para- types: USNM 148321a, 148320. COMPARISON.—Ptygmactrum extensum is charac- terized by its gently uniplicate commissure, wide outline, nearly straight cardinal margin, extraordi- narily well developed interareas, open delthyrium without deltidial plates, and its gentle and nearly uniform convexity without reflexed anterior mar- gins nor thornlike projections on the crests of the costae. These features, and its somewhat stronger growth laminae, distinguish it from the other two species of the genus found in the Glass Mountains, P. mordicum and P. spiculatum, both new species. DISCUSSION.—The interareas of P. extensum are unusually wide and the cardinal margin abnor- mally straight for a species of rhynchonellid. The other species of Ptygmactrum also show similar tendencies although in them they are not so well developed. All the peculiar features of the hinge region seem to be interpendent, with the broad interareas merely the result of the extreme diver- NUMBER 21 1943 gence of the side which has produced the nearly straight cardinal margin. Internally the hinge teeth and dental plates are arranged similarly to other species of the genus, according to the pattern typi- cal of species in other genera of Permian rhyn- chonellids. Ptygmactrum mordicum, new species PLATE 505: FICURES 19, 20 Average size for genus, flatly biconvex, strongly costate, with 7 or 9 costae on brachial valve, 6 or 8 on pedicle valve, beginning at or near beaks, ante- rior margin of crests slightly reflexed, occasionally bearing small thornlike projections, crests and intertroughs narrowly rounded, no bifurcation or intercalation; outline broadly triangular with pos- terolateral extremities forming angle of 96° to 107°; commissure without fold or sulcus. Growth lines conspicuous, producing rough surface on shell, stronger and more crowded toward anterior margins. Pedicle valve with sharp beak, interareas nearly flat, apsacline; delthyrium triangular, open, slightly constricted at base by rudimentary deltidial plates in some specimens. Sulcus originating at beak, narrow and deep. Flanks broad and gently convex. Brachial valve moderately convex in lateral pro- file, broadly and gently convex in anterior profile. Fold formed by median costa, narrow and elevated above others. Flanks broadly triangular, gently convex. Interior unknown. MEASUREMENTS (in mm).—Holotype USNM 148315a: length 3.5, brachial valve length 3.0, max- imum width 4.7, thickness 1.8, apical angle 107°. STRATIGRAPHIC OCCURRENCE.—Cathedral Moun- tain and Road Canyon formations. LOCALITIES.—Cathedral Mountain: USNM 702, 702b. Road Canyon: USNM 735a. DIAGNOSIS.—Wide Ptygmactrum with closely crowded costae. TYPES.—Holotype: USNM 148315a. Figured par- atype: USNM 148315b. COMPARISON.—This species is similar to P. ex- tensum, new species, but is narrower and has stronger, narrowly rounded, and more crowded costae. Ptygmactrum spiculatum, new species PLATE 505: FICURES 26-30 Large for genus, flatly convexo-concave in adult lateral profile, broadly triangular outline, postero- lateral margins converging at angle of 90° to 100°. Lateral extremities subangular. Anterior margin broadly rounded, surface flattened. Beak long, del- thyrium long and with rudimentary deltidial plates at basal angles. Interareas strongly developed, apsacline. Surface costate; costae angular, 4 on pedicle valve, 5 on brachial valve, each costa strongly angular and terminating in short, thorn- like projection. Pedicle valve with uneven lateral profile, poste- rior half very gently convex but anterior half bent at wide angle in ventral direction to give concave effect. Anterior profile nearly flat. Umbonal and median regions flatly convex; sulcus originating at beak, angular, deepening anteriorly and with steep and high bounding costae. Flanks somewhat concave and triangular. Brachial valve very gently convex in lateral pro- file and very broadly and slightly convex in ante- rior profile. Umbonal region with faint sulcus occu- pied by median costa which anteriorly becomes high angular fold, moderately elevated above those on flanks. Lateral slopes of fold wide and steep. Flanks narrow, gently convex and triangular in outline. Pedicle valve interior with small posteriorly notched teeth, supported by short, almost indis- tinguishable but thick dental plates. Median sulcus of exterior forming median ridge on interior. Muscle region not resolvable into individual scars. Brachial valve interior with strong socket ridges and divided hinge plate; other details not preserved. MEASUREMENTS (in mm).—From locality AMNH 512 specimen 152862a (holotype), and from USNM 706b, 148323a, respectively: length 3.7, 2.3; brachial valve length 3.3, 2.0; width 4.3, 2.9; thickness 1.5, 1.5; apical angle 100°, 90°. STRATIGRAPHIC OCCURRENCE.—Cherry Canyon For- mation (Getaway Member): Word Formation (lens between Willis Ranch and Appel Ranch members). LOCALITIES.—Getaway: AMNH 512. Lens: USNM 706b. DIAGNOSIS.—Fairly large Ptygmactrum with 5 strong angular plications. TYPES.—Holotype: USNM 152862a. Figured par- 1944 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY atypes: USNM I48323a,b, 152862b. Measured para- type: USNM 148323a. COMPARISON.—Ptygmactrum spiculatum is fairly large for the genus, has strongly angular costae bowing outward, and a somewhat convexo-concave lateral profile. It differs from P. mordicum, new species, in its more apsacline beak, less well devel- oped dental plates, lesser number and more strongly angular costae, lesser proportional width, and the tendency toward anterior concavity of the pedicle valve exterior. DISCUSSION.—Features of note in this species are both exterior and interior. Knowledge of the species is limited by its extreme rarity: only two speci- mens from each locality. On the exterior the pedicle valve has a tendency anteriorly to become concave by a bending of the front half in a ventral direction. This is accompanied by an anterior thickening of the margin, which is complemented by thickening of the marginal region of the pedicle valve, producing a flattening of the anterior surface along the commissure. Inside the pedicle valve the teeth are strongly notched on the posteromedian side, making them appear small and knoblike. The musculature could not be resolved, but the sulcus of the exterior is reflected on the inside as a median ridge that serves as a myophragm. Iotina, new genus [Greek iota (smallest letter in Greek alphabet)] Minute, pentagonal in outline, beak long, nearly straight, long delthyrium not modified by deltidial plates. Unequally biconvex. Interareas well devel- oped. Anterior commissure narrowly and strongly uniplicate. Surface costate, costae strong, direct, extending from beak to anterior margin. Pedicle valve interior with thick teeth parallel to hinge edge; dental plates aborted. Muscle region not preserved. Brachial valve interior with elevated socket ridges; outer hinge plates small; hinge plate deeply divided and with no inner hinge plates. Crura falcifer, short, laterally compressed, concave toward midvalve. No median septum. TYPE-SPECIES.—Iotina minuta, new species. DIAGNOSIS.—Minute Rhynchonellacea having no dental plates, divided hinge plate, strong fold and sulcus, and strong direct costae covering the entire surface. COMPARISON.—This is one of several genera of tiny rhynchonellids characterized by strong costae and prominent interareas on each side of the del- thyrium. It differs from Elassonia, new genus, in having a narrowly, dorsally folded anterior com- missure with prominent fold and sulcus. It also suggests Petasmatherus Cooper and Grant, but that genus has only a slight folding of the anterior commissure and it has no fold and sulcus on the exterior. Ptygmactrum, new genus, is also a small rhynchonellid but its few angular costae and gen- erally rectimarginate valves separate the two gen- era. All three of the genera named have well- developed dental plates and thus differ from Iotina. DISCUSSION.—The pedicle valve is notable for the absence of dental plates and for its fairly large teeth. The brachial valve cardinalia are elevated and have strong socket ridges but the outer hinge plates are only moderately wide. The crura form the notothyrial margin, are stout, short, scarcely curved, and laterally compressed. The inner hinge plates are not formed in the one good brachial valve interior available. The genus is so far known only from a few specimens and is not likely to be collected by con- ventional means. It should be searched for in any residues from Bone Spring Limestone. Iotina minuta, new species PLATE 513: FIGURES 19-29 Minute, strongly pentagonal outline, maximum width somewhat posterior to midvalve, producing shouldered appearance. Sides moderately rounded; anterior truncated. Profile triangular, thickest at anterior margin, anterior commissure narrowly uniplicate. Beak long, straight to suberect, open delthyrium unmodified by deltidial plates. Surface strongly costate, two prominent costae on fold, one in sulcus and three or four on flanks. Costae direct, extending from umbones to front margin. Pedicle valve flatly convex in lateral profile, moderately convex in anterior profile but median region deeply indented. Umbonal region narrowly swollen, marked medially by strongest costa. Sulcus originating on anterior slope of umbonal region, narrow but deep, and deepening anteriorly, there NUMBER 21 1945 bent toward opposite valve in moderately long tongue. Sulcus occupied by median costa from umbo to anterior margin. Brachial valve nearly flat in anterior profile but with anterior region slightly swollen; anterior pro- file broadly convex but marked medially by narrow hump formed by fold. Umbonal region flattened and with shallow median sulcus. Fold originating slightly posterior to midvalve, narrow and height- ening anteriorly to form prominent projection. Flanks moderately swollen and convex, depressed below fold. Pedicle valve interior with large teeth and no dental plates. Brachial valve interior with divided hinge plate, no median septum. MEASUREMENTS .(in mm).—Specimens 152818a and b (holotype) respectively: length 4.2, 3.5; bra- chial valve length 3.4, 2.7; width 4.2, 3.4; thickness 2.2, 2.0; apical angle 90°, 80°. STRATIGRAPHIC OCCURRENCE.—Bone Spring Lime- stone. LOCALITY.—AMNH 591. DIAGNOSIS.—Iotina with long beak, thick ante- rior, deep sulcus, and high fold. TYPES.—Holotype: USNM 152818b. Figured par- atypes: USNM 152818a,i,j. Measured paratype: USNM 152818a. Unfigured paratypes: USNM 152818c-h. COMPARISON.—No other species of this genus is known to which this one may be compared. It differs from other minute rhynchonellids described herein by its strong fold and sulcus and lack of dental plates. DISCUSSION.—This is a rare species which is read- ily overlooked because of its small size. Family TRIGONIRHYNCHIIDAE McLaren, 1965 TRICORIINAE, new subfamily Small Rhynchonellacea with completely costate shell, rectimarginate to uniplicate with broad sul- cus in fold, dental plates obsolescent; no deltidial plates. Brachial valve with strong median septum and variable hinge plate. Genera in West Texas: Tricoria, new genus. Very rare and locally restricted at the base of the Skinner Ranch Formation in the Glass Moun- tains. Tricoria, new genus [Latin tricor (trickster)] Moderate size, transversely triangular to penta- gonal outline, profile oval; valves unequally convex, brachial valve deeper; beak of pedicle valve small, usually acute, straight to suberect. Delthyrium open, no deltidial plates. Anterior commissure rec- timarginate to uniplicate but with fold bearing prominent sulcus beginning at umbo. Exterior costate, costae direct from beak to margin. Pedicle valve with small teeth supported by thin dental plates in young, dental plates becoming obsolescent in adults. Muscle field anterior to del- thyrial cavity, triangular in outline, individual scars not discernible. Brachial valve interior with divided hinge plate having prominent, strong socket ridges overlying corrugated sockets; outer hinge plates broad, con- cave; crural bases narrow, ridgelike; inner hinge plates variable, usually not united but rarely unit- ing and producing elongated foramen. Falcifer crura long, slender blades with distal end obliquely pointed on ventral side, laterally compressed but thickest on ventral edge. Median septum long, strongly elevated, bearing short, oblique lateral plates attaching ventral edge of septum to inner side of crural bases, thus producing shallow cham- ber or septalium nowhere contacting valve floor. Adductor field not clearly visible. TYPE-SPECIES.—Tricoria hirpex, new species. DIAGNOSIS.—Rhynchonellaceans having a sulcate fold, obsolescent dental plates in the adult, and a shallow apical chamber on the median septum. COMPARISON AND DISCUSSION.—This genus is most like Cupularostrum Sartenaer in its interior details and is undoubtedly related to it. The exte- rior is, however, entirely unlike that of Cupula- rostrum. Although some species of Cupularostrum have the dental plates forming a veneer on the valve wall, this is not the usual condition. The dental plates of Cupularostrum are generally fairly thick and are set off by well-marked umbonal cav- ities. Tricoria has well-marked dental plates in the young, but in old specimens these plates are nearly eliminated by filling of the umbonal cavities. Some specimens show no trace of the plates when the shell is seen in interior view. Inside the brachial valve the cardinalia of both genera are clearly characteristic of the family 1946 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY Trigonirhynchiidae. Generic differences appear in the formation of the apical chamber which, in Cupularostrum, is fairly large, deep, and attached on the floor of the- valve at the apex. In Tricoria the plates of the chamber are not steeply inclined, are given off from the septum, and extend postero- laterally to join the crural bases, defining a de- pressed chamber. Inner hinge plates are more spo- radically developed in Tricoria than in Cupula- rostrum. Most specimens, therefore, have a divided hinge plate, but in others the inner plates meet medially to produce a complete hinge plate like that of Cupularostrum. The median septum of Tricoria is generally more elevated than in Cupularostrum. Although the differences just mentioned are mostly small, they are important in the aggregate. When the difference between the crural plates of Tricoria and Cupularostrum are added to the ac- cumulated small differences mentioned above, the distinction between the two genera becomes evi- dent. The crura of Tricoria are long, slender, diverge laterally, and are bladelike, with the blades laterally compressed. The crura of Cupularostrum, on the other hand, are just the opposite, being compressed in an anterior-posterior direction, curved in a posteroventral direction, and are con- cave toward the anterior side. Tricoria is common at only one locality, but occurs sporadically in the lower part of the Skinner Ranch Formation with Scacchinella. Tricoria hirpex, new species PLATE 503: FIGURES 24-41; PLATE 507: FIGURES 57-71 Size moderate, outline transversely subtriangular to subpentagonal; profile flattened to strongly bi- convex; sides diverging between 60° and 120°, normally near 90°; commissure uniplicate, fold low to moderately high, extending nearly to beak, maximum convexity of profile near anterior mar- gin; sulcus shallow, extending nearly to beak, uni- formly convex in longitudinal profile; costae strong, sharp, extending to beaks, numbering 4 to 9 on fold, with the inside costae lower than those forming margin of fold, one less in sulcus, 2 to 5 on each flank. Concentric striae moderately strong; growth lines widely spaced posteriorly, becoming closely crowded near margins. Pedicle valve moderately convex; flanks not re- flexed; beak short, sharp, straight to slightly curved dorsally; beak ridges poorly developed, blunt; lat- eral pseudointerareas absent: no overlap of valves. Delthyrium triangular, open, without deltidial plates. Brachial valve deeper and more strongly con- vex; fold normally with wide shallow median de- pression; beak blunt, somewhat attenuate, apex within pedicle valve. Pedicle valve interior with sides of delthyrium widening to receive brachial beak; hinge teeth knoblike; dental plates supporting hinge teeth, extending to floor of valve, normally closely fused to side of valve or invisible. Muscle area triangular, with apex in beak area slightly excavated; adduc- tor scars elongate, median, in posterior part of muscle area between and anterior to dental plates; diductor scars lateral and anterior to adductor scars, anteriorly widening, left and right scars meeting along median line in anterior part of muscle area. Brachial valve interior with triangular hinge plate, divided by wedge shaped notch; two small plates converge from edges of notch to top of median septum, forming small, usually uncovered crural or apical chamber; sockets long, deep, ante- riorly widening, smooth or indistinctly corrugated; crura diverging forward from anterior edges of hinge plate, strongly curved ventrally, dorsal edges carinate; median septum high, thin, short, bisect- ing posterior part of muscle area, upper edge of posterior end fused with pair of plates forming small V-shaped crural cavity. Inner hinge plates small. Muscle area elongate oval; posterior adduc- tor scars elongate, narrow, widely separated, slightly diverging anteriorly; anterior adductor scars longer, anteriorly widening slightly, lying along median line of valve. STRATIGRAPHIC OCCURRENCE.—Skinner Ranch Formation (base). LOCALITIES.—USNM 705a, 715v, 720e, 720g, 726h. DIAGNOSIS.—Broadly triangular Tricoria with broadly sulcate fold on the brachial valve. TYPES.—Holotype: USNM 154652. Figured par- atypes: USNM 148155b-d,f,h,j-m,p. Measured para- types: USNM 148155a-g. Unfigured paratypes: USNM 148155a,e,g,i,n,o. COMPARISON.—Tricoria hirpex is characterized by its strong costae that extend to the beaks, nu- NUMBER 21 1947 MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 705a 148155a 4.1 3.8 4.3 2.3 75 148155b 5.8 5.4 5.8 3.0 73 148155c 7.2 6.3 6.2 4.6 60 148155d 7.4 6.8 8.1 5.4 97 148155e 8.1 6.9 9.2 4.9 95 148155f 9.2 8.2 10.9 7.1 102 148155g 9.5 8.4 11.9 7.0 119 154652 8.2 7.2 10.4 7.2 100 (holotype) merous costae on the fold, triangular outline, short but only slightly curved pedicle beak, sulcate fold, and its dental plates that normally are fused to the side of the pedicle beak area. In outline and number of costae this species resembles Camarotoe- chia wynnei (Waagen), differing in its sharper costae, transversely depressed rather than highly arched fold, lower convexity of the brachial valve, and weaker dental plates that are cemented to the sides of the valve. Camarotoechia plicata (Kutorga) is much larger and more rotund, and has broadly rounded costae rather than sharp costae as in T. hirpex. The sulcate fold of Pugnoides mesicostalis Girty gives this species an appearance like that of Tri- coria hirpex but Girty's species is much larger, wider, has a larger apical angle, more extended flanks, and the sulcation of the fold is narrower than that of Tricoria hirpex. Internally of course the two species are quite different. It is interesting to note that the fold with its depressed median costae also is similar to that of species of Antronaria which are so common in the Skinner Ranch Formation. DISCUSSION.—The distinctive shape of this spe- cies is due to the union of the sulcus of the pedicle valve with the sulcate part of the median fold of the brachial valve. This is like the union of two opposite sulci in some of the Mesozoic rhynchonel- lids or terebratulids which produce an emarginate anterior. In the development of the interior, the young Tricoria is generally elongate and strongly triangular in outline. Widening takes place with age. Tricoria hirpex varies in the shape of the shell and in the ribbing, especially of the fold and sulcus. The normal adult is generally much wider than long but a small number of adults do not attain the usual width. The fold and sulcus generally contain numerous costae; a few specimens have as few as 4 on the fold, but one has 9. The hinge plate of the brachial valve generally is divided by a narrow slit but in a few specimens the apical part is closed by the union of the inner hinge plates. In one specimen the inner hinge plates unite anteriorly and produce a hinge part with an elongate foramen, somewhat similar to that seen in Cupularostrum. The apical chamber of Tricoria is variable but usually is shallow be- cause of shell substance deposited in it. The small oblique plates producing the chamber, which unite with the septum, are thin and short. This combina- tion of plates produces a structure very similar to the septalium common in some of the Mesozoic rhynchonellid genera. AMPHIPELLIDAE, new family Small, smooth, broadly uniplicate to sulciplicate Rhynchonellacea with dental plates and without deltidial plates. Brachial valve with divided hinge plate and falcifer? crura. Both valves with postero- lateral pouches (apricatria). Genus in West Texas: Amphipella Cooper and Grant. Common in one area in five loose blocks at the base of the Cathedral Mountain Formation; very rare in the Road Canyon Formation nearby. Genus Amphipella Cooper and Grant, 1969 Amphipella Cooper and Grant, 1969:11. Shell small, smooth, rhynchonelliform, biconvex, broadly uniplicate to shallowly sulciplicate; out- line elongate to transversely subpentagonal; pos- terolateral slopes with small open slots perpen- dicular to plane of commissure, leading into apri- cate sinuses. Growth lines weak, strongest near anterior margins. Pedicle valve moderately strongly convex; sulcus shallow, barely visible anterior to margin; beak short or long, attenuate, straight or curved dorsally; beak ridges blunt, ill-defined; interareas small or absent; lateral pseudointerareas absent; delthyrium triangular, open, without del- tidial plates. Brachial valve flat medially, abruptly deflected toward commissure; beak bluntly pointed, 1948 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY not strongly curved; fold low, obscurely outlined, with broad shallow median depression. Pedicle valve interior with small teeth, projecting anteriorly, supported by short dental plates, partly or completely fused to sides of valve; posterolateral margin invaginated to form deep, narrow-necked sulcus open to outside of shell. Muscle area weakly impressed; position of adductor scars not certain; diductor scars small, anteriorly widening, forming heart-shaped mark in posterior quarter of valve. Brachial valve interior with hinge plate small, deeply notched or divided, medially unsupported; crura short, diverging anteriorly from edges of hinge plate, falcifer?, slightly curved ventrally, sup- ported by crural bases extending from underside of hinge plate; sockets elongate, anteriorly widen- ing, corrugated; median line of valve normally without septum, rarely with low ridge; postero- lateral margins invaginated to form brachial halves of apricatria. Muscle area weakly impressed, short and wide, with several narrow lobes widening an- teriorly; details of pattern uncertain. TYPE-SPECIES.—Amphipella arcaria Cooper and Grant (1969:11, pi. 1: figs. 13-21). DIAGNOSIS.—Small, smooth rhynchonellaceans having deep spoon-shaped invaginations of the shell on each side of the beak (apricatria). COMPARISON.—Amphipella is characterized by its small size, pentagonal outline, sulciplicate commis- sure, lack of deltidial plates and lateral pseudointer- areas, divided or deeply notched hinge plate, lack of a median septum or brace, normal absence of a median ridge, thin, partly fused dental plates, and especially by its deeply recessed posterolateral slopes producing small subspherical sulci that open to the outside through narrow slots running per- pendicular to the plane of commissure. We are calling each of these apricatrium (from Latin apricus, open, and atrium, vestibule); they are similar to but not the same as the "marginal pouches" of Uncites Defrance (Winterfeldia Sprie- stersbach; see Hall and Clarke, 1894:114, fig. 103, and Jux and Strauch, 1966) which are longer and cling to the sides of the shell, but do not open to the exterior through narrow slots. Most nearly similar are the "parathyridia" of the Pennsylvanian genus Cardiarina Cooper (1956a:527). These less fully formed channels appear to have formed sim- ilarly by indentation of the posterolateral margins, but they have not developed to the stage seen in Amphipella where the opening to the outside is narrowly constricted and pouches are formed internally. DISCUSSION.—The most distinct feature of Amphi- pella is the presence of the apricatria, one on each side of the beak, on the posterolateral slopes. These recesses form by invagination of the margins of both valves, and the complete sinus on each side is equal in each valve and a mirror image of its counterpart. Small juvenile shells do not have these sinuses; they form about 0.75 mm from the beak along the lateral slopes, so shells must be about 1.5 mm wide before they begin to develop. Actually, the apicatria do not begin to form until the shell is nearer 2 mm across and their sites are already present. The margins of shells smaller than 2 mm are normal, without any true invagination, only a pair of very small notches, one at the site of each sinus. As the shell gets larger the apricatria begin to form, starting as very shallow recesses and extending deeper with increasing size. In smallest shells in which they have begun to form they are mere pits; in larger shells they are re- cesses without constricted necks: the opening and the recess are about equal in width. The apricatria in larger shells increase in width as well as length, and become wider than their external openings, producing the appearance of constriction of the openings. The external openings of the apricatria do not change their size after the original recess is formed. The function of the apricatria is not certainly known. Their construction and position are such that they must open along their plane of commis- sure when the valves open, thus providing a pair of posterior openings for the shell. Therefore we speculate that the apricatria were involved in the feeding of the animal, and acted as channels for incoming currents. Amphipella arcaria Cooper and Grant PLATE 512: FIGURES 1-47 Amphipella arcaria Cooper and Grant, 1969:11, pi. 1: figs. 13-21. Biconvex, boxlike; outline sharply and nearly equilaterally pentagonal, sides diverging between 75° and 115°; commissure broadly and shallowly sulciplicate; fold low and sulcus shallow, apparent NUMBER 21 1949 only at anterior margin, depression in fold present on shell surface; posterolateral slopes with small open slots perpendicular to plane of commissure, leading into apricatria. Costae and concentric striae absent; radial fibers faintly visible; growth lines weak, strongest near anterior margins. Pedicle valve moderately convex, margins abruptly bent toward commissure; beak short, occa- sionally slightly attenuate, straight to slightly curved dorsally; beak ridges blunt, poorly defined; interareas small or absent; lateral pseudointerareas absent; no overlap of valves; delthyrium triangular, open, without deltidial plates. Brachial valve flatly convex medially, sides bent abruptly toward com- missure; beak bluntly pointed, somewhat attenuate in some specimens, not strongly curved; fold low, with broad shallow median depression. Pedicle valve interior with sides widely diverging anterior to delthyrium; lateral margins deeply in- vaginated to form pedicle half of deep, narrow- necked channels, open to outside of shell; teeth small, projecting forward from sides of valve just anterior and lateral to delthyrium; dental plates short, thin, nearly vertical, partly or completely fused to sides of valve. Muscle area weakly im- pressed; position of adductor scars uncertain, prob- ably near dental plates; diductor scars small, ante- riorly widening, forming heart-shaped mark ex- tending about one-fourth length of valve. Brachial valve interior with small hinge plate, divided or deeply notched; sockets wide, shallow, anteriorly expanding, finely and weakly cor- rugated; crura short, slender, slightly diverging anteriorly from edges of hinge plate, slightly curved ventrally, laterally compressed, supported by crural bases extending from underside of hinge plate and along dorsal edges. Median ridge low, rarely present, margins of posterolateral slopes deeply invaginated to form brachial halves of each apricatrium. Muscle area weakly impressed, short and wide, with several narrow lobes slightly widening anteriorly; details of pattern uncertain: proximal lobes probably belong to anterior adductor scars, lateral lobes to posterior adductor scars. STRATIGRAPHIC OCCURRENCE.—Cathedral Moun- tain (base). LOCALITIES.—USNM 702, 708u. DIAGNOSIS.—Pentagonal Amphipella having a box- like shape. TYPES.—Holotype: USNM 148098a. Figured par- MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 708u 148098a' 1.8 1.6 1.8 0.9 74 148098b' 1.9 1.5 2.0 0.9 88 148098c' 2.3 2.0 2.4 1.0 90 148098d' 2.5 2.2 2.4 1.3 91 148098e' 3.0 2.7 3.0 1.5 105 148098P 3.5 3.2 3.3 2.3 103 148098^ 3.8 3.5 3.6 2.3 110 148098h' 4.0 3.7 4.0 2.2 112 atypes: USNM 148098b,d,e,a',d'. Figured hypotypes: USNM 148098f',g'; 154700a-l,n,o; 154702a,d,f,h,i. Measured hypotypes USNM 148098a'-h'. COMPARISON.—Amphipella arcaria is characterized by its nearly equilaterally pentagonal outline, short pedicle beak, sulciplicate commissure, boxlike shape with the greatest part of each valve flatly convex and the edges near the margins abruptly bent to the plane of the commissure, and relatively large apricatria. It is larger, more transverse than A. attenuata, new species, less strongly convex, and has a shorter pedicle beak and larger sinuses. DISCUSSION.—In spite of the unusual feeding adaptation of Amphipella, this genus is basically a rhynchonellid, a fact manifest in the morphology of both valves. Amphipella is unusual among Paleozoic rhynchonellaceans in having a smooth exterior, and the folding of the anterior commis- sure is exceptional for a rhynchonellacean. The brachial valve has a broad fold that is medially broadly sulcate to produce the peculiar folding of the anterior commissure. The stratigraphic occurrence of this species needs explanation. The majority of the specimens are from USNM 708u, which represents the yield from five loose blocks found about half a mile east of Split Tank, between the first bioherms of the Institella zone (USNM 702 inst) and the basal small-pebble conglomerate that was designated the base of the Leonard by P. B. King ( = base of Cathedral Mountain Formation). These loose blocks were found together, but no others were found subsequent to the main discovery, although several exhaustive searches were made. These blocks probably represent parts of a single lens, including a mass of dead shells swept together. Oddly, the general assemblage constituting the fauna of these blocks (USNM 708u) is not known elsewhere, and 1950 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY most of the species in it are unique to this group of blocks (see faunal list of USNM 708u). Amphipella attenuata, new species PLATE 512: FIGURES 48, 49 Small for genus, biconvex; outline elongate sub- pentagonal, sides diverging about 60°; commissure uniplicate; fold low, sulcus shallow, expressed only at anterior margin; posterolateral slopes with small open slots perpendicular to plane of commissure, leading into apricate sinuses. Costae and concentric striae absent; growth lines weak, strongest near anterior margins. Pedicle valve moderately and evenly convex; beak long, somewhat attenuate, gently curved dor- sally; beak ridges blunt, obscure; interareas very small; lateral pseudointerareas absent; delthyrium wide, long, triangular, open, without deltidial plates. Brachial valve not known. Interior with small hinge teeth; dental plates incompletely fused to sides of valve; lateral mar- gins invaginated to form small, narrow necked apricatria. Muscle pattern unknown. MEASUREMENTS (in mm).—Holotype USNM 148102: length 1.5, maximum width 1.3, thickness (?), apical angle 60°. STRATIGRAPHIC OCCURRENCE.—Road Canyon For- mation. LOCALITY.—USNM 703a. TYPES.—Holotype: USNM 148102. DIAGNOSIS.—Long, slender Amphipella. COMPARISON AND DISCUSSION.—Amphipella at- tenuata is characterized by its small size, narrow elongate pentagonal outline, long pedicle beak with large delthyrium, nearly uniform convexity without abrupt marginal bends, and its small apri- cate sinuses located relatively far forward on the posterolateral slopes. It differs from the type spe- cies, A. arcaria Cooper and Grant in these features. Unfortunately only one valve of A. attenuata is available; perhaps when more are discovered fur- ther differentiating features will be observed. Family WELLERELLIDAE Licharew, 1956 Subfamily WELLERELLINAE Licharew, 1956 Smooth, semicostate to completely costate Rhyn- chonellacea with plicate anterior commissure; ped- icle valve with strong dental plates; brachial valve with undivided hinge plate supported by elevated median septum; crura falcifer to modified falcifer. Genera in West Texas: Wellerella Dunbar and Condra, 1932; Phrenophoria Cooper and Grant, 1969; Holosia, new genus; Tautosia Cooper and Grant, 1969; Cenorhynchia, new genus. Genus Wellerella Dunbar and Condra, 1932 Medium, subtriangular, unequally biconvex, uniplicate; fold and sulcus strongly costate, flanks weakly to strongly costate; costae expanding ante- riorly, rarely increasing in number, normally begin- ning 1 or 2 mm anterior to apexes of beaks. Con- centric ornamentation weak, growth laminae rarely visible except near shell margins. Pedicle beak sharp, straight or curved; delthyrium normally anteriorly closed by small deltidial plates, produc- ing oval, submesothyridid foramen. Brachial valve beak blunt, apex inside pedicle valve, covered by deltidial plates. Pedicle valve interior with strong nodular teeth, supported by vertical dental plates from floor of valve. Muscle area beginning at anterior ends of dental plates, extending from a third to a half valve length, its boundary subparallel to shell mar- gin; adductor scar single or bilobed, elongate to round, surrounded by two wide diductor scars. Brachial valve interior with triangular, undi- vided hinge plate bounded laterally by groovelike, laterally expanding sockets and supported by high or low, short median septum extended anteriorly as a low ridge in some specimens. Crura modified falcifer, diverging anteriorly, strongly curved toward pedicle valve, often twisted as much as 90°, usually longitudinally and dorsally carinate. Sep- tum rudimentary. Muscle area small, transverse to elongate, bisected by median ridge, anterior adduc- tor scars relatively large and median, posterior adductor scars small, elongate, diagonal, contiguous with part of anterior scar, or separated by low ridges. TYPE-SPECIES.—Wellerella tetrahedra Dunbar and Condra (1932:291, pi. 37: figs. 11-16). DIAGNOSIS.—Variable, semicostate rhynchonella- ceans having dental plates, undivided hinge plate, and apically confined median septum. COMPARISON.—Wellerella is distinguished by a NUMBER 21 1951 combination of characters of the exterior and the interior of the brachial valve. The most distincitve feature is the undivided hinge plate supported by an apical septum. Thus defined, Wellerella is ex- ternally similar to a number of semicostate rhyn- chonellids of the Pennsylvanian and Permian. It differs from Cenorhynchia, new genus, in having costate flanks and only an apical septum, the other genus having smooth flanks and a long median septum. Pontisia Cooper and Grant differs in hav- ing an undivided hinge plate but no median sep- tum, apical or otherwise. Some species of Phreno- phoria and Tautosia Cooper and Grant are homeo- morphs of Wellerella but Phrenophoria contains a long median septum. Aphaurosia, new genus, is like Wellerella internally but the costae are finer and more even, giving a characteristic external appearance to the shell. DISCUSSION.—Identification of Wellerella at pres- ent is difficult and, as with many other brachiopods, if the interior cannot be satisfactorily established, it is impossible to put a correct generic name to a species. Furthermore, by the usual serial sectioning methods an apical septum of small proportions can be overlooked. The type species of Wellerella is said to have an apical septum under the hinge plate, yet the one published serial section of the species shows no median septum; it may have been buried in the solid tissue of the brachial umbo and not be visible in an inked diagram. Two other species figured by Dunbar and Condra show the septum well in only one slice. Stehli (1954:334) interpreted Wellerella as pos- sessing a highly variable septum or none at all. His species, therefore, vary from having no septum, as in W. longicosta, to W. magnisepta in which this structure is conspicuous. It is difficult, however, always to be consistent in interpreting what is an "apical septum." Even the strictest attention to the septum of the brachial valve as a prime generic character cannot avoid simultaneous trouble with the ornament. This is true regardless of the combi- nation of interior characters used. Pontisia appears to be as composite a group as Wellerella or Phreno- phoria when their exteriors are compared. On the other hand sorting by exterior produces similar difficulties. We have therefore used the interior details as our chief generic guides. Examination of Pennsylvanian species currently assigned to Wellerella indicates similar difficulties because some of the wellerelliform shells have long and erect median septa, whereas others conform more strictly to the present generic diagnosis. Some forms that are wellerelliform but yet have occa- sional intercalated costae appear to be referable to camarotoechiid stocks. The Glass Mountains species most characteristic of Wellerella is W. girlyi, new species, one of the most abundant rhynchonellids of the Word For- mation. The species is not so rotund as the type species of Wellerella and is more robust and coarsely costated. It has the characteristic extremely short median septum in the apex. The hinge plate is narrow and the socket ridges are strong and ele- vated, bounding wide corrugated sockets. The outer hinge plates are short but the inner hinge plates are wide and stretch across the delthyrial cavity like a membrane. The suture may be visible or not, or the median junction in some specimens is anticlinal. The crura are wide, concave toward midvalve, and lie somewhat oblique to the hori- zontal. The oblique distal edge is serrated. Al- though this species answers to the definition of Wellerella, it does not accord strictly with the type; this is true of most of the species we have assigned to the genus. Wellerella? bidentata (Girty) Pugnax bidentata Girty [part], 1909:318, pi. 21: figs. 20-20c [not pi. 24: figs. 17—17c, = Wellerella swalloviana (Shu- mard)]. Not Pubnoides bidentatus (Girty), R. E. King, 1931:107, pi. 34: fig. 1. One peculiar little specimen is the only one of its kind known. The species has been widely iden- tified, but every example we have observed has been incorrectly determined. Rhynchonellids with two costae on the fold and one in the sulcus are uncommon, although several are described in this paper and some are known to us which we have not included here. Several specimens in the collec- tion suggest Girty's species, but they are from widely scattered levels and from the Glass Moun- tains or elsewhere. Usual occurrences consist of single specimens, leading to the suspicion that they are aberrant. This may be true also of W.f biden- tata. At any rate we have not found any other specimens of the species in the Cherry Canyon Formation or any other unit. 1952 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY Wellerella? bidentata was found with Bryorhyn- chus nitidum and Wellerella girtyi, new species, and therefore must have come from the Cherry Can- yon Formation as explained under discussion of B. nitidum. Bicostate forms occur fairly commonly as aberrancies in normally tricostate species. This is true also of narrowed and elongated forms. The rarity of W. bidentata may therefore be due to the fact that it is a deformed or aberrant form that lived under adverse and crowded conditions. TYPES.—Holotype: USNM 118568. LOCALITY.—USGS 2920 (green). Wellerella girtyi, new species Medium size for genus, biconvex, flattened to globular; outline ovoid to bluntly triangular, sides diverging between 85° and 115°; profile lenticular to subtrigonal; commissure uniplicate; fold low, beginning 4 to 6 mm anterior to brachial beak, profile evenly convex from beak to anterior mar- gin, occasionally slightly flattened where costae begin; sulcus correspondingly shallow, beginning 6 to 8 mm anterior to pedicle beak, rather uni- formly convex from beak to anterior margin. Costae moderately high and sharp on fold and pedicle flanks, lower and more blunt in sulcus and on brachial flanks, beginning 3 to 6 mm anterior to beaks, numbering 2 to 4 on fold, normally 3, one less in sulcus, 3 to 5 on flanks. Concentric ornamentation faint; growth lines light, present on some specimens. Pedicle valve moderately convex, slightly inflated in smooth area near beak, costae of flanks prom- inent, slightly reflexed in some specimens; beak sharp, somewhat attenuate, curved dorsally, beak ridges blunt; lateral pseudointerareas normally absent. Delthyrium triangular, base covered by two strongly arched deltidial plates; apical part open; foramen elongate oval. Brachial valve more strongly convex than pedicle valve; smooth part of posterior slightly flattened longitudinally, evenly rounded transversely; apex of valve within pedicle valve, covered by deltidial plates. Pedicle valve interior with delthyrium widely expanding anterior to deltidial plates; teeth elon- gate parallel to valve edge, supported by strong vertical dental plates reaching floor of valve. Mus- cle area beginning just anterior to dental plates, transversely oval, multilobate; adductor scars small, median, semiovate to semicircular, separated by low median ridge or myophragm; diductor scars wide, surrounding smaller adductors laterally and anteriorly. Brachial valve interior with large triangular hinge plate, bounded laterally by deep, elongate, anteriorly expanding, finely corrugated hinge sockets; inner hinge plates united to form flat plate between crura, bridging across notothyrial cavity. Crura projecting forward from anterior edges of hinge plate, diverging anteriorly, strongly curved ventrally, often twisted as much as 90 degrees, dorsal edges keeled; median ridge long, low, thin. Muscle area bisected by median ridge, elongate to transversely oval; posterior adductor scars small, elongate, anteriorly diverging, proximal ends sep- arated by median ridge; anterior adductor area larger, oval, lying on both sides of ridge. COMPARISON.—Wellerella girtyi is characterized by its average size for the genus, but small in com- parison to several other Glass Mountains species, its rotund shape, relatively narrow flanks, moder- ately low fold that is convex near the anterior margin, brachial valve with the smooth part of the beak slightly flattened in profile, but normally not flattened transversely, and by its comparatively large hinge plate and thin, low median ridge. It differs from Pontisia stehlii Cooper and Grant (1969) in its smaller average size, normally lower fold (except for the low-fold variety, P. stehlii tumidosa, new subspecies), lower costae that begin farther forward on the beaks, and its thin narrow rather than broad median ridge. A species from the Capitan Formation compar- able in size to W. girtyi is Tautosia elegans (Girty) which differs in its more transverse outline, higher fold and deeper sulcus, less convex fold especially near the anterior margin, depressed median costa in the fold, and by its high bladelike septum. Among foreign species the most similar is Rhyn- chonella negrii Gemmellaro (1899). Wellerella girtyi differs in its lower, less protruding fold, non- reflexed flanks, and greater number of costae on the flanks. Pugnax Utah Marcou of Kozlowski (1914) from the Carboniferous = Wolfcampian of Boliyia also is similar, differing in its higher fold, reflexed flanks, and fewer costae on the flanks. Pug- nax pseudoutah Huang (1933) from the Permian of China differs in its reflexed flanks with fewer costae, larger average size, and nearly straight, NUMBER 21 1953 rather than strongly convex, anterior portion of the profile of the fold. Wellerella girtyi girtyi, new subspecies PLATE 515: FIGURES 26-28; PLATE 528: FIGURES 1-46; PLATE 553: FICURES 33-34 This is the common subspecies in the Guadalu- pian of the Glass Mountains. It differs from W. girtyi seorsa, the new subspecies of the Guadalupe Mountains, in its sharper costae that are more numerous on the flanks (normally 4 rather than 3) and begin farther back on the beaks, and its more transverse, oval outline. The populations of W. girtyi in the two areas are sufficiently distinct to be recognized, and most individuals can be identi- fied subspecifically if there are specimens available for direct comparison. There is morphological overlap, however, and not all individuals from the one area differ from all individuals of the other region. MEASUREMENTS (in mm).— apical thick- angle ness (°) brachial valve length length width 6.4 7.0 8.0 10.0 10.6 3.0 3.2 4.3 5.0 5.1 5.2 6.1 7.4 8.8 9.7 10.8 7.5 8.3 9.7 11.4 12.5 3.7 3.8 4.8 5.8 6.0 6.3 7.3 8.7 10.6 11.4 13.4 6.9 7.5 9.9 12.0 14.0 3.1 3.7 4.3 5.3 5.9 6.7 6.8 8.0 11.3 12.1 14.0 3.0 3.7 6.2 8.6 10.8 1.5 1.5 1.8 2.3 2.5 2.6 3.1 5.1 7.1 8.5 10.5 85 90 111 95 110 60 70 80 80 85 90 80 80 90 95 90 USNM 706 148556a 148556b 148556c 148556d 148556e USNM 706e 154732a 154732b 154732c 154732d 154732e 154732f 154732g 154732h 154732i (holotype) 154732J 154732k STRATIGRAPHIC OCCURRENCE.—Cherry Canyon For- mation (Getaway Member); Word Formation (China Tank, Willis Ranch and Appel Ranch members and lens between Willis Ranch and Appel Ranch members); San Andres Formation. LOCALITIES.—Getaway: AMNH 21, 496, 512, 600; USNM 728, 730, 732. China Tank: USNM 703e, 706c, 733q. Willis Ranch: AMNH 505; USNM 706, 706e, 7l8d, 723t, 724u, 735c. Appel Ranch: 715i, 719z, 722t, 727j. Lens: 706b. San Andres: AMNH B188-8. DIAGNOSIS.—Average size Wellerella with rotund shape and large hinge plate. TYPES.—Holotype: USNM 154732i. Figured par- atypes: USNM 148565J; 154732a-h,j,k,m,n; 154733b; 154810; 15481 la-g. Measured paratypes: USNM 148556a-e; 154732a-h,j,k. Unfigured paratypes: USNM 148565a-i, 154733a. Wellerella girtyi seorsa, new subspecies PLATE 527: FIGURES 32-39 This subspecies occurs in the Guadalupian (Cherry Canyon Formation, Getaway Member) in the Guadalupe Mountains. It differs from the Glass Mountains subspecies, W. girtyi girtyi, in its more rounded costae that begin slightly farther forward, its more elongate, triangular outline, and its lower, fewer costae on the flanks: normally 3 instead of 4. In other respects the two subspecies are the same. Not every individual is subspecifically distinct, but the populations from the two areas can be recog- nized without difficulty. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 728 148582a 11.4 9.9 11.6 7.5 90 148582b 10.9 9.0 10.5 7.9 90 148582c 10.0 8.7 11.0 6.4 90 I48582d 10.0 8.4 10.5 5.6 90 148582e 9.0 7.8 8.7 6.0 85 I48582g 11.5 10.0 12.5 6.5 95 (holotype) STRATIGRAPHIC OCCURRENCE.—Cherry Canyon For- mation (Getaway Member). LOCALITIES.—Getaway: AMNH 21, 496, 512, 600; USNM 728, 730, 732. TYPES.—Holotype: USNM 148582g. Figured par- atypes: USNM 148582f,h,i. Measured paratypes: USNM 148582a-e. Unfigured paratypes: USNM 148582a-e. DISCUSSION.—The collections from the Getaway Member contain some interesting variations. A few specimens occur with 4 costae on the fold but a fair number contain only 2 costae on the fold and 1 in the sulcus. These have been confused 1954 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY with Pugnax bidentata (Girty) which has not yet been certainly identified generically. Wellerella? nitidula, new species PLATE 528: FIGURES 47-62 Small for genus, strongly biconvex; outline rounded, subcircular to subtrigonal, usually globu- lar sides diverging between 65° and 105°; anterior commissure uniplicate, fold moderately high at anterior, standing high above flanks farther back, beginning 4-5 mm anterior to brachial beak; sulcus very shallow, only slightly depressed below flanks, but extending dorsally as broad tongue at anterior commissure, beginning 5-6 mm anterior to pedicle beak. Costae strong on fold and sulcus, weaker on flanks beginning 3-5 mm anterior to beaks, crests rounded to obtusely pointed, numbering 3 on fold, 2 in sulcus, 2 to 4 on each flank. Growth lines and concentric ornamentation normally not visible. Pedicle valve with umbonal region somewhat swollen, evenly convex transversely and longitudi- nally; flanks gently curved, not reflexed; beak short to moderately long, slightly hooked, slightly atten- uate; beak ridges sharp, short; lateral pseudointer- areas narrow, elongate, partly covered by edge of brachial valve; delthyrium narrowly triangular, base of triangle narrowed by small, disjunct or barely conjunct deltidial plates with distal edges slightly flared outwardly, leaving elongate, oval foramen. Brachial valve with smooth part of umbo evenly convex, rarely slightly flattened; beak bluntly pointed, apex within pedicle valve beneath deltidial plates. Pedicle valve interior with teeth parallel to side of valve, supported by vertical dental plates ex- tending nearly vertically to floor. Muscle area tear- shaped, widening anteriorly, individual muscle marks not observed. Brachial valve interior with semicircular or crescentic, undivided hinge plate, bounded later- ally by elongate, deep, finely corrugated hinge sockets; crura keeled, diverging slightly forward from anterior edge of plate, moderately strongly curved ventrally, not twisted. Muscle area faintly impressed; posterior adductor marks small, elon- gate, one on each side of broad, only slightly raised median ridge; anterior adductor marks fused together, lying on midline of valve anterior to end of median ridge, flanked by anterior ends of posterior adductor marks. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (") AMNH 492 152865a 5.8 5.0 5.9 3.0 90 152865b 6.0 5.0 5.7 4.0 86 152865c 6.8 5.9 6.6 5.4 92 AMNH 591 152866a 6.6 5.6 6.8 4.8 90 152866b 7.5 6.6 7.7 5.8 100 152866c 8.7 7.7 8.5 7.2 84 (holotype) 152806d 9.1 8.0 10.O 8.6 95 152866e 9.4 8.4 10.6 9.2 101 152866f 9.6? 8.6 10.7 8.5 95 STRATIGRAPHIC OCCURRENCE.—Bone Spring For- mation (lower). LOCALITIES.—AMNH 492, 497, 591, 592, 624; USNM 728g. DIAGNOSIS.—Globular Wellerella with high fold. TYPES.—Holotype: USNM 152866c. Figured par- atypes: USNM 152866a,d,f,-i; 154812. Measured paratypes: USNM 152865a-c; 152866a,b,d-f. Unfig- ured paratypes: USNM 152865a-c; I52866b,e. COMPARISON.—Wellerella? nitidula is character- ized by its small size, rounded outline, fold that stands high above the flanks and bears 3 costae, normally evenly rounded brachial umbonal region, slightly swollen pedicle umbonal region, sharp beak ridges, and moderately well developed deltidial plates. Externally it most closely resembles Pontisia franklinensis, new species. Wellerella? nitidula at- tains a slightly larger size, is more rounded than triangular in outline, has the brachial smooth area more convex both longitudinally and transversely, sharper beak ridges, and elliptical rather than trig- onal profile. Tautosia podistra, new species, is small, but is narrower, flatter and smoother than W.I nitidula and its fold is relatively low, standing in relief above flanks only at its extreme anterior. Juveniles of Pontisia stehlii Cooper and Grant are similar in some features to W.? nitidula, but differ in their longitudinally more convex folds that consequently do not stand as high at the anterior, their longer beaks with more fully developed del- tidial plates, and less consistent number of costae on the fold. DISCUSSION.—This species is common at AMNH NUMBER 21 1955 591 but most of the specimens are filled with silica, making it impossible to study the interior details. We have accordingly queried the generic designa- tion but used Wellerella because the short median septum was observed in some specimens. Genus Phrenophoria Cooper and Grant, 1969 Phrenophoria Cooper and Grant, 1969:12. Small to large, rhynchonelliform, biconvex, uni- plicate; generally slightly wider than long; outline bluntly elongate subtrigonal, fold and sulcus mod- erately to strongly semicostate; fold usually sulcate in varying degree; flanks weakly to strongly semi- costate. Concentric ornamentation weak. Growth laminae commonly weak, strongest and most fre- quent near anterior margins. Pedicle valve moderately convex; beak sharp, nearly straight to suberect; beak ridges prominent; delthyrium triangular, closed at base by pair of large conjunct or disjunct deltidial plates, pro- ducing elongate oval mesothyridid to submeso- thyridid foramen; lateral pseudointerareas well developed where brachial valve overlaps pedicle valve; flanks convex to reflexed. Brachial valve more strongly convex and deeper than pedicle valve; umbonal region slightly flattened or in- dented; beak within pedicle valve under deltidial plates. Pedicle valve interior with sides of delthyrium diverging, wider anterior to deltidial plates; teeth elongate, parallel to sides of delthyrium, supported by nearly vertical dental plate reaching valve floor. Muscle area beginning between anterior ends of dental plates, widening greatly anteriorly; adduc- tor scars small, forming heart-shaped mark point- ing anteriorly along midline in posterior part of muscle area; diductor scars large, surrounding ad- ductor scars laterally and anteriorly, forming heart- shaped patch pointing posteriorly. Brachial valve interior with large, undivided triangular hinge plate bounded laterally by deep, elongate, anteriorly expanding, corrugated sockets; crura modified falcifer, diverging anteriorly, strongly curved ventrally; crural bases extending from beneath hinge plate along dorsal edges of crura as sharp keels, making extremities of crura concave anteriorly; median septum high, bladelike, supporting hinge plate, bisecting part of muscle area, and extending about a third length of valve. Muscle area beginning about halfway along sep- tum; posterior adductor scars, narrow, elongate, anteriorly slightly divergent, flanking larger, sub- elliptical anterior adductor scars. TYPE-SPECIES.—Phrenophoria subcarinata Cooper and Grant (1969:13, pi. 1: figs. 4-12). DIAGNOSIS.—Rhynchonellids having strong, long median septum, generally naked umbones, and strongly costate anterior regions. COMPARISON.—Phrenophoria is characterized by its strong costae, usually sulcate fold, normally flat- tened or indented brachial umbonal region, well- developed lateral pseudointerareas, large conjunct deltidial plates, large undivided hinge plate, and its high, thin, bladelike median septum. The high median septum separates it from Wellerella Dun- bar and Condra and Pontisia Cooper and Grant, and the large conjunct deltidial plates and large undivided and unnotched hinge plate distinguish it from Anteridocus, new genus, and Cenorhynchia, new genus. Some species of Phrenophoria are leior- hynchiform in external appearance but differ in having the hinge plate without median trough, the sulcate fold on the brachial valve, and the flanks strongly costate. The latter feature distin- guishes Phrenophoria from Bryorhynchus but more knowledge of the form of the hinge plate is needed to separate it confidently from Leiorhynchoidea. Two other probably related genera with long median septa can be readily distinguished from Phrenophoria. Tautosia Cooper and Grant is usu- ally transverse and has prominent anterolateral extremities on the ventral side as well as strong angular costae, features more exaggerated than those usually found in Phrenophoria. Holosia, new genus, is totally costate and elongate. DISCUSSION.—Numerous species with a strong median septum and undivided hinge plate are assigned to this genus. Although every effort has been made to conform ornament types, it has not been possible to limit the assignments in strict conformity to the definition of the genus. It is thus possible to notice at least two groups of species. One of these, the P. subcarinata or P. pinguis group is the type form and thus strictly speaking is Phrenophoria. This one generally is hemicostate, has a sulcate dorsal umbo, the sulcus extending onto the fold and depressing one or more of the costae. The sulcus is not deep and the 1956 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY anterolateral extremities of the ventral side are not strongly angular or protuberant. Another species group is less costate than the preceding and is characterized by P. repugnans, new species. In this type the pedicle valve is mostly smooth but is fairly deeply sulcate and has fairly prominent antero- lateral extremities. The brachial valve, however, is like that of the type species in having a sulcate umbonal region and a depression in the fold. Phrenophoria corpulenta, new species, is more ro- tund than usual and the costae invade more of the posterior than in the P. subcarinata group, but the brachial valve umbo is sulcate and the sulcus affects the fold. Like the bicostate species in other genera, P- bicostata is completely atypical on its exterior but no other niche can be found for it. Phrenophoria nesiotes, new species, is most like the P. subcarinata group and has all of the essentials of the genus but the valves are not as strongly costate as usual, nor so anteriorly truncated, and are quite wide. Some species of Phrenophoria such as P pinguis, P. pinguiformis, P. nesiotes, and P. subcarinata are strongly leiorhynchiform and might be confused with some genera of that family, especially earlier Paleozoic ones such as Basilicorhynchus Crickmay (1952). Phrenophoria might be confused with the young of Leiorhynchoidea Cloud, with which it occurs; but beak characters, nature of the fold, and interior details separate them. Generally the beak of Phrenophoria is only mod- erately long and the foramen is small but usually elongate-oval and mesothyridid or submesothyridid in position. It is usually straight to suberect, with only a small amount of curvature. The teeth are elongated and are parallel to the lateral margins and are separated from the margin by narrow slots that receive the socket ridges. The musculature of the pedicle valve is fairly well shown in the type species. The field is large and somewhat cordate, with the lobate portion anterior and the point posterior. The adductor patch lies just anterior to the delthyrial cavity and is completely surrounded by the broadly expanded diductor scars. Other details of the interior have left no marks on the shell. The brachial valve is characterized by a strong median septum in all species. These support an undivided hinge plate, although the latter feature is variable in gross form and in detail. The socket ridge is strong, long, curved, and hangs over a minutely corrugated narrow socket. The outer hinge plates are moderately broad and attach long strong crura with a narrow keel. The crura, as shown by those of P. pinguiformis, are fairly wide, crescentric in cross section, but concave toward the anterior or anteromedially. The distal extremity is rough. The inner hinge plates are developed variably in the same species, a fact well shown by P. sub- carinata. Specimens show inner hinge plates that have grown horizontally and coalesced to form a nearly flat hinge plate, but others display varying degrees of concavity, with the result that the hinge plate has a narrow or shallow trough. In one specimen the inner hinge plates are overlapped, failing to meet medially and one grew over the other. Other species show similar variations. The median septum does not show great variation but in some specimens it is thickened posteriorly where it attaches to the hinge plate; rarely traces of a small chamber may be seen in connection with the inner hinge plates. Phrenophoria is widespread in the Permian rocks from which brachiopods under discussion were taken. It is fairly common in the Word For- mation and its equivalents, but less abundant above and below. Phrenophoria anterocostata, new species PLATE 519: FICURES 19-23 Small for genus, subpentagonal in outline, maxi- mum width at midvalve; length slightly greater than width. Sides broadly rounded; anterior trun- cated. Anterior commissure strongly uniplicate. Beak small, nearly straight; foramen narrowly elon- gate; deltidial plates small, disjunct. Posterior half naked but anterior half strongly costate: 2 costate in sulcus, 3 on fold, 3 on flanks. Costae in sulcus not extending beyond sulcus. Pedicle valve barely convex in lateral profile and broadly concave in anterior profile. Umbonal re- gion slightly but narrowly swollen to origin of sulcus, just anterior to midvalve. Tongue long and serrated. Flanks strongly reflected in ventral direc- tion, serrate on anterior edges. Brachial valve gently and evenly convex in lat- eral profile but narrowly and strongly domed in anterior profile. Umbonal region gently concave; NUMBER 21 1957 fold originating near midvalve, moderately ele- vated. Lateral slopes swollen and steep. Median septum of brachial valve seen as long slit. MEASUREMENTS (in mm).—Specimens USNM 153486a (holotype) and b, respectively: length 13.7, 11.8; brachial valve length 12.1, 10.6; width 12.3, 11.4; thickness 9.2, 8.2; apical angle 98°, 103°. STRATIGRAPHIC OCCURRENCE.—Cathedral Moun- tain Formation (lower). LOCALITY.—USNM 721u. DIAGNOSIS.—Small pentagonal Phrenophoria with costae of sulcus confined to sulcus. TYPES.—Holotype: USNM 153486a. Figured par- atype: USNM 153486b. COMPARISON.—See Phrenophoria? nudumbona for comparison. DISCUSSION.—An extremely rare species; only 2 specimens were obtained in the digestion of about 24 large blocks. Phrenophoria bicostata, new species PLATE 514: FIGURES 29-39; PLATE 515: FIGURES 30-35 Small for genus, subtrigonal outline, rounded sides and truncated anterior margin; posterolateral margins converging at 90° or less; valves subequal in depth. Beak small, suberect, with submesothyri- did foramen and small, conjunct deltidial plates occasionally with elevated rim on side against pedicle. Surface costate, costae direct from beak to anterior margin; 2 costae on fold, 1 in sulcus, and 4 or 5 on flanks. Pedicle valve gently and evenly convex in lat- eral profile, broadly and flatly convex in anterior profile. Umbonal region narrowly convex; median region moderately convex; sulcus narrow, moder- ately deep, widening gradually anteriorly, orig- inating posterior to midvalve. Flanks gently convex, moderately steep. Brachial valve moderately and evenly convex in lateral profile, more broadly and gently convex in anterior profile with moderately steep sides. Me- dian region moderately convex; fold originating posterior to midvalve, narrow, expanding slightly anteriorly, and narrowly grooved medially. Fold moderately elevated anteriorly, flanks moderately convex and with moderate slopes. Pedicle valve with small knoblike teeth supported by stout, vertical dental plates. Brachial valve inte- rior with stout socket ridges, small sockets, and undivided hinge plate. Outer hinge plates narrow, but inner ones united without suture and broad with slight anterior notch. Crura long, laterally compressed, concave toward midvalve. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 7l9z 152825a 7.2 6.2 7.0 4.0 85 152825b 7.0 6.0 7.0 3.1 90 152825c 6.5 5.7 6.0 4.0 80 152825d 5.8 5.0 5.9 2.9 80 152825e 5.4 4.7 4.8 2.3 80 152825f 3.6 2.9 3.1 1.5 80 154729a 5.8 4.8 5.8 3.5 83 (holotype) STRATIGRAPHIC OCCURRENCE. —Word Formation (Appel Ranch Member). LOCALITY.—USNM 719z. DIAGNOSIS.—Small triangular Phrenophoria hav- ing 2 costae on fold and 1 in sulcus and strongly costate flanks, the costae reaching the umbo. TYPES.—Holotype: USNM 154729a. Figured par- atypes: USNM 152825i,k,m,n; 154729b,c. Measured paratypes: USNM 152825a-f. Unfigured paratypes: USNM 152825a-h,j,l. COMPARISON.—No other Phrenophoria has only 2 costae on the fold and 1 in the sulcus. DISCUSSION.—The exterior of this little species is atypical because of the bicostate fold and the fact that the costae almost reach the umbones. Despite this, the cardinalia are like those of the type spe- cies and the median septum in the brachial valve is long and slender. It is a rare species known from only one locality. Phrenophoria? compressa, new species PLATE 522: FIGURES 4-7 Small for genus, narrowly compressed, narrowly triangular in outline. Greatest width at midvalve. Sides gently rounded; anterior margin truncated. Anterior commissure uniplicate. Beak fairly long, suberect; foramen elongate-oval; deltidial plates vestigial (?). Surface with posterior half smooth but anterior half marked by strong, subangular costae, 3 occupying fold, 2 in sulcus, and 2 on flanks. 1958 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY Pedicle valve gently convex in lateral profile, but narrowly and gently concave in anterior profile. Umbonal region with narrow elevation joining 2 costae in sulcus. Sides abrupt and steep. Tongue short. Sulcus originating anterior to midvalve, nar- row and shallow and nearly completely occupied by 2 crowded costae. Flanks very narrow and slightly reflected in ventral direction. Brachial valve evenly and gently convex in lat- eral profile but narrowly and roundly domed in anterior profile. Posterior half and umbonal region marked by narrow depression extending from beak to fold. Flanks, narrow, rounded, and somewhat inflated. Fold originating near midvalve, only slightly elevated and abruptly truncated anteriorly. Interior unknown. MEASUREMENTS (in mm).—Holotype USNM 153489: length 10.0, brachial valve length, 8.6, width 8.5, thickness 8.2, apical angle 70°. STRATIGRAPHIC OCCURRENCE.—Road Canyon For- mation. LOCALITY.—USNM 706f. DIAGNOSIS.—Elongate, narrow Phrenophoria? with short fold and sulcus and flanks laterally compressed and narrow. TYPES.—Holotype: USNM 153489. COMPARISON.—The elongate and compressed form of this species is unique. It has some characters of P. planiventra, new species, from the Road Canyon Formation but it is smaller, more finely orna- mented, and much narrower in outline. The holo- type is the only known specimen of the species. Phrenophoria corpulenta, new species PLATE 514: FIGURES 40-54 Shell about average size for genus, strongly bi- convex; outline narrowly to broadly subpentagonal, sides diverging between 95 and 120 degrees; com- missure uniplicate, fold high and nearly square, not standing high above flanks behind anterior margin, beginning 6-8 mm anterior to brachial beak, bearing shallow, elongate median depression reaching nearly to beak with 3 costae; sulcus shal- low, barely depressed below flanks, beginning about 8 mm anterior to pedicle beak, extending forward as flat, strongly geniculated tongue at anterior. Costae low, crests subangular, beginning about 3 mm from beaks along median line, about 7 mm from beaks on each side, numbering 3-5 on fold, one less in sulcus, 4-7 on each flank. Growth lines faint, not preserved on most specimens. Pedicle valve gently convex except at anterior, there strongly curved toward commissure; beak short, sharp, slightly attenuate, somewhat de- pressed, with sharp beak ridges, not strongly curved; lateral pseudointerareas narrow, elongate but short, covered by edge of brachial valve; delthyrium broadly triangular, constricted by small, nearly conjunct, outwardly flaring deltidial plates, leaving nearly circular foramen. Brachial valve strongly convex in profile, umbonal region flattened, ante- rior part strongly curved toward commissure; deep median trough extending from smooth part of umbonal area along fold, lowering median costae; beak blunt, within pedicle valve, beneath deltidial plates. Pedicle valve interior with strong, corrugated hinge teeth, supported by nearly vertical dental plates reaching valve floor. Muscle area heart- shaped, adductor scars small, subcircular, in pos- terior part of area; diductor scars larger, surround- ing adductors, widening anteriorly. Brachial valve interior with large, subtrigonal hinge plate. Socket ridges strong, overhanging cor- rugated sockets; outer hinge plates broad, sloping medially, crural bases narrow, depressed; inner hinge plates broad, conjunct medially and with suture line unhealed; median septum high, blade- like extending about a third valve length. Muscle area on floor of valve on each side of median sep- tum; individual muscle marks not observed. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length zvidth ness (°) AMNH 678 152826a 7.0 6.8 9.0 2.4 100 152826b 10.6 9.8 12.4 5.4 110 152826c 10.6 10.0 11.6 9.5 108 152826d 10.8 9.G 12.0 8.5 106 152826e 11.5 10.6 12.2 9.4 109 152826f 13.0 12.0 14.8 9.6 116 (holotype) STRATIGRAPHIC OCCURRENCE.—Bone Spring For- mation (Cutoff Member). LOCALITIES.—AMNH 678, USNM 747. DIAGNOSIS.—Medium-sized, rotund Phrenophoria with a broad depression or sulcus in the fold. NUMBER 21 1959 TYPES.—Holotype: USNM 152826f. Figured par- atypes: USNM 152826a,d,h; 154718. Measured para- types: USNM 152826a-e. Unfigured paratypes: USNM 152826b,c,e,g. COMPARISON.—Phrenophoria corpulenta is char- acterized by its rotund shape, each valve flexed toward commissure near its anterior margin, by its numerous, strong but rather low costae that begin far from the beaks, and especially by its deep, wide median trough in the brachial valve that begins near the beak and depresses the crest of the fold along its entire length. It looks most like P. pinguis (Girty), from which it differs in its smaller size, normally wider outline, more numerous and nar- rower costae, deeper median trough in the brachial valve, more abrupt bending of the anterior part of each valve and lack of a gablelike ridge along the median line of the pedicle valve. In addition, P pinguis has noticeable radiating fibers, and strong growth lines concentrated near the margins of the valves, whereas P. corpulenta has only faint hints of radiating fibers, and few visible growth lines. Antronaria mesicostalis (Girty) is superficially sim- ilar to P. corpulenta, but the latter differs in its smaller size, more abruptly bent contours, deep trough along the fold (instead of one depressed costa), and by internal generic features, mainly its high median septum. DISCUSSION.—This species at first glance suggests Rhynchopora with its squarish front, broadly rounded costae, and short beak. It is typically phrenophoriform in having a strong depression in the fold of the brachial valve and in the character of the cardinalia which do not have the apical chamber so characteristic of punctate Rhynchopora. Phrenophoria corpulenta is a very rare species. Phrenophoria depressa, new species PLATE 514: FIGURES 55-71 Small for genus, outline subtriangular, usually slightly wider than long as adult, maximum width at midvalve; lateral margins rounded; anterior margin truncated and medially emarginated. Ante- rior commissure uniplicate. Beak short, straight; deltidial plates small. Surface hemicostate, anterior half marked by subangular costae, 3 on fold, me- dian costa deeply depressed, 2 in sulcus and 3 or 4 on flanks. Pedicle valve nearly flat in lateral profile and gently concave in anterior profile. Umbonal region nearly flat; sulcus originating at midvalve; abruptly deepening and extended into narrow tongue. Flanks nearly flat, slightly deflected anteriorly, and strongly protuberant at anterolateral extremities. Brachial valve bulbous, fairly strongly convex in lateral profile, narrowly and roundly domed in anterior profile, sides precipitous. Umbonal region swollen, but medially sulcate, narrow, shallow sulcus extending into fold and strongly depressing median costa, or median two. Fold originating at midvalve, moderately elevated and with steep sides. Flanks swollen, and considerably depressed below fold. Pedicle valve interior with short, thin dental plates separated from valve wall by very narrow cavities. Brachial valve interior with curved socket ridges, narrow outer hinge plates and wide, inner hinge plates with deep reentrant. Crura not well preserved. Median septum long and delicate. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 707d 148773a 8.8 7.8 10.1 6.8 90 (holotype) 148773b 9.6 8.2 9.6 5.4 80 148773c 8.7 7.6 9.4 4.3 90 STRATIGRAPHIC OCCURRENCE.—Skinner Ranch For- mation (Sullivan Peak Member). LOCALITY.—USNM 707d. DIAGNOSIS.—Small Phrenophoria with flat-pedi- cle valve, bulbous brachial valve with deeply de- pressed median costa in the fold. TYPES.—Holotype: USNM 148773a. Figured par- atypes: USNM 148773b,h,i. Measured paratypes: USNM 148773b,c. Unfigured paratypes: USNM 148773c-g. COMPARISON AND DISCUSSION.—This is a very rare species, most similar to P. planiventra and repugnans, both new species. It differs from the former in its much smaller size and more strongly costate flanks. It has almost the same size as P repugnans but has more strongly costate valves, more triangular shape, and deeper brachial valve. In spite of the differences, the three species seem to form a characteristic group. 1960 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY Phrenophoria incomitata, new species PLATE 521: FIGURES 1-9 Small for genus, elongate oval outline, well but broadly rounded sides, posterolateral margins form- ing angle of 90°. Anterior margin narrowly rounded. Maximum width near midvalve. Beak moderately long, nearly straight. Surface semi- costate, 3 costae on fold, 2 in sulcus, 2 on flanks; median costa of fold wide and strongly depressed. Pedicle valve moderately and fairly evenly con- vex in lateral profile, faintly concave in anterior profile. Umbonal region slightly swollen; sulcus originating at midvalve, shallow, moderately wide, forming moderately long tongue. Flanks gently convex and protruding moderately anterolaterally. Brachial valve about same depth as pedicle valve, moderately convex in lateral profile but anterior somewhat geniculated; anterior profile a flat-topped dome with very steep sides. Fold orig- inating somewhat anterior to midvalve, inconspicu- ous but slightly elevated above flanks anteriorly; fold in sulcus originating in umbonal region and strongly depressing median costa of fold. Flanks moderately swollen but with precipitous sides. Pedicle valve interior with small teeth but strong dental plates. Brachial valve with small hinge plate and strong median septum. MEASUREMENTS (in mm).—Holotype USNM 152827a: length 11.9, brachial valve length 10.6, maximum width 9.9, thickness 7.2, apical angle 90°. STRATIGRAPHIC OCCURRENCE.—-Bone Spring For- mation (Cutoff Member). LOCALITY.—AMNH 678. DIAGNOSIS.—Small oval Phrenophoria with three costae on the fold. TYPES.—Holotype: USNM 152827a. Figured par- atype: USNM 152827b. COMPARISON AND DISCUSSION.—Although only two specimens of this species are known we have named it because so little is known of the Cutoff Shale fauna. The specimens consist of a complete one conveniently broken on one side to reveal the hinge plate and median septum, so that little doubt exists as to its correct generic determination. The other specimen is a pedicle valve interior display- ing the dental plates and teeth. The specimen, judging by its interior and the strong development of the fold, is clearly an adult. It is most like P. subcarinata Cooper and Grant of the Word Formation in the Glass Mountains, but differs from it in a number of particulars. Speci- mens of P. subcarinata of comparable size have stronger and more rounded costae, a much less prominent sulcus in the fold of the brachial valve, more of the posterior smooth, and narrower flanks. No other species of Phrenophoria is similar. Phrenophoria irregularis, new species PLATE 525: FIGURES 13-25 Medium size for genus, wider than long, trans- versely pentagonal in outline. Widest at midvalve; sides rounded; anterior margin broadly rounded. Anterior commissure narrowly uniplicate. Beak short, straight; deltidial plates small, conjunct. Surface multicostate, costae generally narrowly rounded, irregular in strength, occasionally inter- calated, generally numbering 4, often 3 on fold, one less in sulcus; costae on flanks numbering 3 to 5; umbones smooth; strong growth lamellae crowded at anterior. Pedicle valve gently convex in lateral profile, greatest convexity in posterior half; anterior profile very gently concave medially. Umbonal and median regions somewhat narrowly swollen, swelling con- tinuing into sulcus, there merging with surface; sulcus broad and shallow, originating anterior to midvalve, forming long, strongly geniculated tongue. Flanks gently concave and slightly deflected. Anterolateral extremities protruding moderately. Brachial valve moderately convex in lateral pro- file, most convexity in posterior third. Anterior profile broadly and strongly domed, median region conspicuously flattened. Umbonal region moder- ately swollen but marked medially by narrow shal- low sulcus merging with fold but not reaching margin. Fold originating slightly anterior to mid- valve, fairly broad and flattened, not conspicuously elevated at front. Flanks strongly swollen and only slightly depressed below fold at front margin. Pedicle valve interior with elongated large teeth situated on valve edge; dental plates thick, short, and separated from valve wall by very narrow chambers. Muscle field large, occupying median region, with deeply impressed, large adductor patch located just at anterior ends of dental plates. Brachial valve interior with fairly wide and strongly corrugated sockets bounded by thick, NUMBER 21 1961 curved socket ridges. Hinge plate, narrow, variable, divided or undivided depending on age (?); outer hinge plates narrow; inner hinge plates concave (?) to flat, united or not, depending on age. Median septum strong, thin, highly elevated and reaching midvalve there serving as myophragm to divide lateral halves of large rounded adductor field. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) AMNH 512 152836a 12.9 11.2 15.6 8.2 110 (holotype) 152836b 11.8 10.6 13.3 7.0 110 152836c 11.5 10.6 13.7 6.5 110 STRATIGRAPHIC OCCURRENCE.—Cherry Canyon For- mation (Getaway Member). LOCALITIES.—AMNH 512; USNM 728. DIAGNOSIS.—Transversely pentagonal Phrenopho- ria having irregularly developed costae and crowded growth lamellae at the anterior. TYPE:.—Holotype: USNM 152836a. Figured par- atypes: USNM 152836c-e. Measured paratypes: USNM 152836b,c. Unfigured paratypes: USNM 152836b. COMPARISON AND DISCUSSION.—This species is characterized by its rounded outlines and trans- verse form. It also has small and narrow costae and fairly numerous costae on the flanks. It is not like Tautosia magnisepta (Stehli), which has nu- merous costae, because of its greater width, stronger costae, and rounded contours. This is an uncom- mon species. Phrenophoria nesiotes, new species PLATE 516: FIGURES 6-42 About average size for genus, variable, biconvex; outline roundly and bluntly triangular to subpen- tagonal, normally transverse; sides diverging be- tween 80° and 120°, averaging about 105 ; com- missure narrowly to broadly uniplicate, fold anterior, low to moderately high, beginning 8 to 10 mm anterior to brachial beak, slightly arched transversely, profile flatly convex, with slight dorsal flexure at anterior boundary of smooth area of umbo; sulcus shallow, beginning 9 to 11 mm anterior to pedicle beak, longitudinal convexity uniform. Costae weak to moderately strong, strong- est on fold and pedicle flanks, usually wide, begin- ning 6 to 11 mm anterior to beaks, crests angular, numbering 3-5 on fold, one less in sulcus, 2-6 on each flank. Concentric striae faint, closely crowded over surface of shell; growth lines irregularly spaced, prominent only near anterior margins. Pedicle valve nearly flat, umbonal area with blunt, low median crest; flanks slightly reflexed, with anterior terminations blunt; beak short, sharp, not attenuate, not curved dorsally, but pointing slightly ventrally; beak ridges sharp, short; lateral pseudointerareas narrow, sharply delimited, partly covered by edge of brachial valve. Tongue strongly geniculated, fairly long. Delthyrium triangular, base normally covered by pair of small deltidial plates; apex open, forming elongate oval submeso- thyridid foramen. Brachial valve more strongly convex transversely than longitudinally; umbonal region with shallow median longitudinal impres- sion; apex of valve within pedicle valve, covered by deltidial plates. Flanks moderately swollen. Pedicle valve interior with delthyrium open ante- rior to deltidial plates, sides moderately divergent; teeth small, elongate; dental plates supporting hinge teeth, slightly converging apically and toward floor of valve, forming narrow delthyrial cavity; umbonal chambers wide. Muscle area heart-shaped, lying between and anterior to forward edges of dental plates; adductor scars small, median, nar- row; diductor scars larger, surrounding adductors, widening anteriorly, meeting at median line; ad- juster scars elongate, narrow, lying along posterior flanks of diductors. Brachial valve interior with large, triangular, undivided hinge plate, often medially depressed, simulating crural cavity; median notch shallow; sockets elongate, deep, finely corrugated, slightly widening anteriorly; crura slender, strong, diverg- ing anteriorly, strongly curved ventrally, dorsal edges carinate. Median septum high, thin in the young, long, bisecting part of muscle area; posterior end supporting hinge plate, often thickened. Outer hinge plates narrow; inner hinge plates with healed suture, flat or subangularly arched. Muscle area elongate oval; posterior adductor scars relatively large, subelliptical, lying at posterior flanks of slightly larger, subcircular anterior adductor scars. STRATIGRAPHIC OCCURRENCE.—Cathedral Moun- tain Formation (base). 1962 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY MEASUREMENTS (in mm).- brachial apical valve thick- angle length length width ness (°) USNM 708u 148355a 1.6 1.4 1.5 0.7 90 148355b 3.7 3.0 3.4 1.1 90 148355c 6.0 5.5 6.2 2.0 86 148355d 8.9 8.2 9.7 3.1 87 148355e 11.3? 10.6 12.9 4.9 104 I48355f 13.0 11.7 16.3 8.4 120 148355g 14.4 13.4 16.8 9.8 109 148355h 16.7 15.9 19.3 11.0 105 (holotype) LOCALITIES.—USNM 702, 708u. DIAGNOSIS.—Large, transverse Phrenophoria with broad costae and posteriorly thickened median septum. TYPES.—Holotype: USNM 148355h. Figured par- atypes: USNM 148355a,b,c,f,g,i,j,a'; 148673a-d; 154375a-e. Measured paratypes: USNM 148355a-g. Unfigured paratypes: USNM 148355d,e,h. COMPARISON.—Phrenophoria nesiotes is character- ized by its transversely triangular to subpentagonal outline, its short beak that is not dorsally curved, its fold and sulcus that begin far forward, fold with 3 to 5 broad costae beginning far forward, visible adjustor muscle scars in the pedicle valve, posterior and anterior adductor muscle scars in the brachial valve that are subequal in size, and the posteriorly thickened median septum in old adults. It most nearly resembles juveniles of Tautosia fastigiata, new species, differing in its more round- ed outline, shorter and less attenuate beak that points ventrally instead of curving dorsally as in most species, more numerous costae on the fold, transversely slightly arched fold, and its only slightly reflexed pedicle valve flanks whose costae terminate bluntly, curving slightly dorsally anterior to the commissure. Other species of Phrenophoria from West Texas are easily distinguishable from P. nesiotes, especially by their costae that begin farther back. Phrenophoria nesiotes resembles Pugnax osagen- sis Swallow of Tschernyschew (1902:64, 482, pi. 23: figs. 5-9), differing in its rounder outline and less attenuate pedicle beak, less sharply reflexed flanks, normally more costae on the fold, absent crural cavity, and its high median septum rather than low median ridge (Tschernyschew, 1902:65). DISCUSSION.—As with the rest of the fauna with which P. nesiotes occurs, this species is unusual in its appearance. Its costae are broadly angular but subdued and the adult form does not have the usual squared-off front of the type species and related forms. Furthermore, the posterior half of the shell is completely bare of costae. These char- acters and the fairly transverse outline make this form distinctive. The interior is as distinctive as the exterior. The dental plates are very short, fairly approximate, and subparallel; the muscle field is small and does not reach midvalve, is well rounded, and is not strongly expanded laterally. The cardinalia of the brachial valve are delicate and with narrow crura, but concave anteriorly and with the broad posterior surface nearly horizontal. The inner hinge plates are well developed and show the same types of variation as those of the type species. Some specimens have a median suture when the plates are not completely united, but others have a small fold along the midline. Phrenophoria? nudumbona, new species PLATE 522: FIGURES 1-3 Small for genus, subpentagonal outline, length and width about equal; brachial valves much more convex than pedicle valve. Greatest width near midvalve. Anterior commissure strongly uni- plicate. Surface with posterior half smooth but anterior half strongly costate, fold having 3 costae, flanks 2 or 3. Pedicle valve gently convex in lateral profile, broadly but gently concave in anterior profile; maximum convexity anterior to umbo. Beak nearly straight, apical angle 102°; foramen elongate oval; surrounded by convex but disjunct deltidial plates. Sulcus originating at midvalve, deepening abruptly and producing long, serrated tongue. Costae on tongue extending to umbo. Flanks abruptly and strongly reflected in ventral direction. Brachial valve unevenly convex in lateral profile, umbonal region flattened, maximum convexity in anterior half. Anterior profile narrowly and strongly domed.. Umbonal region gently and longitudinally concave, concavity extending to fold beginning at midvalve. Fold moderately elevated anteriorly with short, steep lateral slopes. Flanks swollen and steep sided. MEASUREMENTS (in mm).—From locality USNM NUMBER 21 1963 703d holotype USNM 148373: length 11.9, brachial valve length 10.2, width 12.3, thickness 8.8, apical angle 102°. STRATIGRAPHIC OCCURRENCE.—Road Canyon For- mation. LOCALITIES.—USNM 703d, 72lr. DIAGNOSIS.—Small, pentagonal Phrenophoria? with deep sulcus and costae of sulcus extended onto umbonal region. TYPES.—Holotype: USNM 148373. COMPARISON.—This species is of about the same size, shape, and general aspect as P. anterocostata, new species, but differs from that species by having the costae of the sulcus extended posteriorly to the umbonal region, by having a stronger development of the deltidial plates, a narrower sulcus, and a more convex pedicle valve. Phrenophoria repug- nans resembles P.(?) nudumbona, but differs in hav- ing less angular costae, the median costa of the fold depressed, the beak suberect, and more costae on the flanks. Phrenophoria pentagonalis, new species PLATE 517: FIGURES 36, 37 Small for genus, transversely pentagonal in out- line, width greater than length; maximum width anterior to midvalve; sides narrowly rounded; ante- rior margin truncated. Anterior commissure mod- erately uniplicate. Beak small, suberect; foramen elongate-oval; deltidial plates vestigial, disjunct. Surface with posterior half smooth but anterior moderately strongly costate. Costae narrowly rounded, numbering 3 on fold, 2 or 3 on flanks. Pedicle valve gently convex in lateral profile, maximum convexity in posterior half; anterior profile broadly and gently concave. Umbonal re- gion longitudinally swollen, swelling extending to originating point of costae. Sulcus, originating at midvalve, fairly narrow and moderately deep. Slopes of flanks long and gentle. Flanks marginally deflected in ventral direction; flanks flattened. Brachial valve evenly and gently convex in lat- eral profile; broadly domed in anterior profile. Umbonal region gently inflated and bearing nar- row, shallow depression extending from beak to fold; fold low, short, originating near midvalve. Flanks moderately swollen and with moderately steep slopes. Median septum of brachial valve long and sharp, viewed from break in holotype. MEASUREMENTS (in mm).—Specimens USNM 148575a (holotype) and b, respectively: length 9.4, 10.4; brachial valve length 8.6, 9.5; width 12.4, 13.0; thickness 6.6, 6.4; apical angle 116°, 98°. STRATIGRAPHIC OCCURRENCE.—Road Canyon For- mation. LOCALITY.—USNM 703d. DIAGNOSIS.—Small pentagonal Phrenophoria with narrowly rounded flanks, short fold and sulcus, and costae of sulcus not extending posterior to midvalve. TYPES.—Holotype: USNM 148575a. Figured par- atype: USNM 148575b. Measured paratype: USNM 148575b. COMPARISON.—Phrenophoria pentagonalis has a fairly common type of exterior but the combina- tion of characters is different from any others. It is like Tautosia elegans (Girty) in general outline and ornament but has finer costae, a more convex brachial valve, and the median costa of the sulcus is not depressed. Another species having the same general expression as P. pentagonalis is T. shumar- diana (Girty) but that is a much larger species with prominently depressed costa or costae in the fold of the brachial valve. Tautosia transenna, new species, is differently shaped, more robust, with stronger costae, and more costae on flanks than P. pentagonalis. Phrenophoria perplexa, new species PLATE 508: FIGURES 34-39; PLATE 516: FIGURES 43-58; PLATE 521: FIGURES 65-73 Usual size for genus, leiorhynchiform, length and width nearly equal; sides well rounded; postero- lateral margins forming angle of 100° to 110°; out- line subpentagonal. Anterior margin truncated. Anterior commissure strongly uniplicate. Beak short, with small elongate submesothyridid fora- men; deltidial plates well formed, conjunct. Surface mostly costate but umbonal regions smooth; costae broad, angular, 4 or 5 on fold, one less in sulcus and 2 or 3 flattened costae on flanks. Concentric lamellae crowded at anterior margin. Pedicle valve unevenly convex in lateral profile, most convexity just anterior to umbo; anterior pro- file broadly concave. Umbonal region narrowly 1964 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY convex, convexity merging into sulcus near mid- valve. Sulcus broad and shallow, originating ante- rior to midvalve and extending into long, blunt, serrated tongue. Anterolateral extremities subangu- lar and fairly prominent. Brachial valve much deeper than pedicle valve, evenly and moderately convex in lateral profile but narrowly domed and strongly convex in lateral profile and with precipitous sides. Umbonal region marked by shallow sulcus extending onto fold nearly to front margin. Fold originating just ante- rior to midvalve, flattened and low, not strongly differentiated anteriorly. Flanks moderately swol- len, very steep. Pedicle valve interior with small teeth elongated parallel to shell margin and offset from it by nar- row slit. Dental plates short, with poorly defined and narrow umbonal cavities. Muscle field cordate, adductors surrounded by diductors and possible adjustor muscle scars appearing outside diductors anterior to dental plates. Brachial valve interior variable. Cardinalia mod- erately large with strong socket ridges and finely corrugated sockets. Outer hinge plates of moderate size attaching keeled crural bases to socket ridges. Inner hinge plates variously developed, some healed to close median notch but others with inner plates only modestly developed and hinge plate divided. Crura long, curved, concave anteriorly and flat- tened posteriorly. Median septum variously devel- oped and forming an apical chamber in some specimens. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 725f 152828a 16.6 13.2 15.4 7.7 100 152828b 17.3 16.1 17.2 12.6 100? 152828c 18.3 16.8 17.0 12.0 110 USNM 740j 154595a 16.6 15.6 20.0 9.6 110 (holotype) STRATIGRAPHIC OCCURRENCE.—Bell Canyon For- mation (Hegler, Pinery, and Rader members). LOCALITIES.—Hegler: USNM 731, 732a, 740c. Pinery: USNM 725n, 733. Rader: AMNH 403; USNM 725f, 725g, 740a, 740i, 740j. DIAGNOSIS.—Leiorhynchiform Phrenophoria with costae extending to umbonal region, flanks with flattened costae, and fold with four or five costae. TYPES.—Holotype: USNM 154595a. Figured par- atypes: USNM 152828a, 154595a,b; l54665a,b; 154736-1, 154770a-d; 155074f,c; 155075-1. Measured paratypes: USNM 152828a-c. Unfigured paratypes: USNM I52828b,c; 154736a-k; 154665b. COMPARISON.—This is a much larger and differ- ently ornamented species than P. pinguis (Girty). The costae are more angular and broader, the brachial valve is much deeper, and the pedicle valve develops a long anterior tongue. It differs from P. pinguiformis, new species, in having much more delicate valves, a much more convex brachial valve, and a different shape and outline. It is not likely to be confused with P. subcarinata Cooper and Grant, which has stronger costae, is more elon- gated, has more nearly equally deep valves, and the costae do not extend as far posteriorly as on the Bell Canyon species. The elongate costation, inequivalved profile, long tongue on the pedicle valve, and the costation of the flanks separates P. perplexa from P nesiotes, new species. DISCUSSION.—The exterior of this species, with its broad and irregular costae that become some- what vague on the lateral slopes, has a strong leiorhynchid aspect. The costae are stronger, how- ever, than on most leiorhynchids and extend far- ther toward the beaks. The interior of this species also presents some interesting features in the bra- chial valve. The inner hinge plates in all the adult speci- mens available do not coalesce but act in the nature of deltidial plates partly bridging the gap between the proximal ends of the crura. In one of the largest specimens the anterior ends of the inner plates approach closely but do not join. It is prob- able that they do join in some specimens to leave a dorsal foramen. The inner hinge plates at the posterior appear to join the valve floor apically to form a small apical chamber that is only visible in broken specimens. Anteriorly the chamber seems to be closed by dorsal coalescence of the plates to form the median septum which is always apical and never conspicuous. Perhaps the most perplexing feature of this species is the erratic development of the median septum. In some specimens it is well formed and quite typical of Phrenophoria. In others it seems to be aborted, perhaps partially resorbed, but at any rate not well formed. It is possible that the septum in these specimens was not well silicified NUMBER 21 1965 but the good preservation of other features is not in accordance with this view. In two specimens the hinge plate meets the valve floor apically and the median septum is extended anteriorly as a low ridge. It seems evident from the specimens at hand that this is a variable feature in a possibly un- stable species. Phrenophoria pinguiformis, new species PLATE 518: FIGURE 1-24 Large for genus, outline subtrigonal to oval; apical angle of adult 90° to 100°; posterolateral extremities straight, lateral margins somewhat nar- rowly rounded; anterior margin truncated but me- dially emarginate. Anterior commissure broadly uniplicate. Beak short suberect; foramen small sub- mesothyridid. Surface strongly semicostate, costae few, broad, narrowly rounded to subangular. Valves of unequal depth, brachial valve deeper. Pedicle valve gently convex in lateral profile, maximum convexity posterior to midvalve, where narrow keel forms; anterior profile nearly flat. Umbonal and posterior region marked by low, subangular ridge extending from beak to about midvalve; there lost in sulcus. Beak ridges short but strongly angular. Sulcus broad and shallow, defined only at anterior half, occupied by two or three costae. Flanks gently sloping, occupied by three or four costae. Brachial valve unevenly convex in lateral profile, most convex in posterior half, anterior half flat- tened; anterior profile broadly domed, top slightly concave at midvalve, sides strongly curved and nearly parallel. Umbonal region marked by shal- low, narrow sulcus extending to anterior margin and occupied by 2 costae. Fold low, flattened, usually composed of 4 or 5 costae, median two depressed below level of bounding ones. Flanks swollen. Anterior usually strongly geniculated to meet fold of pedicle valve. Pedicle valve interior with small, elongated, cor- rugated teeth parallel to valve margin; dental plates thick, subparallel and forming somewhat nar- row delthyrial chamber. Muscle field subtrigonal to trapezoidal in outline, narrow proximal extremity just within anterior end of delthyrial cavity, ad- ductor scars forming long triangular patches united medially and surrounding adductor scars. Brachial valve interior with small cardinalia; socket ridges moderately thick and overhanging corrugated sockets; outer hinge plate small and narrow; crural bases narrow; inner hinge plates variable, attached to median septum, depressed and medially grooved in some specimens but in others with healed suture and flat surface. Median septum delicate, and uniformly thin throughout its length. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 728 148394a 9.6 8.0 9.8 4.4 80 148394b 12.6 10.8 11.3 6.3 85 148394c 14.2 12.4 13.6 6.9 90 148394d 15.5 14.1 17.2 11.5 95 148394e 17.4 15.2 17.9 11.0 90 (holotype) I48394f 17.7 15.8 17.7 10.6 95 148394g 18.5 16.6 18.0 10.6 95 STRATIGRAPHIC OCCURRENCE.—Cherry Canyon For- mation (Getaway Member). LOCALITIES.—AMNH 512, 600; USNM 728, 732. DIAGNOSIS.—Large coarsely costate Phrenophoria with emarginate anterior. TYPES.—Holotype: USNM I48394e. Figured par- atypes: USNM 148394d,h,n-p. Measured paratypes: USNM 148394a-d,f,g. Unfigured paratypes: USNM 148394a-c,f,g,i-m. COMPARISON.—This species suggests P. pinguis (Girty) and P. subcarinata Cooper and Grant of the Glass Mountains. It is readily distinguished from the former by its thicker shell, broader and more rounded costae, more robust form, swollen valves, and its geniculated front. It is unlike the Glass Mountains species in having a wider outline, less swollen valves, a wider fold and sulcus, emar- ginate anterior, and a more prominently sulcate umbonal region. DISCUSSION.—This species has thick and robust valves on which the details of the musculature are fairly well impressed and in which the various inte- rior structures are well developed. The exterior is variable, but the collection is too small to be sure of anything more than the extremes. Most speci- mens have 4 costae on the fold, but one has 3. The costae of some specimens are wider than that of others and give them the appearance of being more numerously costate, but the numbers are the same. 1966 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY Inside the pedicle valve the dental plates are fairly long and the musculature is well impressed; the field is somewhat triangular, with rather straight sides to the diductor scars. The adductor scars are well enclosed. In the brachial valve the sockets are strongly corrugated and the hinge plate shows the same types of variation noted in the type species. Several specimens have a narrow groove between the two inner hinge plates; in one specimen the inner hinge plates are overlapping, in others they unite with healed suture. A feature seldom seen in late Paleozoic rhyncho- nellids is the scar of attachment of the diductor muscles on the dorsal hinge plate. In one excep- tional specimen this appears as a short but wide pit under the apex. This pit has each extremity roughened. The structure is similar to that figured by Cooper (1959, pi. 6, figs. 14-17) in the Recent genus Notosaria. The adductor scars are fairly well preserved and form an elongate scar on each side of the median septum. Phrenophoria pinguis (Girty) PLATE 518: FIGURES 25-32; PLATE 522: FIGURES 8-13 Pugnax pinguis Girty 1909:319, pi. 21: figs. 21-21c Not Pugnoides pinguis (Girty), R. E. King, 1931:106, pi. 34: figs. 15-17 [= Antronaria voluminosa, new species]. The residues from the Guadalupe Mountains have produced only three specimens referable to this species, and we have not found it among any of the collections obtained by more conventional methods. The species may be rare, but it is also possible that the type specimen is so badly dam- aged that we have been unable to identify any others with it. Actually the damage does not seem sufficient to prevent discernment of the true char- acter of the species. The specimen has been squeezed sideways to such an extent that the right side (when viewed from the dorsal side) has been telescoped into the left side. Nevertheless, it seems clear that the holotype has a strong median sep- tum which is one of the requisite characters of Phrenophoria. The holotype is said to come from the "Dark Limestone" on the north side of Pine Spring Can- yon (chiefly float), probably from the Pinery Mem- ber of the Bell Canyon Formation. We have it from the Hegler Member at USNM 732a, the Pin- ery Member at USNM 725n, and the Capitan Formation at USNM 748a. The three specimens besides the type are two brachial valves showing the interior well. The third specimen is a nearly perfect complete one. They all have the characteristic strong and long median septum of Phrenophoria as well as the undivided hinge plate. TYPES.—Holotype: USNM 118570. Figured hypo- types: USNM 154755, 154784. Phrenophoria planifrons, new species PLATE 518: FIGURES 33-38 Large for genus, strongly pentagonal in outline, width slightly greater than length; sides moderately rounded; posterolateral extremities short, forming right angle. Valves subequal in depth. Anterior margin nearly flat and strongly truncated. Anterior commissure strongly uniplicate. Beak short, sub- erect; foramen moderately large, submesothyridid. Maximum width near midvalve. Surface finely costate, costae not reaching umbones. Growth lines crowded at anterior. Pedicle valve evenly and moderately convex in lateral profile; broadly and gently convex in ante- rior profile. Umbonal region slightly convex me- dially, convexity extending to sulcus; median re- gion gently convex. Sulcus originating anterior to midvalve, broad and shallow, defined best at mar- gin, forming broad and flat tongue geniculated about 90°. Sulcus occupied by 5 costae. Flanks gently concave and marked by 5 costae. Brachial valve gently convex in lateral profile, umbonal region most convex; anterior profile forming square dome with straight and parallel sides and flat top except for slightly concave median region. Umbonal region marked by shallow sulcus extending to anterior margin. Fold flat, low, short, defined at anterior, occupied by 6 costae, median four depressed and median two more deeply sunk than others. Flanks narrow, rounded and precipi- tous, marked by 4 costae, these more rounded than those on flanks of opposite valve. Interior not known. MEASUREMENTS (in mm).—Specimens USNM 148378a holotype and b (paratype), respectively: length 15.2, 15.3; brachial valve length 13.0, 13.1; maximum width 16.6, 15.8; thickness 13.6, 12.7; apical angle 90°, 90°. NUMBER 21 1967 STRATIGRAPHIC OCCURRENCE.—Cathedral Moun- tain Formation (Institella Zone). LOCALITY.—USNM 702b. DIAGNOSIS.—Pentagonal Phrenophoria with great- ly flattened anterior. TYPES.—Holotype: USNM 148378a. Unfigured but measured paratype: USNM 148378b. COMPARISON AND DISCUSSION.—This species is unusual for thick shell, triangular lateral profile, and the flat front with its strongly lamellose orna- ment. The anterior surfaces of both valves are strongly geniculated, the two geniculated parts meeting to form the broad base for the shell. The ornament is fairly fine and the fold and sulcus sub- dued. The fold has the median costae sunken in a shallow sulcus as usual for the genus. No other species has this bizarre form. Phrenophoria planiventra, new species PLATE 518: FIGURES 39-50 Medium size for genus, longer than wide, outline oval to subtrigonal; posterolateral margins straight and forming angle of 90°. Sides narrowly rounded; anterior margin truncated. Anterior commissure strongly uniplicate; valves very unequal in depth and curvature, brachial valve having the greater degree of each. Surface semicostate, costae confined to anterior slopes that occupy anterior third. Costae broad and rounded. Beak suberect; foramen small, submesothyridid. Pedicle valve slightly convex in lateral profile, most convex in umbonal region; anterior profile irregular, median region narrowly convex, areas bounding middle gently concave, with flanks nar- row and abruptly deflected. Umbonal and median regions marked by narrow fold disappearing at sulcus; fold strongest near midvalve. Sulcus broad and shallow, originating just anterior to midvalve, occupied by 2 broad costae and extending into short tongue geniculated at angle of about 90°. Flanks with 3 marginal costae. Beak ridges strong; planareas narrow. Brachial valve strongly convex in lateral profile, narrowly domed and with parallel sides in anterior profile. Umbonal and median regions swollen and marked by shallow, narrow, but prominent sulcus extending from beak to anterior margin; fold low convex longitudinally but flattened transversely, marked medially by depression of median costa continuous with sulcus from umbonal region. Flanks swollen and steep, marked by 3 or 4 broad, indistinct costae. Interior not known. MEASUREMENTS (in mm).—From locality USNM 703 holotype USNM 148381a: length 14.5, brachial valve length 12.5, maximum width 13.6, thickness 9.8, apical angle 90°. STRATIGRAPHIC OCCURRENCE.—Road Canyon For- mation. LOCALITIES.—USNM 703, 707e. DIAGNOSIS.—Medium-sized Phrenophoria having valves of greatly disproportionate convexity and depth and a few strong costae. TYPES.—Holotype: USNM 148381a. Unfigured paratype: USNM 148381b. Figured specimen: USNM 154754. COMPARISON AND DISCUSSION.—This species is similar to P. repugnans, new species, and P. de- pressa, new species, in the more than half of the posterior part that is smooth, and in the short costae. It is bigger than either of these two species and is more strongly costate than P. repugnans but less strongly costate than the other. This is a rare species in the Road Canyon Formation, only three specimens having been found. Phrenophoria repugnans, new species PLATE 519: FIGURES 1-18 Small for genus, moderately to strongly unequally biconvex; outline narrowly oval to subpentagonal, sides diverging between 75° and 110°; anterior commissure narrowly uniplicate; fold narrow, an- teriorly standing in high relief above flanks, begin- ning about 7 mm anterior to brachial beak; sulcus rather shallow, broadly trough-shaped, beginning about 6 mm anterior to pedicle beak, projecting as broad, strongly geniculated tongue into fold. Costae weak to moderately strong on fold, with middle one normally somewhat depressed, fine and low on flanks, beginning 6-8 mm anterior to beaks, numbering 3 on fold, 2 in sulcus, 3-6 (nor- mally about 5) on each flank. Growth lines absent over most of shell, rather strong and closely crowded near margins. Pedicle valve fairly flat in lateral profile, broadly concave in anterior profile; low longitudinal gable 1968 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY on smooth part of umbonal region; flanks normally slightly concave, prominent or reflexed in ventral direction; beak sharp, straight, flattened, with sharp beak ridges; lateral pseudointerareas wide, extend- ing from valve edge to beak ridge, only partly covered by overlapping edge of brachial valve; delthyrium triangular, with deltidial plates con- junct in adults, leaving elongate, eye-shaped, sub- mesothyridid foramen. Brachial valve strongly convex transversely, only slightly less convex longitudinally along crest of fold; umbonal region slightly flattened or longi- tudinally indented, continuing course of depression of median costa; beak blunt, apex within pedicle valve, beneath deltidial plates. Pedicle valve interior with strong hinge teeth, supported by strong, nearly vertical dental plates reaching floor of valve and with anterior edges distinctly separate from sides of valve. Muscle area subtrigonal, with apex between anterior edges of dental plates; individual marks not observed. Brachial valve interior with large undivided but medially notched hinge plate, bounded laterally by deep, anteriorly widening, apparently denticu- late sockets; crura diverging forward from anterior edge of hinge plate, strongly curved ventrally, flat dimension parallel to valve floor; median septum moderately high, but short, supporting hinge plate. Muscle area extending about one third length of valve, further details not observable. MEASUREMENTS (in mm).— and median costa of fold depressed below the others on the fold. TYPES.—Holotype: USNM I52829g. Figured par- atypes: USNM 152829b-e, 154759a, 154760. Mea- sured paratypes: USNM 152829a-f. Unfigured par- atypes: USNM 152829a,f; 154759b. COMPARISON AND DISCUSSION.—Phrenophoria re- pugnans is characterized by its relatively flat pedicle valve and strongly convex brachial valve, sharp beak ridges, 3 costae on the fold with the middle one normally depressed, numerous fine costae on the flanks, and by its moderately high, but rather short, median septum. The low median gable on the smooth part of the pedicle valve, and the slightly longitudinal depression of the umbonal region in the brachial valve are reminiscent of similar features in P. subcarinata Cooper and Grant and to a less degree in P. corpulenta, new species. Its flatly concave pedicle valve with winglike flanks bearing many fine costae, and its shortened median septum distinguish it from both of these species. The depressed median costa of the fold is similar to that in Tautosia elegans (Girty), but P. repug- nans differs in its narrower outline, finer and weaker costae on the flanks, and < flatter pedicle valve with less sharply reflexed flanks. Phreno- phoria repugnans is similar to T. galbina, new species, in shape, but attains a greater size, has stronger costae on the fold, a flatter pedicle valve, more prominent beak ridges, and depressed median costa on the fold. brachial apical valve thick- angle length length width ness (°) AMNH 591 152829a 5.0 4.4 5.5 2.2 97 152829b 7.8 6.8 8.0 3.3 91 152829c 9.3 8.3 9.9 4.6 88 152829d 9.7 9.1 9.9 8.1 92 152829e 10.4 9.6 11.4 8.7 106 152829f 11.0 9.9 11.8 9.0 97 152829g 9.8 8.9 10.8 8.3 88 (holotype) STRATIGRAPHIC OCCURRENCE.—Bone Spring For- mation; Skinner Ranch Formation (Sullivan Peak Member). LOCALITIES.—Bone Spring: AMNH 591. Sullivan Peak: USNM 722-1. DIAGNOSIS.—Small Phrenophoria with flatly con- cave pedicle valve, strongly swollen brachial valve, Phrenophoria subcarinata Cooper and Grant PLATE 522: FICURES 14-50; PLATE 553: FICURES 35-39 Phrenophoria subcarinata Cooper and Grant 1969:13, pi. 1: figs. 4-12. Larger than average for genus, strongly bicon- vex; outline bluntly triangular to elongate oval, sides diverging between 90° and 115°; anterior commissure uniplicate, fold low, beginning 6-9 mm anterior to brachial beak, sharply to gently genicu- lated near anterior; sulcus shallow, beginning 8-10 mm anterior to pedicle beak, strongly geniculate near anterior margin, forming short tongue. Costae broad, low, beginning 3-6 mm anterior to beaks, numbering 4-6 on fold, one less in sulcus, 4 or 5 on flanks. Concentric ornamentation consisting of faint striae; growth lines prominent or abundant NUMBER 21 1969 only near margins of some individuals, producing lamellar appearance. Pedicle valve with subcarinate crest or ridge along smooth part of beak area, flattening toward sulcus; beak sharp, not attenuate, slightly curved dorsally to suberect; beak ridges prominent, sharp, giving beak flattened aspect; lateral pseudointer- areas very narrow or absent, covered by overlap of brachial valve. Delthyrium triangular, base covered by pair of slightly arching deltidial plates, forming elongate oval submesothyridid foramen. Brachial valve with shallow longitudinal depression on smooth part of umbonal area posterior to fold; apex within pedicle valve, covered by deltidial plates. Flanks gently swollen, sloping steeply to margins. Pedicle valve interior with sides of delthyrium widely diverging anterior to deltidial plates, teeth parallel sides, supported by vertical dental plates reaching floor of valve. Muscle area lying anterior to edges of dental plates; adductor mark small, subcircular, in posterior part of muscle area; di- ductor scars larger, anteriorly expanding, surround- ing adductor mark laterally and anteriorly. Brachial valve interior with undivided triangular hinge plate, bounded laterally by strong socket ridges overhanging elongate, anteriorly widening, finely corrugated sockets; outer hinge plates broad, crura diverging anteriorly, strongly curved ven- trally, dorsal edges carinate; inner hinge plates fused, concave to convex; median septum high, thin, long, supporting hinge plate, extending for- ward to near anterior edge of muscle area, bisecting it. Muscle area elongate oval; posterior adductor scars elongate, narrow, oriented diagonally, diverg- ing anteriorly, contiguous with larger suboval ante- rior adductor scars. STRATIGRAPHIC OCCURRENCE.—Word Formation (China Tank, Willis Ranch, and Appel Ranch members; lens between Willis Ranch and Appel Ranch members). LOCALITIES.—China Tank: USNM 703e, 706c. Willis Ranch: AMNH 505. USNM 706, 706e. Appel Ranch: USNM 704, 715i, 719z, 727j. Lens: USNM 706b. DIAGNOSIS.—Oval, coarsely costate Phrenophoria with posterior of pedicle valve subcarinate and posterior of brachial valve sulcate. TYPES.—Holotype: USNM 148385e. Figured par- atype: USNM 148385c,d,f-i. Unfigured paratypes: MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 706b 148385a 12.9 11.0 11.2 9.3 70 148385b 13.0 11.4 11.0 9.1 70 148385c 13.8 12.0 11.9 9.4 80 148385d 15.6 14.1 14.9 10.8 90 148385e 17.5 15.6 17.5 14.4 100 (holotype) USNM 719z 152830a 15.5 13.0 13.6 14.0? 80 152830b 17.3 16.6 19.2 10.3? 100 USNM 706c 148387a 19.0 16.8 16.9? 15.0 95 USNM 148385a,b. Measured paratypes: USNM 148385a-d. Figured hypotypes: USNM 148387a; 152830a,b; 154783; 154785. Measured hypotypes: USNM 148387a; 152830a,b. COMPARISON AND DISCUSSION.—This species is fairly common in the Word Formation especially in the Willis Ranch Member. It is generally an elongate oval form of moderate size for the genus, with strong rounded to subangular costae. At the anterior margin the fold and sulcus are not strongly differentiated but generally three costae appear on the fold and the median one is de- pressed below the others. This species belongs to the same group as P. pinguis (Girty), and the new species P. pinguifor- mis, P perplexa, and P. vetula. It differs from the first of these in generally being smaller, having thinner shells, in having a more oval outline rather than triangular as in P. pinguiformis, the Getaway species, and in having less costae. It differs from P. perplexa in being smaller, having stronger and a lesser number of costae, in having an oval out- line, and in having the two valves more nearly the same depth. It differs from P vetula in size, shape, and ornamentation. Phrenophoria ventricosa, new species PLATE 523: FIGURES 1-11 Small for genus, strongly inequivalved, brachial valve strongly ventricose; outline longitudinally oval to subtrigonal; maximum width anterior to midvalve; sides gently rounded; anterior margin gently rounded. Beak short, straight to suberect; 1970 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY deltidial plates conjunct. Surface costate, costae narrowly rounded, 3 on fold, 2 in sulcus, and 3 or 4 on flanks. Pedicle valve gently convex in lateral profile, maximum convexity near midvalve; anterior profile gently concave. Umbonal region subcarinate and marked by extension of two costae of sulcus onto umbo, terminating near beak in some specimens, farther anteriorly in others. Sulcus originating at midvalve, narrow and deep, forming long narrow tongue; flanks narrow and flattened but extending moderately at anterolateral extremity. Brachial valve very deep and strongly convex in lateral profile, very narrowly and strongly domed in anterior view, with sides precipitous and paral- lel. Umbonal region marked by shallow, narrow sulcus extending onto fold but not depressing median costa significantly. Midregion strongly bellied. Fold originating at midvalve, low and fol- lowing curvature of valve; fold narrow. Flanks moderately swollen and depressed below anterior part of fold. Pedicle valve interior with strongly developed dental plates. Brachial valve interior with undi- vided hinge plate and long slender crura concave toward midvalve. Median septum, long and slender. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 703d 148382a 10.5 9.4 10.0 8.8 80 (holotype) 148382b 9.5 8.0 8.6 7.5 70 148382c 8.7 7.5 8.3 6.1 80 148382d 8.2 7.4 7.9 6.4 80 148382e 9.6 8.2 9.8 8.0 80 STRATIGRAPHIC OCCURRENCE.—Road Canyon For- mation. LOCALITY.—USNM 703d. DIAGNOSIS.—Small, strongly ventricose Phreno- phoria with narrow fold and sulcus. TYPES.—Holotype: USNM 148382a. Figured par- atypes: USNM 148382b,e-g. Measured paratypes: USNM 148382b-e. Unfigured paratypes: USNM 148382c,d. COMPARISON AND DISCUSSION.—This is a small and very ventricose species not at all typical of the genus. Its form and size suggest those of the new species P. planiventra, P. repugnans, and P. de- pressa. It differs from the first in being smaller and more completely costate; from the second in having a swollen brachial valve and the costae farther posteriorly; and from P depressa it differs in being more completely and more strongly costate, al- though it is about the same size. The most remarkable features of these specimens are the concentric bands of darker color that sug- gest a possible gaily colored shell. The bands are narrow and fairly evenly spaced. Only 4 of the 6 specimens exhibit the bands. If these prove to be color bands, this will be one of the few colored rhynchonellids known (Richter 1919:83). Phrenophoria vetula, new species PLATE 518: FIGURES 51-59; PLATE 519: FICURE 38; PLATE 524: FIGURES 10-14; PLATE 541: FICURES 59-63; PLATE 552: FIGURE 17 Large for genus, wider than long, outline sub- trigonal; posterolateral margins gently convex, forming angle of 90° to 110°. Sides narrowly rounded; anterior margin truncated. Anterior com- missure uniplicate. Beak nearly straight, short, with fairly large submesothyridid foramen. Surface co- state but umbones smooth; costae broad and rounded, 3 on fold, 2 in sulcus, and 4 on each flank; costae of brachial valve lower and more rounded than those of opposite valve. Pedicle valve moderately convex in lateral pro- file, broadly convex in anterior profile, medial region narrowly convex. Umbonal region subcari- nate, forming low fold uniting with median costae occupying sulcus. Sulcus originating anterior to midvalve, extending into short tongue. Flanks con- cave, narrow. Brachial valve moderately convex in lateral pro- file, broadly domed in anterior profile. Umbonal region moderately deeply sulcate, sulcus depressing median costa of fold. Median region moderately swollen. Fold low, defined only at anterior third; flanks moderately swollen and rounded. Pedicle valve interior not known. Brachial valve interior with thin socket ridges, broad outer hinge plates and inner hinge plates united with healed suture. Median septum delicate, high, and long, reaching about to midvalve. STRATIGRAPHIC OCCURRENCE.—Cathedral Moun- tain Formation. LOCALITIES.—USNM 702, 702b, 702inst, 702-low, 721u. NUMBER 21 1971 MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 721u 154757a 17.7 15.5 17.3 12.7 101 (holotype) USNM 702 152832 14.6+ 13.3 15.5 12.4 95 USNM 702inst 152831 15.0? 12.6? 17.8 7.8? 105 DIAGNOSIS.—Large Phrenophoria with keeled ped- icle umbo and strong rounded costae. TYPES.—Holotype: USNM 154757a. Figured par- atypes: USNM 148373, 152832, 154757b, 154888, 154914. Measured paratypes: USNM 152831, 152832. COMPARISON AND DISCUSSION.—This is a rare spe- cies and the specimens are not well preserved. Nevertheless, this is one of the earliest species of the genus and an important representative of it. The specimens are most like P. subcarinata Cooper and Grant in having the keeled pedicle valve umbo, the depression in the fold of the brachial valve, and strong costae. It differs from P. subcarinata in having coarse, rounded costae with 3 on the fold, and in having a more transverse outline and smaller cardinalia. It is quite unlike P. pinguiformis, new species, in shape, outline, and thickness of costae as well as interior details. It is also larger and more strongly costate than P. pinguis (Girty). Inside, the brachial valve has an undivided hinge plate with the inner hinge plates united without suture but a minute chamber is present between these plates and the long median septum. One of the specimens assigned to this species is elongated and not characteristic. It is similar to an elongate form which is a variant of P. pingui- formis. It is likely that elongate forms may appear among any of the species groups. Phrenophoria species 1 PLATE 519: FIGURES 35-37 A fine species of Phrenophoria is indicated by two brachial valves and a fragmentary third. The best specimen measures 14 mm in length, 15 mm in width, and 7.5 mm in thickness. The sides are well rounded and the umbonal region is sulcate, the sulcus continuing onto the fold, which is short and flattened on its surface. The fold orig- inates at about midvalve, is low and slightly spreading, and contains 6 costae, the median ones of which are slightly depressed. The flanks are well rounded and swollen, with steep sides. They have 6 costae and a possible faint seventh. The interior has corrugated sockets, a small undi- vided hinge plate supported by a long, delicate but strong median septum. STRATIGRAPHIC OCCURRENCE.—Skinner Ranch For- mation (Sullivan Peak Member). LOCALITIES.—USNM 707d, 722h. Phrenophoria species 2 A second named species of Phrenophoria is represented by three specimens, two of which are complete but partly crushed. They are wider than long, strongly costate, one with 4 costae on the fold but the other with only 3. The flanks are provided with 5 costae which are smaller and more angular than those of the fold. A marked depres- sion runs from the umbonal region through the fold to the anterior margin. The better preserved specimen measures 14.8 mm long, 17.9 mm wide, and 9.7 mm thick. The specimens come from the Road Canyon Formation at USNM 707e. Phrenophoria species 3 PLATE 508: FIGURES 68-71 A large semicostate brachial valve with narrow, undivided hinge plate supported by a long, thin, elevated median septum indicates an undescribed species. The specimen is from the Road Canyon Formation at USNM 721j. Holosia, new genus [Greek holos (all)] Holosia is suggested for a group of species having the internal characteristics of Phrenophoria but having elongated shells that are completely costate. TYPE-SPECIES.—Holosia regularis, new species. DISCUSSION.—This genus includes only a few spe- cies at the present time, all rare. They make a striking contrast to such typical specimens of Phrenophoria as the type species and the widely triangular form called Tautosia Cooper and Grant (1969). 1972 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY Holosia ovalis, new species PLATE 523: FIGURES 12-23 Large for genus, elongate oval in outline, sides gently expanding to widest part anterior to mid- valve, there narrowly rounded; anterior margin rounded; anterior commissure uniplicate. Beak short, suberect, foramen submesothyridid. Costae narrowly rounded, nearly reaching beaks, 4 on fold, 3 on flanks. Pedicle valve gently convex in lateral profile, maximum convexity posterior to midvalve; anterior profile gently concave with flanks sharply reflected in dorsal direction. Umbonal region smooth, nar- rowly convex; median region gently convex to concave; sulcus shallow, broad, originating at mid- valve, forming strongly geniculated short tongue at anterior. Sulcus containing 2-4 costae; flanks flattened, beak ridges short, angular. Brachial valve moderately convex in lateral pro- file, strongly domed in anterior profile, sides sub- parallel. Umbonal region smooth, median region moderately swollen. Fold low, narrow, originating at midvalve, occupied by 3 or 4 costae. Flanks swol- len but precipitous, occupied by 6 curving costae. Interior imperfectly known; median septum long, strongly elevated and thin, supporting broad, un- divided hinge plate. MEASUREMENTS (in mm).—Holotype USNM 152833c: length 15.5, brachial valve length 13.4, width 13.9, thickness 12.4, apical angle 80°. STRATIGRAPHIC OCCURRENCE.—Road Canyon For- mation. LOCALITY.—USNM 707e. DIAGNOSIS.—Elongate Holosia with nearly com- pletely costate valves, only the umbones being smooth. TYPES.—Holotype: USNM 152833c. Figured par- atypes: USNM 152833a,b,d. COMPARISON.—This species is like Holosia ovoi- dea, new species, but differs in having a less ele- vated fold and less pronounced sulcus, stronger costae, and a truncated anterior. DISCUSSION.—This species is represented by four specimens, two of them complete and fairly well preserved, a third with one side broken away reveal- ing the interior with its long median septum, and the fourth a brachial valve showing the hinge plate. Holosia ovoidea, new species PLATE 523: FICURES 24-28 Large for genus, elongate oval in outline, sides gently rounded, anterior margin somewhat narrow- ly rounded; valves of unequal depth, brachial valve deeper; apical angle 90°. Anterior commissure strongly uniplicate. Beak short; foramen not seen; surface nearly completely costate except in umbonal regions of both valves. Costae fine and narrow, 5 on fold, and 4 or 5 on flanks. Concentric lines crowded along anterior commissure. Pedicle valve moderately and evenly convex in lateral profile except for sharply geniculated tongue; anterior profile broadly and gently convex; umbonal and median regions slightly keeled; sul- cus scarcely discernible, marked only at anterior. Flanks narrow and merging into convexity of valve. Brachial valve gently convex in lateral profile except in vicinity of fold, there strongly genicu- lated in ventral direction; anterior profile narrowly domed, top nearly flat, flanks sharply deflected and approximately parallel. Umbonal and median re- gion gently swollen; umbonal region with shallow narrow sulcus beginning near midvalve. Fold scarcely defined at anterior, best seen along com- missure. Flanks flatly convex, precipitous. Interior details, except for long crura, not visible. MEASUREMENTS (in mm).—Holotype USNM 148398: length 15.8 plus, brachial valve length 14.5, width 14.1, thickness 12.0, apical angle 90°. STRATIGRAPHIC OCCURRENCE.—Cherry Canyon For- mation (Getaway Member). LOCALITY.—USNM 728. DIAGNOSIS.—Oval Holosia with poorly developed fold and sulcus. TYPES.—Holotype: USNM 148398. COMPARISON.—Only one other species, Holosia ovalis, new species, is like this one, but the two are different in detail. Holosia ovalis has a well-marked fold and sulcus and much stronger costae than the Guadalupe Mountains species. The peculiar genic- ulation at the anterior of the brachial valve of H. ovoidea is unlike the steep but evenly convex slopes of the Glass Mountain species. DISCUSSION.—Only a single specimen of this spe- cies has been found. When one considers the large samples of other species obtained at this locality, the great rarity of this species becomes evident. The specimen is broken at the beak and thus the NUMBER 21 1973 crura can be seen. A trace of the median septum is visible on the outside, in the middle of the umbonal depression. The ornament of this specimen is unusual for the complete cover it makes of the entire shell including the beaks. The costae are also very reg- ular and evenly spaced. Nevertheless, the brachial valve bears a median depression suggesting Phreno- phoria. The hinge plate is narrow and the inner hinge plates are united in a small anticline. The median septum is stouter than usual in Phrenophoria. Holosia regularis, new species PLATE 523: FICURES 22-32 Usual size for genus, longer than wide, long posterolateral margins converging at about 70°. Maximum width anterior to midvalve; outline elongate subtrigonal; sides narrowly rounded and anterior margin gently rounded. Anterior commis- sure gently and broadly uniplicate. Beak short, straight, with small deltidial plates. Costae extend- ing from beaks to anterior margin, direct and regular, and broad and angular, 5 on fold, one fewer in sulcus, and 4 on flanks. Pedicle valve moderately but unevenly convex in lateral profile, most curvature in anterior region; anterior profile broadly, evenly and moderately convex. Umbonal region moderately convex but median region somewhat swollen. Sulcus broad and very shallow, not well defined, beginning anterior to midvalve; tongue short and broad. Flanks nar- row, convex, steep. Brachial valve about same depth as pedicle valve, fairly evenly and moderately convex in lateral profile; anterior profile broadly and moderately convex with moderately steep sides. Umbonal and median regions gently convex; fold originating anterior to midvalve, broad and flattened, scarcely elevated; flanks narrow, moderately swollen, and steep. Pedicle valve interior with small knoblike teeth, dental plates plastered against valve wall, visible but without umbonal cavities. Muscle field small. Brachial valve interior with small narrow hinge plate having stout socket ridges, narrow outer hinge plates, narrow crural bases, and inner hinge plates coalesced to form elevated ridge. Median septum elevated, stout, supporting hinge plate but extending anteriorly only about a fifth of valve length. MEASUREMENTS (in mm).—Holotype USNM 152834: length 11.0, brachial valve length 10.0, width 10.9, thickness 7.5, apical angle 70°. STRATIGRAPHIC OCCURRENCE.—Bell Canyon For- mation (Rader Member). LOCALITY.—AMNH 401. DIAGNOSIS.—Medium-size Holosia having com- pletely costate valves and nearly obsolete dental plates. TYPES.—Holotype: USNM 152834. COMPARISON.—This species is readily distin- guished from Phrenophoria subcarinata Cooper and Grant, and P. pinguiformis, new species, by its smaller size and the completely costate shell. In the latter respect it resembles Holosia ovoidea, and H. ovalis, both new species, but it is much smaller, has different proportions, stronger costae less thick- ness, and lacks the long anterior tongue of the other two species. Holosia species 1 PLATE 519: FIGURES 39, 40 A large nearly circular brachial valve 16 mm long by 19 mm wide and completely costate repre- sents an undescribed species. The median region and umbonal area are marked by a shallow depres- sion which becomes a low fold anteriorly. Costae are narrowly rounded and number 6 on the low poorly preceptible fold and about 8 on the flanks. The strong median septum supports a narrow hinge plate not quite completely united or damaged. STRATIGRAPHIC OCCURRENCE.—Word Formation (China Tank Member). LOCALITY.—USNM 706c. Genus Tautosia Cooper and Grant, 1969 Tautosia Cooper and Grant 1969:14. Tautosia includes a group of species related to Phrenophoria that externally is typically wellerelli- form. The species are generally transverse and have a strong fold and sulcus, are usually paucicostate, and have strong, angular anterolateral extremities 1974 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY on the pedicle valve. Internally these species are like Phrenophoria with a strong median septum in the brachial valve and an undivided hinge plate with modified falcifer crura. TYPE SPECIES.—Tautosia fastigiata Cooper and Grant (1969:14, pi. 4: figs. 11-14). DISCUSSION.—As with many genera, a clean line of distinction cannot always be drawn between some species. We have placed under Phrenophoria a few species that in external appearance are some- what wellerelliform but which do not completely accord with Tautosia. Generally the name Phreno- phoria may be used for the somewhat elongate or oval forms with leiorhynchiform exterior and Tautosia for those transverse species with strong costae. Tautosia angulata, new species PLATE 521: FIGURES 22-29 Usual size for genus, widely and angularly pen- tagonal in outline; wider than long with postero- lateral shoulders narrowly rounded and sides sloping medially; posterolateral margins gently concave, apical angle about 1110. Anterior margin truncated; anterior commissure uniplicate. Surface semicostate, costae thick and distant, 3 on fold, possible on each flank. Pedicle valve much shallower than brachial valve, gently convex in lateral profile but broadly and fairly deeply concave in anterior profile. Sulcus and median costae originating at midvalve; poste- rior half somewhat flattened with moderate slopes to posterolateral extremities; flanks narrow, con- cave, and with steep slopes. Brachial valve flatly convex in lateral profile with most convexity in anterior region; anterior profile strongly domed with gently rounded top but pre- cipitous slopes. Fold originating near midvalve, flat-topped, not strongly elevated. Flanks depressed, very narrow, and narrowly rounded. Pedicle valve interior unknown. Brachial valve interior with long slender median septum. MEASUREMENTS (in mm).—Holotype USNM 154767: length 10.5, brachial valve length 10.3, width 13.2, thickness 8.2, apical angle 111°. STRATIGRAPHIC OCCURRENCE.—Road Canyon For- mation. LOCALITY.—USNM 732j. DIAGNOSIS.—Angularly pentagonal Tautosia with thick and rounded costae on fold and sulcus and flanks consisting of one costa. TYPES._Holotype: USNM 154767. COMPARISON.—In its squat pentagonal outline and strong distant costae this species is unlike any other known Tautosia. The specimen is mostly silica filled, but a part of the long slender median septum is clearly exhibited in a fracture in the shell made after the specimen was photographed. Tautosia distorta, new species PLATE 544: FIGURES 41-47 Small for genus, subpentagonal in outline; wider than long; maximum width anterior to midvalve; sides narrowly rounded; anterior margin broadly curved. Beak erect; foramen small; deltidial plates conjunct. Anterior commissure strongly uniplicate. Posterior surface smooth but anterior strongly costate; costae few and angular, 3 on fold, 2 or 3 on flanks. Pedicle valve gently but unevenly convex, um- bonal region moderately swollen; anterior profile broadly concave. Sulcus originating just anterior to umbonal region and posterior to midvalve, broad and deep with long steep slopes to tongue; costae in sulcus extending onto umbonal region. Tongue long and strongly serrated, with broad angle of geniculation. Flanks narrow and strongly deflected in ventral direction. Brachial valve nearly flat to slightly concave in lateral profile but forming flat-topped, broad dome in anterior profile. Lateral slopes short but steep. Umbonal region marked by long depression ending at distal termination of median costa of fold; fold originating near midvalve, nearly flat to slightly concave, distal margin slightly elevated; flanks depressed, narrow, and completely occupied by costae. Interior of pedicle valve with strong dental plates and small teeth. Interior of brachial valve with long median septum visible through hole in holotype. MEASUREMENTS (in mm).—Holotype USNM 153488a: length 12.0, brachial valve length 10.0, width 13.3, thickness 10.0, apical angle 91°. STRATIGRAPHIC OCCURRENCE.—Word Formation (Appel Ranch Member). NUMBER 21 1975 LOCALITY.—USNM 727j. DIAGNOSIS.—Small Tautosia with angular outline, oblique fold, and depressed lateral profile of the brachial valve. TYPES.—Holotype: USNM 153488a. Figured par- atype: USNM 153488b. COMPARISON.—This species is unique in the genus, with its depressed profile and relatively shallow valves. It is similar to Tautosia transenna from the Word Formation, but that species has a less prominent fold, weaker costae, and different profiles. The two type specimens are the only ones of this species recovered from the residues. Tautosia elegans (Girty) PLATE 519: FIGURE 24; PLATE 523: FIGURES 33-51; PLATE 553: FIGURE 40; PLATE 780: FIGURES 66-68 (in part V) Pugnax elegans Girty, 1909:315, pi. 15: figs. 13-14a. Not Pugnoides elegans (Girty) R. E. King, 1931:106, pi. 33: figs. 12-13 [= Pontisia stehlii Cooper and Grant, 1969] or pi. 34, fig. 4 [= Antronaria speciosa, new species]. Not Wellerella elegans? (Girty) Stehli, 1954:335, pi. 25: figs. 13-17 [= Antronaria speciosa, new species]. Not Pugnax bidentata Girty [part], 1909:318, specimen USNM 118569b. Average size for genus, biconvex, somewhat in- flated; outline bluntly and transversely triangular, sides diverging between 80° and 120°; profile nar- rowly subtrigonal; commissure strongly uniplicate; fold beginning 6-8 mm anterior to dorsal beak, increasing in height to anterior margin, profile of fold slightly convex; sulcus moderately deep, begin- ning 6-8 mm anterior to ventral beak, maximum convexity between anterior points of costae on flanks. Costae weak to moderately strong, beginning 5-8 mm anterior to beaks, crests angular on fold and pedicle flanks, bluntly rounded in sulcus and on brachial flanks, numbering 2-4 on fold, nor- mally 3, with median costa slightly, to strongly depressed, one less in sulcus, 2-5 on each flank, normally 3. Concentric ornamentation not ob- served; growth lines normally present only near margins. Pedicle valve slightly inflated on smooth pos- terior area anterior to beak; flanks slightly to strongly reflexed; lateral profile gently convex; anterior profile broadly and gently concave; beak sharp, moderately attenuate, with blunt beak ridges; lateral pseudointerareas narrow, partly cov- ered by slightly arched trapezoidal conjunct del- tidial plates anteriorly labiate or alate in adults, foramen elongate oval, mesothyridid to submeso- thyridid. Brachial valve deeper and more strongly convex from beak to flanks than opposite valve; smooth part of beak area slightly flattened or evenly arched transversely; apex within pedicle valve, covered by deltidial plates. Flanks moderately swollen and convex. Pedicle valve interior with delthyrium spreading widely anterior to deltidial plates; teeth elongate, parallel to sides, supported by dental plates reach- ing valve floor. Umbonal cavities narrow, muscle area bluntly triangular, lying just anterior to dental plates; adductor scars median, forming small oval impression; diductor scars large, lateral to ad- ductors, converging to median line anterior to adductors. Brachial valve interior with undivided triangular hinge plate, bounded laterally by deep, anteriorly expanding, finely corrugated sockets; crura strong, attached to sloping, broad outer hinge plates, di- verging anteriorly and strongly curved ventrally, slightly twisted, with dorsal edges keeled; inner hinge plates united, often medially arched at their junction. Median septum variable, usually high, thin, long, supporting hinge plate, extending to near middle of muscle area, bisecting it. Muscle area oval; posterior adductor scars narrow, ante- riorly diverging from median septum, anterior adductor scar large, extending beyond median septum. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 738 148332a 8.0 7.0 8.1 4.4 88 148332b 8.8 8.2 10.0 c.5. 95 148332c 10.4 9.2 12.3 c.6. 98 148332d 12.0 10.6 14.0 6.9 117 148332e 11.0 10.0 15.3 9.3 112 118565 11.0 10.1 14.4 7.8 105 (lectotype) 118565a 8.9 7.9 10.8 7.4 105 USNM 738b 152835a 7.3 6.7 8.0 3.9 90 152835b 8.3 7.7 10.3 4.9 105 152835c 10.0 8.8 11.5 6.0 100 152835d 10.3 9.1 12.4 7.9 951976 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY STRATIGRAPHIC OCCURRENCE.—Capitan Formation; Bell Canyon Formation (Pinery, Rader, and Lamar members). LOCALITIES.—Capitan: USGS 2926 (green); USNM 737a, 739, 740, 740n, 740k. Pinery: USNM 733. Rader: AMNH 403; USNM 725g, 740j. Lamar: AMNH 37, 38, 40, 401, 430; USNM 725e, 728p, 738, 738b. DIAGNOSIS.—Triangular Tautosia with median costa of fold depressed. TYPES.—Lectotype: USNM 118565. Figured hypo- types: USNM 154758; 157490c,d; 154791a,c,d,e; 154921. COMPARISON.—Tautosia elegans is characterized by its triangular outline, only slightly convex bra- chial profile along the crest of the fold, commonly slightly depressed median costa on the fold, weak costae on the brachial flanks, and its prominent, thin, long median septum in the brachial valve. It most nearly resembles T. transenna, new species, from lower in the Guadalupian, differing in its wider outline (in adults), normally depressed mid- dle costa of the fold, normally 2 or 3 weaker costae on the flanks instead of 3 or 4 strong costae, somewhat more convex profile of the fold, and costae that begin farther back toward the beaks. The depressed middle costa of the fold produces a recess in the anterior margin of this species, a feature not present in T. transenna. Tautosia ele- gans also is externally similar to Wellerella girtyi, new species, from which it differs in its less longi- tudinally convex, and therefore more protruding fold, its normally depressed median costa on the fold, more transverse and triangular outline, and high median septum. These features also distin- guish it from Pontisia stehlii, new species, from the Leonardian of West Texas, and Wellerella osagensis (Swallow) from the Pennsylvanian. Apparently on the basis of the depressed median costa, this species was identified by R. E. King (1931) and Stehli (1954) with specimens that now are called Antronaria speciosa, new species. Tauto- sia elegans is a rare Guadalupian species, and does not occur in the Leonardian with A. speciosa, from which it differs in its smaller size, less strongly and less consistently depressed median costa, less strongly transverse outline, fewer and weaker costae on the flanks, and especially in its high median septum. The general aspect of T. elegans is rather com- mon, and several foreign species are similar. Pugnax pseudoutah Huang (1933) from the Permian of China is similar in profile, but is not as transverse nor as triangular, and it has stronger costae on the fold, of which the median one is not depressed, and fewer, weaker costae on the flanks. Rhyncho- nella edelsteini Tschernyschew (1914) is smaller, more convex in profile, and less transverse in out- line, although it has a similarly depressed median costa on the fold. Tautosia elegans differs from Rhynchonella negrii Gemmellaro (1899) in its de- pressed median costa, more consistently 3 costae on the fold, more transverse outline, larger size, and more prominent fold. DISCUSSION.—This is a variable species on the exterior. The collection includes a fair number of lots from several localities but none is represented by a collection large enough to give a good idea of its variation. It is possible that subsequent col- lecting will show the presence of more than one species. Tautosia expansa, new species PLATE 524: FIGURES 1-9 Small for genus, wider than long, maximum width near midvalve; outline subtrigonal to sub- pentagonal; posterolateral margins forming angle of about 90°; sides narrowly rounded; anterior margin truncated to slightly emarginate. Anterior commissure uniplicate. Beak moderately long, foramen oval, often encroaching on apex, deltidial plates disjunct. Surface except umbones costate, costae broadly rounded and somewhat flaring ante- riorly, 3 or 4 (rarely 2) on fold, one less in sulcus, and 4 or 5 on flanks. Pedicle valve gently but unevenly convex in lat- eral profile, maximum convexity between mid- valve and umbo; anterior profile very slightly con- vex, flanks scarcely deflected. Umbonal region swollen; sulcus originating near midvalve, usually fairly broad and shallow, and produced into short tongue. Flanks flattened and slightly deflected. Brachial valve slightly deeper than pedicle valve, moderately and evenly convex in lateral profile, moderately and broadly domed in anterior profile, sides moderately steep. Umbonal region moderately convex but median region swollen; fold originating at midvalve, low, anteriorly spreading, moderately NUMBER 21 1977 convex in longitudinal section, only slightly ele- vated anteriorly. Flanks moderately swollen, slightly depressed below fold. Pedicle valve interior with strong dental plates. Brachial valve interior with strong socket ridges and broad outer hinge plates supporting long curved crura, narrow near base but expanding dis- tally, giving appearance of being twisted near junc- tion with hinge plate. Inner hinge plates medially coalesced but anteriorly notched. Median septum thin, not extending to midvalve. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 747 148589a 7.2 6.1 8.1 4.6 90 148589b 7.4 6.4 8.0 4.3 90 148589c 6.7 5.8 7.4 4.2 90 148589d 6.4 5.6 6.9 3.5 85 (holotype) 148589e 6.4 5.5 6.9 3.8 85 148589f 6.0 5.0 6.3 3.4 80 STRATIGRAPHIC OCCURRENCE.—Bone Spring For- mation (Cutoff Member). LOCALITY.—USNM 747. DIAGNOSIS.—Tautosia with soft contours and low fold. TYPES.—Holotype: USNM 148589d. Figured par- atypes: USNM 148589c,e,g,. Measured paratypes: USNM 148589a-c,e,f. Unfigured paratypes: USNM 148589a,b,f. COMPARISON.—This species superficially looks like Wellerella girtyi, new species, but that species is a larger one with half the valve smooth at the pos- terior end. Wellerella nitidula and Pontisia frank- linensis are.small new species but both of them are strongly convex and attain a greater thickness than the Cutoff specimens. This is true also of most of the Pennsylvanian species figured by Dunbar and Condra (1932) except for W. delicata. The latter is ornamented quite differently from the Cutoff species. Tautosia fastigiata Cooper and Grant PLATE 524: FIGURES 15-53; PLATE 525: FIGURE 1 Tautosia fastigiata Cooper and Grant, 1969:14, pi. 4: figs. 11-14. Large for genus, biconvex, flattened to some- what inflated; outline transversely triangular, about one third wider than long; sides diverging between 80° and 120°, averaging 104°; profile subtrigonal; commissure uniplicate; fold high, beginning 6-8 mm anterior to brachial beak, increasing in height anteriorly, ending abruptly, not flexed at anterior, transversely nearly straight or slightly arched; sul- cus deep, beginning 10-12 mm anterior to pedicle beak, evenly curved anteriorly, not geniculate. Costae strong, angular, beginning about 6 mm anterior to brachial beak, about 9 mm anterior to pedicle beak, numbering 3-7 on fold, normally 5, invariably one less in sulcus, numbering 5-7 on flanks; crests of costae nearly concordant. Concen- tric ornamentation obscure; growth laminae promi- nent only near margins. Pedicle valve slightly convex longitudinally from beak to flanks, with greatest convexity about 4 mm anterior to beak; strongly convex from beak through sulcus; gently convex transversely; beak straight, sharp, flat, attenuate, may have slight median crest, more-or-less prominent beak ridges; lateral pseudointerareas narrow to moderately wide, straight, extending from posterior costa of flanks to edge of delthyrium, width dependent upon amount of overlap by brachial valve. Delthyrium on dorsal side of beak, narrowly triangular, base covered by two flat trapezoidal deltidial plates, leaving apical part open as elongate oval meso- thyridid foramen. Brachial valve moderately convex along median line, strongly convex toward flanks, strongly convex transversely; smooth part of umbo flattened or slightly indented, producing gently rounded beak ridges; apex of beak within pedicle valve, just beneath deltidial plates. Pedicle valve interior with delthyrium wide open anterior to deltidial plates, each side with a strong nodular, elongate tooth, parallel to edge of del- thyrium, supported by strong, vertical dental plate reaching floor of valve. Muscle area anterior to ends of dental plates; adductor scars small, oval, bilobed at posterior end, lying along each side of median line; diductor scars somewhat wider, elon- gate, lateral, and anterior to adductor scars. Brachial valve interior with triangular undivided hinge plates bounded laterally by deep elongate corrugated hinge sockets; crura projecting forward from edge of hinge plate, on each side of midline, diverging anteriorly and strongly curving toward pedicle valve, normally only slightly twisted, dorsal 1978 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY edge carinate; median septum high, supporting hinge plate to apex of valve, extending about half- way along septum; posterior adductor scars small, elongate, anteriorly divergent; anterior adductor scars larger, lying on either side of septum, but extending beyond end of septum, slightly expand- ing anteriorly. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 702b 148342a 4.0 3.1 3.2 1.2 85 148342b 4.9 3.9 4.2 1.5 90 148342c 5.9 4.8 4.9 1.5 70 I48342d 8.0 6.3 7.6 2.5 83 148342e 8.9 7.0 7.8 2.9 80 148345a 12.7 ? 12.8 p 90 148345b 18.0 15.4 21.6 12.2 90 148345c 18.3 16.5 20.0 8.3 97 148345d 20.9 18.0 25.0 11.4 100 148345e 22.4 19.6 28.3 12.8 111 148345f 21.7 18.7 29.5 15.0 111 (holotype) STRATIGRAPHIC OCCURRENCE.—Cathedral Moun- tain Formation; Skinner Ranch Formation. LOCALITIES.—Cathedral Mountain: AMNH 500F, 500H, 500M; USNM 702, 702b, 702un, 703b, 726x, 731b. Skinner Ranch: 724q. DIAGNOSIS.—Large, wide Tautosia with straight beak. TYPES.—Holotype: USNM 148345f. Figured par- atypes: USNM 148345e. Figured hypotypes: USNM 148342c,e; 154792a-c; 154793a,c-f; 154794a,c,d; 154795; 154796a. Measured paratypes: USNM 148345a-e. Measured hypotypes: USNM 148342a-e. Unfigured paratypes: 148345a-d. COMPARISON.—Tautosia fastigiata is characterized by its large size, transverse outline, strong and numerous costae whose crests are nearly equal to one another in height, its attenuate beak with beak ridges, flattened or slightly indented dorsal umbo, and by its high, bladelike median septum. Among species of the Glass Mountains it closely resembles Antronaria voluminosa, new species, in its size and outline. Tautosia fastigiata differs in its somewhat smaller, sharper and more numerous costae (normally 5 on the fold, in contrast to 4 on the fold of A. voluminosa), more attenuate beak with beak ridges, and less widely divergent sides, and higher median septum. In A. voluminosa the crests of the costae on the fold bend sharply ven- trally immediately posterior to the commissure, whereas in T. fastigiata the crests terminate abruptly, forming a sharp point. Furthermore, the sulcus of T. fastigiata is nearly uniformly convex from beak to anterior margin, but that of A. voluminosa is more strongly flexed at some point near, but pos- terior to the anterior margin. Another large and transverse species is A. mesi- costalis (Girty). However, it is smaller than the average specimen of T. fastigiata, more transverse, and its costae lower and finer. The middle costa of the fold of A. mesicostalis is depressed in most specimens below the level of the others. DISCUSSION.—Tautosia fastigiata varies in size, convexity, outline, and number of costae. Most adult specimens have 5 costae on the fold, but most juveniles smaller than 10 mm in length have only 3. When the shell is between 7 and 12 mm in length, 2 costae are normally added, one on each side of the fold. Juveniles are sufficiently different from the adults to produce confusion unless a continuous growth series is available for study. The features that are constant from juvenile to adult, and which unite the species are the dorso- ventrally flattened pedicle valve that is only slightly curved dorsally and has sharp beak ridges, the relatively large smooth area of the umbones, with the brachial umbonal area flattened and nor- mally slightly longitudinally indented, and the high median septum. The species that is most likely to be confused with the juveniles of T. fastigiata is Pontisia stehlii Cooper and Grant. The above-mentioned characters distinguish them, and, in addition, juveniles of T. fastigiata are rather sharply bent at the posterior edge of the smooth area of the brachial umbo, whereas in P. stehlii the convexity of the brachial valve is more uniform, producing a much more elevated anterior end of the fold. Nearly full grown specimens of Antronaria dis- sona, new species, bear some resemblance to juve- niles of T. fastigiata. The latter may be distin- guished by their less transverse outline, more frequent possession of more than 3 costae on the fold, flattened pedicle beak with sharp beak ridges, and especially by the high median septum in the brachial valve. NUMBER 21 1979 Tautosia galbina, new species PLATE 525: FIGURES 2-12 Small for genus, biconvex; outline bluntly tri- angular, sides diverging between 80° and 110°; profile lenticular; anterior commissure uniplicate, fold low to moderately high, beginning 3-6 mm anterior to brachial beak, profile gently convex; sulcus shallow, beginning 4-6 mm anterior to pedicle beak, maximum convexity between anterior ends of costae of flanks. Costae weak to moderately strong, narrow crests rounded, beginning 4-6 mm anterior to beaks, strongest on fold, there number- ing 3, 2 in sulcus; costae strong on pedicle flanks, numbering 4-6, becoming weaker laterally, weak- est on brachial flanks. Concentric ornamentation absent; growth lines faint and few. Pedicle valve moderately convex, smooth part of umbonal area slightly inflated; flanks slightly con- vex to slightly reflexed; beak relatively blunt, slightly flattened, not attenuate, suberect; beak ridges sharp, short; lateral pseudointerareas very narrow or absent; little overlap of valves. Del- thyrium triangular, base covered by two small, slightly arching deltidial plates; apical portion open, forming elongate oval submesothyridid for- amen. Brachial valve strongly and narrowly con- vex in anterior profile; smooth area of umbo flat- tened in profile, slightly flattened to evenly arched transversely; beak within pedicle valve, covered by deltidial plates. Pedicle valve interior with widely expanding delthyrium, with elongate teeth, supported by short dental plates reaching valve floor. Muscle area large, between and anterior to dental plates, widely expanding anteriorly, occupying as much as half valve length; adductor scars median, forming small subcircular mark; diductor scars surrounding ad- ductors laterally and anteriorly, much larger, greatly widening anteriorly. Brachial valve interior with undivided triangu- lar hinge plate, bounded laterally by elongate, deep, anteriorly widening, finely corrugated sockets; crura diverging anteriorly from forward edges of hinge plate, strongly curved ventrally, often twisted, dorsal edges keeled; median septum high, bladelike, long, bisecting posterior part of muscle area, supporting hinge plate. Muscle area elongate oval; posterior adductor scars elongate, anteriorly divergent, flanking larger, median, anteriorly widening anterior adductor scars. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness C) USNM 707e 148352a 5.6 5.1 6.5 3.4 90 148352b 6.2 5.6 6.1 4.0 85 148352c 6.9 6.0 6.7 4.5 91 148352d 7.7 6.4 7.8 5.0 100? USNM 722g 154798b 7.2 6.2 7.7 4.5 101 (holotype) STRATIGRAPHIC OCCURRENCE.—Road Canyon For- mation. LOCALITIES.—AMNH 509; USNM 703, 707e, 722g. DIAGNOSIS.—Small Tautosia with flanks having many costae. TYPES.—Holotype: USNM 154798b. Figured par- atypes: USNM 148352a,d,e; 154797; 154798a. Mea- sured paratypes: USNM 148352a-d. COMPARISON.—Tautosia galbina is characterized by its small size, slightly flattened smooth part of umbonal area, low costae on the flanks, and its high, bladelike median septum. A similar species is Wellerella tetrahedra Dunbar and Condra (1932, pi. 37: figs. 11-16) from the Pennsylvanian of Mis- souri. Tautosia galbina differs in its more numerous lateral costae, normally nonreflexed pedicle flanks, less inflated brachial umbonal area, and especially in its much higher and longer median septum. The species does not closely resemble others from the West Texas Permian. It is similar to Cenor- hynchia fracida, new species, from which it differs in its smaller maximum size, more transverse out- line, less strongly curved pedicle beak, and espe- cially its many costae on the flanks. This is a smaller and very rare species. The collection contains only four lots and none with abundant specimens. Tautosia lenumbona (Stehli) PLATE 525: FIGURES 26-35 Terebratuloidea? lenumbona Stehli, 1954:338, pi. 25; figs. 28-30. Small for genus, slightly wider than long; sub- triangular to subpentagonal in outline, maximum width near midvalve; sides somewhat narrowly 1980 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY rounded; apical angle variable up to 100°. Ante- rior commissure uniplicate. Deltidial plates rudi- mentary; beak short, acute, generally erect. Surface, except beaks and umbonal region, costate, costae narrowly rounded, direct, usually 4 or 5, rarely 6, on fold, one less in sulcus, and 3 or 4 on flanks. Pedicle valve very gently convex in lateral pro- file and nearly flat in anterior profile; umbonal region narrowly swollen; sulcus originating poste- rior to midvalve, broad and shallow, extending into long tongue. Flanks fairly strongly deflected, narrow, gently concave. Brachial valve fairly strongly convex in lateral profile, broadly domed and with very steep sides in anterior profile. Umbonal region moderately swollen. Fold beginning near midvalve, low, flat- tened, only slightly elevated above flanks at ante- rior. Median region marked by narrow, shallow sulcus extending along midline to anterior margin and depressing median costae of fold. Flanks fairly strongly swollen. Pedicle valve interior with small teeth, elongated and attached just inside valve margin; dental plates variable, usually thin, with very narrow um- bonal chambers filled by shell in some specimens, thus obscuring dental plates. Muscle field short, triangular. Brachial valve with strong curved socket ridges and corrugated sockets; hinge plate undivided, with broad outer hinge plates and long slender, bladelike flattened crura. Median septum thin, strong and extending to midvalve; adductor field forming heart-shaped pattern with point posterior. Anterior adductors lying inside posterior pair. MEASUREMENTS (in mm).—Hypotypes USNM 152837 and 152838, respectively: length 7.3, 6.8; brachial valve length 6.4, 6.0; width 8.2, 6.8; thick- ness 4.5, 3.8; apical angle 90°, 80°. STRATIGRAPHIC OCCURRENCE.—Bone Spring For- mation (lower). LOCALITIES.—AMNH 625, 629; USNM 728f, 728h. DIAGNOSIS.—Small Tautosia with 4 or more co- stae on the fold; sulcus originating posterior to midvalve. TYPES.—Holotype: AMNH 27320/1:1. Figured paratype: AMNH 27320/1:2. Figured hypotypes: USNM 152837, 154799a, 155105a-c. COMPARISON AND DISCUSSION.—This species is characterized by its numerous costae and its small size. Stehli assigned it to Terebratuloidea with a query, in the belief that it had no dental plates. He also did not have the brachial valve. We ob- tained additional specimens and have both valves. The species proves to have dental plates and the brachial valve has a thick median ridge. It is there- fore not referable to Terebratuloidea. Among Sierra Diablo species it might be con- fused with Tautosia magnisepta (Stehli), but it is smaller than that species, commonly has more costae on the fold and in the sulcus, and is differ- ently shaped. It is also similar to Pontisia longi- costa (Stehli) but is larger; the pedicle valve of that species is flatter, more triangular, the fold and sulcus have only 3 and 2 costae, respectively, and dorsal valve lacks a median septum. Tautosia expansa, new species, from the Bone Spring For- mation (Cutoff Shale Member) is similar, but the Sierra Diablo species has more costae and they extend farther posteriorly than those of T. expansa. Tautosia magnisepta (Stehli) PLATE 525: FIGURES 36-45^ Wellerella magnisepta Stehli, 1954, pi. 25: figs. 10-12. Medium size for genus, length and width about equal; maximum width at midvalve; outline sub- triangular, sides long and rounded but anterior narrowed and truncated. Anterior commissure strongly uniplicate. Beak short, deltidial plates small, conjunct. Surface costate, except for beaks and umbonal regions. Costae narrow and angular, 4 or 5 on fold, median costae generally depressed; 3 or 4 costae in sulcus and 4 or 5 on flanks. Pedicle valve with gently convex lateral profile, most of curvature posterior to midvalve; anterior profile nearly flat, varying from slightly concave to slightly convex. Umbonal and median region slightly carinated and marked by posterior exten- sion of median costae. Sulcus originating anterior to midvalve, broad and shallow and extending into strongly geniculated but short tongue. Flanks slightly concave; anterolateral extremities slightly extended. Brachial valve moderately convex in lateral pro- file, most convex in posterior part; anterior profile strongly and broadly domed with top flattened. NUMBER 21 1981 Fold low and inconspicuous, originating at about midvalve, usually with median depression extend- ing from umbonal region to anterior margin, de- pressing median costae. Flanks swollen and slightly depressed below fold at anterior part. Pedicle valve interior with elongated teeth lo- cated on shell margin; dental plates stout, vertical, slightly divergent. Muscle field somewhat posterior in location, subtriangular; adductor scars small, situated near ends of dental plates. Brachial valve with long thick socket ridges and corrugated sockets; hinge plate undivided, not medially indented, separate elements not clearly defined. Outer hinge plates broad, inner hinge plates narrow, usually tightly welded; apex with minute pit. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (*) SNM 728f 148355a 10.8 8.8 10.9 7.0 95 148355b 12.7 P 14.4 ? 100 148355c » 10.6 13.6 ? ? STRATIGRAPHIC OCCURRENCE.—Bone Spring For- mation (lower). LOCALITIES.—AMNH 629, USNM 728f. DIAGNOSIS.—Nearly completely costate Tautosia, costae fine, and with short sulcus and low fold. TYPES.—Holotype: AMNH 27334/1:2. Figured paratypes: AMNH 27334/1:2,3. Figured hypotypes: USNM 148355a-d, 154800. Measured hypotypes: USNM 148355a-c. COMPARISON AND DISCUSSION.—This species is characterized by its fairly large size, the numerous costae, and their extension onto the umbonal region of both valves. They differ from Tautosia lenum- bona (Stehli) in size, in generally having less costae on the surface, and in having more elongated valves. The prominent median septum serves to distinguish T. magnisepta from any species of Wellerella. This is an uncommon species in the Sierra Diablo. Several specimens of this species have the inner hinge plates united without suture and the hinge plate surface is nearly smooth. A few specimens, however, have the inner hinge plates overlapped medially but not anteriorly united. No evidence of an apical chamber was seen in any of the specimens. Tautosia podistra, new species PLATE 525: FIGURES 46-51 Small for genus, biconvex; outline bluntly equi- laterally triangular to subpentagonal, sides diverg- ing between 70° and 115°; anterior commissure uni- plicate, fold moderately low, beginning 3 or 4 mm anterior to brachial beak, profile gently convex, curvature strongest near anterior margin; sulcus shallow, beginning 3-5 mm anterior to pedicle beak, curvature of profile nearly uniform. Costae moderately high, crests blunt, beginning 2 or 3 mm anterior to beaks, strongest on fold and pedicle flanks, numbering 3 on fold, 2 in sulcus, 2 or 3 on flanks. Concentric ornamentation absent; growth lines few, faint. Pedicle valve with smooth part of umbo slightly inflated; flanks moderately convex, normally not reflexed or only slightly reflexed; beak sharp, some- what attenuate, moderately curved dorsally; beak ridges blunt, short; lateral pseudointerareas narrow or absent, only slight overlap of valves. Delthryium triangular, base covered by pair of triangular to trapezoidal conjunct deltidial plates, slightly arched dorsally; apical part open, forming elongate oval foramen. Brachial valve moderately convex, longi- tudinal profile of smooth part of umbonal area flattened, transverse profile flattened to slightly indented; highest part of fold slightly convex; beak within pedicle valve, covered by deltidial plates. Pedicle valve interior with delthyrium expand- ing at same rate as externally, each side with an elongate tooth, supported by vertical dental plate reaching floor of valve. Muscle area lying anterior to dental plates, narrowly expanding anteriorly; adductor scars not observed: probably as in other species of genus. Brachial valve interior with undivided triangular hinge plate, bounded laterally by elongate, deep, anteriorly expanding, finely corrugated sockets; crura diverging forward from anterior edge of hinge plate, strongly curved ventrally, dorsal edges carinate; median septum short, high, supporting hinge plate, descending anteriorly as moderately long, thin ridge bisecting posterior part of muscle field. Muscle area oval, subdivisions on available specimens too faint to be observed. STRATIGRAPHIC OCCURRENCE.—Skinner Ranch For- mation (Sullivan Peak Member). 1982 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 707-1 152839a 4.4 3.6 4.0 2.0 71 152839b 6.0 5.0 6.1 4.4 89 152839c 6.9 5.9 7.1 4.9 102 (holotype) 152839d 7.3 5.9 8.2 4.5 110 USNM 7l0r 152840a 8.5? 7.4 8.4 6.2 100 152840b 8.6? 7.5 10.0 c.6.5 111 LOCALITIES.—Sullivan Peak: USNM 707-1. Skin- ner Ranch: 71 Or, 712p. DIAGNOSIS.—Small Tautosia with flattened bra- chial umbo. TYPES.—Holotype: USNM 152839c. Figured par- atypes: USNM 152839e,g. Measured paratypes: USNM 152839a,b,d; 152840a,b. Unfigured para- types: USNM 152839a,b,d,f. COMPARISON.—Tautosia podistra is characterized by its small size, flattened profile of the brachial umbonal area, slightly inflated pedicle umbonal area, relatively narrow outline, and its high blade- like median septum. It most nearly resembles juve- niles of Tautosia fastigiata Cooper and Grant from the Cathedral Mountain Formation of the Glass Mountains, differing in its narrower outline, less attenuate pedicle beak with blunt beak ridges, fewer costae on the flanks, costae on the fold that begin much farther back, and especially by its small maximum size. It is distinguished from Pon- tisia kingi, new species, which also occurs in the Wolfcampian, by its smaller size, less strongly hooked pedicle beak, and high median septum. Externally it is somewhat similar to Wellerella girtyi, new species, from the Guadalupian, and to Pontisia stehlii Cooper and Grant, from the Leonar- dian, but differs from both of these in its smaller size, more flattened profile of the brachial umbonal area, and by the presence of a high median septum. Tautosia pulchra, new species PLATE 515: FIGURE 29; PLATE 526: FIGURES 1-20 Medium size for genus, subtrigonal to subpen- tagonal in outline, posterolateral margins straight, forming apical angle of 80° to 95°. Sides narrowly rounded, maximum width near midvalve. Anterior margin broadly rounded to truncated. Anterior commissure fairly strongly uniplicate. Beak short, foramen small, submesothyridid and bounded an- teriorly by conjunct, gently convex deltidial plates, some specimens with elevated rims. Surface semi- costate, costae subangular, appearing near mid- valve, and usually somewhat variable. Concentric lines weak or not preserved. Pedicle valve gently convex in lateral profile, most convex in posterior half; anterior profile flatly convex with flanks only slightly deflected. Umbonal region swollen narrowly and forming indistinct fold extending to sulcus; median region slightly swollen. Sulcus originating at midvalve, broad and shallow, occupied by 2 costae, more in rare specimens. Flanks flattened, slightly deflected in dorsal direction and marked by 4 or 5 costae. Brachial valve fairly strongly and evenly convex with maximum convexity near midvalve; anterior profile somewhat narrowly domed but median region narrowly and gently sulcate and sides steeply descending. Umbonal region moderately swollen and medially sulcate. Median region strongly swol- len, producing fairly steep anterior slope. Fold low, formed of 3 costae, median one slightly depressed. Flanks swollen, steep, marked by 4 costae. Pedicle valve interior with strong but small teeth and strong, subparallel dental plates. Brachial valve interior with thin socket plates overhanging elongate, corrugated sockets; outer hinge plates narrow; crura long and slender; inner hinge plates united, usually flat but concave in some specimens, united with strong but thin and long median septum, this not reaching midvalve. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (") 148374a 11.8 10.4 12.6 7.4 90 148374b 12.0 10.1 13.4 7.8 90 (holotype) SNM 702ent 148368a 3.0 2.4 2.6 1.1 80 148368b 4.2 3.3 3.8 1.4 80 148368c 5.7 4.7 5.4 1.7 90 148368d 7.4 6.3 7.1 2.5 80 I48368e 8.2 7.1 8.0 4.0 85 148368f 8.8 7.7 9.6 4.7 85 148368g 10.0 8.4 10.3 6.0 90 148368h 10.8 9.1 9.9 6.6 85 148368i 11.5 10.0 13.0 6.4 90 148368J 11.8 10.2 13.2 8.2 95NUMBER 21 1983 STRATIGRAPHIC OCCURRENCE.—Cathedral Moun- tain Formation. LOCALITIES.—USNM 702a. 702, 702ent, 702 low, 708, 721u. DIAGNOSIS.—Paucicostate Tautosia with anterior of brachial valve moderately geniculated. TYPES.—Holotype: USNM 148374b. Figured par- atypes: USNM 148368b-d, f-h; 148374a; 154801a,c; 154730. Measured paratypes: USNM 148368a-j, 148374a. Unfigured paratypes: USNM 148368a,e; 154801b. Figured specimen: USNM 154730. COMPARISON AND DISCUSSION.—This is a variable species with 3-5 costae on the fold and a conse- quent difference in the size of the costae. The species is unlike any of the other septum-bearing wellerelliform species. It has some resemblance to Tautosia transenna, but its sides are rounder and softer in appearance and its costae distinctly less coarse. It suggests Pontisia stehlii Cooper and Grant (1969), but has finer costae, is a less robust species, and has the geniculated front not present in other species. Although T. pulchra is about average size, the shell is extremely thin and delicate. The hinge plate is small but the septum is stout. The hinge plates are healed and no trace of an apical plate was seen. Tautosia shumardiana (Girty) PLATE 526: FIGURES 21-51; PLATE 553: FIGURES 1-9; PLATE 757: FIGURES 8-17 (in volume 5) Pugnax shumardiana Girty, 1909:316, pi. 15; figs. 15-17c. Not Pugnoides shumardianus (Girty) R. E. King, 1931:107, pi. 34: figs. 13-14 [= Pontisia cf. P. stehlii Cooper and Grant, 1969]. Large for genus, biconvex, .somewhat flattened to inflated; outline elongate to transversely triangu- lar, sides diverging between 75° and 115°; profile elongate lenticular to convexly subtrigonal; com- missure uniplicate; fold moderately high, begin- ning 7-10 mm anterior to brachial beak, longi- tudinal profile flatly convex; sulcus shallow, strong- est longitudinal convexity just behind anterior margin, continuing nearly to pedicle beak as slight indentation of smooth part of umbo. Costae weak, beginning 4-7 mm anterior to beaks, highest on fold, weak in sulcus and on pedicle flanks, weak or absent on brachial valve flanks, numbering 3-5 on fold, 5 formed by branching of lateral two, middle one commonly depressed, one less in sulcus than on fold, 3 or 4 on flanks. Concentric ornamenta- tion weak or absent; growth lines faint. Pedicle valve strongly convex longitudinally near beak; transverse profile indented by back- ward continuation of sulcus; flanks gently convex, slightly reflexed in few individuals; beak sharp, attenuate, dorsally curved; beak ridges rounded; lateral pseudointerareas absent, with no overlap of valves. Delthyrium triangular, open, without del- tidial plates. Brachial valve more strongly convex, profile somewhat flattened along crest of fold; apex only slightly curving into pedicle valve. Pedicle valve interior with widely expanding del- thyrium; teeth elongate parallel to side of delthy- rium, supported by vertical dental plates reaching floor of valve. Muscle area just anterior to edges of dental plates, oval, with small median adductor scar surrounded laterally and anteriorly by larger diductor scars. Brachial valve interior with triangular undi- vided hinge plate bounded laterally by elongate, anteriorly widening, finely corrugated hinge sock- ets; crura diverging anteriorly from edges of hinge plate, curving ventrally, dorsal edges carinate; median septum long, thin, bladelike, moderately high. Muscle area large, oval, located in smooth area of umbo, details of pattern unknown. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 740 148680a 7.8 7.3 7.8 3.4 84 148680b 9.8 8.7 10.9 5.3 95 148680c 13.3 11.2 16.4 8.0 104 USNM 737a 148675 10.9 10.0 12.9 5.6 114 USGS 2926 118566a 15.2 13.2 15.2 9.9 94 (holotype) STRATIGRAPHIC OCCURRENCE.—Capitan Formation; Bell Canyon Formation (Hegler, Pinery, Rader, and Lamar members). LOCALITIES.—Capitan: AMNH 804, 847; USGS 2926 (green); USNM 725-1, 732q, 737a, 738a, 739, 740, 740k, 740m, 740n, 750a, 750b. Hegler: USNM 731. Pinery: AMNH 33, 398, 401, 524; USNM 725n. Rader: USNM 725g, 740a, 740i. Lamar: AMNH 1984 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY 347 ( = L-2), 348 ( = L-3), 430; USNM 725e, 728p, 728r, 738. DIAGNOSIS.—Large Tautosia with weakly costate flanks. TYPES.—Holotype: USNM 118566a. Unfigured paratypes: USNM 118566c (not 118566b = ?). Fig- ured hypotypes: USNM 148675; 148680c,d; 154802b; 154803a-d; 154804; 154805; 154920a-c. COMPARISON.—Tautosia shumardiana is charac- terized by its triangular outline, longitudinally flat- tened fold with 3 costae, or with 5 if the lateral two have branched, weakly costate to smooth bra- chial flanks, costae that begin far forward of the beaks, sulcus that extends as a shallow indentation nearly to the apex of the pedicle beak, and its thin, prominent median septum. Some individuals resemble specimens of T. elegans (Girty) but the greatly extended sulcus and weakly costate flanks distinguish them. The triangular outline and pedi- cle indentation distinguishes T. shumardiana from the more nearly round outline and brachially indented Phrenophoria pinguis (Girty). Anteridocus swallovianus (Girty) is smaller, has a triangular to pentagonal outline, no median septum, and greatly inflated rather than indented or troughed beak areas. DISCUSSION.—As with most of the rhynchonellid species of the Bell Canyon Formation members and the Capitan Limestone it is difficult to obtain large lots. This is true of T. shumardiana. Consequently the full range of variation cannot be stated for the species. As usual the number of costae on the fold is variable, some specimens having 4 or 5 rather than 3, and in some the median costa or costae are more strongly depressed than in others. Two speci- mens from the Pinery Member have the costae bounding fold more strongly elevated than in most specimens, and they may be a separate species. The median septum is somewhat variably developed but is generally fairly strong. Tautosia transenna, new species PLATE 527: FICURES 1-31; PLATE 553: FIGURES 41-44 Wellerella? sp. Stehli, 1955:73, figs. 37-39. Average size for genus; biconvex; outline bluntly triangular to pear-shaped, sides diverging between 85° and 125°; lateral profile subtrigonal; anterior commissure uniplicate, fold beginning 6-8 mm anterior to brachial beak, longitudinal convexity low, anterior termination sharp; sulcus moderately deep, beginning 6-8 mm anterior to pedicle beak, maximum convexity between anterior proximal ends of flanks. Costae strong with sharp crests on fold and pedicle flanks, weak to moderately strong with blunt crests in sulcus and on brachial valve flanks, beginning 4-7 mm anterior to beaks, num- bering 2-4 on fold, normally 3, one less in sulcus, 2-5 on each flank, normally 3. Concentric orna- mentation not seen; growth laminae faint, widely spaced. Pedicle valve with low crest along smooth area forward of beak; profile from beak to flanks gently convex to slightly reflexed; beak sharp, somewhat attenuate; beak ridges blunt, short; lateral pseudo- interareas narrow, obscurely delimited, partly cov- ered by overlapping edge of brachial valve. Del- thyrium triangular, base covered by two slightly arched trapezoidal deltidial plates, forming elon- gate submesothyridid oval foramen. Brachial valve strongly convex from beak to flanks, and transversely slightly convex along fold, anterior end of fold slightly reflexed; smooth part of umbonal region slightly flattened transversely; apex broad, concealed within pedicle valve, covered by deltidial plates. Pedicle valve interior with delthyrium spreading widely anterior to deltidial plates, teeth elongate, parallel to edge of delthyrium, supported by verti- cal dental plates reaching valve floor. Muscle area subtrigonal to oval, lying just anterior to dental plates; adductor scars small, median, in posterior part of muscle area, forming oval to circular mark; diductor scars large, anteriorly expanding, sur- rounding adductor mark laterally and anteriorly. Brachial valve interior with undivided triangular hinge plate, bounded laterally by deep, wide, ante- riorly expanding, finely corrugated sockets; crura diverging anteriorly, strongly curved ventrally, slightly twisted, dorsal edges keeled; median sep- tum high, thin, long, supporting hinge plate, bisect- ing posterior half of muscle area. Muscle area oval; posterior adductor scars elongate, narrow, diverging anteriorly from median septum, fused to postero- lateral edges of larger, anteriorly expanding ante- rior adductor scars. STRATIGRAPHIC OCCURRENCE.—Cherry Canyon For- mation (Getaway Member); Word Formation NUMBER 21 1985 MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 706b 148402a 1.9 1.6 1.8 0.7 ? 148402b 3.0 2.4 2.6 1.5 J 148402c 5.1 4.5 4.2 2.0 c.110 148402d 6.9 6.2 5.7 3.2 80 I48402e 9.2 7.8 8.8 4.0 80 (holotype) 148402f 10.1 8.7 10.1 7.4 80 I48402g 10.7 9.2 11.3 8.7 80 148402h 11.4 9.6 12.2 10.1 85 148402i 11.9 10.3 12.0 11.5 85 USNM 728 148409a 6.9 6.1 7.1 3.8 86 148409b 10.0 8.6 11.5 7.1 108 148409c 12.0 10.8 13.0 8.3 106 148409d 13.3 12.1 15.0 12.3 98 148409e 13.7 12.2 15.2 9.2 100 USNM 706 148399a 8.5 7.5 8.9 5.5 94 148399b 9.9 8.6 9.9 6.8 85 (China Tank, Willis Ranch, Appel Ranch members and lens between the last two). LOCALITIES.—Getaway: AMNH 512, 600; USNM 728, 732. China Tank: 706c, 713. Willis Ranch: 706, 706e. Lens: 706b. Appel Ranch 706d, 719z. DIAGNOSIS.—Tautosia with median costa of fold not depressed. TYPES.—Holotype: USNM 148402e. Figured par- atypes: USNM 148402c,d; 148409e; 154807a-e; 154808a-c; 154809a,b,c. Measured paratypes: USNM 148399a,b; 148402a-d,f-i; 148409a-e. Unfigured paratypes: USNM 148402a,b,d,f-i; 148409a,b,d. COMPARISON.—Tautosia transenna is characterized by its bluntly triangular outline, slightly convex to slightly reflexed longitudinal profile of the fold, abrupt anterior termination of the fold, nonde- pressed median costa of the fold, anterior margin without embayment at juncture of fold and sulcus, and its high median septum. It appears to be closely related, probably ancestral to T. elegans (Girty), a rare, late Guadalupian species. It differs from that species in its normally less transverse outline, more strongly costate flanks, more nearly flat profile of the fold, normally nondepressed me- dian costa of the fold, more flattened smooth area of the brachial umbo, its unindented smooth area of the brachial umbo, and its unindented anterior margin. It differs from Anteridocus swallovianus (Shumard) in its larger size, more triangular out- line, less inflated umbones, stronger costae, more flattened profile of the fold, and its high median septum. This species is distinguished from Cenorhynchia fracida, new species, also Guadalupian in age, by its strongly costate flanks, costae that begin farther back, greater proportional width, and especially by its broader, flattened brachial umbonal area. An- tronaria speciosa, new species, from the Hess For- mation also is similar; T. transenna differs in its narrower outline, less strongly reflexed pedicle flanks, smaller average size, high median septum, nondepressed middle costa of the fold, and its un- indented anterior margin. Pontisia kingi, new spe- cies, from the Wolfcampian also has a fold with only slightly convex profile. Tautosia transenna is distinguished by its somewhat larger size, broader outline, less strongly convex fold profile, straight pedicle beak, deeper sulcus, and high median sep- tum. Other West Texas species differ from T. tran- senna in having the convex profiles of their folds more strongly convex, reducing greatly the thick- ness from the anterior end of the fold to the ante- rior end of the fold to the anterior end of the pedicle flanks, and normally displacing the position of the point of maximum thickness from the ante- rior end to nearer the middle of the shell. Among foreign species "Pugnax" pseudoutah Huang (1933) most nearly resembles T. transenna. That species is narrower, proportionately somewhat thicker, has an inflated brachial umbonal area, and less strongly costate flanks than does T. transenna. The interior of P. pseudoutah is unknown, so com- parison is impossible. Externally it appears to belong to Wellerella, but nevertheless it might have a high median septum, or a low median ridge. Specimens regarded by Huang (1933:65) as con- specific with the "cotypes" lack the median septum, further contrasting that species with T. transenna. Rhynchonella edelsteini Tschernyschew (1914) also is similar, but its brachial valve is inflated, its flanks have fewer and weaker costae, and the median septum of the fold is slightly depressed, as in T. elegans. T. transenna differs from Rhyn- chonella negrii Gemmellaro (1899) in its less in- flated pedicle umbonal area, more strongly costate flanks, and sharper anterior termination of the fold. The interior of Gemmellaro's species is not known. DISCUSSION.—Tautosia transenna occurs in the 1986 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY Word Formation with Wellerella girtyi, new spe- cies. Although the two are similar, the strong me- dian septum of Tautosia is a ready means of sep- aration. The species is not common. Brachial valve interiors have a fairly large hinge plate and the inner hinge plates are sealed without suture in most cases. In some specimens the inner hinge plates are slightly domed. Cenorhynchia, new genus [Greek kenes (empty) + rhychos (beak)] Small, rhynchonelliform, biconvex, uniplicate; outline bluntly trigonal to subpentagonal; fold and sulcus smooth to weakly semicostate, flanks nor- mally smooth, rarely weakly costate. Concentric ornamentation and growth lines weak. Pedicle valve moderately convex; beak sharp, short to moderately long, not attenuate, slightly to strongly curved dor- sally; beak ridges blunt, poorly defined; delthyrium triangular, open, without deltidial plates. Valves meeting without overlap, hence no lateral pseudo- interareas. Brachial valve strongly convex; umbonal area normally not flattened or depressed; beak bluntly pointed, not strongly incurved. Pedicle valve interior with small knoblike hinge teeth supported by vertical dental plates reaching floor of valve. Muscle area beginning between ante- rior edges of dental plates, cordate, widening an- teriorly, occupying about a fourth to a third of valve length; adductor scars small, median, lying in posterior part of muscle area; diductor scars large, lobe-shaped, surrounding diductors laterally and anteriorly, meeting one another along midline of valve in anterior part of muscle area. Brachial valve interior with well-developed hinge plate moderately deeply notched at midline, may have median groove with sides dipping to meet top of median septum; hinge sockets deep, narrow, elongate, widening anteriorly, finely corrugated; crura falcifer, slightly diverging anteriorly from edge of hinge plate, only slightly twisted, dorsal edges carinate, keels extending under hinge plate as crural bases; median septum thin, bladelike, sup- porting hinge plate, bisecting posterior part of muscle area, extending about a fourth length of valve. Muscle area subelliptical, posterior adductor scars small, narrow, anteriorly divergent, flanking larger, rounded, medially located anterior adductor scars. TYPE-SPECIES.—Cenorhynchia fracida, new species. DIAGNOSIS.—Smooth to anteriorly costate rhyncho- nellids with strong median septum and absent or incipient deltidial plates. COMPARISON.—Cenorhynchia is characterized by its small size, weak costae, absent lateral pseudo- interareas, open delthyrium without deltidial plates or with incipient plates, widely notched and commonly medially troughed undivided hinge plate, and its distinct, thin dorsal median septum. Lack of deltidial plates or their incipient develop- ment distinguishes it from Wellerella Dunbar and Condra and Phrenophoria Cooper and Grant which resembles it externally; its median septum distin- guishes it from Wellerella Dunbar and Condra, Pontisia Cooper and Grant, and Anteridocus, new genus. Lack of a well-developed apical chamber and its straight pedicle beak and shorter costae differentiate it from Shumardella Weller (1910). Acolosia, new genus, is similar externally but has no median septum. DISCUSSION.—Most species of this genus are small, ranging in length from 5 to 10 mm. Most of the smaller species are smooth, or at any rate nonco- state, but the larger ones have costae, largely con- fined to the margins of the fold and sulcus, or occasional costae on the margins of the flanks. The beak usually is straight or suberect and either has an unmodified delthyrium or shows traces of del- tidial plates at the anterolateral extremities of the delthyrium. The valves are usually subequal in depth but some species have a deeper brachial valve. Internally the pedicle valve is characterized by small knoblike teeth supported by strong dental plates standing out from the walls and defining deep umbonal chambers. The musculature lies an- terior to the ends of the dental plates. The brachial valve of most specimens has an undivided hinge plate that is supported by a strongly elevated thin median septum. The socket ridges are strong, slightly incurved and with a thickened rim, bounding deep, finely corrugated sockets. The outer hinge plates are broad and gently concave. The crural bases form the margin of the outer hinge plate and all these plates are welded by fusion of the broad inner hinge plates. These meet in a plane or are medially arched in many specimens. The crura are slender, keeled, concave toward midvalve, and have expanded distal NUMBER 21 1987 extremities. Their bases are keeled and the keels extend along the underside of the hinge plate. The muscle area is divided medially by the median ridge. Cenorhynchia atmeta, new species PLATE 543: FIGURES 34-50 Average size for genus, strongly biconvex; out- line tear-shaped, sides diverging between 60° and 90°; commissure uniplicate, fold moderately high only at commissure, but standing in low relief above flanks farther posteriorly, beginning about 3 mm anterior to brachial beak; sulcus not depressed below flanks except at extreme anterior in largest specimens. Fold not costate; flanks smooth or with 1 costa on each side, adjacent to fold. Growth lines weak, irregularly spaced; other concentric ornament absent; radial ornament absent except for weak fibrous texture of shell. Pedicle valve somewhat inflated, strongly convex transversely, moderately convex longitudinally through sulcus; beak sharp, slightly curved dorsally; beak ridges blunt, short; lateral pseudointerareas absent, so valves meeting without overlap; del- thyrium narrow, triangular, open, without deltidial plates. Brachial valve strongly convex transversely, moderately convex longitudinally, most strongly curved at posterior; beak blunt, apex within pedicle valve. Pedicle valve interior with small, knoblike or elongate teeth, dental plates short, nearly vertical, close to sides, normally partly fused to sides; muscle area elongate, heart-shaped, apex between dental plates; adductor scars not observed; diductor scars separated by faint myophragm. Brachial valve interior with hinge plate deeply notched anteromedially; sockets deep, relatively wide, very short, finely corrugated, crura delicate, anteriorly diverging, ventrally curved, untwisted or only slightly twisted; median septum thin, blade- like, highest immediately below hinge plate, reduc- ing to become low median ridge at anterior end. Muscle area on floor of valve on each side of median septum; individual muscle marks not observable. STRATIGRAPHIC OCCURRENCE.—Road Canyon For- mation. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°> USNM 710u 148162a 3.0 2.6 2.3 1.6 60 148162b 3.8 3.0 2.9 2.1 68 148162c 4.5 4.0 3.5 2.8 64 148162d 5.1 4.6 4.0 3.3 72 (holotype) 148162e 5.5 4.9 4.5 3.6 71 LOCALITIES.—USNM 702c, 703a, 709c, 710u, 719x, 721o, 724j, 726f. DIAGNOSIS.—Small, smooth Cenorhynchia with poorly developed median septum. TYPES.—Holotype: USNM 148162d. Figured par- atypes: USNM 148162e,f,h; 154896; 154897a; 154898a,b. Measured paratypes: USNM 148162a-c,e. Unfigured paratypes: USNM 148162a-c,g; 154897b. COMPARISON.—Cenorhynchia atmeta is character- ized by its narrow outline, smooth shell, low fold and shallow sulcus, inflated umbonal regions, dental plates that fuse to the shell walls, and its short median septum. The lack of costation and any vestige of deltidial plates distinguishes it from C. fracida, C. saginata, and C. ventricosa, all new species. Its narrower outline and shorter beak dis- tinguish it from C. hebata, new species. The low median septum that becomes reduced anteriorly to a low median ridge separates C. atmeta from all the above species. Cenorhynchia camerata, new species PLATE 510: FIGURES 27-32; PLATE 521: FIGURES 48-57, 62-64 Usual size for genus, length and width nearly equal, rounded subpentagonal in outline with narrowly rounded sides and posterolateral margins forming angle from 85° to 95°. Beak suberect, del- thyrium open, no trace of deltidial or lateral plates seen. Surface paucicostate, posterior half smooth; anterior half with poorly and variably developed costae, 3 or 4 on fold, one less in sulcus; flanks with 1 costa. Pedicle valve gently and evenly convex in lat- eral profile; anterior profile broadly and gently concave; sulcus originating posterior to midvalve, wide and shallow forming broad, long serrated tongue. Umbonal region moderately swollen. 1988 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY Flanks demarcated by low ridge and with steep slopes. Brachial valve fairly evenly and gently convex in lateral profile but narrowly and roundly domed in anterior profile; sides of dome steep. Fold origi- nating near midvalve, low, somewhat flattened but moderately elevated above gently swollen flanks. Pedicle valve interior with well-marked dental plates in young, but with umbonal cavities filled and dental plates obsolete, or nearly so, in adults. Brachial valve interior with undivided hinge plate; socket ridge strong; outer hinge plates narrow; inner hinge plates fused without suture, anteriorly notched and folded in ventral direction. Median septum thin, strong, attached to hinge plate apically, often forming minute chamber just ante- rior to place of contact. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) 8.5 7.5 8.6 6.4 93 8.7 7.6 8.2 7.2 89 7.8 6.9 8.2 6.4 90 8.5 7.6 8.5 6.9 90 8.2 7.3 7.7 5.8 92 7.7 7.0 7.4 5.0 91 USNM 727e 155069a 155069b 155069c 155069d (holotype) 155069e 155069f STRATIGRAPHIC OCCURRENCE.—Neal Ranch Forma- tion (bed 4). LOCALITY.—USNM 727e. DIAGNOSIS.—Cenorhynchia with valves nearly equal in length and width, variable number of costae on fold, and dental plates obsolete in the adult. TYPES.—Holotype: USNM 155069d. Figured par- atypes: USNM 155069a,g-i. Measured paratypes: USNM 155069a-c,e,f. Unfigured paratypes: USNM 155069b,c,e,f. COMPARISON AND DISCUSSION.—This species has some similarities to C. mitigata, new species, but that species has a more transversely elliptical form, coarser costae, and fewer of them. Cenorhynchia saginata, new species, has wider costae more ante- riorly confined than those of C. camerata, more costae on the flanks, and in the adult, well-defined dental plates, which can scarcely be seen in adults of C. camerata. The dental plates of C. camerata are evidently eliminated by filling of the umbonal cavities. Young specimens about half the size of adults have clearly defined dental plates with narrow umbonal cavities between them and the shell. These were filled in as the shell reached adulthood. Cenorhynchia fracida, new species PLATE 515: FIGURES 1-4, 36-42; PLATE 544: FIGURES 1-21; PLATE 552: FIGURES 11-13 Slightly larger than average size for genus, un- equally biconvex, often dorsally inflated; outline elongate suboval, sides diverging between 55° and 100°; profile subtrigonal to wedge shaped; com- missure strongly uniplicate; fold low, confined to anterior part only, slightly convex in profile, ante- rior termination abrupt; sulcus shallow, beginning 5-8 mm anterior to pedicle valve beak, longitudinal convexity rather uniform and gentle. Costae few, weak, blunt, confined to anterior third or quarter, strongest at anterior end of fold, there usually numbering 3, one less in sulcus; costae weak in sulcus and on pedicle valve flanks, numbering 2 or 3 on flanks and normally visible only near com- missure. Concentric ornamentation not observed; growth lines weak and widely spaced. Pedicle valve slightly inflated in beak area, nar- rowly arched transversely; gently convex toward flanks, margins of flanks not reflexed; beak sharp, strongly curved, suberect, without beak ridges; lateral pseudointerareas absent, no overlap of valves. Delthyrium triangular, normally open, base rarely narrowed by rudimentary deltidial plates; foramen small, triangular. Brachial valve strongly convex toward flanks, inflated on smooth part of umbonal area, narrowly arched transversely, with- out flattening or indentation; beak narrow, sharp, apex covered by curvature of pedicle beak. Pedicle valve interior with delthyrium widely expanding, teeth small and narrow, supported by short vertical dental plates that reach valve floor. Muscle area anteriorly expanding, longitudinally striated, lying anterior to dental plates; muscle marks faint. Diductor marks narrowly expanding anteriorly. Brachial valve interior with undivided triangu- lar hinge plate, bounded laterally by deep, elon- gate, anteriorly widening sockets; socket ridges thick, overhanging sockets, crura diverging ante- NUMBER 21 1989 riorly from edge of hinge plate, long and strongly curved ventrally, often twisted, dorsal edges cari- nate; median septum high, thin, long, bisecting muscle area and supporting hinge plate but not forming chamber. Muscle area elongate; posterior adductor scars elongate, anteriorly diverging, flank- ing larger, anteriorly widening anterior adductor scar. MEASUREMENTS (in mm).—From locality USNM 706b specimens 148167a (holotype) and b, respec- tively: length 9.8, 7.8; brachial valve length 8.2, 6.7; width 8.7, 6.7; thickness 6.8, 6.4; apical angle 70°, 65°. STRATIGRAPHIC OCCURRENCE.—Word Formation (China Tank, Willis Ranch and Appel Ranch members; lens between Willis Ranch and Appel Ranch members). Cherry Canyon Formation (Get- away Member). LOCALITIES.—China Tank: USNM 706c. Willis Ranch: USNM 706e, 735c. Appel Ranch: USNM 727j. Lens: USNM 706b. Getaway: USNM 730. DIAGNOSIS.—Elongate-oval Cenorhynchia with strong median septum. TYPES.—Holotype: USNM 148167a. Figured par- atypes: USNM 148167b,d; 148168a-c,f,g; 154721; 154722. Measured paratype: USNM 148167b. Un- figured paratypes: USNM 148167c; 148168d,e. COMPARISON.—Cenorhynchia fracida is character- ized by its elongate outline, normally narrowly diverging sides, hooked pedicle beak, narrowly arched umbonal area of the brachial valve, costae that are weak on anterior parts of the shell, and very low or absent on the brachial flanks, and its high, bladelike median septum. The longitudinal profile of the fold is relatively flat, aligning this species with others having that feature: Tautosia elegans (Girty), T. transenna, new species, Anteri- docus swallovianus (Shumard), Antronaria spe- ciosa, new species, and Pontisia kingi, new species. Among Guadalupian species it most closely re- sembles T. elegans from the Guadalupe Mountains, differing in its hooked beak which has obsolescent deltidial plates or none at all, nondepressed middle costa of the fold, and especially in its smooth, nearly uncostate flanks and evenly arched, unflattened brachial umbonal area. Several of the features that separate it from T. elegans suggest P. kingi from the Wolfcampian. Cenorhynchia fracida differs in its narrower outline, costae that begin farther for- ward, noncostate flanks on the brachial valve, and especially in its high median septum. The other species mentioned above all differ from C. fracida in their markedly stronger costation, slightly to strongly reflexed pedicle flanks, and flattened or slightly indented smooth part of the brachial um- bonal area. Cenorhynchia fracida also resembles C. saginata, new species, but it is longer than the Road Canyon form, more ovate, and attains a larger size. Cenorhynchia hebata, new species PLATE 544: FIGURES 22-40 Small for genus, biconvex; outline bluntly sub- trigonal to elongate subpentagonal, sides diverging between 75° and 95°; commissure uniplicate, fold low, strongly arched transversely, crest extending to brachial beak; sulcus shallow, barely perceptible except at commissure. Costae normally absent, oc- casionally present as slight, weak indentation near anterior end of fold; flanks smooth. Concentric ornamentation not observed; growth lines weak, strongest near anterior margins. Pedicle valve moderately convex, flanks not re- flexed; beak short, somewhat blunted, nearly straight to nearly erect; beak ridges blunt, poorly defined; delthyrium small, triangular, open, without deltidial plates; lateral pseudointerareas absent: no overlap of valves. Brachial valve more strongly convex transversely; profile gently convex, without flattening; beak rather prominent, not strongly incurved. Pedicle valve interior with sides widely diver- gent; teeth supported by nearly vertical dental plates reaching floor of valve and solidly fused to side of valve. Muscle area broadly triangular, be- ginning between edges of dental plates; details of pattern unknown, probably as in other species of genus. Brachial valve interior with hinge plate small, anteriorly notched, solid or with median groove, depressed at posterior apex to form shallow pit for attachment of diductor muscles; sockets narrow, elongate, anteriorly widening, shallow; median septum high, thin, short, extending about a fifth valve length; crura delicate, diverging slightly an- teriorly from forward edge of hinge plate, crural bases extending from underside of hinge plate 1990 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY along dorsal edges of crura. Muscle area small, subelliptical, details of pattern unknown. MEASUREMENTS (in mm).— brachial maxi- apical valve mid- mum thick- angle length length width width ness (°) SNM 701a3 148186a 1.8 1.7 1.4 1.6 0.8 ? 148186b 3.9 3.4 2.7 3.0 2.1 81 SNM 701d 148182a 2.7 2.5 2.1 2.1 1.3 } 148185a 4.3 3.9 3.1 3.7 2.5 90 (holotype) 148185b 5.5 5.0 4.4 4.8 3.7 92 148185c 6.2 5.8 5.3 5.3 5.0 96 STRATIGRAPHIC OCCURRENCE.—Neal Ranch Forma- tion (Beds 2,4, 9-14). LOCALITIES.—Bed 2: USNM 701. Bed 4: USNM 701d, 721g 727d, 727e, 742c. Beds 9-14: USNM 701a3, 701c, 701k, 712w. DIAGNOSIS.—Small, seldom costate, elongate Cen- orhynchia with dental plates fused to shell wall. TYPES.—Holotype: USNM 148185a. Figured par- atypes: USNM 148185b,e-g. Measured paratypes: USNM 148182a; 148185b,c; 148186a,b. Unfigured paratypes: USNM 148182a. COMPARISON.—Cenorhynchia hebata is character- ized by its comparatively small size, short beak, lack of costae, low fold and shallow sulcus, dental plates that are fused to the shell walls, and its slightly excavated or depressed hinge plate. It is smaller and smoother than C. saginata, new species, and C. fracida, new species. It differs from C. miti- gata, new species, in its somewhat smaller size, lower fold, shallower sulcus, shorter beak, and nor- mally absent costae. Cenorhynchia mitigata, new species PLATE 545: FIGURES 1-28 Average size for genus, biconvex; outline elon- gate subelliptical to subtrigonal or subpentagonal, sides diverging between 70° and 105°; commissure uniplicate, fold low, convex in profile, strongly arched transversely, extending nearly to brachial beak; sulcus shallow, extending forward as broad tongue, backward as shallow trough to within 2 or 3 mm of pedicle beak. Costae absent or weak, nor- mally 2 low, rounded, short asymmetrical costae on fold, 1 in sulcus, flanks smooth. Concentric ornamentation absent; growth lines faint, strongest near anterior margins. Pedicle valve moderately convex, flanks not re- flexed; beak sharp, moderately long, not attenuate, slightly curved dorsally; beak ridges blunt, short; delthyrium triangular, open, without deltidial plates; lateral pseudointerareas absent: no overlap of valves. Brachial valve moderately convex in pro- file, strongly convex transversely, without flattening of umbonal area; beak somewhat prominent, blunt, not strongly incurved. Pedicle valve interior with elongate teeth sup- ported by nearly vertical dental plates reaching floor of valve. Muscle area heart-shaped, with point between edges of dental plates; adductor scars small, median, lying in posterior part of muscle area; diductor scars larger, anteriorly widening, meeting one another at midline anterior to adduc- tor marks. Brachial valve interior with hinge plate widely notched, deep groove along median line, forming small crural cavity with sides dipping down to meet top of median septum; sockets elongate, ante- riorly widening, corrugated; beak of valve slightly elevated above hinge plate, providing surface for attachment of diductor muscles; median septum high, thin, bladelike, relatively short, extending about a fifth to a fourth length of valve; crura slightly diverging forward from anterior edge of hinge plate, moderately strongly curved ventrally, strengthened by crural keels extending from under- side of hinge plate and along dorsal edges of crura. Muscle area not observed, pattern probably as in other species of genus. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) 4.8 4.1 3.9 2.4 85 5.1 4.7 4.7 3.0 85 6.0 5.4 5.0 3.4 85 6.0 5.4 5.5 3.3 85 6.7 6.0 6.5 4.6 90 6.7 6.0 6.4 4.6 88 8.9 8.0 8.2 6.0 89 9.3 8.4 9.2 7.1 90 USNM 702a 148193a 148193b 148193c 148193d I48193e 1481931 148193g 148193h (holotype) STRATIGRAPHIC OCCURRENCE.—Cathedral Moun- tain Formation; Road Canyon Formation. LOCALITIES.—Cathedral Mountain: AMNH 500F; NUMBER 21 1991 USNM 700x, 702, 702a, 702b, 702-low, 702un, 708, 727p, 727q, 731b. Road Canyon: AMNH 507; USNM 702c, 716x, 719x, 721o, 721w. DIAGNOSIS.—Nearly smooth Cenorhynchia with fold and sulcus nearly reaching beaks. TYPES.—Holotype: USNM 148193h. Figured par- atypes: USNM 148205a; 148193e,f; 154899; 154900; 154901a,b. Measured paratypes: USNM 148193a-g. Unfigured paratypes: USNM 148205b; 148193a-d,g. COMPARISON.—Cenorhynchia mitigata is charac- terized by its fold and sulcus that nearly reach the beaks, smooth convexity, and absent or weakly developed costae. It is larger and more convex than C. hebata, new species, its beak is longer and somewhat more strongly curved, and its fold and sulcus are stronger and begin much farther poste- riorly. The brachial valve of C. mitigata has a pro- file more convex than that of C. saginata, new species, and its costae are fewer and weaker. It differs from C. fracida and C. ventricosa, both new species, in its smaller size, weaker costae, wider outline, less convex brachial valve, and less strongly curved pedicle beak. Cenorhynchia nasuta, new species PLATE 545: FIGURES 42-51 Small for genus, length and width about equal; outline and profile strongly triangular; maximum width near midvalve; sides strongly rounded; apical angle 80°-90°. Anterior strongly nasute; anterior commissure uniplicate. Beak short, suberect; no delitidial plates. Surface nearly smooth except for costae at anterior ends of fold and sulcus; fold with 3 costae, each flank with 1 poorly defined costa. Pedicle valve lateral profile unevenly convex, posterior part gently convex but anterior strongly geniculated. Anterior profile gently to moderately concave. Umbonal region somewhat narrowly swollen; sulcus originating somewhat posterior to midvalve, shallow to deep and extended anteriorly as long narrow tongue. Flanks narrow, gently con- vex, slightly deflected. Anterolateral extremities protruding moderately. Brachial valve gently convex in lateral profile but narrowly domed in anterior profile; umbonal region narrowly swollen to subcarinate. Fold orig- inating well anterior to midvalve rounded to sub- carinate, median costae elevated above lateral ones. Flanks moderately swollen, steep. Pedicle valve interior with small teeth and short, thin, dental plates. Brachial valve interior with variable hinge plate supported by strong, thin, and long median septum. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) AMNH 512 152813a 10.5 9.0 9.5 7.0 90 152813b 9.2 8.3 8.9 5.7 90 152813c 9.6 8.7 10.0 8.8 95 (holotype) STRATIGRAPHIC OCCURRENCE.—Cherry Canyon For- mation (Getaway Member). LOCALITIES.—AMNH 512, 585. DIAGNOSIS.—Elongate triangular Cenorhynchia with nasute anterior. TYPES.—Holotype: USNM 152813c. Figured par- atypes: USNM 152813a,d; 154903a,b. Measured paratypes: USNM 152813a,b. Unfigured paratype: USNM 152813b. COMPARISON.—This species is characterized by its narrow and nasute anterior and pentagonal form. In the latter respect it is readily separated from C. fracida and C. triangulata, both new. It is also a thicker shell than the latter. Although it has a somewhat pentagonal form, it is readily distin- guished from C. pentagonalis, new species, by the wider fold which usually has 4 low costae rather than 3 strongly angular ones. This is an extremely rare species: only 9 specimens are known. Cenorhynchia parvula, new species PLATE 545: FIGURES 29-41 Small for genus, usually longer than wide, some- what tear-shaped, with rounded sides and the maxi- mum width anterior to midvalve. Unequally bicon- vex, brachial valve deeper and more convex. Ante- rior commissure uniplicate. Beak short, suberect, with open, unmodified delthyrium. Surface smooth except for incipient costa in sulcus and 1 on each flank. Pedicle valve fairly and evenly convex in lateral profile; nearly flat in anterior profile except for dorsally and abruptly deflected flanks. Umbonal 1992 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY region moderately convex; sulcus broad and shal- low, originating anterior to midvalve and in adults occupied by short median costa; sulcus anteriorly bounded by short costa; median region gently con- vex and flanks narrowly rounded. Brachial valve fairly evenly and moderately con- vex but with maximum curvature near midvalve, umbonal region strongly curved under beak of pedicle valve; anterior profile narrowly and strong- ly domed with long gently swollen flanks; fold, short, narrow, and anteriorly indented in adults, originating in anterior quarter and strongest when viewed from anterior. Pedicle valve interior with small, obliquely elon- gated teeth notched at posterior end; dental plates receding, strong but with narrow umbonal cavities. Muscle field anterior to delthyrial cavity, not strongly impressed and without detail. Brachial valve interior with cardinalia variable, socket ridges strong, outer hinge plates narrow, and crura short. Inner hinge plates varying from in- completely closed to complete, concave to convex, usually concave in young. Median septum short, best defined at apex. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 703a 148189a 1.4 1.2 1.2 0.7 ? 148189b 2.3 2.1 2.0 1.2 70 148189c 2.9 2.6 2.5 1.5 84 148189d 4.1 3.8 3.2 2.2 78 148189e 5.0 4.3 3.7 2.8 70 148189f 5.4 4.7 4.4 3.9 85 I48189g 6.8 6.0 5.5 4.4 74 (holotype) STRATIGRAPHIC OCCURRENCE.—Cathedral Moun- tain and Road Canyon formations. LOCALITIES.—Cathedral Mountain: USNM 703a1, 703b, 703bs. Road Canyon: AMNH 507; USNM 702c, 703a, 708c, 721s, 724b. DIAGNOSIS.—Small Cenorhynchia with reduced median septum and incipient costa in sulcus in the adult. TYPES.—Holotype: 148189g. Figured paratypes: USNM 148189f,h; 154902a,b. Measured paratypes: USNM 148189a-f. Unfigured paratypes: USNM 148189a-e. COMPARISON.—This species is most like C. atmeta, new species, also from the Road Canyon Forma- tion, in size and general outline. It is, however, more robust, with greater development of the me- dian septum, and attains larger size, is deeper, and has the development of the costa at the anterior margin. Cenorhynchia pentagonalis, new species PLATE 520: FIGURES 1-10, 49 Large for genus, slightly wider than long, outline pentagonal. Maxmium width near midvalve; sides narrowly rounded; apical angle near 90°. Anterior margin truncated; anterior commissure uniplicate. Beak moderately long, pointed, straight to suberect, no deltidial plates. Surface nearly smooth except for fold with 4 narrowly rounded costae; flanks each with 1 costa. Pedicle valve gently convex in lateral profile, strongest curve near midvalve; anterior profile gently concave. Umbonal and median regions slightly convex; sulcus originating anterior to mid- valve, broad, shallow, and extended into long tongue geniculated at nearly right angle. Flanks, narrow, slightly convex. Brachial valve fairly evenly and gently convex in lateral profile, most curvature in umbonal re- gion; anterior profile narrow, steep-sided dome, flattened on top. Umbonal and median regions swollen; umbo not sulcate. Fold low, inconspicu- ous, originating anterior to midvalve; flanks swol- len, depressed slightly below fold. Pedicle valve interior with delicate, subparallel dental plates. Brachial valve interior with variable hinge plate, divided in young, complete in adults. Crura long, curved, concave toward midvalve; inner hinge plates small, uniting but attached to long, high, thin median septum nearly reaching midvalve. MEASUREMENTS (in mm).—From locality USNM 706c specimen 152814a (holotype): length 9.9, brachial valve length 8.0, width 10.0, thickness 6.8, apical angle 90°. STRATIGRAPHIC OCCURRENCE.—Word Formation (China Tank Member). LOCALITIES: Word: USNM 731u. China Tank: USNM 706c. DIAGNOSIS.—Pentagonal, fairly large Cenorhyn- chia with 4 subequal, crowded costae on the fold. TYPES.—Holotype: USNM 152814a. Figured par- NUMBER 21 1993 atypes: USNM 152814b,d,f,g,j. Unfigured paratypes: USNM 152814c,e,h,i. COMPARISON.—This is one of the larger species of Cenorhynchia which is readily distinguished from C. triangulata and C. fracida, both new, by its pentagonal form and comparatively broad fold, with 4 costae at the anterior end. It shares a pen- tagonal form with C. nasuta, new species, which differs in its narrow fold, with only 3 costae. Cenorhynchia pentagonalis is very rare; only 10 specimens have been recovered from many large blocks. Cenorhynchia saginata, new species PLATE 508: FIGURES 65-67; PLATE 510: FIGURES 33-37; PLATE 515: FIGURES 45-56; PLATE 546: FIGURES 1-24 Average size for genus, biconvex; outline sharply trigonal to bluntly subpentagonal, widest anterior to midvalve, sides diverging between 70° and 105°; commissure uniplicate, fold moderately high at anterior end, nearly flat in lateral and transverse profiles, crest becoming lower posteriorly, extend- ing to beak; sulcus shallow, extending as barely perceptible trough to within 2 or 3 mm of pedicle valve beak. Costae moderately strong at anterior end of fold, numbering 2-4, normally 3, weak and low elsewhere, normally numbering 1 or 2 on flanks. Concentric ornament absent; growth lines weak over most of shell, slightly stronger near anterior margins. Pedicle valve with strongest convexity near umbo, flanks not reflexed but nearly flat; beak sharp, moderately long, somewhat attenuated, straight to suberect, curvature increasing with size of shell; beak riges short, blunt; delthyrium nar- row, triangular, open, without deltidial plates; lateral pseudointerareas absent: no overlapping of valves. Brachial valve more convex transversely, gently convex in anterior profile; beak somewhat prominent due to crest of fold, blunt, not strongly incurved. Pedicle valve interior with sides diverging widely anterior to delthyrium, teeth small, supported by nearly vertical dental plates reaching floor of valve. Muscle area cordate, pointing posteriorly, details of pattern unknown. Brachial valve interior with hinge plate deeply and narrowly notched, having shallow median- groove and small crural cavity; apex of beak arched over hinge plate forming place of attachment for diductor muscles; sockets deep, elongate, anteriorly widening, corrugated; crura slender, diverging slightly from forward edge of hinge plate, moder- ately strongly curved ventrally; crural bases extend- ing from underside of hinge plate along dorsal edges of crura; median septum high, thin, blade- like, connected at posterior to plates forming small crural cavity or to center of hinge plate, extending forward about a fifth valve length. Muscle area faintly defined; posterior adductor marks elongate, anteriorly diverging, flanking larger subelliptical anterior adductor scars lying adjacent to midline of valve. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 702c 148212a 2.0 1.7 1.7 0.9 ? 148212b 2.3 2.0 1.9 1.2 ? 148212c 3.6 3.0 2.9 2.0 ? 148212d 4.5 3.9 4.0 2.5 88 148212e 5.3 4.5 4.2 2.2 73 148212f 5.7 4.8 5.7 2.8 81 148212g 7.1 6.1 7.0 3.6 82 148212h 8.2 7.2 8.6 5.1 88 148212i 9.0 7.8 8.8 5.5 92 148212J 10.0 9.0 11.3 8.4 95 (holotype) USNM 706f 148170a 4.8 4.0 3.9 1.8 81 148170b 6.2 5.1 5.0 2.7 85 148170c 7.1 6.0 5.9 3.8 70 USNM 707e 148174a 7.8 6.9 7.3 5.9 70 148174b 8.4 7.0 8.1 6.3 94 STRATIGRAPHIC OCCURRENCE.—Cathedral Moun- tain, Road Canyon, and Cibolo formations. LOCALITIES.—Cathedral Mountain: USNM 702, 702-low. Road Canyon: USNM 702c, 703d, 706f, 707e, 719x, 721j, 721t, 726z, 726za. Cibolo: USNM 738g, 738-1. DIAGNOSIS.—Large Cenorhynchia with com- pressed valves and costae on fold and in sulcus. TYPES.—Holotype: USNM 148212J. Figured par- atypes: USNM 148212g-i,k,m,n; 148174a,b; 148176; 153487; 154666a; 154731a-c; 154904. Measured par- atypes: USNM 1482I2a-i; 148170a-c; 148174a,b. Unfigured paratypes: USNM 148212a-f,l; 154666b. COMPARISON.—Cenorhynchia saginata is charac- 1994 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY terized by the flat profile of its fold which gives the fold a moderately high anterior end, the short but relatively strong costae on the anterior end of the fold of adults,,the suberect beak of adults and the rather strong angularity of its outline. It is larger and more strongly costate than either C. hebata or C. mitigata, both new. It most nearly resembles C. fracida, new species, from which it differs in its more triangular and less pentagonal outline, lower convexity, less strongly curved pedicle beak, lower fold, and fewer costae on the fold. TYPES.—Holotype: USNM 154769. COMPARISON.—This species is fairly large and need be compared only to the larger species of Cenorhynchia. It is similar to C. mitigata, new species, but differs in having a lower fold and sulcus with more costae on the fold. It differs from C. saginata, new species, in the same characters. It is smaller than C. pentagonalis, new species, and has a less well-defined fold and sulcus than that species. Only a single specimen of C. transversa is known. Cenorhynchia transversa, new species PLATE 521: FIGURES 42^47 Usual size for genus, wider than long, valves subequal in depth: subpentagonal outline with narrowly rounded sides and long flattened postero- lateral margins; anterior margin truncated: ante- rior commissure moderately uniplicate, serrate. Foramen open, no deltidial plates. Surface semi- costate, costae low and narrow, strongest at ante- rior, 5 on fold, 1 distinct one on each flank and trace of a second. Pedicle valve moderately convex in lateral profile, broadly domed in anterior profile, dome broadly flattened on top and with short steep sides. Urn- gonal and median regions moderately convex; sul- cus wide and shallow originating just anterior to midvalve, forming short serrated tongue. Interior unknown. Brachial valve has same convexity as opposite valve in lateral profile but broadly and evenly domed in anterior profile. Sides moderately steep; umbonal and median regions gently inflated; fold poorly defined and originating in anterior half. Brachial valve interior with narrow outer hinge plates rising to narrow socket ridges; hinge plate undivided, slightly domed medially; crura short; median septum moderately elevated, extending about a third valve length. MEASUREMENTS (in mm).—Holotype USNM 154769: length 7.8, brachial valve length 7.1, width 9.0, thickness 6.1, apical angle 97° STRATIGRAPHIC OCCURRENCE.—Road Canyon For- mation. LOCALITY.—USNM 732j. DIAGNOSIS.—Wide Cenorhynchia with 5 costae on the fold. Cenorhynchia triangulata, new species PLATE 546: FIGURES 26-39 Large for genus, triangular in outline, maximum width just anterior to midvalve. Posterolateral mar- gins straight; sides narrowly rounded and anterior truncated. Valves unequal in depth, brachial valve deeper. Anterior commissure strongly uniplicate. Surface semiplicate, fold with 3 costae, flanks usually with 1. Pedicle valve unevenly convex in lateral profile, greatest convexity in posterior half, anterior half somewhat flattened; anterior profile medially gen- tly concave to slightly convex, flanks narrow and abruptly deflected. Umbonal region convex; sulcus originating just anterior to midvalve and drawn anteriorly into fairly long tongue deflected toward opposite valve at angle of almost 90°. Sulcus bounded by narrow, short costa. Beak suberect to erect, elongate; delthyrium modified by incipient deltidial plates. Brachial valve moderately convex in lateral pro- file, most convex in umbonal region; highly and narrowly domed in anterior profile. Umbonal region narrowly swollen; flanks gently inflated and marked by single costa. Pedicle valve interior with small teeth and stout dental plates with narrow umbonal cavities. Mus- culature not known. Brachial valve interior with hinge plate divided; socket ridges strong; outer hinge plates broad; crura long and slender, strongly curved and with strong keels. Inner hinge plates long and narrow not meeting medially. Median septum long, strongly elevated, extending nearly to midvalve. STRATIGRAPHIC OCCURRENCE.—Word Formation (Willis Ranch Member). NUMBER 21 1995 MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 706 148165a 10.6 9.3 9.4 5.8 64 148165b 10.2 8.6 8.9 6.0 70 (holotype) 148165c 9.4 8.2 8.1 5.2 70 LOCALITY.—USNM 706. DIAGNOSIS.—Triangular Cenorhynchia with strong median septum. TYPES.—Holotype: USNM 148165b. Figured paratypes: USNM 148165a,d-f. Measured para- types: USNM 148165a,c. Unfigured paratypes: USNM 148165c. COMPARISON.—This species is completely unlike C. pentagonalis and C. nasuta, both new, in its elongate triangular outline and generally lesser depth. It is similar to C. fracida, new species, but is still more triangular than that form, with a more subdued median fold and less deep brachial valve. Like those species with which it is compared, this one is extremely rare. Fold originating just posterior to midvalve, strongly elevated and with steeply sloping flanks. Pedicle valve interior with strong dental plates having deep umbonal cavities. Brachial valve with strong socket ridges overhanging finely corrugated sockets. Outer hinge plates narrow; inner hinge plates united; hinge plate often widely notched. Median septum strong, slender, and high. MEASUREMENTS (in mm).—Specimens USNM 153485a (holotype) and c, respectively: length 10.6, 9.3; brachial valve length 8.9, 7.9; width 12.3, 10.2; thickness 8.9, 7.3; apical angle 99°, 99°. STRATIGRAPHIC OCCURRENCE.—Cathedral Moun- tain Formation {Institella zone). LOCALITY.—USNM 72lu. DIAGNOSIS.—Small Cenorhynchia with 2 costae on the fold. TYPES.—Holotype: USNM 153485a. Figured paratypes: USNM 153485b,e-h. Unfigured para- types: USNM 153485c,d. COMPARISON.—The ornament of this species with its single costa in the sulcus and the 2 strong costae forming the fold is unique to the genus. This is a rare species, seen only at USNM 721u. Cenorhynchia unicostata, new species PLATE 519: FIGURES 25-34 Small for genus, subpentagonal to subtriangular in outline; widest near midvalve; wider than long; sides narrowly rounded; anterior margin slightly emarginate; anterior commissure uniplicate; del- tidial plates disjunct. Surface paucicostate: fold marked by two subangular costae with deep median indentation; sulcus with one strong costa and flanks with one or two costae. Pedicle valve very gently convex in lateral profile, anterior half strongly geniculated to form long tongue with two distal teeth; anterior profile broadly concave. Umbonal region moderately swollen. Flanks widely extended, gently concave to flat. Sulcus originating at midvalve but median costa arising just anterior to umbo. Brachial valve having much greater depth than pedicle valve, fairly strongly convex in lateral profile but strongly domed in anterior profile, top of dome deeply notched and with two points on each side, sides of dome rounded and very steep. Cenorhynchia ventricosa, new species PLATE 547: FIGURES 1-5 Large for genus, biconvex; profile bulbous; out- line bluntly triangular, sides diverging about 90°; commissure uniplicate, fold high, beginning 7 mm anterior to brachial beak, profile highly convex; sulcus fairly deep, beginning 6 or 7 mm anterior to pedicle beak. Costae low, fine, crests rounded to sharp, beginning 7 mm anterior to beaks, number- ing 5 on fold, 4 in sulcus, 1 or 2 on flanks. Pedicle valve somewhat inflated, uniform con- vexity from beak to anterior margin, slightly con- vex toward nonreflexed flanks; beak short, strongly curved dorsally; beak ridges short, blunt; lateral pseudointerareas narrow or absent: little or no overlap of valves. Delthyrium triangular, open, no deltidial plates observed. Brachial valve strongly inflated; profile from beak to anterior margin moderately convex; transverse profile strongly and narrowly arched; smooth part of umbo strongly arched, not flattened; beak slightly protrusive, within pedicle valve. Interior unknown. 1996 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY MEASUREMENTS (in mm).—Holotype USNM 148762: length 12.5, brachial valve length 11.0, width 12.7, thickness 11.3, apical angle 85°. STRATIGRAPHIC OCCURRENCE.—Neal Ranch For- mation (beds 12-14). LOCALITY.—USNM 701d. DIAGNOSIS.—Large Cenorhynchia with strongly ventricose and subcarinate brachial valve. TYPES.—Holotype: USNM 148762. COMPARISON.—Cenorhynchia ventricosa is char- acterized by its prominent fold with 5 fine costae, strong and uniform convexity of profile, and sharp convexity transversely, without flattening; also its hooked pedicle beak, and open delthyrium. It most nearly resembles C. fracida, new species, differing in the convexity of the profile of the fold, much more prominent fold, larger size, and normally 5 costae on the fold. C. fracida has the smooth area of the pedicle umbo slightly flattened in profile, producing a lower fold. Cenorhynchia species 1 PLATE 517: FIGURES 26-35 A species of this genus is represented by 5 speci- mens of subpentagonal outline and small size. Specimen 153492a is 7.5 mm long, 7.4 mm wide at the widest point, which is anterior to midvalve, and is 4.5 mm thick. The specimens are mostly smooth except for the anterior margins which are costate, 2 costae on the fold and 1 in the sulcus and another on the flanks. All are marked this way except one which has two costae in the sulcus. The valves are subequal in depth. STRATIGRAPHIC OCCURRENCE.—Skinner Ranch For- mation. LOCALITY.—USNM 726h. TYPES.—Figured specimens: 153492a,b. STRIGIRHYNCHIINAE, new subfamily Completely costate, hinge plate undivided and supported by median septum. Falcifer crura. Genera in West Texas: Strigirhynchia Cooper and Grant, 1969; Madarosia, new genus; and Chaeniorhynchus, new genus. These genera are all rare and stratigraphically restricted, the first and second to the Guadalupian, the third to the Leonardian. Genus Strigirhynchia Cooper and Grant Strigirhynchia Cooper and Grant, 1969:14. Medium size, rhynchonelliform, strongly bicon- vex; outline bluntly triangular to nearly circular; commissure gently uniplicate; fold low, sulcus shallow; costae distinct but fine, low, beginning at or near apexes of beaks, crests sharp, or blunt without bifurcation or intercalation. Concentric ornamentation consisting of faint, closesly spaced striae. Beak of pedicle valve sharp, straight to sub- erect; delthyrium triangular, may be completely open, or closed at base by deltidial plates; lateral pseudointerareas wide to absent; little or no over- lap of valves; regions lateral to beaks smooth, may be somewhat flattened or pinched. Brachial valve inflated, cross section of umbonal area flattened or moderately deeply indented; beak within pedicle valve. Pedicle valve interior with sides of delthyrium moderately diverging, teeth knob-shaped, supported by vertical dental plates reaching floor of valve, fused to side of valve. Muscle area triangular, widening anteriorly; adductor scars narrow, elon- gate, median and posterior, located in beak area between dental plates; diductor scars anteriorly ex- panding, one on each side of median line. Brachial valve interior with undivided triangular hinge plate; hinge sockets deep, long, finely den- ticulate, anteriorly expanding; median septum high, thin, long, bisecting part of muscle area, posterior end beneath hinge plate terminating bluntly against plate; crura diverging forward from anterior edges of hinge plate, strongly curved ven- trally, dorsal edges carinate. Muscle area elongate oval; posterior adductor scars elongate, narrow, widely separate, flanking larger, anteriorly widen- ing, medially contiguous anterior adductor scars. TYPE-SPECIES.—Rhynchonella? indentata B. F. Shumard (1860:393; Girty, 1909:321, pi. 15: figs. 20a-c, as interpreted herein and with neotype des- ignated by Cooper and Grant, 1969:14). DIAGNOSIS.—Medium-sized Rhynchonellacea hav- ing fine, direct costae, concave brachial valve umbo, and undivided hinge plate supported by a long, thin septum. COMPARISON.—Strigirhynchia is characterized by bulbous convexity, fine, low, rounded, nonbifurcat- ing costae that begin at or near the apexes of the beaks, and by its undivided hinge plate and high NUMBER 21 1997 median septum. Internally it is identical to species of Phrenophoria Cooper and Grant in which the median septum is high. It differs from those species in its completely or nearly completely costate shell, and costae that are finer, lower, and more densely arranged, and begin normally nearer to the beaks than is usual in semicostate Phreno- phoria. Allorhynchus Weller is similar externally, but Stirgirhynchia differs in its undivided hinge plate and high median septum. It is distinguished from genera of the Camarotoechiidae by its lack of a septalium or cural cavity between the top of the median septum and the underside of the hinge plate. Strigirhynchia elongata, new species PLATE 510: FIGURES 1-12, 38 Small for genus, elongate, triangular in outline with broadly rounded sides and narrowly rounded anterior margin; sides forming angle of 64°. Beak long, suberect, foramen oval, submesothyridid; del- tidial plates large, conjunct. Anterior commissure uniplicate. Valves costate except for umbonal re- gions, costae crowded, narrow, 4 on fold, 3 in sulcus, and 7 or 8 on each flank. Pedicle valve moderately convex in lateral profile and moderately domed in anterior profile, lateral slopes short but moderately gentle. Sulcus broad and shallow, originating well anterior to midvalve; tongue short; flanks narrowly rounded, slightly protruding anterolaterally. Brachial valve of about the same depth as pedi- cle valve, flatly convex in lateral profile, broadly but flatly domed in anterior profile with short steep sides. Umbonal region concave; fold orig- inating about two-thirds distance from beak, low, narrow, defined best by wider costae forming. Brachial valve with undivided hinge plate and strong, thin, bladelike septum. Other details not preserved. MEASUREMENTS (in mm).—Holotype USNM 154688a: length 10.0, brachial valve length 7.9, width 8.2, thickness 5.5, apical angle 64°. STRATIGRAPHIC OCCURRENCE.—Bell Canyon For- mation (Lamar Member). LOCALITY.—USNM 728p. DIAGNOSIS.—Elongate, narrowly triangular Stri- girhynchia. TYPES.—Holotype: USNM 154688a. Figured par- atypes: USNM 154687, 154688b. COMPARISON.—The long slender form and long beak distinguish this species from the other two members of the genus. Strigirhynchia indentata (Shumard) PLATE 508: FICURES 6-29; PLATE 520: FIGURES 35-39; PLATE 521: FICURES 30, 31 Rhynchonella? indentata Shumard, 1860:393.—Girty, 1909: 321, pi. 15: figs. 20-20c. Strigirhynchia indentata (Shumard) Cooper and Grant, 1969: 14. Moderately large, biconvex, adults somewhat globose; outline bluntly triangular, sides diverging between 85° and 105°; profile elongate oval to lenticular; anterior commissure uniplicate; fold low, beginning 6-8 mm anterior to brachial beak, evenly convex in profile except for flattening near umbo; sulcus shallow, beginning 7-9 mm anterior to pedicle beak, profile evenly convex. Costae low, narrow, crests rounded, beginning 3-6 mm anterior to beaks, numbering 4-7 on fold, one less in sulcus, 7-10 on each flank. Concentric ornamenta- tion consisting of zigzag striae; growth lines weak. Pedicle valve moderately strongly convex along sulcus and toward flanks; beak sharp, attenuate, not curved dorsally; beak ridges short, rounded; lateral pseudointerareas long, broad, bounded on pedicle valve by sharp, slightly arcuate line, strongly overlapped by brachial valve along lateral commissure. Delthyrium triangular, base covered by pair of large conjunct deltidial plates, foramen oval to nearly circular. Brachial valve slightly more strongly convex, umbonal area longitudinally indented; sides of umbonal area pinched and flattened opposite flat lateral pseudointerareas of pedicle valve, making brachial beak somewhat attenuate, producing strong beak ridges between flattened sides and flattened umbo; apex within pedicle valve, covered by del- tidial plates. Fold broad, flattened to moderately concave medially. Pedicle valve interior with sides of delthyrium diverging anterior to deltidial plates, teeth elon- gate, parallel to valve sides and supported by ver- tical dental plates reaching floor of valve. Muscle area beginning near anterior edges of dental plates, 1998 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY slightly excavate, triangular to oval; adductor area oval to round, small, median, surrounded laterally and anteriorly by larger, anteriorly expanding diductor scars. Brachial interior with undivided triangular hinge plate, bounded laterally by elongate, ante- riorly widening, deep, finely denticulate sockets; crura long, diverging forward, strongly curved ven- trally, concave toward midvalve, dorsal edge cari- nate; median septum high, thin, delicate, moderately long, and supporting hinge plate, extending into muscle area. Muscle area elongate oval, posterior adductor scars small, elongate, anteriorly diverging from midline of valve; anterior adductor scars large, anteriorly expanding, separating posterior scars. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 737a 148530a 8.2 7.4 8.0 3.6 93 148530b 9.7 8.6 9.6 6.6 93 148530c 10.9 9.6 10.5 8.4 86 USGS 2926 (green) 118572 12.9 11.5 14.6 9.4 95 (neotype) AMNH 806 154662 11.9? 10.6 11.7 8.6 90 STRATIGRAPHIC OCCURRENCE.—Capitan Formation. Bell Canyon Formation (Rader and Lamar members). LOCALITIES.—Capitan: AMNH 799, 806, 847, 853; USGS 2926 (green), 7404 (blue); USNM 725i, 725-1, 737a, 738a, 739, 740k, 740n, 740o. Rader: USNM 740g. Lamar: USNM 725e, 728p, 738. DIAGNOSIS.—Moderate size, variable Strigirhyn- chia, usually elongate or slightly transverse. TYPES.—Neotype: USNM 118572. Figured hypo- types: USNM 148530a; 148531; 154659a; 154660; 154661a; 154762a,b; 154771; 155107; 155108. Mea- sured hypotypes: USNM 148530a-c, 154662. COMPARISON.—Strigirhynchia indentata is charac- terized by its high convexity, small and numerous costae that arise near the beaks very gradually rather than abruptly, low fold and shallow sulcus, and especially by its indented brachial umbonal area, pinched sides, and large, flat lateral pseudo- interareas. It differs from the other known species of the genus, S. transversa, new species, in its nar- rower form, wider fold and sulcus, smaller angle of divergence of sides, and more narrowly rounded lateral extremities. An externally similar species is Rhynchonella salinasi Gemmellaro (1899:120, pi. 27: figs. 43-47), which has a similarly pinched brachial beak and wide lateral pseudointerareas. However, Gemmel- laro's species is indented longitudinally on both valves, the indentations extend farther forward, costae begin nearer the beak than in S. indentata, and the commissure is not uniplicate. The internal characters of R. salinasi are unknown, so its generic position is not certain. DISCUSSION.—The generic position of this species has been questionable since it first was described, because the interior was poorly known. Shumard (1860) did not illustrate his specimens, so the pres- ent concept of the species is Girty's (1909) inter- pretation of Shumard's description. The species is so distinctive, however, and its stratigraphic posi- tion so consistent that there is little doubt that it has been correctly identified. Specimens from the Guadalupe Mountains in the Museum collection have the internal features well preserved. Exter- nally they appear to be conspecific with Girty's illustrated specimen; internally they have generic characters that relate them to Strigirhynchia. Shumard's measurements indicate a specimen about 14 mm long by 13 mm wide, but none of the specimens in the Museum collection conform to these measurements. His specimen is distinctly longer than wide which is not true of Girty's illus- trated specimen which is distinctly wider than long although it agrees well in other respects. Shumard also speaks of the beak being moderately incurved which is not in accordance with any of our speci- mens. Our illustrated specimen USNM 148530c is much more in accordance with Shumard's species. King (1931) assigned several specimens to "Cam- arophoria?" indentata (Shumard). His description is based on an admittedly atypical individual from Mexico, but his specimens from the Glass Moun- tains differ from the Mexican one only in being somewhat more convex. There is no mention of an indented brachial umbonal area, pinched sides, nor broad lateral pseudointerareas. He mentions internal features that include a spondylium in the pedicle valve, but no hinge plate in the brachial valve. As King (1931:111) has said, "It may be seen that the description does not accord very well in some respects with that of Shumard," and we NUMBER 21 1999 believe that his specimens are not S. indentata, but an elongated Stenoscisma. Strigirhynchia transversa, new species PLATE 514: FIGURES 1-28 Large for genus, transversely triangular in out- line, greatest width anterior to midvalve; postero- lateral margins gently concave; sides narrowly rounded; anterior margin slightly emarginate. An- terior commissure uniplicate. Lenticular in profile. Beak small, pointed, straight to suberect. Surface costate, costae fine and numerous, 7 or 8 on fold, one less in sulcus; 7-10 on flanks. Pedicle valve gently convex in lateral profile; anterior profile broadly concave except for gently convex flanks; umbonal region, gently and nar- rowly convex; sulcus originating near midvalve, broad and shallow. Anterolateral extremities mod- erately protuberant. Flanks narrow. False interarea broad, almost completely overlapped by brachial valve. Brachial valve moderately convex in lateral pro- file but umbonal region conspicuously flattened. Anterior profile broadly and moderately domed. Umbonal region flattened and indented by con- spicuous oval trough. Fold originating at midvalve, low, not well defined anteriorly and often with shallow median sulcus tending to depress anterior margin of fold. Flanks gently convex and only slightly deflected below fold. Interior details unknown except for dental plates and long delicate median septum in brachial valve. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 750a 152863a 13.0 11.5 17.1 8.2 105 (holotype) 152863b 13.0 11.6 17.2 11.3 105 USNM 725k 152864a 11.1 9.4 12.4 6.1 90 152864b 8.2 7.1 7.6 4.0 75 USNM 740 148534 11.0 9.7 13.0? 4.7 80 STRATIGRAPHIC OCCURRENCE.—Capitan Formation. LOCALITIES.—USNM 725k, 725-1, 738a, 740, 750a, 750b. DIAGNOSIS.—Transverse Strigirhynchia with wide fold and sulcus. TYPES.—Holotype: USNM 152863a. Figured par- atypes: USNM 152863b,c; 154716; 154717. Measured paratypes: USNM 148534; 152863b; 152864a,b. COMPARISON.—This species differs from 5. inden- tata (Shumard) by its strong width compared to length and the more prominent fold and sulcus. DISCUSSION.—Young of this species tend to be elongate rather than transverse as is usual in young rhynchonellids. Furthermore, the concave umbonal region occupies nearly the entire brachial valve except for the marginal 2 mm in a specimen 8 mm long. Another juvenile with the brachial valve 10 mm long has a depressed area measuring 7.5 mm. Chaeniorhynchus, new genus [Greek chainos (open) + rhynchus (beak)] Average size for rhynchonellid, valves subequal in depth, usually elongate brachial valve slightly larger; outline oval to subtrigonal; anterior com- missure uniplicate. Beak long, suberect to erect; delthyrium open; no deltidial plates. Surface com- pletely costate. Pedicle valve interior with small teeth parallel to shell margin; dental plates well developed. Muscle field not well impressed. Brachial valve interior with strong socket ridges and uncorrugated sockets. Outer hinge plates broad; crural bases keeled; crura falcifer, curved, appearing to be twisted and flattened at distal extremity; inner hinge plates united medially with- out visible suture. Median septum slender, strong, high, extending anteriorly for about a third valve length, and acting as myophragm to divide elon- gate adductor muscle field. TYPE-SPECIES.—Chaeniorhynchus inauris, new species. DIAGNOSIS.—Completely costate Rhynchonellacea having dental plates, undivided hinge plate, and long thin median septum. COMPARISON.—This genus in its completely co- state exterior is similar to Allorhynchus Weller but differs in having an undivided hinge plate and a strong median septum, both of which are lacking from Allorhynchus. DISCUSSION.—This genus also has the exterior expression of Trophisina, new genus, but the fine 2000 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY ribs and aborted median septum of that genus separate Chaeniorhynchus and prevent confusion. Absence of deltidial plates in large specimens of Chaeniorhynchus is an unusual feature in such a relatively late, geologically speaking, rhynchonellid genus. Most of the genera of the late Paleozoic rhynchonellids have the deltidial plates well devel- oped, or at least in a rudimentary state. It shares this unusual feature with the new genus Tricoria. The interior of the pedicle valve appears to have no unusual features, but as in some other genera, the dental plates have the tendency to lie close to the walls of the valve and are not always easy to see. The brachial valves of young specimens have the hinge plate undivided, a feature that is estab- lished at an earlier age than in the related genus Trophisina . Unfortunately, most brachial valve interiors available for study do not have well- preserved crura. Two good specimens indicate slender elongate crura that are compressed laterally, as is common in many Permian genera. The me- dian septum is variable but generally is long and slender. Chaeniorhynchus inauris, new species PLATE 507: FIGURES 1-20 Average size for genus, biconvex, bulbous; out- line somewhat pear-shaped, sides diverging between 80° and 110°; profile oval; anterior commissure uniplicate; fold low, evenly convex longitudinally, strongly arched transversely, bearing 4 or 5 fine low costae; sulcus shallow. Costae fine, low, crests sharp or rounded, extending to apexes of beaks; surface entirely costate except posterior lateral surfaces near hinge; flanks bearing 5-7 lower, finer costae. Concentric ornamentation absent, growth lines infrequent. Pedicle valve strongly convex; beak sharp, weakly to strongly curved dorsally; beak ridges weak; lat- eral pseudointerareas not present, no overlap of valves lateral to beaks. Delthyrium triangular, open, deltidial plates absent. Brachial valve strongly and evenly convex; apex within pedicle valve. Pedicle valve interior with small hinge teeth, elongate, parallel to shell edge, supported by strong vertical dental plates reaching valve floor. Muscle area oval, lying anterior to ends of dental plates; scars too faint to be differentiated. Brachial valve interior with broadly triangular, undivided hinge plate, bounded laterally by elongate, finely denticulate sockets; crura projecting forward, diverging anteriorly, strongly curved ventrally, dorsal edge carinate; median septum high, blade- like, supporting hinge plate, extending forward about a third length of valve. Muscle area small, oval, posterior adductor scars obscurely separated from larger anterior adductor scars. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 702 148520a 10.3 9.1 9.1 7.4 80 148520b 9.2 7.9 8.8 7.3 80 USNM 702-low 148784a 10.0 8.4 8.8 c.6.0 86 (holotype) STRATIGRAPHIC OCCURRENCE.—Cathedral Moun- tain Formation. LOCALITIES.—USNM 702, 702-low, 735b. TYPES.—Holotype: USNM 148784a. Figured par- atypes: USNM 148520a,b; 154654a-c,e. Measured paratypes: USNM 148520a,b. Unfigured paratypes: USNM 148784b; 154654d,f. DIAGNOSIS.—Chaeniorhynchus having strongly de- veloped fold and sulcus occupied by few costae. COMPARISON.—Chaeniorhynchus inauris is charac- terized by its small size, bulbous convexity, low fold and sulcus, numerous fine costae that extend to the apexes of the beaks, open delthyrium with- out deltidial plates; its complete costation of the shell distinguishes it from species of Wellerella that occur in the Glass Mountains; and its undivided hinge plate and median septum distinguish it from externally similar species of Allorhynchus. Pontisia longicosta (Stehli, 1954:336) from the Bone Spring Formation in the Sierra Diablo is costate to the apexes of the beaks. C. inauris differs from it in its larger size, proportionately finer costation, greater convexity, and especially by its high median sep- tum, which is in contrast to the "low broad ridge" of P longicosta. DISCUSSION.—This is one of the rarest of the brachiopods from the prolific Split Tank area of the Cathedral Mountain Formation. NUMBER 21 2001 Chaeniorhynchus salutare, new species PLATE 507: FICURES 21-31 Usual size for genus, length and width nearly equal but some slightly elongate; outline elongate oval to subtrigonal. Maximum width slightly ante- rior to midvalve. Sides moderately to strongly rounded; divergence of sides 80° to 90°. Anterior commissure strongly uniplicate. Beak fairly long, strongly suberect; delthyrium open, long and nar- row. Surface costate, costae narrowly rounded, 5 or 6 on fold, one less in sulcus, about 6 on each flank. Pedicle valve fairly evenly and moderately con- vex in lateral profile; anterior profile slightly convex but median region slightly concave. Um- bonal region narrowly convex; sulcus originating near midvalve, broad and shallow, scarcely deep- ening anteriorly. Flanks gently swollen, narrowly rounded, not strongly differentiated from median region. Brachial valve fairly strongly and evenly convex in lateral profile; strongly and narrowly domed in anterior profile, top well rounded. Umbonal and median regions swollen. Fold poorly defined, visible chiefly where slightly elevated above flanks. Fold originating near midvalve. Flanks inflated but steep. Pedicle valve interior with small teeth and strong dental plates extended forward. Brachial valve with strong socket plates and smooth sockets. Hinge plate and crura not well preserved. Median septum thin and extending about a quarter valve length. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 703a 148522a 11.9 10.0 10.4 8.7 80 (holotype) 148522b 11.0 9.6 10.7 8.0 85 148522c 10.0 8.7 8.8 5.0? 80? 148522d 7.8 7.0 7.6 5.5 80 STRATIGRAPHIC OCCURRENCE.—Road Canyon For- mation. LOCALITY.—USNM 703a. DIAGNOSIS.—Chaeniorhynchus having a fairly wide but shallow and low sulcus and fold. TYPES.—Holotype: USNM 148522a. Figured par- atypes: USNM I54653b,g. Measured paratypes: USNM 148522b-d. Unfigured paratypes: USNM 148522b-d; 154653a,c-f. COMPARISON.—This species differs from C. inauris, new species, in reaching slightly greater size, in having a less prominent fold and sulcus, but in having, generally, more costae on these features. The Road Canyon species is somewhat less rotund than the earlier one and the tongue of the pedicle valve is longer. Inside the brachial valve the me- dian septum of C. inauris is more strongly devel- oped than that of the Road Canyon species. DISCUSSION.—This species is as rare as its rela- tives in the Cathedral Mountain Formation, only a dozen specimens having been recovered. Chaeniorhynchus transversum, new species PLATE 508: FICURES 48-55 Large for genus, pentagonal outline, wider than long, sides narrowly rounded and anterior margin broadly rounded; posterolateral margins forming angle of 94°. Anterior margin broadly uniplicate; beak suberect, delthyrium open, no trace of del- tidial plates. Surface completely costate, costae direct, not intercalated, 6 on fold, 5 on each flank. Pedicle valve evenly and gently convex in lat- eral profile, broadly and gently domed in anterior profile with very short sides. Median and umbonal regions moderately swollen; sulcus originating near midvalve, broad and shallow, forming short serrated tongue anteriorly; geniculation of tongue gradual and gentle. Flanks gently convex, slopes gentle. Brachial valve deeper than pedicle valve, strongly and evenly convex in lateral profile; anterior profile forming strong evenly rounded dome with very steep sides. Fold poorly defined, scarcely elevated above swollen flanks. Interior not known. MEASUREMENTS (in mm).—Holotype USNM 148523: length 12.1, brachial valve length 10.3, width 12.5, thickness 9.0, apical angle 94°. STRATIGRAPHIC OCCURRENCE.—Cathedral Moun- tain Formation. LOCALITY.—USNM 703b. DIAGNOSIS.—Large transverse Chaeniorhynchus with poorly defined fold and sulcus. TYPES.—Holotype: USNM 148523. COMPARISON.—This species is most like C. salu- tare, new species, but that species is smaller, has a 2002 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY more incurved beak, finer costae, a narrow and better defined fold and sulcus, narrower shell, and longer tongue than C. transversum. Chaeniorhyn- chus inauris, new species, is smaller, has weaker costae, is narrower, and is more narrowly shoul- dered than C. transversum. Only one specimen of this rare species has been found. Unfortunately the dorsal structures are covered by silica but strong dental plates are visible through a hole in the anterior. Madarosia, new genus [Greek madaros (bald)] Medium size, subpentagonal outline; inequi- valved, brachial valve deeper; profile convexiplane; uniplicate, anterior commissure strongly plicated but fold weakly developed. Beak suberect. Del- thyrium open, deltidial plates absent or marginal. Exterior smooth except for short lamellae at ante- rior margin. Pedicle valve interior with short dental plates defining narrow delthyrial chamber; muscle field extending anterior to anterior ends of dental plates. Brachial valve interior with small and delicate cardinalia; hinge plate concave to flat, undivided; socket ridges small; outer hinge plates broad; crura falcifer, delicate, long, slender, and with keeled dorsal edge. Median septum long, slender, elevated, and supporting hinge plate. TYPE-SPECIES.—Madarosia anterolamellala, new species. DIAGNOSIS.—Smooth rhynchonellaceans having narrowly confined cardinalia; undivided hinge plate having wide outer hinge plates and a strong median septum. COMPARISON.—In sorting specimens from Bell Canyon residues this genus is often confused with Bryorhynchus. Although the exteriors are similar, Madarosia has no costae or costellae, no deltidial plates or a mere trace of them, and the tongue of the ventral valve is angular rather than rounded as in most of the Camarotoechiids. Internally Mad- arosia is very distinct from Bryorhynchus because it has an undivided hinge plate whereas that of Bryorhynchus is divided and the crura are longer and more strongly curved. The smooth shell and subpentagonal form distinguish Madarosia from all of the costate and semicostate genera. DISCUSSION.—The almost complete lack of del- tidial plates in this genus is a primitive character. Although the collection is not large, only one pedicle valve showed any indication of deltidial plates and these are mere traces on the delthyrial margins of specimen USNM 154916h. Madarosia anterolamellala, new species PLATE 517: FIGURES 48-54; PLATE 552: FIGURES 38-58 Medium size, subpentagonal in outline, wider than long, maximum width near midvalve; sides rounded; anterior truncated. Anterior commissure narrowly rounded to angular. Surface smooth ex- cept for short growth lamellae at anterior. Pedicle valve with small beak and triangular delthyrium; umbonal region narrowly swollen, swelling not extending to midvalve; flanks flat- tened to narrowly concave and depressed below lateral margin; sulcus originating just anterior to midvalve, abrupt but shallow and forming long, narrowly rounded to angular tongue. Brachial valve gently convex in lateral profile; umbonal region flattened; anterior half broadly arched transversely to form low fold; flanks de- scending steeply. Interior of both valves as described for genus. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 725f 154744a 12.0 10.5 13.5 7.4 122 (holotype) 154744b 11.3 10.6 13.2 7.2 122 USNM 740j 154916b 10.0 9.3 10.2 5.3 116 154916c 12.0 11.0 14.6 7.0? 116 154916d 10.5 9.2 12.1 7.0 119 USNM 731 154933 11.8 10.4 13.4 6.7 119 STRATIGRAPHIC OCCURRENCE.—Bell Canyon For- mation (Hegler, Pinery, and Rader members). LOCALITIES.—Hegler: USNM 731. Pinery: AMNH 33. USNM 736. Rader: USNM 725f, 740j. DIAGNOSIS.—Madarosia with narrow anterior lamellae in the adult. TYPES.—Holotype: USNM 154744a. Figured par- atypes: USNM 154744b,c; 154916a-h. Measured NUMBER 21 2003 paratypes: USNM 154744b, 154916b-d, 154933. Un- figured paratypes: USNM 154933. COMPARISON.—This species differs from M. pen- tagona, new species, in its somewhat smaller size, less thickness, and the presence of the growth lamellae at the anterior. Differences also appear in the brachial valves of the two species, that of M. anterolamellala being much more delicate but with a proportionately longer hinge plate and more prominent outer hinge plates. DISCUSSION.—This is a rare and delicate species. It occurs in the lower three members of the Bell Canyon Formation but has not yet been taken- from the Lamar Member. The shell is so thin that some specimens were lost in handling them for study. Madarosia pentagona, new species PLATE 513: FIGURES 39-41; PLATE 548: FIGURE 18 Large for genus, pentagonal in outline, wider than long, with gently rounded sides and truncated anterior. Unequally biconvex, pedicle valve gently convex, but brachial valve deeper. Anterior com- missure strongly angular and extended in dorsal direction. Delthyrium open, no deltidial plates. Surface smooth. Pedicle valve interior with short dental plates sloping medially and defining narrow delthyrial chamber. Muscle field narrow and extending ante- rior to delthyrial cavity. Brachial valve interior with short, undivided hinge plate; outer hinge plates moderately wide; crura long and slender, dorsally keeled and with flattened distal extremity. Median septum long and slender. MEASUREMENTS (in mm).—Specimen USNM 154930 (holotype): length 13.0, brachial valve length 11.3, width 14.1, thickness 9.0, apical angle 116°. STRATIGRAPHIC OCCURRENCE.—Cherry Canyon For- mation (Getaway Member). LOCALITY.—AMNH 512. DIAGNOSIS.—Thick Madarosia without anterior lamellae and with fairly stout cardinalia. TYPES.—Holotype: USNM 154930. COMPARISON.—This is a more robust species than M. anterolamellata; it is much thicker and has stouter cardinalia. The hinge plate is less extended anteriorly than that of M. anterolamellata and the outer hinge plates not so prominent. This is a very rare species: only one specimen was taken from the vast amount of residues from AMNH 512 = USNM 728. ALLORHYNCHIDAE, new family Rhynchonellacea with ventral fold and dorsal sulcus, completely or nearly completely costate. Pedicle valve with dental plates and variable del- tidial plates; brachial valve without median septum but with divided hinge plate. Crura falcifer or modified falcifer. Genera in West Texas: Allorhynchus Weller, 1910; Ptilotorhynchus, new genus; Deltarina, new genus; Fascicosta Stehli, 1955; Hemileurus, new genus. Genus Allorhynchus Weller, 1910 Allorhynchus Weller, 1910:509; 1914:197.—Stehli, 1955:74. Shell rhynchonelliform, biconvex; outline bluntly triangular; profile subtrigonal to semiovate; anterior commisure uniplicate, fold low, sulcus shallow; costae low but distinct, crests rounded, without bifurcation or intercalation, beginning at or near beaks. Concentric ornamentation and growth lam- inae weak. Pedicle beak sharp, straight to moder- ately curved dorsally; delthyrium triangular, sides slightly constricted by rudimentary, usually dis- junct, deltidial plates; lateral pseudointerareas narrow, normally covered by slight overlap of bra- chial valve. Brachial beak rounded, lying inside pedicle valve beneath small disjunct deltidial plates. Pedicle valve interior with delthyrium widened to receive beak of brachial valve; teeth supported by vertical dental plates reaching valve floor. Mus- cle area triangular, between and anterior to for- ward edges of dental plates; adductor scars small, forming elongate oval mark in posterior part of muscle area; diductor scars lateral and anterior to adductor scar, widening abruptly at posterior end, gradually expanding from there forward. Brachial valve interior with medially divided or deeply notched hinge plate, bounded laterally by deep, anteriorly widening, finely to coarsely corru- gated hinge sockets; socket ridges strong, crura 2004 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY falcifer, diverging anteriorly, strongly curved ven- trally, commonly appearing twisted, dorsal edges carinate, with keel extending beneath hinge plate; median septum absent; low myophragm present or absent. Muscle area elongate oval; posterior ad- ductor scars narrow, elongate, posterior ends sep- arate, diverging anteriorly, flanking larger, ante- riorly widening, lobate anterior adductor scars. TYPE-SPECIES.—Rhynchonella heteropsis N.H. Winchell, 1865:121. TYPES.—Lectotype: USNM 142567a from Win- chell's type lot. COMPARISON.—Allorhynchus is distinguished by its relatively low fold and shallow sulcus, fine, blunt costae that cover the shell, usually extending to the beaks, by its divided hinge plate, and lack of a median septum. Its costate umbonal areas and divided hinge plate distinguish it from Wellerella. Strigirhynchia, new genus, is costate to the beaks, but its undivided hinge plate and high median septum separate it from Allorhynchus. DIAGNOSIS.—Completely costate Allorhynchidae having a divided hinge plate and no median septum. DISCUSSION.—Stehli (1955:74) remarked that the combination of features characterizing Allorhyn- chus is distinctive, and not likely to be confused with that of other genera. But he assigned his Permian specimens only tentatively to the genus, giving two reasons for his doubt. One is the ab- sence of known species of Allorhynchus from the Pennsylvanian. The other involves anatomical details of the shell. He cites the presence of con- centric striae on the Mississippian shells and their absence on the Permian species known to him. One new species in the Museum collections has faint concentric striae, but we consider that to be a specific character at most, certainly not eliminating from the genus the two other species which do not exhibit it. Furthermore, that feature may be de- stroyed by silicification of the shell, leaving con- centric ornamentation visible only on a few speci- mens. The other feature that Stehli believes may distinguish the Mississippian species from the Per- mian species is denticulation of the hinge sockets. This feature cannot be observed on the calcareous specimens of the type species from Iowa, but minute denticulation or corrugation is present in a few silicified Mississippian specimens of a species from the Warsaw Formation of Tennessee. Coarse silicification can destroy fine denticulation, so it is not visible on all specimens of that Mississippian species, but its presence on a few is sufficient to link them generically with the more coarsely den- ticulate Permian species. We believe that all the known species have generic characters in common, and that assignment of Permian species to the Mississippian genus need not await discovery of species of Allorhynchus in Pennsylvanian strata. The type-species A. heteropsis (Winchell) shows the exterior characters to perfection, with the beaks and umbones of both valves covered by costae. We here select specimen USNM 142567a as type speci- men for the species. This specimen was formerly one of Winchell's cotypes. It shows all of the exte- rior characters and, in addition, the nature of the deltidial plates may be clearly seen. They are small and disjunct. This feature is fairly general among species of the genus. Only one specimen of a new species from the Mississippian (Warsaw) of Ten- nessee shows conjunct deltidial plates. Two addi- tional specimens show the socket plates and the myophragm of the brachial valve. The Permian specimens and the new species from the Mississip- pian (Warsaw) of Tennessee alluded to above yielded most of the information on the interior details. The specimens from Tennessee are small, rotund forms. The teeth of the pedicle valve are almost horizontal and are flattened in the direction of the shell width but they have a strong socket on their posterior side. The teeth of the Permian species are more knoblike but also have a deep socket on the outside of the tooth. The dental plates of the Mississippian forms are strong and have deep um- bonal chambers but the Permian ones usually have narrow, slitlike umbonal cavities. The muscle scars were not clearly discerned in any of the specimens but they lie anterior to the ends of the dental plates. Inside the brachial valve the sockets are minutely corrugated in the Permian forms but these struc- tures were not seen in the Mississippian specimens. The socket ridges of the Mississippian examples are strong and somewhat elevated. They bear broad and concave outer hinge plates that are bordered by the crural bases. Inner hinge plates can be seen on both Mississippian and Permian specimens but they were not seen to unite in any of the sped- NUMBER 21 2005 mens. The divided hinge plate is thus a persistent character in the genus. The falcifer crura of the Mississippian specimens are generally long, slightly bowed, somewhat ex- panded anteriorly, and form hollow plates with the concavity facing toward the midline of the shell. The plates are crescentic in cross section. On the underside of the hinge plate the crura are strongly keeled and the keels extend to the apex. The Mississippian specimens have a strong myo- phragm that divides the muscle field but does not reach the apex. In most of the Permian species no trace of a myophragm was seen. A semicostate allorhynchid from the Neal Ranch Formation is here separated as the new genus Hemileurus in allusion to this difference in its exterior. Some of the Permian specimens have non- costate umbones but this shell is half smooth and thus presents a greatly different appearance from typical Allorhynchus. Allorhynchus is common at several levels but it is not abundant at any place in the Glass or Guada- lupe Mountains. Allorhynchus circulare, new species PLATE 780: FIGURES 19-24 (in part V) Medium size for genus, subcircular to roundly subpentagonal in outline, length slightly greater than width; sides strongly rounded; anterior mar- gin broadly rounded. Posterolateral margins form- ing angle of 80° Valves subequal in depth. Del- tidial plates small, disjunct. Surface costate, costae crowded, 5 on fold and 5 on flanks. No concentric ornament preserved. Pedicle valve evenly and moderately convex in lateral profile and broadly and gently convex in anterior view; sulcus originating just posterior to midvalve, shallow throughout and forming short, serrated tongue. Flanks rounded. Brachial valve moderately convex in lateral pro- file but somewhat more so in anterior view; fold poorly defined, originating posterior to midvalve but never highly elevating. Flanks rounded and convex, only slightly depressed below fold at anterior. Pedicle valve interior with strong dental plates. Brachial valve with strong socket ridges, narrow sockets, narrow to nonexistent outer hinge plates, and short crura. MEASUREMENTS (in mm).—Holotype USNM 148059a: length 7.5, brachial valve length 6.2, width 6.9, thickness 5.3, apical angle 80°. STRATIGRAPHIC OCCURRENCE.—Cherry Canyon For- mation (Getaway Member). LOCALITY.—USNM 732. DIAGNOSIS.—Rotund, thick and rounded Allor- hynchus with poorly defined fold and sulcus. TYPES.—Holotype: USNM 148059a. Figured par- atypes: USNM 148059b,c. Unfigured paratypes: USNM 148059d-m. COMPARISON.—The intermediate size of this spe- cies limits comparison to A. concentricum, new species, from which it differs in its narrower out- line, more circular form, greater thickness, and lack of any concentric ornament such as is con- spicuous on A. concentricum. Allorhynchus concentricum, new species PLATE 509: FIGURES 74-77 Usual size for genus, length and width nearly equal; valves subequal in thickness; outline pen- tagonal, sides rounded; posterolateral margins forming angle of 110°. Anterior commissure gently uniplicate. Delthyrium open, no trace of deltidial plates. Fold with 5 costae, 6 or 7 on flanks; entire surface covered by fine concentric lines. Pedicle valve gently and evenly convex in lateral profile; anterior profile broadly and gently convex; beak somewhat elongated; umbonal region mod- erately inflated; sulcus originating at about mid- valve, wide and shallow; tongue short. Flanks some- what flattened, with gentle slopes. Brachial valve gently convex in lateral profile but moderately domed in anterior profile with short steep sides. Median region and umbonal region swollen; fold originating slightly posterior to mid- valve, poorly defined, barely elevated above mod- erately swollen and steep flanks. Interior unknown. MEASUREMENTS (in mm).—Holotype USNM 154676: length 8.6, brachial valve length 7.6, width 8.9, thickness 5.5, apical angle 110°. STRATIGRAPHIC OCCURRENCE.—Road Canyon For- mation. LOCALITY.—USNM 732j. 2006 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY DIAGNOSIS.—Finely costate Allorhynchus with low fold, shallow sulcus, and strong concentric lines. TYPES.—Holotype: USNM 154676. COMPARISON.—In size this species suggests A. triangulatum and A. variabile, both new, but it is much more finely costate than either of these spe- cies. It is also suggests Petasmatherus nitidus, new species, but is larger, has more and crowded co- stae, and is provided with concentric lines which do not appear on P. nitidus. Allorhynchus formulosum, new species PLATE 540: FICURES 4-14 Average size for genus, subtrigonal to subpen- tagonal in outline, sides rounded, maximum width anterior to midvalve. Anterior margin truncated. Anterior commissure strongly uniplicate. Apical angle usually about 90°. Completely costate, but indistinct at apexes; costae moderately elevated, narrowly rounded with fairly wide interspaces, 5 costae on fold, 4 or 5 on flanks, last ones indistinct. Pedicle valve moderately convex in lateral pro- file, greatest convexity just posterior to midvalve; anterior profile gently and broadly convex. Beak short, straight or nearly erect, with oval foramen and small disjunct deltidial plates. Median and umbonal regions gently convex; sulcus wide, shal- low, originating at midvalve, forming moderately long tongue. Flanks narrowly elevated in antero- lateral extremities, short but steep. Brachial valve gently convex in lateral profile but strongly domed and with precipitous sides in anterior profile. Umbonal region moderately con- vex; median region moderately swollen. Fold, short, low, poorly defined, originating at midvalve. Flanks moderately swollen and steep. Pedicle valve interior with narrow, oblique den- tal plates oriented parallel to shell margin and located well forward of deltidial plates. Dental plates thin, delicate, short, and defining narrow umbonal chambers. Muscles not clearly impressed. Brachial valve interior with strong socket ridges and moderately wide outer hinge plate. Inner hinge plates rudimentary. No median septum or myo- phragm. Crura moderately long. STRATIGRAPHIC OCCURRENCE.—Cherry Canyon For- mation (Getaway Member). MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) AMNH 585 154881a 8.2 7.3 9.3 5.5 98 (holotype) 154882a 3.4 3.0 3.5 1.4 80 154882b 4.4 3.6 4.2 1.8 80 154882c 5.1 4.2 4.8 2.2 80 154882d 5.4 4.7 5.3 2.8 80 154882e 7.0 6.2 7.4 3.6 85 154882£ 7.6 6.6 8.0 4.6 90 154882g 7.5 6.7 8.3 4.8 85 154882h 8.6 7.7 10.4 5.5 105 LOCALITIES.—AMNH 585; USNM 730. DIAGNOSIS.—Fairly wide, short Allorhynchus with broad fold, shallow sulcus, and short beak. TYPES.—Holotype: USNM 154881a. Figured par- atypes: USNM I54881c,d; 154882g,h. Measured paratypes: USNM 154882a-h. Unfigured paratypes: USNM I54881b,e,f. COMPARISON.—This species approaches A. per- mianum Stehli in size but no specimen actually attains the size of that species. The two may be distinguished, beside the size, by the stronger rib- bing of A. formulosum when compared to A. per- mianum of the same size, the generally wider form and much shorter beak of the pedicle valve of A. formulosum. Specimens of similar size must be compared because the young of A. permianum are more elongate than adults of A. permianum of the same size. Allorhynchus aff. A. macrum (Hall) PLATE 780: FIGURES 69-77 (in part V) Aff. Rhynchonella macra Hall, 1856:11. Aff. Allorhynchus macrum (Hall) Weller, 1914:199, pi. 25: fig- 1-4- Figures of a Mississippian species of Allorhyn- chus are introduced here for comparison with the interiors of the Permian species assigned to the genus. The figures illustrate well the divided hinge plate. STRATIGRAPHIC OCCURRENCE AND LOCALITY.—War- saw Formation, Clarksville, Tennessee. TYPES.—Figured specimens USNM 155071. NUMBER 21 2007 Allorhynchus permianum Stehli Allorhynchus} permianus Stehli, 1955:74, figs. 18-31. Large for genus, biconvex; outline bluntly tri- angular to subpentagonal, sides diverging from 50° in juveniles to 120° in largest adults; profile len- ticular to semiovate; commissure uniplicate, fold high, with moderately convex profile; sulcus shal- low, evenly convex longitudinally. Costae moder- ately high, strong, beginning at beaks or slightly anterior, numbering 4 or 5 on fold, normally 5, one less in sulcus, 6 or 7, rarely 8 on each flank. Pedicle valve slightly inflated in umbonal area, gently convex toward nonreflexed flanks; beak sharp, somewhat attenuate, slightly curved dorsally; beak ridges blunt, relatively short; lateral pseudo- interareas narrow, entirely or partly covered by overlapping brachial valve. Delthyrium triangular, in adults constricted along sides by disjunct del- tidial plates, open in juveniles; foramen eyeshaped or rounded triangular. Brachial valve strongly convex toward flanks, gently convex longitudinally along fold; umbonal area slightly flattened in transverse cross section, some with shallow longitudinal indentation; beak often attenuate, end blunt, within pedicle valve below deltidial plates. Pedicle valve interior with sides of delthyrium abruptly widened anterior to deltidial plates, form- ing notch to accommodate brachial beak, each side with one knob-shaped, slightly elongate hinge tooth supported by a vertical dental plate reaching floor of valve. Muscle pattern roughly triangular, lying between and anterior to forward edges of dental plates; adductor scars elongate, in posterior part of muscle area, one on each side of median line, surrounded laterally and anteriorly by wider, longer, anteriorly expanding diductor scars. Brachial valve interior with hinge plate divided by wedge-shaped notch, bounded laterally by deep, anteriorly widening, socket ridges which define finely to coarsely denticulate hinge sockets; crura short, diverging anteriorly, strongly curved ven- trally, often twisted, dorsal edges carinate; myo- phragm low, rounded, bisecting posterior part of muscle area, often completely absent. Muscle area elongate oval; posterior adductor scars narrow, elongate, widely separated, slightly diverging ante- riorly, flanking larger, bilobate, anteriorly widening anterior adductor scars. STRATIGRAPHIC OCCURRENCE.—Road Canyon For- mation; Word Formation; Cherry Canyon Forma- tion (Getaway Member). LOCALITIES.—See subspecies below. DIAGNOSIS.—Large for the genus with high fold having 5 costae. TYPES.—Holotype: AMNH 27905/5. Figured hy- potypes: USNM 148054a-h. Measured hypotypes: USNM 148078; 148088; 148094a,b. COMPARISON.—Allorhynchus permianum is char- acterized by its comparatively large size, high fold with 5 strong costae that extend to the beak or close to it, relatively short crura, strongly corru- gated sockets, and broad low myophragm in the brachial valve. It differs from A. heteropsis (Win- chell) from the Mississippian of Iowa in its large size, more numerous costae, and absence of a well- defined median groove on the exterior of the bra- chial umbonal area. It differs from Hemileurus runcinalus, new species, from the Neal Ranch For- mation in its larger size, more numerous and stronger costae that begin farther back on the beaks, longer and less strongly curved pedicle beak, and valves that overlap slightly anterior to the beaks, commonly producing a narrow lateral pseudoin- terarea. Allorhynchus permianum permianum Stehli PLATE 541, FIGURES 1-30 Allorhynchus? permianus Stehli 1955:74, figs. 18-31. COMPARISON.—This subspecies occurs in the Get- away Member of the Cherry Canyon Formation in the Guadalupe Mountains, Guadalupian in age. Its costae extend to the apexes of the beaks, a feature that distinguishes it from the otherwise similar Glass Mountains subspecies, A. permianum word- ense, new subspecies. MEASUREMENTS (in mm).—From locality USNM 728 specimen AMNH 27905/5 (holotype): length 12.5, brachial valve length 10.5, width 13.9, thick- ness 9.5, apical angle 105°. STRATIGRAPHIC OCCURRENCE.—Cherry Canyon For- mation (Getaway Member). LOCALITIES.—AMNH 496, 512, 547, 600; USNM 728. DOUBTFUL OCCURRENCE.—Bell Canyon Formation (Hegler and Lamar members). Capitan Formation. 2008 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY LOCALITIES.—Hegler: USNM 731. Lamar: AMNH 37; USNM 728r. Capitan: 738a, 740, 750. Allorhynchus permianum wordense, new subspecies PLATE 542: FICURES 1-51 COMPARISON.—This subspecies occurs in the Word Formation of the Glass Mountains. It is dis- tinguished from the subspecies from the Guadalupe Mountains by its incomplete costae that normally begin 1-2 mm anterior to the apexes of the beaks. In other characters the two groups are indistin- guishable. STRATIGRAPHIC OCCURRENCE.—Word Formation (China Tank, Hess Canyon, and Willis Ranch members; lens between Willis Ranch and Appel Ranch members). MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 706 148084a 5.5 4.6 4.3 2.2 55 148084b 7.7 6.2 7.0 3.3 60 148084c 9.3 7.8 9.0 3.7 80 148084d 10.0 8.5 9.9 6.0 80 148084e 9.3 8.2 9.4 3.7 80 148084f 10.0 8.3 10.6 6.7 96 148084g 15.0 12.6 15.4 10.6 113 154889c 12.9 11.2? 13.7 9.7 88 (holotype) USNM 706b 148088a 4.1 3.2 3.1 1.6 ? 148088b 4.6 3.6 3.9 1.9 p USNM 706e 148078 11.9 10.4 12.6 8.0 114 USNM 706z 148094a 13.8 11.8 15.8 9.0 100 148094b 5.9 5.3 5.5 2.9 05 LOCALITIES.—China Tank: USNM 703e, 706c, 706z, 713, 726r. Willis Ranch: AMNH 505; USNM 706, 706e. Appel Ranch: USNM 715i, 719z, 722t, 724u. Lenses: USNM 706b, 732c, 737w. Word For- mation (undifferentiated): USNM 731p. TYPES.—Holotype: USNM 154889c. Figured par- atypes: USNM 148081a-e; 148084e-g; 154889a-f,h; 154890a-d. Measured paratypes: USNM 148078; 148084a-g; 148088a,b; 148094a,b. Unfigured para- types: USNM 148084a-d, 154889g, 154890e. Allorhynchus triangulatum, new species PLATE 542: FIGURES 52-60 Medium size, longer than wide in all growth stages; elongate triangular outline with apical angle approaching 89° Sides gently rounded; maximum width anterior to midvalve. Anterior margin straight. Surface nearly completely costate but beaks variable, ranging from costate to nearly smooth. Surface marked by crowded, rounded to subangular costae, 4 or 5 on fold, usually 4, one less in sulcus. Flanks marked by 3-5 costae, last two usually indistinct. Pedicle valve shallower, evenly and moderately convex in lateral profile; medially flat to slightly concave in anterior profile. Beak long, suberect, with large elliptical to oval foramen. Deltidial plates small, disjunct. Umbonal region narrowly swollen; sulcus originating just anterior to mid- valve, shallow and narrow, approximating about half valve width. Tongue long and flattened. Flanks narrow, rounded. Brachial valve moderately convex in lateral pro- file, most convex in posterior half; anterior profile narrowly domed and with steep .parallel sides. Umbonal region moderately convex; fold originat- ing near midvalve, narrow, moderately strongly elevated at anterior end. Flanks gently swollen and only slightly depressed. Pedicle valve interior with moderately long den- tal plates separated from valve wall by narrow slits; muscle scars not impressed. Brachial valve interior with long crura, crescentic in section, concave toward midvalve, and with keels under crural base. No inner hinge plates. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 706c 148092a 12.0 9.8 11.4 10.0 77 148092b 9.7 7.9 9.3 7.9 75 (holotype) 148092c 9.2 7.6 8.3 5.7 72 148092d 8.9 7.6 7.3 5.5 64 148092e 8.9 7.3 7.8 6.0 68 148092f 7.6 6.3 6.8 5.4 64 I48092g 5.3 4.2 4.5 3.3 63 STRATIGRAPHIC OCCURRENCE.—Word Formation (China Tank, Willis Ranch, and Appel Ranch members and lens between the last two). NUMBER 21 2009 LOCALITIES.—Word: USNM 731u, 732s. China Tank: USNM 706c, 733q. Willis Ranch: AMNH 505; USNM 706, 706e, 724u. Appel Ranch: USNM 7l4o. Lens: USNM 742b. DIAGNOSIS.—Elongate, thick Allorhynchus with narrow fold and long beak. TYPES.—Holotype: USNM 148092b. Figured par- atypes: USNM 148092c-e,h,i. Measured paratypes: USNM 148092a,c-g. Unfigured paratypes: USNM 148092a,f,g. COMPARISON.—This species occurs with A. vari- abile, new species, but is readily distinguished by its long, triangular outline, and narrow fold. Its narrow form, narrow fold, and fine costae distin- guish it from A. permianum Stehli. Allorhynchus variabile, new species PLATE 543: FIGURES 1-13 Medium size for genus, slightly wider than long in adults, subtrigonal in outline; valves subequal in depth. Sides narrowly rounded; maximum width at or slightly anterior to midvalve. Anterior mar- gin truncated. Apical angle about 90° or slightly greater. Surface nearly completely costate; costae narrow, rounded; interspaces narrower than co- stae; costae numbering 4-6 on fold, usually 4; one less costa on sulcus; flanks marked by 3-7, last ones usually indistinct. Pedicle valve evenly and moderately convex in lateral profile, slightly sulcate in anterior profile. Beak moderately long, suberect, pointed; foramen elongate, elliptical, usually restricted anteriorly by disjunct deltidial plates. Umbonal region moder- ately swollen; sulcus originating at midvalve, deep- ening rapidly. Flanks narrow, gently convex. Brachial valve moderately convex in lateral pro- file, maximum curvature in posterior part and flat- tened anteriorly; anterior profile narrowly domed with steep sides. Fold low, somewhat spreading anteriorly, occupying more than half of width and originating just anterior to midvalve. Flanks rounded, gently depressed. Pedicle valve interior with short dental plates, defined by narrow umbonal cavities. Brachial valve interior with divided hinge plate, no inner hinge plates. Socket ridges low; crura short, curved, and with strong keels. MEASUREMENTS (in mm). brachial apical valve thick- angle length length width ness (°) USNM 706c 148090a 10.6 9.0 12.0 8.0 95 (holotype) 148090b 10.1 8.6 11.0 6.8 88 148090c 9.4 7.8 9.5 6.7 78 148090d 7.7 6.3 7.4 4.7 73 148090e 7.0 5.9 6.7 4.1 73 148090f 7.5 6.4 7.4 4.5 77 STRATIGRAPHIC OCCURRENCE.—Word Formation (China Tank and Willis Ranch members). LOCALITIES.—China Tank: USNM 706c. Willis Ranch: 706. DIAGNOSIS.—Medium size, transverse Allorhyn- chus with low fold marked by five costae and smooth umbones. TYPES.—Holotype: USNM 148090a. Figured par- atypes: USNM 148090a-h; 154892a,b. Measured paratypes: USNM 148090b-f. COMPARISON.—In the adult form this species is slightly wider than long and has fairly crowded costae. It is smaller than A. permianum Stehli, with more even and finer costae and with a some- what narrower sulcus in the young and some adults, but this feature is variable. The costae of the fold of A. permianum are strong and conspicuous but those of A. variabile are subdued and fairly even in size. Allorhynchus venustulum, new species PLATE 542: FIGURES 61-64; PLATE 543: FIGURES 14-33 Rhynchonella longaeva Girty, 1909:322, pi. 15: figs. 19a-c [not 18]. Small, with rounded contours and subtrigonal to subpentagonal outline; apical angle about 75°; lenticular in profile, brachial valve having slightly greater depth; sides rounded but maximum width slightly anterior to midvalve; anterior margin gen- tly rounded; anterior commissure gently uniplicate. Surface completely costate but costae often indis- tinct at umbones; costae broad and gently rounded and with narrow interspaces, 3-5 on fold and 5 or 6 on each flank. Pedicle valve evenly and gently convex in lateral profile but broadly and moderately domed in ante- rior profile. Beak nearly straight to suberect, 2010 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY usually short, except in young; foramen elongate oval; deltidial plates small, lateral and basal, dis- junct; posterior and median regions gently convex; sulcus, shallow and poorly defined, originating near midvalve and producing short tongue. Flanks short and moderately steep. Brachial valve moderately convex in lateral pro- file, most curvature in umbonal region; anterior profile broadly and moderately domed and with short steep sides. Median and umbonal regions moderately inflated; fold low, poorly defined and best seen at anterior; flanks swollen and moderately steep. Pedicle valve interior with narrow teeth, com- pressed in the direction of width and located well anterior to deltidial plates; dental plates delicate, short, defining very narrow delthyrial chamber; muscle field anterior to delthyrial cavity, but scars poorly impressed. Brachial valve interior with strong, inclined socket ridges defining narrow, corrugated sockets; outer hinge plates narrow, crural bases narrow; inner hinge plates moderately developed. Crura of falcifer type. Median ridge low, wide, clearly secondary, adductor scars near midvalve. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (") 2.9 2.2 2.7 1.2 60 3.5 2.7 3.0 1.9 60 4.5 3.5 4.0 2.1 60 6.0 4.8 5.4 3.8 60 7.0 5.7 5.8 4.0 70 6.8 5.7 6.3 4.0 70 7.4 6.4 7.1 4.7 75 USNM 738b 152804a 152804b 152804c 152804d 152804c 152804f 152804g (holotype) STRATIGRAPHIC OCCURRENCE.—Bell Canyon For- mation (Hegler, Pinery, Rader, and Lamar members). LOCALITIES.—Hegler: USNM 731. Pinery: USNM 725h. Rader: USNM 725g. Lamar: AMNH 38, 40, 347( = L-2), 348( = L-3),351( = L-6), 430; USNM 725e, 728i, 728p, 728r, 738, 738b. DIAGNOSIS.—Small elongate Allorhynchus with low, rounded costae. TYPES.—Holotype: USNM 152804g. Figured par- atypes: USNM 152804f, 154891a-d, 154893a-d, 154894, 154895. Measured paratypes: USNM 152804a-f. Unfigured paratypes: USNM 152804a-e. COMPARISON.—This is a small elongated species and may be compared only to Petasmatherus niti- dus and pumilus, both new. It is readily distin- guished from the latter by its stronger and some- what subdued ribbing and less elongated beak of the pedicle valve. It is more like P. nitidus but is generally a smaller species, with less well-defined fold and sulcus, more variable costation in the fold and sulcus, and more subdued costation. It is much smaller and more trigonal than any of the species of Allorhynchus from the Word Formation of the Glass Mountains or the Getaway Member in the Delaware Basin. DISCUSSION.—The species is rare, and has been found only in the dark limestones of the Bell Canyon Formation. Allorhynchus species unidentified The above named species do not include all of the forms this genus takes in the residues or broken from their matrix in the Glass Mountains. Speci- mens referable here were taken from the Skinner Ranch Formation (Decie Ranch Member) at USNM 71 Id; a coarse-ribbed species occurs in the Road Canyon Formation at USNM 703d, and 721j. An- other more rotund species occurs in the Willis Ranch Member of the Word Formation at USNM 723w; a specimen of Allorhynchus comes from the Word Formation at USNM 731m. In the Guadalupe Mountains the Getaway Mem- ber of the Cherry Canyon Formation produced a rotund species at AMNH 496. A species occurs in the Cutoff Shale Member of the Bone Spring For- mation at AMNH 678. Small collections from the Capitan and Bell Canyon formations also cannot be assigned to known species. These occur in the Capitan at USNM 738a, 740, 750, and in the Bell Canyon Hegler Member at USNM 731, and Lamar Mem- ber at AMNH 37, USNM 728r. Ptilotorhynchus, new genus [Greek ptilotos (winged) + rhynchus (beak)] Rhynchonellid about medium size, triangular in outline, biconvex and strongly inequivalve, bra- chial valve deeper and more convex. Anterior com- missure uniplicate, fold low, sulcus shallow but NUMBER 21 2011 long. Beak short, straight; deltidial plates conjunct and strongly alate. Surface multicostellate, costellae increasing by implantation and bifurcation in sev- eral generations. Pedicle valve interior with small teeth and dental plate greatly reduced or obsolete in adults. Muscle area large and rounded. Brachial valve interior with deeply notched hinge plate with non corrugated sockets and thick socket plate; outer hinge plates narrow; crura, flat- tened falcifer, moderately long, laterally com- pressed blades with broad faces toward midline of valve; inner hinge plates not formed in young, forming short narrow arch in adults. Median ridge confined to apex in adult and supporting hinge plates, not present in young; median ridge often thick; adductor field elongate and divided medially by low, thin myophragm. TYPES-SPECIES.—Ptilotorhynchus delicatum, new species. DIAGNOSIS.—Rhynchonellida with numerous bi- furcated costellae, obsolescent dental plates, and a median ridge in the brachial valve supporting a deeply indented hinge plate. COMPARISON.—This genus can be recognized easily by its distinctively marked exterior with the bifurcating costellae. In this respect it resembles Fascicosta Stehli and Divaricosta Cooper and Grant, but differs from both of them in having the dental plates of the pedicle valve aborted or obsolete and the hinge plate deeply indented. The strongly alate deltidial plates, which are carried from youthful stages to the adult, are also an unusual feature that lends distinction to the genus. In the above respects it differs from the multicostate forms as well as those with direct costae. DISCUSSION.—This interesting genus has a num- ber of characters peculiar to it. The alate deltidial plates are a rarity among Paleozoic genera. They occur in the Glass Mountains fauna in the young of Rhynchopora, where they are conspicuous but usually not so strongly developed as in the present genus. Perhaps, if the young of more Paleozoic rhynchonellids were known, these peculiar plates would prove to be of wider occurrence. In Ptiloto- rhynchus they are'developed in the adult as well as in the young and are as strongly marked as in some of the late Mesozoic genera. They serve to strengthen the foraminal margin and help to pro- duce a pedicle tube. Another feature unique to this genus among the Glass Mountains and other West Texas rhyncho- nellids is the obsolescence of the dental plates. These are greatly reduced in the leiorhynchids but are seldom lost completely. The Permian faunas of Russia have rhynchonellids, such as Pseudo- loellerella and Denticuliphoria, (both Licharew 1956), in which the dental plates have atrophied. In Ptilotorhynchus dental plates were not observed in the young specimens available. These specimens were, perhaps, in a young-adult stage rather than immature, only their size suggests their youth. The teeth in this genus are very small; running in a curve from them along the lateral shell wall is a low ridge that probably represents the growth track of the tooth and is not a remnant of a dental plate. The cardinalia of this genus are also unusual for Permian rhynchonellids. In the smaller specimens, probably young adults, the hinge plate is deeply indented, with no trace of inner hinge plates; but in the largest specimen, truly an adult, the inner hinge plates form a low ridge between the crural bases. The outer hinge plates are narrow and the crural bases are a keel on their inner edge. The crura are laterally compressed blades, rather rigid, and with the concave side facing midvalve. In the younger specimens no trace of a median septum is evident, although in the largest specimen a rudi- mentary ridge occurs at the apex and joins the inner hinge plates in the support of the hinge plate. Anteriorly the ridge is extremely short, but between the adductors in this large specimen a narrow myophragm appears as a continuation of the ridge. In some of the younger specimens the median de- pression on the brachial valve is translated in the interior to a broad rounded ridge. Ptilotorhynchus delicatum, new species PLATE 508: FIGURES 72-76; PLATE 513: FIGURES 1-18; PLATE 552: FIGURES 15, 16 Medium size for rhynchonellid, elongate oval to subtrigonal in outline, sides diverging at about 90°. Maximum width near midvalve. Sides broadly rounded. Anterior commissure uniplicate with moderate amplitude. Beak short, straight. Surface multicostellate, fold poorly defined, costellae nar- rowly rounded, with interspaces about same size as costellae; fila strong in interspaces. 2012 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY Pedicle valve moderately convex in lateral profile, maximum convexity near midvalve; anterior profile flatly and broadly concave. Umbonal region nearly flat. Sulcus variable, originating just anterior to umbo, shallow and narrow, deepening and widen- ing anteriorly, but nowhere very deep; flanks mod- erately rounded; sulcus occupied by 11 costellae in one specimen. Flanks moderately convex, narrowly rounded and usually moderately strongly marked. Brachial valve of about equal or slightly greater depth than pedicle valve; strongly convex in lateral profile, maximum convexity near midvalve; anterior profile narrowly domed, sides steep and precipitous. Umbonal region moderately concave, especially in young, but lessening in adults and giving way to low, inconspicuous fold slightly posterior to mid- valve; fold variable, generally low and rounded in both profiles; flanks somewhat swollen and not strongly deflected. Interior details of both valves as described for genus. MEASUREMENTS (in mm).—Holotype USNM 148219: length 13.9, brachial valve length 12.5, width 12.6, thickness 10.6, apical angle 90°. STRATIGRAPHIC OCCURRENCE.—Cherry Canyon For- mation (Getaway Member), Capitan Formation, Bell Canyon Formation (Hegler, Pinery, Rader, and Lamar members). LOCALITIES.—Getaway: USNM 732. Capitan: USGS 7404 (blue); USNM 725j, 739, 740. Hegler: USNM 731, 740c. Pinery: USNM 733. Rader: USNM 725g, 740a, 740g, 740i, 740j, Lamar: AMNH 430; USNM 725e, 728p, 738, 738b. DIAGNOSIS.-—Ptilotorhynchus with long, shallow sulcus in the pedicle valve. TYPES.—Holotype: USNM 148219. Figured par- atypes: USNM 154710a,e,h; 154711; 154712a,b; 154713; 154714; 154668a,b; 154670. Unfigured par- atypes: USNM 154710b-d, f,g. COMPARISON.—This is the only species of this genus known, but inasmuch as species of Divaricosta and Fascicosta have similar exteriors they might be confused with it. The lack of dental plates and the nature of the hinge plate of Ptilotorhynchus distin- guishes them readily. DISCUSSION.—The available material on which this species and genus is based indicates either var- iable species or possibly more than one species. Specimens from USNM 725e include young and adult individuals. The young are variable, some specimens being widely triangular but others elon- gate triangular. The adults have the long shallow sulcus on the pedicle valve that appears to be a generic as well as specific character. The measured paratype is preserved in limestone and is undis- torted. It is elongate triangular and appears more elongate than the specimen from AMNH 430. The latter is crushed, however, and does not reveal its true character. It has seemed best to regard all of the specimens as belonging to a single variable species. Deltarina, new genus [Greek delta] Small, triangular in outline, with narrowly rounded sides; subequivalve; lenticular in profile, both valves shallow. Greatest width anterior to midvalve; anterior commissure broadly to narrowly uniplicate. Beak straight, moderately long, narrow and sharply pointed; foramen elongate triangular; deltidial plates rudimentary, disjunct. Interareas small. Surface multicostate, costae strong and prominent. Pedicle valve with small narrow teeth lying paral- lel to shell margin and posteriorly grooved; dental plates thin, convergent, with narrow umbonal cavities, often difficult to distinguish; muscle field fairly strongly impressed, with large diductor scars. Brachial valve with smooth sockets defined by cup-like fulcral plates and strong inner socket ridges overhanging sockets. Hinge plate divided; outer hinge plates narrow, bearing laterally flat- tened, short falcifer crura; inner hinge plates not developed, or rudimentary. Median ridge slender or absent. Adductor field not impressed strongly enough to distinguish details. TYPE-SPECIES.—Deltarina magnicostata, new species. DIAGNOSIS.—Strongly and completely costate rhyn- chonellids with rudimentary, disjunct deltidial plates, divided hinge plate, and with brachial valve septum absent or rudimentary. COMPARISON.—The exterior of this genus is very distinctive in having the fold composed of two costae and the one corresponding costa in the sulcus, and with the flanks having occasional bifur- cation or intercalation. Lack of deltidial plates (or at best, mere vestiges) combined with a fairly long NUMBER 21 2013 tapering beak are characteristic. The genus suggests Divaricosta Cooper and Grant, but in that genus the fold and sulcus are occupied by numerous costae and the deltidial plates are elaborate. It differs from Fascicosta Stehli (1955) in lacking nu- merous bifurcations and intercalations of the costae, and in having more pronounced costae and a shorter beak. Deltarina is like Ptygmactrum, new genus, Peta- smatherus Cooper and Grant and Elassonia, new genus, in the possession of a divided hinge plate, but it differs from all three in size but more espe- cially in the ornamentation. The first has a few direct angular costae, and the second has a peculiar straight hinge, while Elassonia has a broadly sulcate anterior commissure. DISCUSSION.—This interesting but rare genus has a distinctive exterior with its triangular outline, narrowly lenticular profile, and strong costae that increase by intercalation or bifurcation. The beak is fairly long, with a long triangular foramen which, at first glance, appears to be unmodified. The del- tidial plates are usually so narrow that they escape attention in complete specimens. The separated valves reveal them readily because of the small notch at their anterior where the curved umbonal region of the brachial valve is inserted under or against them. Inside the pedicle valve the dental plates are variably developed, although easily seen. They are delicate and convergent. In some specimens the cavities between them and the inner wall of the valve are so narrow that they might be overlooked. The teeth bear notches at the posterior where they are inserted under the strongly overhanging inner socket ridge. Inside the brachial valve the cardinalia are narrow but thick, and are elevated considerably above the sides of the shell. All the plates except the crura are fairly thick. This is true of the young as well as adults and old age specimens. In the very young the outer hinge plates are narrow or not developed but they expand with age. A septum or ridge seems not to play a role in the develop- ment of the cardinalia. The sockets are defined by thick fulcral plates as well as the bounding socket ridges. The outer hinge plates are broad but the inner hinge plates are variously developed. In most specimens they are united medially, but in some they are deeply notched, in others united posteriorly so that the hinge plate seems undivided. The crura are mod- erately long and curved, are keeled anteriorly, and lie oblique to the midline; the distal extremity is obliquely truncated, the sharper, narrower extrem- ity on the posterior side. This genus is not common at any locality but dissolution of large blocks usually yields a few specimens. It is necessary to dissolve a considerable quantity of limestone to obtain a collection ade- quate for detailed study. Deltarina magnicostata, new species PLATE 507: FIGURES 32-56; PLATE 508: FIGURES 30-33; PLATE 552: FICURES 18-21; PLATE 780: FIGURES 1-6 (in part V) Small, broadly triangular in outline and long, sharply pointed beak. Posterolateral sides slightly concave; lateral margins narrowly rounded and anterior margin broadly rounded to truncated. An- terior commissure broadly to narrowly uniplicate. Surface multicostate, costae strong and fairly broadly rounded. Growth interruptions distant. Pedicle valve evenly and gently convex in lateral profile, broadly and gently convex in anterior pro- file. Umbonal region narrow and convex; sulcus originating at beak and extending to anterior mar- gin as short tongue. Sulcus marked by single costa implanted anterior to beak and extending to ante- rior margin; flanks marked by 4 costae. Flanks somewhat flattened. Brachial valve evenly convex in lateral profile, more convex than opposite valve, maximum con- vexity near midvalve. Anterior profile broadly and moderately domed. Fold broad, originating as shal- low sulcus with single intercalated bifurcation just posterior to midvalve to form 2 prominent costae elevated above flanks to form fold. Flanks gently rounded, occupied by 3 or 4 costae. Interiors as described for genus. STRATIGRAPHIC OCCURRENCE.—Bell Canyon For- mation (Hegler, Pinery, Rader, and Lamar mem- bers). LOCALITIES.—Hegler: USNM 731. Pinery: AMNH 398, 401; USNM 725h, 725n, 733. Rader: AMNH 410; USNM 725f, 740a. Lamar: AMNH 37, 347 ( = L-2), 373, 430; USNM 725e, 728p, 728q, 738, 738b. TYPES.—Holotype: USNM 154651c. Figured par- 2014 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY MEASUREMENTS (in mm).- brachial apical valve thick- angle length length width ness (°) 5.3 4.2 5.4 2.7 74 8.1 6.8 8.2 4.4 81 8.6 7.4 9.2 5.5 83 9.7 7.7 9.8 6.0 80 9.2 7.6 9.6 4.7 84 USNM 738 152815a 152815b 152815c 152815d 152815e 9.8 97 7.3 6.6 USNM 725e 154651c (holotype) USNM 738b 152816 5.0 90 8.5 7.3 9.2 atypes: USNM 152815d; 15465la,b,d-f; 154656a,c-e, g-i; 154658; 154915; 155109a,b. Measured paratypes: USNM 152815a-e, 152816. Unfigured paratypes: USNM 152815a-c,e; 152816; 154656b,f. DIAGNOSIS.—Strongly costate, triangular Deltarina. COMPARISON.—No other species of the genus is known to which this one can be compared. DISCUSSION.—The folding in this species indicates a reversion from a youthful sulcate condition to a uniplicate commissure in the adult. The smallest specimen in the collection is 3 mm long and has a smooth ventral beak for a short distance. It is con- vex, and on the umbonal region is preserved a shallow sulcus, also smooth. On the pedicle valve of this small specimen the smooth part becomes a fairly deep narrow sulcus in which a single costa is inserted 1.5 mm from the beak. On the brachial valve, about 0.5 mm anterior to the beak, a single costa is inserted which immediately bifurcates and extends to the anterior margin. The costae bound- ing the initial sulcus on the pedicle valve extend from beak to margin and really define the fold, but they are usually not elevated to a height equal to that of the median two which are the more con- spicuous. On the pedicle valve the costae bounding the sulcus meet the troughs on the outside of the median bifurcated pair of costae. These sulcus- bounding costae are slightly elevated above those on the flanks. Together witli the sulcus this pair makes a sort of fold. Genus Fascicosta Stehli, 1955 Fascicosta Stehli, 1955:71. Small, rhynchonelliform, biconvex, uniplicate; outline subelliptical to subtrigonal, transverse to elongate. Anterior commissure uniplicate. Costae fine or coarse, beginning at beaks, number increas- ing anteriorly by bifurcation; concentric ornament absent; radial costellae and growth lines weak. Pedicle valve flatly to moderately convex; beak sharp, straight, suberect or slanted ventrally; beak ridges bordering interareas; delthyrium triangular or trapezoidal, may perforate beak; deltidial plates absent; lateral pseudointerareas absent: no over- lapping of valves. Brachial valve somewhat more convex, umbonal area may be flattened or indented; beak blunt, may be nearly straight, producing nearly straight hinge line; apex external or curved into pedicle valve. Pedicle valve interior with small teeth; dental plates short, convergent, supporting hinge teeth. Muscle area tear-shaped; adductor scars central or near posterior apex of muscle area, small, subellip- tical; diductor scars larger, anteriorly widening. Brachial valve interior with divided hinge plate supported by a low, thin median ridge; sockets deep, denticulate, anteriorly Avidening; socket ridges thick; outer hinge plates broad; crura falci- fer, long and slender, expanded distally, diverging slightly from anterior edge of hinge plate, curved ventrally; crural bases strong, extending from un- derside of hinge plate along dorsal edges of crura; inner hinge plates poorly developed. Muscle area narrowly elliptical; posterior adductor scars elon- gate, narrow, widely separate from one another, diverging slightly anteriorly, located at flanks of muscle area; anterior adductor scars somewhat larg- er, anteriorly widening, lying along midline of valve, extending farther forward; diductor muscle pit shallow, small, located in apex of hinge plate. TYPE-SPECIES.—Rhynchonella? longaeva Girty, 1909:322, pi. 15: figs. 18-19. The larger of Girty's two syntypes (118573a) is selected as lectotype. DIAGNOSIS.—Rhynchonellacea having bifurcated and intercalated costae, divided or deeply notched hinge plate, and median ridge. COMPARISON.—Fascicosta is characterized exter- nally by its rhynchonelliform shape, costae that begin at the beaks and increase in number ante- riorly by bifurcation, nearly straight beak with wide delthyrium and with rudimentary or absent deltidial plates. Internally it is distinguished by the convergent dental plates in the pedicle valve, and, in the brachial valve, by the divided hinge plate NUMBER 21 2015 that is supported by a thin median ridge, and by the relatively narrow muscle area with only slightly diverging posterior adductor muscle scars. Exter- nally it most nearly resembles Divaricosta Cooper and Grant in its bifurcating costae, differing in its open delthyrium, straighter hinge line, smaller, more knoblike hinge teeth without lateral sockets, absent lateral pseudointerareas, and lack of overlap of valves lateral to beaks. In shape and outline it resembles species of Petasmatherus Cooper and Grant or Allorhynchus Weller, but it is easily dis- tinguished by its bifurcating costae, lack of pseudo- interareas, and strong median septum. Although Stehli (1955) assigned specimens from the Getaway Member to Fascicosta, these are not congeneric with Rhynchonella? longaeva Girty, which he designated as the type species; for a dis- cussion see Divaricosta (below) and Cooper and Grant (1969:11). DISCUSSION.—Disappointingly few specimens of this genus have been taken from the residues from the Guadalupe Mountains. Nevertheless, it is pos- sible to give many important details of the interior. The pedicle valve has proved not to have deltidial plates, a fact that helps to distinguish this genus from some of the larger species with bifurcated costae such as those of Ptilotorhynchus, new genus, and Strigirhynchia Cooper and Grant. Inside the pedicle valve the dental plates converge toward the valve floor. Old specimens fill in the cavities between the dental plate and side wall, tending to obscure the dental plates. Although this has taken place in some of the specimens, no instance of the dental plates having been eliminated by this means was seen. The hinge plate is deeply notched, having broad outer plates, but poorly developed inner plates. The latter are seldom well developed but in some specimens may meet near the apex. The median ridge is generally fairly strong and moderately long, simulating a septum, but does not usually reach midvalve. Fascicosta bella, new species PLATE 505: FIGURES 12-15; PLATE 509: FIGURES 68-73; PLATE 552: FICURES 30-37; PLATE 780: FIGURES 28-33 (in volume 5) Small, subpentagonal in outline, inequivalved, brachial valve deeper; sides narrowly rounded; an- terior margin broadly rounded; posterolateral mar- gins forming angle of 102°. Anterior commissure uniplicate. Beak erect to suberect; delthyrium open, no trace of deltidial or marginal plates. Surface costate, 4 on fold and 3-5 on each flank. Pedicle valve gently convex in lateral profile, maximum convexity in posterior half; anterior profile flatly convex but with broad depression rep- resenting sulcus. Umbonal region swollen but with sulcus beginning at beak and expanding anteriorly, occupied by 3 costae, 1 originating at beak but 2 intercalated just anterior to beak; tongue short, not strongly geniculated. Costae bounding fold stronger than others; flanks convex, moderately steep. Brachial valve moderately convex, posterior half more strongly convex than flattened anterior half; anterior profile moderately convex, dome flattened on top; umbonal region swollen, with fairly wide depression containing 2 costae at beak and extend- ing to anterior margin; additional costa implanted on each side of primary two just anterior to beak, forming fold consisting of 4 costae; costae bound- ing depression at beak anterior depressed, forming bounding costae of swollen flanks. Pedicle valve interior with short convergent dental plates; brachial valve interior with divided hinge plate and low median ridge not supporting hinge plate. Other details not clear. MEASUREMENTS (in mm).—From locality USNM 725g specimen 154621 (holotype) and from AMNH 410 specimen 154679, respectively: length 6.9, 7.5; brachial valve length 5.8, 6.4; width 8.2, 8.5; thick- ness 4.8, (?); apical angle 102°, 102°. STRATIGRAPHIC OCCURRENCE.—Bell Canyon For- mation (Hegler, Rader, and Lamar members). LOCALITIES.—Hegler: USNM 731, Rader: AMNH 410; USNM 725f, 725g; Rader: 740i, 740j. Lamar: USNM 728i. DIAGNOSIS.—Fascicosta with two median primary and two implanted costae on the fold. TYPES.—Holotype: USNM 154621. Figured para- types: USNM 154513a-c, 154679, 155079a. Unfig- ured paratype: USNM 154678. Measured paratype: USNM 154679. COMPARISON.—This species is smaller than F. longaeva (Girty) and very differently ornamented. There are fewer costae, and those of the fold and sulcus are fairly regular: 1 primary and 2 inter- calated in the sulcus and 2 median primary and 2 intercalated on the fold. This species could be con- 2016 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY fused with specimens of Divaricosta Cooper and Grant which also has considerable intercalation of costae but that species has an undivided hinge plate. The specimen from the Lamar Member is not in complete accordance in its costation with the Rader Member specimens. It has primary costae like those of the Rader specimens, but the inter- calation is irregular, a costa appearing near the beak but that on the opposite side appearing near midvalve and all the costae somewhat distant. Dis- covery of more specimens may indicate two species. Fascicosta elongata, new species PLATE 509: FICURES 62-67; PLATE 780: FICURES 13-18 (in volume 5) Small, elongate triangular in outline, sides rounded, maximum width slightly anterior to mid- length. Beak long, narrow, suberect, foramen long, triangular; modified slightly by rudimentary dis- junct deltidial plates. Costae narrow and subangu- lar, crowded and bifurcating in three generations. Anterior commissure narrowly uniplicate. Pedicle valve about same depth as brachial valve, moderately convex in lateral profile, greatest curva- ture in umbonal region; broadly and flatly convex in anterior profile. Sulcus narrow and shallow, not defined until midvalve, occupied by single costa on umbo, second costa intercalating 2 mm anterior to beak and extending to anterior margin. Flanks narrow, moderately swollen and occupied by 6-8 costae, sides unequal because of uneven bifurcation. Tongue short and narrow. Brachial valve with moderate convexity in lateral profile, maximum convexity at midvalve; anterior profile somewhat narrowly domed. Fold narrow, low, defined just anterior to midvalve, occupied by 3 costae, 2 initial ones and 1 intercalated. Flanks flatly convex and somewhat depressed, occupied by 6 or 7 costae. Interior not known. MEASUREMENTS (in mm).—Holotype USNM 152817: length 8.4, brachial valve length 6.8, width 7.8, thickness 5.7, apical angle 74°. STRATIGRAPHIC OCCURRENCE.—Bell Canyon For- mation (Hegler, Pinery, Rader, and Lamar mem- bers). LOCALITIES.—Hegler: USNM 731, 732a, 740c. Pinery: AMNH 33; USNM 725h. Rader: USNM 725f, 725g. Lamar: AMNH 430. DIAGNOSIS.—Small, narrowly triangular Fascicosta with long beak and narrow costae. TYPES.—Holotype: USNM 152817. Figured para- type: USNM 155110. COMPARISON.—This species will not be confused with the type species F. longaeva (Girty) because of its narrower outline, more slender costae and the more prominent but narrower fold and sulcus. DISCUSSION.—Although only a few specimens of this species are known, it is so unlike F. longaeva that the two cannot be confused at any stage in their growth. It is probable that F. elongata would prove a variable species because of the sporadic way in which intercalation and bifurcation of costae takes place. The beak of the brachial valve is marked by a short sulcus, as usual in youthful rhyn- chonellids, but, in less than 1 mm, 2 costae appear that oppose the initial costa intercalated in the sulcus of the pedicle valve. Both of these costae bifurcate about 1.5 mm from the beak, the left bifurcation of the right primary costa continues to the anterior margin and forms the center costa of the fold; the right hand bifurcation becomes the outer costa of the fold but bifurcates near mid- valve, the bifurcation descending into the trough bounding the fold. A few short bifurcations appear in the anterior third of the flanks. Fascicosta longaeva (Girty) PLATE 509: FIGURES 27-59 Rhynchonella} longaeva Girty, 1909:322, pi. 15; figs. 18-19. Not Fascicosta longaeva (Girty) Stehli, 1955:71-73, figs. 1-17 [= Divaricosta squarrosa Cooper and Grant, 1969:12]. Average size for genus, moderately strongly bi- convex; outline bluntly transversely subtrigonal to subpentagonal, sides diverging between 90° and 120°; anterior commissure gently and broadly uniplicate; fold low, moderately convex longitudi- nally and transversely, obvious only at anterior end; sulcus very shallow, only slightly depressed below level of flanks, extending forward for short distance as broad, flat tongue. Costae strong, fine, with sharp crests, beginning at beaks, number slightly increased anteriorly by bifurcation, most bifurca- tions located within 7 mm of beaks; costae num- bering 5-7 on fold, one less in sulcus, 5-8 on each NUMBER 21 2017 flank. Concentric striae absent; growth lines weak, irregularly spaced over surface of shell, not ob- viously concentrated or stronger near margins. Shell substance coarsely fibrous. Pedicle valve rather strongly convex, flanks not reflexed; beak short, suberect, slightly curved dor- sally; delthyrium wide, triangular; deltidial plates disjunct, rudimentary or absent; beak ridges short, blunt; lateral pseudointerareas absent: no overlap of valves. Brachial valve slightly more strongly convex; umbonal region with strongest convexity trans- versely and longitudinally, without flattening or indentation; beak bluntly rounded, curved into pedicle valve. Pedicle valve interior with small teeth; dental plates reaching valve floor, converging but not meeting. Muscle field located anterior to delthyrial cavity, moderately deeply impressed, nearly circu- lar. Scars difficult to distinguish. Brachial valve interior with divided hinge plate supported by median ridge extending forward but not reaching midvalve. Sockets elongate, corrugated and widening anteriorly; socket ridges stout; length of crura not known; outer hinge plate narrow. Muscle area broadly semiovate, extending about a third valve length, but details unknown. MEASUREMENTS (in mm).— brachial maxi- apical valve mid- mum thick- angle length length width width ness (°) 104 110 8.7 11.0 9.1 6.0 7.8 6.2 5.3 8.0 9.5? 9.8 9.5 13.2* 13.2* USNM 737a 148247a 148247b 100 9.4 8.2 USGS 2926 118573a (lectotype) USNM 750b 152816a 101 9.3 10.3 9.2 8.3 STRATIGRAPHIC OCCURRENCE.—Capitan Formation; Bell Canyon Formation (Pinery, Rader, and La- mar members). LOCALITIES.—Capitan: USGS 2926 (green); USNM 737a, 740o, 750a, 750b. Pinery: AMNH 524; USNM 725n, 736. Rader: AMNH 410; USNM 725g. Lamar: USNM 725e, 728i, 728p, 728r, 738, 738b. DIAGNOSIS.—Fascicosta with rounded outline and strong costae. TYPES.—Lectotype: USNM 118573a. Figured hy-- potypes: USNM 148246; 148247a; 152816a,b; 154677; 144771. Measured hypotypes: USNM 148247a,b; 152816a. Paratypes: USNM 118573b. COMPARISON.—Fascicosta longaeva is characterized by its rather strong convexity, sharp bifurcating costae, slightly curved pedicle beak, lack of del- tidial plates, low fold and shallow sulcus, nonover- lapping valves with absence of lateral pseudointer- areas, and more convergent dental plates. It suggests Strigirhynchia indentata (Shumard) but differs in its more lenticular profile, less strong con- vexity, and much coarser, more angular and more widely spaced costae that bifurcate less frequently. It differs from F. elongata in its more rounded out- line and larger size. DISCUSSION.—Rhynchonella? longaeva Girty was designated by Stehli (1955) as the type species of his genus Fascicosta. He decribed and illustrated a species from the lower Guadalupian (Cherry Can- yon Formation) of the Guadalupe Mountains which he identified with Rhynchonella? longaeva. Study of Girty's collection of syntypes of this spe- cies, shows that R.? longaeva is not the same species as that illustrated by Stehli, and in our opinion is not congeneric. That species now constitutes the type species of a different genus, and is discussed under Divaricosta squarrosa Cooper and Grant. Fascicosta longaeva has proved to be rare and difficult to identify. A few specimens have been found among the Geological Survey collections and among those made by members of the National Museum in the Guadalupe Mountains. Disappoint- ingly few specimens have been recovered from the residues and most of these have not had well pre- served interiors. The assignment of this species to Stenoscisma by Branson (1948:525) is entirely erro- neous because the type specimen does not have a spondylium or camarophorium. Hemileurus, new genus [Greek hemi (half) + leuros (smooth)] Small; subtriangular in outline; pedicle valve with elongate, nearly straight beak; foramen ellip- tical to oval, modified by rudimentary, disjunct deltidial plates. Broadly uniplicate. Surface ante- riorly costate, umbones and posterior part smooth; shell smooth in young. Pedicle valve interior with stout teeth supported by long, subparallel dental plates. Brachial valve 2018 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY with divided hinge plate; socket ridges strong, bounding deep, uncorrugated sockets; outer hinge plates broad and concave; crura modified falcifer, long, curved, concave toward midvalve, keeled under crural base. Inner hinge plates rudimentary, not uniting. Muscle marks not preserved. Myophragm low and indistinct. TYPE-SPECIES.—Hemileurus runcinatus, new species. DIAGNOSIS.—Interior like Allorhynchus but with the posterior half or less of both valves noncostate. COMPARISON.—The divided hinge plate of this genus eliminates it from comparison with a large body of rhynchonellid genera. Its distinction from Allorhynchus Weller, to which it is related by its interior details, is based on its partially noncostate exterior. Deltarina, new genus, has a divided hinge plate but it is multicostate; the same may be said for Fascicosta Stehli. The completely multicostate exterior of Ptilotorhynchus, new genus, is a ready means of separation on the exterior character but the absence of dental plates in the pedicle valve is further confirmation of the difference. Hemileurus runcinatus, new species PLATE 539: FICURES 1-8 Average size for genus; outline bluntly triangular to subovate, sides diverging between 60° and 110°, normally about 90°; profile subovate to globose; shell frequently distorted; commissure uniplicate, fold low, with uniformly convex profile; sulcus shallow, barely depressed in some specimens. Co- stae low, fine, beginning 2-5 mm anterior to beaks, arising very gradually, point of origin obscure, umbonal areas normally smooth, but with faint hints of incipient costae; number of costae 3-8 on fold, normally 5, one less in sulcus, from 3-6 on each flank. Pedicle valve uniformly convex along median line, moderately convex toward nonreflexed flanks; beak sharp, moderately to strongly curved dorsally; beak ridges poorly defined; lateral pseudointerareas absent, valves normally not overlapping. Delthy- rium triangular, completely open in juveniles, sides slightly constricted in adults by small, disjunct deltidial plates. Brachial valve more strongly convex, smooth part of umbonal area often slightly flattened trans- versely; beak relatively sharp, projecting slightly into pedicle valve below deltidial plates. Pedicle valve interior with sides of delthyrium abruptly widening anterior to deltidial plates, each side with elongate, knoblike tooth supported by vertical dental plate reaching valve floor. Muscle area roughly triangular; adductor scars narrow, median, elongate, lying between and anterior to edges of dental plates; diductor scars producing "shoulders" on triangular muscle area, lying lateral and anterior to adductors, anteriorly widening slightly, one on each side of median line. Brachial valve interior with hinge plate divided by deep, wedge-shaped median notch, bounded lat- erally by deep, anteriorly narrowly expanding, minutely corrugated hinge sockets; crura diverging anteriorly, strongly curved ventrally, commonly twisted, dorsal edges carinate; median ridge or myophragm completely absent. Muscle area oval to nearly circular, relatively small, lying in um- bonal area; posterior adductor scars nearly circu- lar, lying laterally and far back, partly under for- ward edges of hinge sockets; anterior adductor scars larger, median, slightly farther forward. MEASUREMENTS (in mm).-— brachial apical valve thick- angle length length width ness (°) USNM 701k 148071a 2.3 2.0 2.0 1.0 148071b 3.0 2.8 2.5 1.4 65 148071c 4.7 4.0 3.8 2.5 74 14807Id 6.4 5.6 5.3 3.5 91 148071e 7.3 6.4 6.5 4.1 84 14807lf 8.6 7.5 8.6 5.4 90 148071g 9.5 8.0 9.0 6.4 90 148071h 11.2 9.7 10.6 7.5 100 (holotype) STRATIGRAPHIC OCCURRENCE.—Neal Ranch Forma- tion (beds 4-14). LOCALITIES.—USNM 701c, 701d, 701h, 701k, 712w. DIAGNOSIS.—Shape and costation variable. TYPES.—Holotype: USNM 148071h. Figured par- atypes: USNM 148071g,i-l; 154876a,c. Measured paratypes: USNM 148071a-g. Unfigured paratypes: USNM 148071a-f, 154876b. COMPARISON.—This is the only species of this genus known. DISCUSSION.—An extremely variable species, not only as to the shape of the valves but also the costation. The fold is variable and is occupied by NUMBER 21 2019 3-8 costae. The specimens with narrow fold having a low number of costae are usually elongate and narrow: the others are more widely triangular and the fold may contain as many as 8 narrow crowded costae or as few as 4. Obese forms in which the valves are greatly swollen and the shell very rotund are common. The anterior commissure is variable but is usually not strong. Generally the tongue of the pedicle valve is short and the fold low. PONTISIIDAE, new family Semicostate to completely costate Rhynchonella- cea with plicate anterior commissure; pedicle valve with dental plates; deltidial plates variable. Bra- chial valve with undivided hinge plate, no median septum; crura falcifer to modified falcifer. Genera in West Texas: Pontisia Cooper and Grant, 1969; and Aphaurosia, Acolosia, Anteri- docus, Antronaria, Lirellaria, and Divaricosta, all new genera. Genus Pontisia Cooper and Grant, 1969 Pontisia Cooper and Grant, 1969:13.—Stehli and Grant, 1970: 33. Small to medium, triangular to subpentagonal; unequally biconvex, brachial valve deeper; anterior commissure strongly uniplicate; beak suberect; for- amen elongate-oval; deltidial plates usually dis- junct, or uncommonly conjunct. Surface costate, costae strong, usually not extending to beaks. Pedicle valve interior with small teeth; dental plates strong but defining narrow umbonal cham- bers; muscle field anterior to delthyrial cavity; diductors and adjustors subflabellate; adductors central. Brachial valve interior with undivided hinge plate; crura modified falcifer; socket ridges strong, inclined over smooth sockets; outer hinge plates fairly wide, separating narrow crural bases from socket ridge; inner hinge plate forming bridge, often convex, over notothyrial cavity. Median sep- tum absent but myophragm or thick secondary swelling developed in some old specimens. Ad- ductor field with small posterior adductors at end of median ridge, and larger pair anterior to latter and median ridge. TYPE-SPECIES.—Pontisia stehlii Cooper and Grant (1969:13, pi. 4; figs. 7-10). DIAGNOSIS.—Hinge plate similar to that of Welle- rella but not supported by a median septum. COMPARISON.—The exterior of members of this genus strongly resemble Wellerella, at least at the anterior part. Some species are likely to differ in having the costae extended farther back, nearly to the beaks, thus resembling Allorhynchus, which is usually completely costate; but other species strongly resemble Wellerella with their semicostate valves. The interior of the pedicle valves of Wellerella and Pontisia are almost the same, but the brachial valves have a fundamental difference. In Wellerella the inner hinge plate is supported by the median septum which is a high, bladelike plate of varying length. It extends to the hinge plate, whereas in Pontisia young adults have no trace of a median septum but usually have a low ridge. In old speci- mens the low ridge often swells to a boss posteriorly under the hinge plate. This simulates Wellerella, but the boss is never a septum although it may help to support the hinge plate. Pontisia costata, new species PLATE 529: FIGURES 8-26 Average size for genus, wider than long, widest slightly anterior to midvalve; subtrigonal in out- line; posterolateral margins forming right angle or somewhat less; lateral margins narrowly rounded. Anterior margin truncated. Anterior commissure strongly uniplicate. Beak short, deltidial plates small, disjunct. Surface strongly costate but with naked umbonal region; costae thick, rounded on flanks, subangular on fold, 3 costae on fold, median costa often slightly shorter than others, 2 in sulcus, and 4 or 5 on flanks stronger and more prominent. Pedicle valve very gently convex in lateral pro- file, nearly flat in anterior profile. Umbonal and median regions gently convex. Sulcus originating near midvalve, narrow and shallow, forming mod- erate tongue. Flanks flattened and moderately inclined. Brachial valve very gently convex in lateral pro- file, broadly but gently convex in anterior profile but with steep sides. Umbonal and median regions flatly convex; fold originating near midvalve, some- 2020 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY what flattened on top, slightly elevated above the flanks anteriorly; flanks swollen, steep. Pedicle valve with small teeth and stout dental plates. Brachial valve with strong but short socket ridges; outer hinge plates narrow; crura falcifer, long, laterally compressed, hollow toward midvalve; inner hinge plates short, coalesced and with deep reentrant. MEASUREMENTS (in mm).— brachial apical valve thick- angle USNM 705a 152843a (holotype) 152843b 152843c 152843d 152843e 152843£ 8.1 7.3 8.9 90 length length width ness (") 5.0 7.7 6.7 8.2 5.8 90 8.2 7.0 9.1 5.6 90 7.4 6.5 7.6 5.2 90 7.2 6.4 8.9 4.3 90 5.1 4.3 5.0 3.4 80 STRATIGRAPHIC OCCURRENCE.—Skinner Ranch For- mation (base). LOCALITIES.—USNM 705a, 720f, 724q. DIAGNOSIS.—Medium size Pontisia with strongly costate flanks and subtrigonal outline. TYPES.—Holotype: USNM 152843a. Figured par- atypes: USNM 152843b; 154815a,b; 154816a-c,r. Measured paratypes: USNM 152843b—f. Unfigured paratypes: USNM 152843c-f, 154816d-q. COMPARISON.—-This species suggests Pontisia lon- gicosta (Stehli) and P. nanas (Stehli) from the lower Bone Spring Formation. It differs from the former in having larger size, somewhat stronger costae, although the numbers are about the same, greater depth to the valves, more laterally flaring costae on the flanks, and a shorter beak. Pontisia costata has about the same size and ap- pearance as P. nanas (Stehli) but it differs in hav- ing costae which are more closely crowded, extend farther posteriorly, and are more numerous on the flanks. Moreover, the fold and sulcus of this species are narrower and less pronounced than those of P. nanas. DISCUSSION.—This species was found only in the lower part of the Skinner Ranch Formation. The species is especially distinctive for the promi- nently ornamented flanks and the fact that the costae extend far posteriorly. In a few specimens bifurcation of costae appear to take place on the flanks. Specimens are commonly crushed at USNM 705a but several survived the geological processes and acidizing treatment. Pontisia franklinensis, new species PLATE 529: FIGURES 64-70 Small for genus, biconvex; profile subtrigonal; outline transversely subovate to subtrigonal, sides diverging between 90° and 120°; commissure uni- plicate; fold low, beginning 3-4 mm anterior to brachial beak, profile moderately convex near an- terior margin; sulcus shallow, beginning about 4 mm anterior to pedicle beak, maximum curvature between ends of flanks. Costae low, short, crests blunt, beginning about 3 mm anterior to beaks, numbering 3 on fold, 2 in sulcus, 2 or 3 on flanks. Concentric ornamentation or growth lines not observed. Pedicle valve with smooth part of umbonal area gently convex, flanks not reflexed; beak short, blunt; beak ridges short, blunt; lateral pseudoin- terareas narrow or absent; slight overlap of valves. Delthyrium triangular, deltidial plates small. Bra- chial valve with smooth part of umbonal area nearly flat in profile, slightly flattened transversely; beak blunt, within pedicle valve. Pedicle valve interior with sides of delthyrium widely diverging, teeth supported by vertical dental plates reaching floor of valve. Muscle area triangu- lar, anteriorly expanding, slightly excavate, scars of separate muscles not observed, probably located as in other species of genus. Brachial valve interior with undivided triangular hinge plate, bounded laterally by elongate, deep, anteriorly widening, hinge sockets; crura diverging anteriorly from for- ward edge of hinge plate, strongly curving ventrally, twisted, dorsal edges carinate; median ridge low, rounded. Muscle area not observed: probably sub- divided into posterior and anterior adductor scars as in other species of genus. STRATIGRAPHIC OCCURRENCE.—Hueco Canyon For- mation. LOCALITIES.—USNM 712e, 712m, 720b, 725z. DIAGNOSIS.—Small, trigonal, transverse Pontisia with, few strong, rounded, short costae. TYPES.—Holotype: USNM 152846a. Figured par- atypes: USNM 152846b,c,f. Measured paratypes: USNM 152846b-e, 152847a-e. Unfigured paratypes: USNM 152846d,e; 152847a-e. NUMBER 21 2021 MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) 152846a 7.8 6.9 9.8 5.7 110 (holotype) 152846b 6.9 6.2 8.6 5.6 110 152846c 6.5 5.9 7.7 5.0 110 152846d 5.9 5.4 6.7 4.0 100 152846e 5.3 4.7 5.7 3.7 90 USNM 720b 152847a 7.7 6.5 9.8 6.8 110 152847b 7.3 6.2 8.2 6.0 100 152847c 7.0 6.0 7.8 5.6 100 152847d 6.3 5.3 6.5 5.1 100 152847e 4.7 4.3 4.9 1.8 90 COMPARISONS.—Pontisia franklinensis is charac- terized by its small size, transverse outline, low, blunt costae, nearly equiangular trigonal profile with flattened smooth part of brachial umbonal area, fold that is high at the margin relative to the pedicle valve, but low relative to the brachial flanks, and its low median ridge. Externally it most nearly resembles Tautosia podistra, new species, from the Wolfcampian of the Glass Mountains, differing in its weaker, relatively shorter costae, more strongly bulging profile of the brachial valve, lower fold and shallower sulcus, and especially in its low median ridge in the brachial interior. It differs from P. kingi, new species, also from the Wolfcampian of the Glass Mountains, and from P. stehlii Cooper and Grant, from the Leonardian, in its smaller size, weaker costae, more transverse outline, more equiangularly trigonal profile, blunter beak, flatter brachial umbonal area and conse- quently more highly elevated anterior end of the fold. Pontisia franklinensis also resembles Wellerella nitiditla, new species, but that species generally is somewhat larger in its mature forms, is rounded, has more strongly costate flanks, and is not so flatly truncated anteriorly. DISCUSSION.—This species occurs in countless numbers in the lower part of the Hueco Canyon Formation north of Hueco Inn. It does not appear to be the same species referred incorrectly by R. E. King to "Pugnoides" texanus (Shumard). Although the species occurs by the thousand at this place it is difficult to obtain good interior details. The vast majority of the specimens occur with both valves in contact. The Hueco Group contains other species of rhynchonellids, some undoubtedly related to Pontisia but others of unknown generic affinities. Pontisia kingi, new species PLATE 520: FICURES 31-34; PLATE 530: FICURES 16-32 Average size for genus, profile subtrigonal; out- line bluntly triangular to suboval, sides diverging between 80° and 120°; commissure uniplicate, fold low to moderately high, beginning 4-8 mm anterior to brachial beak, longitudinal convexity low, ante- rior termination abrupt; sulcus moderately deep to deep, beginning 5-8 mm anterior to pedicle beak, longitudinal convexity greatest between anterior ends of costae on flanks. Costae moderately high, broad crests normally blunt, beginning 3-5 mm anterior to beaks, strongest on fold and pedicle flanks, moderately strong in sulcus, weak on bra- chial valve flanks, numbering 2-5, normally 3 on fold, one less in sulcus, 2-4, normally 3 on flanks. Concentric ornamentation faint, closely spaced striae; growth laminae weak, widely spaced. Pedicle valve moderately inflated on smooth area near beak, strongly convex through sulcus, slightly convex toward flanks; inner costae of flanks longi- tudinally slightly convex to strongly hooked dor- sally; beak ridges prominent, blunt, short; lateral pseudointerareas very narrow or absent, litttle or no overlap of valves. Delthyrium triangular, base covered in adults by small, nearly flat deltidial plates; apical part open, forming elongate oval foramen. Brachial valve slightly convex along fold, strongly convex toward flanks and transversely; smooth part of umbonal area normally evenly arched transversely, may be somewhat flattened; apex of valve within pedicle valve, covered by deltidial plates. Pedicle valve interior with sides of delthyrium widely expanding, teeth elongate, parallel to sides, supported by vertical dental plates reaching floor of valve. Muscle area elongate, relatively narrow, beginning just anterior to edges of dental plates, slightly expanding anteriorly; adductor scars in posterior part of muscle area astride median line, forming small oval mark; diductor scars elongate, anteriorly expanding, surrounding adductor scars laterally and anteriorly. Brachial valve interior with undivided triangu- 2022 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY lar hinge plate, laterally bounded by narrow, only slightly expanding, finely corrugated sockets; crura diverging forward from anterior edge of hinge plate, strongly curved ventrally, often twisted, dorsal edges carinate; median ridge broad, low, rising near beak and forming short septum support- ing hinge plate, extending forward into muscle area bisecting it. Muscle area elongate; posterior adductor scars narrow, diverging anteriorly from median ridge, flanking anterior adductors, fused with them; anterior adductors narrowly expanding anteriorly, one on each side of median ridge. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 701a3 154837a 1.5 1.2 1.3 0.5 p 154837b 1.9 1.6 1.6 0.7 92 154837c 3.2 2.8 2.5 1.8 90 154837d 4.5 4.0 3.9 2.4 87 154837e 4.8 4.2 3.9 2.6 70 5.0 4.6 4.1 3.4 85 USNM 701d 148593a 6.0 5.2 5.6 3.6 80 148593b 7.7 6.4 8.3 6.0 90 148593c 9.5 7.9 10.0 6.9 100 148593d 10.0 8.4 12.5 10.0 112 USNM 701-1 148598 12.3 10.5 14.4 9.0 112 USNM 721g 152848a 10.6 9.2 11.8 7.8 95 152848b 11.1 9.6 12.6 8.0 105 (holotype) STRATIGRAPHIC OCCURRENCE.—Gaptank Formation (Uddenites-bearing Shale Member); Neal Ranch Formation (beds 2-4, 9-14); Lenox Hills Forma- tion. LOCALITIES.—Uddenities: USNM 701e, 701q, 701v. Neal Ranch, bed 2: USNM 701; bed 4: USNM 701-1, 727e; beds 9-14: USNM 701a3, 701c, 701d, 701g, 701k, 721g. Lenox Hills: USNM 705m, 705s. DIAGNOSIS.—Pontisia of medium size having nar- row flanks, and flattened brachial profile. TYPES.—Holotype: USNM 152848b. Figured par- atypes: USNM 148593d; 148597; 148598; 152848a; 154762a,b; 154763a; 154836a,b,d. Measured para- types: USNM 148593a-d, 148598, 152848a, 154837a-e. Unfigured paratypes: USNM I48593a-c, 154763b-d, 154836c. COMPARISON.—Pontisia kingi is characterized by its relatively narrow flanks, longitudinally only slightly convex fold, transversely evenly arched, or slightly flattened brachial beak area, hooked pedi- cle beak, normally 3 costae on the fold, with the middle one commonly slightly depressed, its low median ridge, and relatively narrow muscle areas. The deltidial plates begin to grow rather late in life, so are absent on juveniles and small on adults, also there is little overlap of the valves lateral to the beaks, so the lateral pseudointerareas are re- duced or absent. This species is similar to Antronaria speciosa and Wellerella girtyi, both new species, and to P. stehlii Cooper and Grant. It differs from A. speciosa in its narrower flanks (the widest specimen of P kingi is about the same width as a narrow specimen of Antronaria speciosa), less consistently and less strongly depressed middle costa on the fold, conse- quently less deeply indented anterior margin, hooked pedicle beak, low median ridge in the brachial interior, and costae that begin farther forward. It is distinguished from W girtyi by its flat fold profile, hooked beak and especially by its low median ridge instead of a high, thin septum. Its primary differences from P. stehlii are its pro- portionately broader outline, broader and blunter costae, commonly depressed middle costa on the fold, flattened profile of the fold, more strongly hooked beak, and smaller average and maximum size. Three stratigraphically remote species that re- semble P- kingi externally are Wellerella osagensis (Swallow) from the Pennsylvanian of the Midcon- tinent, Tautosia elegans (Girty), and T. transenna, new species, from the Guadalupian of the Glass and Guadalupe Mountains. From W. osagensis, P. kingi differs in its somewhat broader outline, com- monly depressed middle costa of the fold, more flattened profile of the fold, costae that start far- ther forward of the beaks, more strongly curved pedicle beak, and its low median ridge rather than a high median septum. From T. elegans and T. transenna it differs in its smaller deltidial plates, less strongly inflated pedicle umbonal area, more strongly hooked pedicle beak, and especially by its low median ridge. DISCUSSION.—This is a very thin and delicate species that is difficult to recover from the residues, as it often falls apart when completely decalcified. Nevertheless it is distinctive and attractive, al- though somewhat variable in its present makeup. NUMBER 21 2023 It is an uncommon species, and the large quantity of blocks dissolved from USNH 701d and 721g is the only reason the collection of it is adequate. Variation is seen in the form of the fold and sulcus, some specimens having these narrowly pinched whereas a few have them more spread out. Narrow forms also occur as well as some with 2, 4, or 5 costae on the fold. Such variations appear to be normal in most of the rhynchonellid species. The species is named in honor of R. E. King in recognition of his important work on the brachi- pods of the Glass Mountains. Pontisia longicosta (Stehli) PLATE 530: FICURES 33-45 Wellerella longicosta Stehli, 1954:336, pi. 25: figs. 23-27. This small and distinctive species is referred to Pontisia because it has no median septum, the medial part of the valve being marked by a broad, low ridge. The species is one of the most easily recognized of the genus because the costae extend almost to the beak, which is unusual for members of this genus. Furthermore, it has a distinctive sharply triangular outline, and a peculiar sulcus on the pedicle valve. This sulcus is narrow and is occupied by two large costae which crowd the nar- row space. The sulcus is also extended into a narrow tongue that is sharply geniculated at right angles to the commissure. Stehli failed to fix a type for the species. We select, therefore, AMNH 27319/1:1, which is a complete specimen illustrated by figure 23 of his plate 25. STRATIGRAPHIC OCCURRENCE.—Bone Spring For- mation. LOCALITIES.—USNM 728f, 728h. DIAGNOSIS.—Neatly and sharply triangular Pon- tisia with the narrowly angular costae reaching almost to the beaks. TYPES.—Lectotype: AMNH 27319/1:1. Figured hypotypes: USNM 154835a-f. COMPARISON.—No other small species of the genus has the costae occupying nearly all of the valves. It cannot therefore be confused with P. magnico- stata, new species, and P. stehlii Cooper and Grant, both also nearly complete costate. Pontisia magnicostata, new species PLATE 531: FIGURES 1-8 Large for genus, wider than long, outline roundly elliptical. Maximum width at midvalve; sides strongly rounded; anterior margin broadly rounded. Anterior commissure uniplicate. Beak short, bluntly pointed; deltidial plates short, con- junct. Surface except for umbones strongly marked by wide, elevated subangular costae, 3 on fold and 4 on each flank. Pedicle valve very gently convex in lateral and anterior profiles; umbonal and median regions gently inflated; sulcus originating at midvalve, shallow, forming moderately geniculated tongue; sulcus crowded by 2 large costae; flanks gently convex to concave, slightly deflected. Brachial valve moderately deep and gently con- vex in lateral profile; broadly domed and with top flattened in anterior profile; umbonal region slightly convex; median region flattened; fold originating near midvalve, fairly strongly elevated anteriorly, gently convex longitudinally; median costa not de- pressed. Flanks moderately inflated, steep sides, and moderately depressed below fold. Pedicle valve interior not known. Brachial valve interior with undivided hinge plate, having strong socket ridges bounding minutely corrugated sockets; outer hinge plates narrow; crura concave medially, broad; inner hinge plates wide, slightly folded me- dially. No median septum. Median ridge low, form- ing inconspicuous myophragm. Adductor field just posterior to midvalve small, posterior adductors narrow and together forming crescent; anterior scars larger and more rounded. MEASUREMENTS (in mm).—Specimens USNM 152850a (holotype) and b (paratype), respectively: length 15.3 (beak estimated), 12.8; brachial valve length 14.0, 11.4; width 17.9, 14.5; thickness 11.5, 7.3; apical angle 110°, 110° STRATIGRAPHIC OCCURRENCE.—Neal Ranch Forma- tion (bed 12 of P. B. King). LOCALITY.—USNM 722w. DIAGNOSIS.—Large, rounded, elliptical Pontisia with strong, thick costae. TYPES.—Holotype: USNM 152850a. Figured par- atypes: USNM 152850c. Measured and unfigured paratype: USNM 152850b. COMPARISON.—This species in its coarse orna- ment and almost complete costation is similar to 2024 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY Pontisia stehlii Cooper and Grant. It differs in its greater size and the magnitude of its costation, which is the coarsest of any of the Glass Mountains rhynchonellids. DISCUSSION.—This species is known from only three specimens, but it is so large and distinctive, and the interior so clearly displayed in the brachial valve, that we did not hesitate to name it. Another unusual feature is its large size and the fact that it comes from the Neal Ranch Formation. Hitherto only small rhynchonellids have been taken from this stratigraphic unit. Pontisia nanas (Stehli) PLATE 515: FIGURES 43,44; PLATE 531: FIGURES 39-58 Wellerella nanas Stehli, 1954:336, pi. 25: figs. 18-22. Small for genus, elongate triangular in outline with narrowly pointed apex, rounded sides, and somewhat narrowed anterior. Anterior commissure uniplicate. Beak short, suberect, and with conjunct deltidial plates. Surface semicostate, costae sub- angular, 3 on fold (median one depressed), 2 on sulcus, and 2 or 3 on each flank. Pedicle valve gently convex in anterior and lat- eral profile; beak and umbonal region smooth and gently convex; sulcus originating near midvalve, short and deep, forming moderately long and strongly geniculated tongue. Costae in sulcus occu- pying complete width and extending onto umbo just beyond midvalve. Flanks narrow, slightly convex, and with strong angular posterolateral extremities. Brachial valve flatly convex in lateral profile but narrowly domed in anterior profile, median region flattened, sides subparallel and nearly perpendicu- lar. Fold originating at midvalve, flattened; flanks rounded and moderately depressed below the fold at anterior. Pedicle valve interior with dental plates; brachial valve interior without median septum or ridge; hinge plate deeply notched medially, inner hinge plates narrowly arched. Outer hinge plates broad; sockets not corrugated. STRATIGRAPHIC OCCURRENCE.—Bone Spring For- mation; Skinner Ranch Formation (base and Sulli- van Peak Member); Hess Formation (Taylor Ranch Member). LOCALITIES.—Bone Spring: AMNH 625, 631, 634; MEASUREMENTS (in mm). brachial apical valve thick- angle length length width ness (°) USNM 728e 152853a 6.4 5.5 6.4 4.5 90 152853b 5.7 4.9 5.6 4.0 90 152853c 5.4 4.6 5.3 3.2 90 USNM 725c, 728e, 728f, 728h, 745. Skinner Ranch (base): USNM 720e. Sullivan Peak: USNM 707d, 722-1. Taylor Ranch: USNM 702d. DIAGNOSIS.—Very small, triangular Pontisia with depressed median costa in fold. TYPES.—Lectotype: AMNH 27318/1. Figured paratypes: AMNH 27318/1:2. Figured hypotypes: USNM 154728a,b; 154842a,c-j. Measured hypo- types: USNM 152853a-c. COMPARISON.—This species suggests Pontisia franklinensis, new species, and is also externally like Wellerella nitidula, new species. It is smaller than either of these species and is readily distinguished by the narrowing of the anterior, by the more de- pressed median costa, and less developed costae on the flanks. It is readily distinguished from P. longi- costa (Stehli) by its smooth posterior half. DISCUSSION.—This is a rare species in the Sierra Diablo but specimens have appeared in the Glass Mountains in the Scacchinella beds at the base of the Skinner Ranch Formation. The hinge plate is variable and is usually fairly wide. The median part is deeply notched and the inner hinge plates unite in a small fold or in a flat area or a shallow depression. The median ridge appears not to be variable to any marked degree. Pontisia parva, new species PLATE 520: FIGURES 23-30 Small for genus, subtrigonal in outline; length and width nearly equal; sides rounded, anterior margin truncated; posterolateral margins nearly straight, forming angle of 85°-95°. Anterior com- missure uniplicate. Deltidial plates conjunct; fora- men mesothyridid, oval. Front flattened from rapid growth along anterior edges of both valves. Surface semicostate, posterior half smooth but anterior half costate, 3 costae on fold and 2 or 3 on each flank. Pedicle valve nearly flat in lateral profile, poste- rior region slightly convex; anterior profile slightly NUMBER 21 2025 concave; sulcus narrow, short, originating anterior to midvalve; umbonal and median regions slightly inflated; flanks slightly concave, poorly demarcated and with scarcely any slope to posterolateral margins. Brachial valve deeper, gently convex in lateral profile but strongly domed in anterior profile, with gently rounded top but nearly straight sides. Fold short and narrow, slightly elevated above strongly rounded flanks. Pedicle valve interior with short but strong plates. Brachial valve interior with fairly wide outer hinge plates and small socket ridges; inner hinge plates united, forming undivided hinge plate with ante- rior edge turned slightly ventrad. Crural bases slender; crura laterally compressed, falcifer. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness n USNM 727e 154928a 8.1 6.9 7.8 6.4 91 154928b 7.6 6.5 8.2 7.0 93 (holotype) 154928c 7.5 6.7 8.8 7.3 92 STRATIGRAPHIC OCCURRENCE.—Neal Ranch Forma- tion (bed 4). LOCALITY.—USNM 727e. DIAGNOSIS.—Small, subtriangular Pontisia with truncated front and narrow fold and sulcus. TYPES.—Holotype: USNM 154928b. Figured par- atypes: USNM 154928a,c-e. Measured paratypes: USNM 154928a,c. COMPARISON.—This species differs from Pontisia costata, new species, in its semicostation, although the two species are nearly the same size. It is a smaller species than P. kingi, new species, and has a narrower fold and sulcus and much flattened anterior. From P franklinensis, new species, it dif- fers in its more triangular shape, narrower fold and sulcus, and broad flat front. It suggests P. nanas (Stehli) but differs in its narrow fold and sulcus, triangular shape, and the flattened front. Pontisia robusta, new species PLATE 508: FIGURES 1-5 Large for genus, subpentagonal in outline, wider than long, sides narrowly rounded; anterior margin broadly rounded; posterolateral margins forming angle of 104°. Beak erect. Deltidial plates conjunct, foramen oval, mesothyridid. Surface costate except in umbonal region of both valves, costae thick and subangular with narrower interspaces, 4 on fold, and 4 on each flank. Pedicle valve with lateral profile gently convex in posterior half, fairly strongly geniculated toward brachial valve in anterior half; anterior profile broadly and gently concave. Sulcus originating at midvalve, broad and shallow, containing 3 costae. Flanks narrow, not strongly deflected anterolateral^ but with steep slopes. Brachial valve deeper than pedicle valve, gently convex in lateral profile with maximum curvature at umbo; anterior profile narrowly domed with top of dome flattened and serrated by costae of fold, sides very steep. Umbonal region and flanks swollen; fold originating near midvalve, low, not rising strongly above steep flanks. Interior without median septum. MEASUREMENTS (in mm).—Holotype USNM 154664a: length 13.5, brachial valve length 11.7, width 15.7, thickness 11.7, apical angle 104°. STRATIGRAPHIC OCCURRENCE.—Cibolo Formation (Breccia Zone of Udden). LOCALITY.—USNM 728-1. DIAGNOSIS.—Large Pontisia with thick, crowded costae. TYPES.—Holotype: USNM 154664a. Unfigured paratypes: USNM 154664b-d. COMPARISON AND DISCUSSION.—This species is like Pontisia kingi and P. magnicostata, both new, and P. stehlii, Cooper and Grant. From the first it differs in being larger, having stronger and more crowded costae, and stronger costae on the flanks. From the second it differs in having more crowded costae, those of P. magnicostata having much wider inter- spaces. P. stehlii is variable, especially in the costa- tion of the fold, but the costae are not so thick and crowded as those of P. robusta, and those on the flanks are much less crowded; furthermore, the anterolateral extremities are more prominent. That P. robusta is variable is shown by paratype 154664b, a young individual that has only three costae on the fold and two in the sulcus. Neverthe- less, the costae are crowded in the sulcus and indi- cate close resemblance to the type when fully grown. Three other paratypes, all poorly preserved, give glimpses of the interior. In the two in which it 2026 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY might be preserved no septum was seen, nor can any trace of a septum be seen on the type when the shell is moistened. Pontisia stehlii Cooper and Grant Pontisia stehlii Cooper and Grant, 1969:13, pi. 4: figs. 7-10. COMPARISON.—Pontisia stehlii is characterized by its moderate size, bulbous shape, convex profile of the fold, relatively narrow flanks with costae that are not reflexed, costae that begin far back on the beak, and its low median ridge in the brachial valve. A similar appearing species in the Hess For- mation is Antronaria speciosa, new species, from which P. stehlii differs in its nondepressed median costa of the fold, much more strongly convex pro- file of the fold, so that the ends of the costae slope ventrally rather than terminate abruptly, its nar- rower flanks with nonreflexed costal crests, and its costae that begin farther back on the beak. In the Capitan Formation, Tautosia elegans (Girty) is ex- ternally similar but it differs in most of the same features that distinguish A. speciosa. A species that resembles P. stehlii externally is Wellerella girtyi from the Word Formation in the Glass Mountains and the Cherry Canyon Forma- tion of the Guadalupe Mountains: the external form is so similar that King (1930) considered them to be the same, yet they are really generically dif- ferent. Pontisia stehlii is larger, has somewhat wider flanks that bear more costae, its costae begin far- ther back on the beaks, and its dorsal umbonal area is flattened or indented instead of being evenly arched transversely. DISCUSSION.—Many specimens exhibit the interior of the species and make excellent material on which to base the genus. The deltidial plates of the pedi- cle valve are conjunct, narrow, elevated toward the anterior, and have elevated rims part way around the foramen. The teeth are small, knoblike, and jut out from under the shell rim, and thus are grooved on the outside. Underneath, the deltidial plates are buttressed by an arching deposit which thickens them and is attached to the dental plates. The dental plates are nearly vertical and nearly parallel. The muscle field is large, located anterior to the delthyrial cavity, and with large rounded diductor scars enclosing the adductors. The sockets of the brachial valve are strongly but minutely corrugated, and are bounded by strong ridges that bear slightly concave broad outer hinge plates. These attach the crura, which are strongly keeled below and are strengthened by an extension of the outer hinge plate along its side. The crura are long, crescentic in section and con- cave toward midvalve. The inner hinge plates are variable but wide, in some specimens coalescing to form a concave plate or flat or uniting in a slight anticline. No trace of a median septum can be seen under the hinge plate, and the median ridge, when present, is low and inconspicuous. This is the most abundant species of Pontisia in the Glass Mountains and a fair sample of it has been obtained from several localities. As here de- scribed, it has a somewhat longer stratigraphic range than most of the other species, since it occurs in the Institella Zone at the base of the Cathedral Mountain Formation and extends into the Road Canyon Formation. Its greatest abundance is at the base of the Road Canyon. A species with as wide a vertical and geographic range is certain to have considerable variation. This is true of P. stehlii, which exhibits variation in both vertical and hori- zontal dimensions. The type locality for the species is USNM 702c, where specimens are mostly trigonal, rather thick anterior to midvalve, and with a fairly long beak. The species is usually elongate until it reaches about 10 mm length, at which point the width becomes greater and the species wider than long. The costae are usually crowded and thick. These features characterize many of the specimens from the Institella Zone in the Split Tank region, and while no real problem in identifying them as P. stehlii is encountered, several aberrations create difficulties. Some specimens are rounder than usual and the costae invade the umbonal region. Further- more, the spaces between the costae are deeper and wider than in the type group and in some speci- mens the costae are enormously thickened and the shell is a gross example of the rounded forms. Inter- mediates are readily found, however, making it clear that these are all related. In fact, odd speci- mens from the type locality exhibit the same gigan- tism in the ribbing. Interesting horizontal variations also occur. At USNM 702c over 87 percent of 56 specimens counted have only 3 costae on the fold; these are crowded and the fold is high; 7 percent of the specimens NUMBER 21 2027 have 4 costae on the fold and 6 percent have 5 costae. At USNM 721s, of 50 specimens counted, 2 percent have 7 costae on the fold, 22 percent have 5 costae, 34 percent have 4 costae, and 42 percent have only 3 costae on the fold. This is considerably different from those of USNM 702c. The collection from USNM 721o is still different. Of 88 specimens counted, 59 percent have only 3 costae on the fold, but 28 percent have 4 costae, and only 13 percent have 5 costae on the fold. From USNM 719x, 39 specimens showed 69 percent with 3 costae, eighteen percent with 4, and thirteen percent with 5 costae on the fold. Inasmuch as each of these lots come from separate local bioherms, it suggests that the variation is due to local conditions. In each case a good solid core of specimens were most like the types in having 3 costae on the fold. Along with these variations are distorted obese or deformed specimens that may appear in any considerable lot of rhynchonellids. We have named as P. stehlii tumidosa a few specimens that are rounded, tumid, globular in outline, and in which the costae extend far onto the umbo. These suggest some of those from the Institella Zone but they are generally more tumid and the characters more per- sistent. They come, however, from the Road Can- yon Formation rather than the earlier beds although they are suggestive of the older forms. Pontisia stehlii stehlii Cooper and Grant PLATE 517: FIGURES 21-25, 38-47; PLATE 533: FICURES 39-60; PLATE 534: FIGURES 1-49; PLATE 552: FIGURE 14 Pugnoides texanus R. E. King [not Shumard], 1931:108, pi. 34: figs. 5-9. Pugnoides elegans [part] R. E. King [not Girty], 1931:106, pi. 33: figs. 12, 13; pi. 34: figs. 4 [not figs. 2, 3 (= Antronaria speciosa Cooper and Grant, new species)]. Average size for genus, biconvex, normally some- what bulbous, brachial valve much deeper than pedicle valve; outline transversely triangular to nearly oval, sides diverging between 80° and 110°; profile subtrigonal; anterior commissure uniplicate; fold low to moderately high, beginning 5-7 mm anterior to brachial beak, profile flattened near beak, abruptly convex near anterior margin; sulcus shallow to moderately deep, beginning 8-10 mm anterior to pedicle beak, convexity strongest be- tween highest points of flanks. Costae strong, broad and crowded, sharp or blunt, beginning 4-5 mm anterior to beaks, numbering 2-6 on fold, normally 3, one less in sulcus, 2-6 on each flank, normally 4, those on flanks lower and less sharp than on fold. Concentric ornamentation absent; growth lines few and faint. Pedicle valve somewhat inflated forward of beak, strongly convex through sulcus, slightly convex toward flanks; inner costae of flanks prominent but not reflexed; beak sharp, dorsally curved, normally somewhat attenuate; beak ridges blunt to sharp; lateral pseudointerareas narrow, partly covered by overlapping brachial valve. Delthyrium triangular, base covered by trapezoidal plates, curved to form low arch; foramen elongate oval. Brachial valve moderately to strongly convex transversely and longitudinally; smooth part of umbo flattened or slightly indented; apex of valve within pedicle valve, covered by deltidial plates. Pedicle valve interior with sides of delthyrium widely diverging anterior to deltidial plates; teeth elongate, supported by vertical dental plates reach- ing floor or valve. Muscle field bluntly triangular to transversely oval, lying anterior to ends of den- tal plates; adductor scar median, small, nearly cir- cular to longitudinally oval; diductor scars wide, tear-shaped, surrounding adductor scar laterally and anteriorly. Brachial valve interior with undivided but deeply notched, triangular hinge plate, bounded laterally by deep, anteriorly expanding, strongly corrugated sockets; falcifer crura projecting forward and ante- riorly diverging, strongly curved ventrally, may twist as much as 90°, dorsal edges carinate; median septum reduced to small median keel on underside of hinge plate and low median ridge along floor of valve. Muscle area partly divided by median ridge; posterior adductor scars elongate, anteriorly diverg- ing, flanking large, oval anterior adductor scars. STRATIGRAPHIC OCCURRENCE.—Cathedral Moun- tain, Road Canyon, and Word (Willis Ranch Mem- ber) formations. LOCALITIES.—Cathedral Mountain: AMNH 500G; USNM 702, 702a, 708, 721u, 726o, 726u, 726y, 735b. Road Canyon: USNM 702c, 703a, 703c, 703d, 709u, 716x, 719x, 720d, 721j, 721o, 721s, 721t, 726f. Willis Ranch: USNM 723w. DIAGNOSIS.—Pontisia with deep brachial valve and closely crowded broad costae but smooth beaks and umbones. 2028 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY MEASUREMENTS (in mm).— brachial apical USNM 702c length valve length width thick- ness angle (°) 148710a 0.7 0.5 0.7 0.3 - 148710b 1.5 1.3 1.4 0.7 - 148710c 2.8 2.3 2.2 1.0 - 1487I0d 4.2 3.5 3.5 1.9 - 1487I0e 5.5 4.6 5.0 2.0 c.IOO 148710f 7.0 6.0 6.7 2.7 c.100 148710g 1487l0h 9.0 9.4 7.6 7.7 8.8 9.3 4.0 6.0 85 101 1487101 11.5 9.7 11.6 7.3 102 148710J 148710k 12.4 12.4 10.9 10.6 14.7 13.5 6.2 10.9 108 102 148710-1 14.4 12.2 15.8 11.8 108 148710m 15.5 13.4 18.5 13.0 100 153835a 13.7 11.6 14.3 12.3 98 (holotype) TYPES.—Holotype: USNM 153835a. Figured hypotypes: USNM 148710h,i; 153835b-i,m-p,r; 154743a,b; 154745a-j; 154848a-c,e; 154849; 154850a; 154851a,b; 154852a-c. Measured hypotypes: USNM 148710a-m. COMPARISON.—Pontisia stehlii stehlii may have descended from the related P. s. tumidosa, new sub- species, which differs from P. s. stehlii in having a more convex pedicle valve, lower fold and shal- lower sulcus, and the costae extending farther onto the umbo, in some specimens suggesting almost com- plete costation but usually the beaks are smooth. Pontisia s. stehlii usually has a longer beak on the pedicle valve than P. s. tumidosa and it is usually more flattened anteriorly. Pontisia s. tumidosa is generally more rounded in outline than P. s. stehlii, which generally is more trigonal. Pontisia stehlii tumidosa, new subspecies PLATE 510: FIGURES 56-62; PLATE 535: FIGURES 52-66 Medium size for genus, subcircular to subtrigonal in outline, brachial valve deeper than pedicle valve; posterolateral extremities approaching 110°. Sides rounded, greatest width near midvalve; anterior margin moderately rounded to subtruncate. Ante- rior commissure uniplicate. Beak short, sharply angular, with elongate oval foramen and elevated, conjunct but short deltidial plates. Surface variably costate, usually with 3 broadly rounded, crowded costae on fold, rarely 4 or 5 and 3 or 4 on each flank. Interspaces much more narrow than costae. Pedicle valve moderately convex in lateral pro- file, broadly and gently convex in anterior profile; umbonal region narrowly convex; median region gently convex; sulcus originating near midvalve, broad, shallow and poorly defined, crowded with costae. Tongue moderately long, strongly genicu- lated and convex transversely. Flanks narrow, rounded, slightly inflated and with poorly devel- oped anterolateral extremities. Brachial valve fairly strongly convex in lateral profile but evenly and strongly domed in anterior profile with nearly vertical sides. Umbonal region gently convex; fold originating near midvalve, mod- erately wide, only slightly elevated above flanks from origin to anterior margin. Flanks rounded and steep. Interior same as that of typical subspecies. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 702c 148623a 8.0 7.0 7.8 5.9 90 148623b 8.5 7.1 8.5 8.4 90 148623c 8.7 7.2 9.2 6.6 100 148623d 9.4 7.5 9.5 8.2 90 148623e 9.5 7.8 9.3 8.5 90 148623f 9.8 8.0 9.8 7.5 90 148623g 10.3 8.7 10.4 8.7 100 148623h 11.4 9.5 11.5 7.9 100 (holotype) STRATIGRAPHIC OCCURRENCE.—Cathedral Moun- tain and Road Canyon formations. LOCALITIES.—Cathedral Mountain: AMNH 500; USNM 702, 702a, 702b, 702inst, 702-low, 702un, 703a1, 703b, 703bs, 708, 726u. Road Canyon: USNM 702c, 703a, 703c, 719x, 721o, 724c. DIAGNOSIS.—Rotund and bulbous Pontisia stehlii with costae extended to but not onto the beaks. TYPES.—Holotype: USNM 148623h. Figured par- atypes: USNM 148623b,c,g; 154682a,b; 154686a-c. Measured paratypes: USNM 148623a-g. Unfigured paratypes: USNM 148623a,d-f. Pontisia truncata, new species PLATE 516: FIGURES 1-5 Medium size for genus, subpentagonal in out- line, wider than long, with narrowly rounded sides NUMBER 21 2029 but broadly truncated front margin; apical angle 94°. Beak erect. Anterior commissure uniplicate and serrate; deltidial plates conjunct; foramen oval, submesothyridid. Surface costate except for um- bonal regions, costae elevated and narrowly rounded with narrow interspaces, 3 on fold, and 3 on each flank. Pedicle valve less deep than brachial valve; gen- tly convex in lateral profile but broadly and gently concave in anterior profile; sulcus originating at about midvalve, wide and shallow, forming short serrated tongue; flanks concave but elevated above sulcus and sharply angular. Brachial valve moderately convex in lateral pro- file, maximum convexity in anterior part; anterior profile broad, rounded dome somewhat flattened on top. Fold low, and flat topped, defined only at front and originating near midvalve. Flanks swol- len and rounded but depressed slightly below fold. Pedicle valve interior with small teeth but thick dental plates; muscle field cordate, large, lying ante- rior to delthyrial cavity. Brachial valve interior with moderately wide outer hinge plates forming ridges overhanging sockets; inner hinge plates united, with slightly elevated suture line and moderately deep anterior notch. Crura not preserved. MEASUREMENTS (in mm).—Holotype USNM 154734: length 13.0, brachial valve length 12.1, width 15.8, thickness 11.5, apical angle 94°. STRATIGRAPHIC OCCURRENCE.—Road Canyon For- mation. LOCALITY.—USNM 732j. DIAGNOSIS.-—Widely pentagonal Pontisia with low fold and only 2 costae in the sulcus. TYPES.—Holotype: USNM 154734. COMPARISON AND DISCUSSION.—This species is similar to several of the medium-sized Antronaria such as Antronaria dissona, A. specialis, new species, and A. mesicostalis (Girty). It differs from all of these in not having a median costa or costae de- pressed below the level of the fold. Pontisia stehlii Cooper and Grant is marked like P. truncata in some of its forms but differs in having a higher fold and greater thickness. Other specimens of P. stehlii are like P. truncata but are thicker, less wide, with thicker costae, and less prominently angular flanks. The brachial valve of P truncata has no median septum and is typical of the genus in all respects. Unfortunately, silica deposition in the adductor field made it impossible to differentiate the pattern of muscles. Pontisia ventricola, new species PLATE 520: FIGURES 50-55; PLATE 536: FIGURES 28-51 Pugnoides texanus R. E. King [not Shumard], 1931:108, pi. 34: figs. 5a-d; 6a-d; 8a, b [not 7a-c]; 9. Medium size for genus, length and width about equal; outline subpentagonal with broadly rounded sides and gently rounded anterior margin. Valves unequal in depth, brachial valve slightly deeper. Sides diverging at obtuse angle in adults. Anterior commissure strongly uniplicate. Beak small, nearly straight; deltidial plates conjunct, defining small, oval, submesothyridid foramen. Surface paucico- state, posterior one-half to one-third smooth, ante- rior one-half to two-thirds marked by strong, broad, rounded to subangular costae, 2-4 occupying fold, usually 3, and one less in sulcus; each flank with 2 or 3 costae, third costa usually not strong. Pedicle valve fairly evenly and moderately con- vex in lateral profile, broadly and slightly convex in anterior profile, costae of the sulcus somewhat protuberent. Umbonal region narrowly convex; me- dian region usually conspicuously swollen where costae of sulcus originate. Sulcus starting anterior to midvalve and anterior to origin of costae. Sulcus short, with long transversely convex tongue only slightly depressed below anterolateral extremities. Flanks very narrow, flattened, sloping slightly. Brachial valve fairly evenly and moderately con- vex in lateral profile; anterior profile broadly and moderately domed with short but with precipitous sides. Umbonal region moderately convex but me- dian region fairly strongly swollen. Fold slightly spreading, originating anterior to midvalve, occu- pying slightly more than half width; fold trans- versely flattened anteriorly, slightly elevated above flanks at anterior. Flanks steeply sloping, swollen. Pedicle valve interior with short dental plates; muscles not impressed. Brachial valve interior with undivided hinge plate having median region de- pressed or elevated; socket ridges slender; falcifer crura moderately long, strongly curved, crescentic in section with concave side facing medially. No trace of median septum. STRATIGRAPHIC OCCURRENCE.—Hess Formation (top). 2030 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY MEASUREMENT s (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 726n 152860a 4.6 4.1 4.2 1.7 76 152860b 5.6 4.7 5.6 2.4 80 152860c 6.4 5.4 5.5 2.5 70 152860d 7.3 6.3 6.9 3.0 72 152860e 8.0 6.9 8.2 5.1 84 152860f 8.8 7.8 8.6 5.6 90 152860g 9.0 8.1 9.3 6.2 93 152860h 9.2 8.3 9.2 6.3 93 152860i 10.0 8.6 10.5 6.2 97 152860J 9.7 8.7 9.5 6.8 96 152860k 10.5 9.3 10.4 6.8 96 152860-1 9.4 8.2 9.4 6.8 85 152860m 11.2 9.7 11.6 7.8 103 (holotype) 152860n 10.6 9.4 10.5 7.8 94 152860o 11.7 10.5 11.3 6.4 98 I52680p 10.7 9.4 10.8 7.5 108 152860q 11.0 9.8 10.9 7.1 99 152860r 11.3 10.3 11.5 7.2 97 152860s 12.4 11.3 13.1 7.7 107 King 223 YPM 12530 11.4 10.3 12.3 7.8 107 STRATIGRAPHIC OCCURRENCE.—Hess Formation (top). LOCALITIES.—King 223; USNM 726n. DIAGNOSIS.—Seminude, coarsely costate Pontisia with medially inflated valves. TYPES.—Holotype: USNM 152860m. Figured paratypes: USNM 152860b,d,h,j,k,s; 154866a-e. Measured paratypes: USNM 152860a-l,n-s. Unfig- ured paratypes: USNM 152860a,c,e-g,i,l-r. COMPARISON.—The swollen median areas of both valves and the strong spreading costae characterize this species. Bicostate specimens differ from Anteri- docus bicostatus, new species, in having their length and width nearly equal, being more strongly co- state farther posteriorly, and in having much less strongly developed anterolateral extremities. Pon- tisia ventricola is larger and more robust than P franklinensis, new species, from the Hueco Can- yon Formation. The valves of P. ventricola are more strongly swollen medially than those of P. kingi, new species, from the Neal Ranch Formation. It is much larger than P. nanas (Stehli) and has a less deep sulcus on the pedicle valve. Pontisia ven- tricola is not so wide as specimens of Antronaria spectabilis, new species, of the same size, but that species attains a much larger size than the Hess species. Furthermore, P. ventricola does not have the depressed median costa in the fold which char- acterizes the Bone Spring species. Pontisia stehlii Cooper and Grant is much larger and much more variable than the Hess species but has less spread- ing and narrower costae in many specimens and is not swollen medially as is P. ventricola. An undescribed species from the Hueco Canyon Formation is most like P. ventricola. A specimen of this species was identified by King with the Hess species (1931:108, pi. 34: fig. 7a-c). This Hueco species (YPM 12527) is readily distinguished by the nearly complete costation of the valves, whereas P. ventricola is usually about half smooth posteriorly. DISCUSSION.—Most specimens of this species have 3 costae on the fold and 2 in the sulcus. Out of 104 specimens 5 had 2 costae on the fold and 5 had 4 costae on the fold. A costa on one specimen was bifurcated to produce 4 on the fold. The young are thin, long beaked, and their sides form an acute angle. The brachial valve is slightly concave anteriorly. This species is abundant at the top of the Hess but is not known elsewhere. Pontisia wolfcampensis, new species PLATE 520: FIGURES 11-18 Small for genus, wider than long, subpentagonal in outline; sides rounded, anterior margin trun- cated, apical angle about 100°. Anterior commis- sure uniplicate; valves unequal in depth, brachial valve deeper. Deltidial plates variable, from dis- junct to conjunct in specimens of same size; fora- men oval, permesothyridid. Surface semicostate, 3 on fold, 2 in sulcus, and 3 on each flank; costae on tongue and anterior side of fold with shallow groove. Pedicle valve gently convex in lateral profile but flatly to gently concave in anterior profile. Um- bonal and median regions moderately swollen; sulcus originating at midvalve, wide, producing long tongue. Flanks flattened, somewhat deflected in anterolateral direction; flanks narrow and rounded. Brachial valve narrowly domed in anterior pro- file with moderately rounded top but precipitous sides. Fold originating at midvalve, low and flat- tened on top, not strongly elevated above inflated flanks. Pedicle valve interior with slender dental plates. NUMBER 21 2031 Brachial valve interior with small cardinalia; outer hinge plates fairly wide; socket ridges slender; inner hinge plates fused and anteriorly notched. Crura laterally compressed, long and curved. MEASUREMENTS (in mm).—Specimens USNM 154764c (holotype) and b (paratype), respectively: length 9.1, 8.4? brachial valve length 8.0, 7.9; width 10.7, 9.8; thickness 8.8, 6.3; apical angle 100°, 100°. STRATIGRAPHIC OCCURRENCE.—Neal Ranch Forma- tion (Bed 4). LOCALITY.—USNM 727e. DIAGNOSIS.—Small Pontisia, semicostate, with short, low fold and small cardinalia. TYPES.—Holotype: USNM 154764c. Figured par- atypes: USNM 154764a,d,e. Measured and unfig- ured paratype: USNM 154764b. COMPARISON.—This species need be compared only to P. parva, new species, with which it occurs, because it differs in the same degree from the species to which the latter species was compared. It also shares some of the characteristics of P. parva, new species, such as the broadly flattened front due to rapid growth along the anterior margins of both valves. It differs from P. parva in being larger, wider, having somewhat stronger costae, and a wider fold and sulcus. Lirellaria, new genus [Latin lirella (small ridge)] Medium size for rhynchonellacea, with rounded contours and subpentagonal to subcircular outline; anterior commissure strongly uniplicate. Beak short, suberect to erect, with submesothyridid foramen and conjunct, small deltidial plates. Beak ridges strong, surface costellate, costellae direct, reaching or nearly reaching beaks. Pedicle valve interior with small teeth supported by thin, short, strong dental plates. Brachial valve with large undivided hinge plate having strong socket ridges, small outer hinge plates and broad coalesced inner hinge plates. Median septum absent. Crura modified falcifer, broad, curved, concave toward midvalve. TYPE-SPECIES.—Lirellaria costellata, new species. DIAGNOSIS.—Medium, costellate rhynchonellacea having an undivided hinge plate, no median septum. COMPARISON.—This genus suggests Allorhynchus Weller and Pontisia Cooper and Grant but differs from both in having a costellate exterior. It fur- ther differs from Allorhynchus in having an undi- vided hinge plate. It differs from Wellerella Dun- bar and Condra in the absence of a median septum and in the costellate exterior. It also differs from Phrenophoria Cooper and Grant in ornamentation and lack of a median septum. It differs from other costellate genera in having the costellae direct and undivided. Ptilotorhynchus, new genus, is multicostellate but differs from Lirel- laria in having a divided hinge plate and elaborate deltidial plates. Strigirhynchia Cooper and Grant is costellate but it has a long, high median septum and a concave brachial valve umbo. Lirellaria differs from Aphaurosia, new genus, in its ornament, the valves being almost completely costellate rather than half smooth as in Aphaurosia. Lirellaria also suggests Trophisina, new genus, but is usually not so globular as that genus. It is also possible that species of Lirellaria of globular form will be found. Sufficient difference exists, how- ever, in the character of the cardinalia to distin- guish the two. Trophisina has a well-formed median septum, a feature not present in Lirellaria. Tro- phisina is also not provided with conjunct and strong deltidial plates as is Lirellaria. DISCUSSION.—Some features of both valves of Lirellaria are worthy of note. In the pedicle valve the teeth are set inside the valve, with a deep groove between them and the valve margin. The dental plates are thus narrowed and elongated and the cavities between them and the valve wall in some specimens are almost completely filled. The dental plates and teeth are thus like these struc- tures in some modern rhynchonellids. As usual with thin-shelled, silicified branchiopods we have not been able to determine the form and individual scars of the muscle field. Concerning the inside of the brachial valve we have information from only a few specimens, con- sequently the inside variation is not understood. The hinge plate in both species has the crura tied to the socket plate by broad outer hinge plates; but in L. crassa, new species, the inner hinge plates are not well developed and the gap between them is plugged by shell tissue. No specimen preserves the crura in perfect condition. They are keeled, mod- erately long, gently curved, and concave toward midvalve. 2032 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY Lirellaria costellata, new species PLATE 508: FIGURES 56-64; PLATE 511: FIGURES 1-20; PLATE 780, FICURES 44-50 (in part V) Medium size, subcircular in outline, margins rounded; posterolateral extremities converging at about 90°; sides and anterior margin broadly rounded. Anterior commisure strongly uniplicate. Beak short, suberect with small foramen and short deltidial plates. Surface costellate, 8 costellae on fold of adults, one less in sulcus, and 12 on each flank. Pedicle valve evenly and moderately convex in lateral profile but broadly and gently convex in anterior profile. Umbonal and median regions swollen. Sulcus originating anterior to midvalve, broad and shallow but produced into long broadly rounded tongue geniculated nearly at right angle. Flanks narrow and moderately convex. Brachial valve moderately and evenly convex, somewhat more rounded at umbo in lateral profile; anterior profile somewhat narrowly domed but smooth and steep sided. Umbonal and median re- gions swollen; fold originating anterior to mid- valve, low and with soft contours and only slightly elevated at anterior. Flanks swollen and steep. Pedicle valve interior with strong dental plates. Brachial valve interior with undivided hinge plate having broad, coalesced inner hinge plates and stout laterally compressed crura. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 728p 155073a 7.6 7.0 8.5 4.4 90 USNM 738 152820 5.8? 4.8 5.8 4.2 90 AMNH 40 152821c 10.0 9.0 10.0 6.5 90 STRATIGRAPHIC OCCURRENCE.—Bell Canyon For- mation (Lamar Member). LOCALITIES.—AMNH 37, 38, 40; USNM 725e, 728p, 738. DIAGNOSIS.—Finely costellate Lirellaria with short, low fold and shallow sulcus. TYPES.—Holotype: USNM 155073a. Figured par- atypes: USNM 152819; 152821a,c; 154667; 154692a,b; 154693a,b; 154696a; 155073b; 155112a,b. Unfigured paratypes: USNM 152821b; I54696b,c. COMPARISON.—Differs from L. crassa, new species, in the greater abundance of, and finer, costellae, especially on the fold and sulcus, and in its smaller size. DISCUSSION.—This is a rare species in the Lamar Member but the specimens, although slightly dis- torted, display their internal characters well. In the few specimens collected, variation in the strength of the ornament was seen. Lirellaria crassa, new species PLATE 780: FIGURES 57-65 (in part V) Usual size for genus; length and width nearly equal; valves subequal in depth; outline subcir- cular to subpentagonal; greatest width slightly an- terior to midvalve; posterolateral margins meeting at about 90°-105°; sides rounded; anterior margin broadly rounded. Beak short with strong beak ridges, oval foramen, and small disjunct deltidial plates. Surface costellate, costellae strong, in adults three on fold, one less in sulcus, and 5 or 6 on flanks, outermost ones small. Pedicle valve evenly and flatly convex in lateral profile and broadly but gently convex in anterior profile. Umbonal and median regions swollen; sul- cus originating near midvalve, broad and shallow, but produced into a short tongue geniculated at obtuse angle. Flanks narrow, moderately convex, moderately steep. Brachial valve moderately but unevenly convex in lateral profile, with the front convex. Anterior profile broadly and gently domed and with steep sides. Umbonal and median regions swollen; fold low, originating near midvalve, flattened, and only slightly elevated at anterior. Flanks swollen, with long, steep slopes. Pedicle valve interior with dental plates obscure. Brachial valve interior with long, curved, laterally compressed crura and inner hinge plates not com- pletely coalesced. MEASUREMENTS (in mm).—Specimens 155072a (holotype) and b, respectively: length 8.7, 7.8; bra- chial valve length 7.5, 6.5; width 8.9, 7.1; thickness 4.6, 4.7; apical angle 105°, 98°. STRATIGRAPHIC OCCURRENCE.—Bell Canyon For- mation (Lamar Member). LOCALITY.—USNM 728p. NUMBER 21 2033 TYPES.—Holotype: USNM 155072a. Figured par- atypes: USNM 155072b,c. Measured paratype: 155072b. Unfigured paratypes: USNM 155072d-h. DIAGNOSIS.—Strongly costellate Lirellaria. COMPARISON.—This species differs from L. costel- lata, new species, in having stronger costellae and smaller size. Lirellaria diabloensis, new species PLATE 511: FIGURES 23-25 A single specimen preserving both valves, con- veniently broken at the anterior of the brachial valve, measures 9.5 mm long, 10.0 mm wide, and 6.4 mm thick. The valves are of about equal depth, the sides rounded, and the anterior commissure shows evidence of uniplication. The pedicle valve is moderately convex in both profiles, and has a somewhat keeled umbonal region and flattened anterior. The brachial valve is moderately convex in both profiles but the fold at the anterior is obscure. The beak of the pedicle valve is moder- ately long and suberect, with a small foramen defined by conjunct and strong deltidial plates. The surface is costellate, the costellae becoming faint but still present in the umbonal regions. The interior is not well preserved and the car- dinalia are thickened by siliceous deposit, neverthe- less the hinge plate is undivided, unsupported, and medially notched. STRATIGRAPHIC OCCURRENCE.—Bone Spring For- mation. LOCALITY.—AMNH 591. TYPES.—Holotype: USNM 152822. COMPARISON.—This species is larger than the others except Lirellaria? sp. 1; it is more robust, has more numerous costellae than L. crassa, new spe- cies, but is not so finely ornamented as L. costellata, new species. Lirellaria? species 1 PLATE 511: FIGURES 21, 22 A possible species of Lirellaria is indicated by a single pedicle valve measuring 13 mm in length and 15 mm in width. It is subpentagonal in out- line and has a long, wide, and rounded tongue. The sulcus originates near midvalve, is wide and shallow, and poorly differentiated except at its anterior. The surface is covered by numerous costel- lae, 12 in the sulcus and 15 or 16 on the flanks. The umbonal region is broadly carinate, the carina- tion melting into the sulcus at about midvalve. The flanks are fairly broad, moderately convex, but not strongly deflected. The beak is short and the posterolateral bound- aries converge at an angle of 110°. The foramen is small, submesothyridid and bounded anteriorly by conjunct deltidial plates. The teeth are small and lie inside of but parallel to the shell margin. Den- tal plates are long and stout. The muscle field is small, with a truncated anterior margin and large diductor scars surrounding the adductors. STRATIGRAPHIC OCCURRENCE.—Word Formation (Willis Ranch Member). LOCALITY.—USNM 706e. Genus Divaricosta Cooper and Grant, 1969 Divaricosta Cooper and Grant 1969:11. Medium size, biconvex; outline bluntly subtri- gonal to subpentagonal; uniplicate, fold low, sulcus shallow to moderately deep. Costae beginning at beaks, increasing anteriorly by bifurcation; con- centric striae faint, fine; growth lines weak over most of shell, becoming strong laminae near an- terior margins. Pedicle valve moderately convex, flanks not re- flexed; beak short, bluntly pointed, straight, or dorsally curved, apsacline; delthyrium wide, nearly completely closed by conjunct deltidial plates, for- amen small, subcircular, mesothyridid; lateral pseudointerareas narrow, partly covered by edge of opposite valve. Brachial valve somewhat more convex; beak bluntly rounded, apex covered by deltidial plates. Pedicle valve interior with recess in delthyrium for brachial beak; teeth strong, somewhat curved; dental plates vertical, supporting hinge teeth, often fused to sides of valve. Muscle area narrowly tri- angular, beginning between dental plates, expand- ing anteriorly; adductor muscle scars small, lying near center of muscle area, surrounded by larger diductor scars. Brachial valve interior with large undivided hinge plate; hinge sockets deep, wide, strongly denticulate; with strong outer socket ridges articu- 2034 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY lating with sockets on outside of teeth. Crura falci- fer, diverging slightly from forward edge of hinge plate, not twisted, gently curving ventrally; crural bases extending from underside of hinge plate along undersides of crura; median ridge moderately high, thick, broadly rounded, extending into posterior part of muscle area. Posterior adductor muscle scars elongate, narrow, widely separated from one an- other, slightly diverging anteriorly, lying lateral to larger, anteriorly slightly expanding anterior ad- ductor scars along median line; diductor muscle impression at apex of valve, at posterior extremity of hinge plate. TYPE-SPECIES.—Divaricosta squarrosa Cooper and Grant (1969:12, pi. 4: figs. 1-6). DIAGNOSIS.—Medium-sized rhynchonellacea hav- ing numerous bifurcating and intercalated costae and an undivided hinge plate. COMPARISON.—Divaricosta is characterized by its costae that begin at the beaks and increase in num- ber anteriorly by bifurcation or intercalation, its low fold and moderately shallow sulcus, its large, conjunct deltidial plates, the narrow lateral pseu- dointerareas that are partly covered by the over- lapping edges of the brachial valve, the large, un- divided hinge plate, and thick, high median dorsal ridge, but absent median septum. It resembles Fascicosta Stehli (1955) in its bifurcating costae, differing in its large conjunct deltidial plates, over- lapping valves that produce lateral pseudointer- areas, undivided hinge plate, and median dorsal ridge but no brace or septum. Ptilotorhynchus, new genus, is similar to Divari- costa in external appearance but the deltidial plates have winglike protuberances and a divided hinge plate. Divaricosta differs from Deltarina, new genus, in more numerous bifurcations of the costae, an undivided hinge plate, and a thick median ridge. DISCUSSION.—The type species of Divaricosta, D. squarrosa Cooper and Grant, was described and illustrated by Stehli (1955:71, 73) as Fascicosta longaeva (Girty). Stehli did not designate any of these specimens as the type for Fascicosta, but in- stead chose Girty's species under the mistaken opin- ion that it belonged to the same species as his Get- away specimens. Our study of Girty's Rhynchonella? longaeva, including the illustrated holotype (Girty, 1909, pi. 15: fig. 18) and all paratypes in the U.S. Geological Survey collections, leads us to conclude that the resemblance between R.? longaeva and D. squarrosa is only in the bifurcation of the costae, and that they are otherwise generically distinct. Several features of interest may be pointed out in the shell anatomy of Divaricosta. The deltidial plates of the pedicle valve are very thick and con- junct but clearly show the suture. The anterior surface of the deltidial plates is excavated into a broad crescent to receive the movement of the bra- chial valve. The teeth are unusual in that they protrude into the valve from the side and are tied to the valve wall by horizontal plates. The teeth are buttressed by strong dental plates that stand away from the valve wall. The teeth are thus set off by a wide gap or socket between the tooth and the valve wall. This receives an elongated tooth that occupies the outside of the socket in the oppo- site valve. In old specimens the cavity between the dental plate and the valve wall is filled by shell substance but the horizontal plate and the deep sockets between the tooth and the valve edge is well developed. Old specimens of the pedicle valve are charac- terized by a broad shelflike extension of the pos- terolateral margin just anterior to the teeth. In one specimen these shelves extend in a dorsal direction as high as the anterior tongue. This shelf is over- lain by the posterolateral region of the brachial valve in a strong overlap. The hinge plate is notable for its solidity and the peculiar development of the socket. The socket is strongly corrugated and bounded by a thick, strong socket plate. On the outside a thin plate forms the outer boundary of the socket, but this plate is inside the margin of the brachial valve. This plate is an accessory tooth in the brachial valve that articulates with the socket on the out- side of the tooth. This arrangement makes for a strong articulation. The hinge plate is composed of the socket ridge which hangs over the socket and to which is fixed a broad outer hinge plate which attaches the crural bases that are anteriorly keeled. The hinge plate also is marked by a fairly elongated fulcral plate under the socket. The inner hinge plates unite medially in a fairly broad fold. These plates are buttressed by a median support that varies from a fairly slender median septum to a thick and solid ridge, usually the latter. The crura are moderately long, stout, slightly NUMBER 21 2035 curved and keeled on the ventrolateral edge. The distal end is oblique, being sharply pointed toward the inside but obtuse dorsolaterally. Divaricosta squarrosa Cooper and Grant PLATE 509: FIGURES 1-26; PLATE 552: FIGURES 6-10 Fascicosta longaeva [not Girty] Stehli, 1955:71-73, figs. 1-17. Divaricosta squarrosa Cooper and Grant, 1969:12, pi. 4: figs. 1-6. Small, moderately strongly biconvex; outline bluntly subtrigonal to subpentagonal, sides diverg- ing nearly 100°; anterior commissure uniplicate; fold low, beginning inconspicuously, gently convex longitudinally and transversely; sulcus shallow, deeper at anterior, beginning 3 or 4 mm anterior to beak. Costae strong, narrow, ropelike, beginning at beaks, increasing anteriorly by bifurcation and intercalation, numbering 3-5 on fold, one less in sulcus, 6-9 on each flank. Concentric striae fine, closely spaced; growth lines weak and widely spaced except near anterior margins, there strong, closely spaced, laminar. Pedicle valve moderately convex in lateral and anterior profiles, flanks not reflexed; beak short, bluntly pointed, slightly attenuate, straight or with delthyrial area slanted ventrally away from hinge; delthyrium wide, triangular, nearly completely closed by large, thick, conjunct deltidial plates, leaving small, round foramen; lateral pseudointer- areas present, width variable, more-or-less covered by overlapping edge of brachial valve. Brachial valve moderately convex, umbonal area slightly flattened or indented; beak bluntly rounded, slightly prominent, apex covered by deltidial plates. Pedicle valve interior with shallow recess for accommodation of brachial beak; teeth strong, tusklike, continuous, with nearly vertical dental plates that are discrete or fused to sides of valve. Muscle area narrowly triangular, beginning be- tween anterior edges of dental plates, expanding slightly anteriorly to about a third valve length, often slightly excavate; adductor scars small, lying near center of muscle area, completely surrounded by larger diductor scars. Brachial valve interior with large semicircular, undivided hinge plate, bounded laterally by deep, wide, strongly denticulate sockets having high, thin outer socket ridges; inner socket ridges curved, narrowly overhanging sockets; outer hinge plates narrow, crura diverging anteriorly from forward edge of hinge plate, narrow, curved ventrally, mod- erately long, not twisted; crural bases vertical, nar- row but strong ridges on underside of hinge plate, extending as keels along dorsal side of crura; me- dian ridge moderately high, thick, broadly rounded, extending about a fourth to a fifth valve length. Muscle area subelliptical, slightly depressed; pos- terior adductor scars narrow, elongate, slightly diverging anteriorly, lying lateral to elongate, ante- riorly slightly widening anterior adductor scars located along median line of valve, lateral and anterior to median ridge. MEASUREMENTS (in mm).—Specimen USNM 148221: length 6.9, brachial valve length 6.3, mid- width 6.9, width 7.1, thickness 4.0, apical angle 100°. STRATIGRAPHIC OCCURRENCE.—Cherry Canyon For- mation (Getaway Member). LOCALITY.—AMNH 512 ( = USNM 728). DIAGNOSIS.—Divaricosta with ragged anterior lamellae. TYPES.—Lectotype: AMNH 27904/1; Figured paratypes: AMNH 27904/2, 4, 6. Figured hypo- types: USNM 148221, 154675a-c. COMPARISON.—Divaricosta squarrosa is character- ized by its strong, ropelike, bifurcating costae, large, thick deltidial plates, small, mesothyridid foramen, thick shell with strong growth laminae which make ragged margins, and internally by its nearly verti- cal dental plates and strong dorsal median ridge. It differs from Fascicosta longaeva (Girty) in its stronger, higher, more bluntly rounded costae that bifurcate or intercalate more frequently, its less inflated umbones, higher fold and deeper sulcus, slightly overlapping posterolateral valves edges that produce narrow lateral pseudointerareas, prominent and crowded growth laminae near the margins, and more nearly vertical dental plates. DISCUSSION.—The details of the interior have been described under the generic discussion. This species is rare in the Getaway Limestone but it has not been seen at any other level in the Guadalupe Mountains. Divaricosta vagabunda, new species PLATE 509: FIGURES 60, 61 Usual size for genus, wider than long, greatest width at midvalve, outline transversely elliptical, 2038 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY median ridge that swells and extends for about a quarter the valve length, but does not give any notable support to the hinge plate. Antronaria emarginata, new species PLATE 530: FIGURES 1-15 Medium size for genus, wider than long, and widely cordate in outline, posterolateral margins forming angle of 90° to 110°, anterolateral ex- tremities narrowly lobed and anterior margin variably lobate and usually deeply emarginate. Beak usually long and straight to slightly curved. Fora- men small. Surface costate, costae narrowly angu- lar, variable in number, usually 4 or 5 in sulcus and 5 or 6 on fold, median ones deeply depressed to form strong sulcus in fold, thus producing deep emargination. Flanks with 3-7 costae. Costae marked by zigzag, concentric lines. Pedicle valve unevenly convex in lateral profile, umbonal region having most convexity; anterior profile nearly flat to gently concave. Umbonal re- gion narrowly swollen. Sulcus originating at mid- valve, deepening and widening suddenly and forming short strongly geniculated tongue, leaving flanks as narrowly rounded lobes with parts bor- dering sulcus strongly protuberant. Flanks gently convex and narrow. Brachial valve fairly strongly convex in lateral profile; anterior profile broadly and strongly domed but deeply sulcate medially; umbonal and median regions somewhat swollen; fold originating slightly posterior to midvalve, defined by outer costae or outer pair of costae; sulcus originating just poste- rior to point of origin of fold, narrow and very deep, helping to form deep anterior emargination. Flanks narrow and rounded. Interior with short dental plates in pedicle valve but no septum and only slight development of me- dian ridge in brachial valve. STRATIGRAPHIC OCCURRENCE.—Skinner Ranch For- mation (Decie Ranch and Sullivan Peak members). LOCALITIES.—Decie Ranch: USNM 707a, 727u. Sullivan Peak: USNM 707, 726h. DIAGNOSIS.—Medium-sized Antronaria with deep- ly emarginated anterior and numerous costae. TYPE.—Holotype: USNM 154838a. Figured par- atypes: USNM 148662, 152844. Measured paratypes: USNM 152844a,b; 152845a-d. Unfigured paratypes: USNM 154838b-d; 152844a,b; 152845a-d. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness n USNM 707a 152844a 12.6? 11.4 17.8 7.8 110 152844b 14.0 11.9 17.5 11.6 115 USNM 727u 152845a 13.2 11.8 17.2 8.9 110 152845b 13.5 11.7 16.2 8.9 105 152845c 11.5 10.4 15.0 7.6 110 152845d 12.7 10.8 15.1 7.6 105 154838a 13.2 11.6 17.3 8.8 104 (holotype) COMPARISON.—This species is most similar to Antronaria mesicostalis (Girty) but differs in hav- ing a more extreme development of the sulcate fold and the anterior emargination. It differs from A. speciosa, new species, which is also deeply emargi- nate, in having more numerous costae. DISCUSSION.—This is a rare species of which only unsilicified specimens are available. Therefore, we do not have all of the details of the interior but from exfoliated specimens come indications that it is typical for Antronaria. Antronaria indentata, new species PLATE 531: FIGURES 9-24 Medium size for genus, widely subpentagonal in outline, sides narrowly rounded, anterior margin with strong emargination. Apical angle 111°. Ante- rior commissure deeply uniplicate. Deltidial plates conjunct, foramen mesothyridid. Surface unevenly costate, posterior third smooth but anterior costate. Costae strong, subangular numbering three on fold, median costa short, deeply sunk below bounding costae, producing emargination; three costae on flanks. Pedicle valve gently convex posteriorly but strongly geniculated anteriorly in lateral profile; anterior profile broadly concave with exaggerated flanks. Umbonal region moderately swollen; sulcus originating posterior to midvalve, narrow and very deep but forming short tongue. Flanks concave and reflected anteroventrally and strongly serrated. Brachial valve fairly strongly convex, most so in anterior region in lateral profile; anterior profile broadly domed, narrowly indented on top; sides NUMBER 21 2039 steep; fold originating about one-third distance from beak, not strongly elevated and marked by two bounding costae. Flanks swollen, steep, depressed below fold. Pedicle valve interior with strong dental plates. Brachial valve interior with undivided hinge plate, narrowly notched medially; crura long. MEASUREMENTS (in mm).—From locality USNM 725c specimens 154839a holotype and b (paratype), respectively: length 11.9, 9.3; brachial valve length 10.1, 7.8; width 16.0, 13.2; thickness 11.0, 9.4; apical angle 111°, 111°. STRATIGRAPHIC OCCURRENCE.—Bone Spring For- mation. LOCALITIES.—AMNH 696; USNM 725c. DIAGNOSIS.—Transverse, deeply indented Antro- naria with strongly reflected anterolateral extremi- ties in the pedicle valve. TYPES.—Holotype: USNM 154839a. Figured par- atypes: USNM 152851a-c; 154839b. COMPARISON.—This species need be compared only to the deeply indented species that character- ize the Skinner Ranch, Cathedral Mountain, and Bone Spring formations. It is smaller than A. emarginata, new species, from the Decie Ranch Member, and is strongly costate and not so elon- gated. It resembles Antronaria speciosa, new spe- cies, but that is a larger and more robust species, having longer valves but less deeply emarginate. It differs from Antronaria mesicostalis (Girty) in being more emarginate and having less costae form- ing the fold and in the sulcus. Antronaria mesicostalis (Girty) PLATE 517: FIGURES 1-17; PLATE 531: FIGURES 25-38; PLATE 552: FIGURES 22-29 Pugnoides mesicostalis Girty, 1929:413, pi. 1: figs. 22-28. Leiorhynchus} mesicostale (Girty) Branson, 1948:382. Large for genus, biconvex; outline strongly and narrowly transverse, sides diverging between 100° and 145° and very narrowly rounded; profile sub- trigonal; anterior emarginate; anterior commissure uniplicate; fold moderately high, wide, beginning about 6 mm anterior to brachial beak, rather strongly but evenly convex longitudinally; sulcus moderately deep, beginning about 8 mm anterior to pedicle beak, evenly convex or geniculate near anterior margin. Costae rather fine, low, numerous, beginning 3 mm anterior to beaks, sharpest on fold, there numbering 3-5, usually 5, with one on the median line normally deeply depressed; one less in sulcus, 4-6 on flanks, averaging 5; concentric orna- mentation weak; prominent growth lines rare. Pedicle valve flat and shallow, maximum con- vexity on umbonal region, or near anterior margin of sulcus, flanks nearly flat to gently concave or slightly reflexed. Tongue short, deeply serrated; beak short, rather thick, apex sharp, slightly curved dorsally, beak ridges gently rounded, obscure; lat- eral pseudointerareas narrow or absent. Delthyrium triangular, on dorsal side of beak, base covered by two flat or slightly arching deltidial plates, leaving apex open as oval foramen. Brachial valve more strongly and evenly convex longitudinally and transversely than opposite valve; smooth part of umbo flattened or slightly indented, indentation becoming deeper anteriorly, merging with depressed median costa of fold; apex of valve within pedicle valve, covered by deltidial plates. Flanks gently swollen, with steep slopes. Pedicle valve interior with sides of delthyrium widely diverging anterior to deltidial plates; teeth small, elongate, parallel to edge of delthyrium, sup- ported by strong vertical dental plate reaching floor of valve. Muscle area anterior to dental plates; adductor scars small, oval, central, surrounded lat- erally and anteriorly by long, anteriorly broad diductor scars. Brachial valve interior with undivided triangular hinge plate, bounded laterally by deep, elongate, finely corrugated (?) sockets; crura long, modified falcifer, projecting forward from hinge plate, di- verging anteriorly, curving strongly ventrally and twisting as much as 90°, dorsal edge keeled; inner hinge plates narrow. Median ridge low, broadly rounded, extending anteriorly between posterior adductor muscle scars to near center of anterior adductor scars. Muscle area oval to nearly circular, posterior adductor scars narrow, elongate, ante- riorly diverging, their posterior ends separated by median ridge, anterior ends contiguous with broadly ovate anterior adductor scar. STRATIGRAPHIC OCCURRENCE.—Bone Spring and Cibolo formations (Breccia Zone of Udden). LOCALITIES.—Bone Spring: AMNH 497, 625, 632, 697, 699; USNM 725c; 728e. Cibolo: USNM 738c, 738s. DIAGNOSIS.—Strongly transverse, deeply emargi- 2040 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) 152852a 10.8 + 9.9 16.5 7.8 125 (lectotype) 152852b 11.6+ 10.5 14.3 9.4 120 USNM 725c 152851a 9.6 8.4 13.3 6.0 115 152851b 10.7 + 10.0 15.8 6.5 120 152851c 8.9 7.8 11.6 5.0 110 152851d 8.5 7.0 11.2 ? 105 152851e 11.7 10.6 16.0 11.0 115 nate Antronaria with one costa in the fold con- spicuously depressed. TYPES.—Lectotype: USNM 152852a. Figured hy- potypes: USNM 154511; 154742a-d; 152851a-c; 1544839a,b; 154840; 154841a,b. Measured paratype: USNM 152852b. Measured hypotypes: USNM 152851a-e. COMPARISON.—Antronaria mesicostalis is charac- terized by its fairly large size, strongly transverse outline, small and numerous costae, with the mid- dle one of the fold normally deeply depressesd, and its low median ridge in the brachial valve. It is nearly as large as A. spectabilis and A. voluminosa, both new; it differs from the former in its longitu- dinally more convex brachial valve, thicker beak without sharp beak ridges, strongly depressed me- dian costa on the fold, and its greater width. It differs from A. voluminosa by its smaller size, more numerous costae, more strongly transverse outline, and by the depressed median costa on the fold. This species is commonly emarginate anteriorly and in this respect is like A. speciosa and A. emar- ginata, both new. It differs from the former in being shorter and more transverse and in having more numerous costae; it differs from the latter in having less numerous costae and generally being less emar- ginate but generally shorter and wider. DISCUSSION.—Antronaria mesicostalis has mistak- enly had R. E. King's Pugnoides transversus added to its synonymy (R. E. King, 1931:108, footnote). We have large collections of King's species from several localities and they are consistently larger and have more numerous costae than Girty's species, and are seldom emarginate. We are, therefore, rec- ognizing King's species as separate and distinct. Branson (1948) recorded this species as belonging to the genus Leiorhynchus. Its ornamentation char- acteristics and the absence of a median septum in the brachial valve as well as the form of the dental plates argue against this assignment. The brachial valve has the low median ridge characteristic of Pontisia and Antronaria which is not primarily a hinge plate support. Girty had two specimens of this species and named the wider of the two as the type. It is differ- ent in shape from the paratype, which is narrower and subtriangular, but it has the same type of fold and sulcus with the same strongly depressed median costa. Obviously the two specimens could be aber- rations of some more intermediate form but it is impossible to tell. The stratigraphic level from which Girty's specimens came is not known. Al- though we have collections from the Apache Can- yon region, this species was not found. Specimens suggesting it were taken at the north end of the Baylor Mountains (USNM 725c) and from the Victorio Canyon region. These also indicate a spe- cies of considerable variation, the extremes being greater than those seen in the type lot. The lots from the Baylor Mountains are ex- tremely wide and suggest A. speciosa but are not so large or coarse, have more costae, and are usually deeply emarginate. Costae on the fold vary from three to five but those on the flanks are more con- stant. Specimens with only 3 costae on the fold tend to have a different appearance from those with 5 costae, yet they come from the same strata, have the same general transverse form, and seem to belong to the same species. Specimens from AMNH 625 and USNM 728e are more like the types and have both transverse and narrow forms that can be matched closely to the types. In view of the paucity of specimens available, we are recognizing forms from both areas as the same species. It is probable that it will be necessary to have collections from the Lower Bone Spring all along the Sierra Diablo and from the Baylor Mountains before the species can be clearly understood. Antronaria pluricosta, new species PLATE 535: FICURES 7-25 Large for genus, transversely triangular in out- line, apical angle variable, usually up to 110°; maximum width slightly anterior to midwidth; NUMBER 21 2041 sides narrowly rounded; anterior margin strongly truncated but slightly emarginate medially. Ante- rior commissure strongly uniplicate. Beak fairly long, straight to suberect, with fairly large fora- men and well-developed conjunct deltidial plates. Surface semicostate, costae narrow on fold and sulcus, broader on flanks, usually subangular; costae numbering 4 or 5 on fold, usually 5, one less in sulcus, and usually 3 or 4 on flanks. Pedicle valve very gently convex in lateral pro- file, maximum convexity just anterior to umbonal region; anterior profile broadly concave. Umbonal and median regions slightly swollen; sulcus origi- nating anterior to midvalve, broad and shallow but forming strongly geniculated tongue; flanks narrow, slightly deflected and with anterolateral extremities strongly projecting. Brachial valve very gently convex but median region conspicuously flattened and anterior sharply but narrowly geniculated to meet edge of pedicle valve; anterior profile squarely domed, sides steep and subparallel, top flattened. Umbonal region with shallow sulcus extending to anterior margin depressing median costa or costae. Fold originating anterior to midvalve, flat and wide, only moderately elevated at anterior margin. Flanks anteriorly swollen, moderately depressed below level of fold. Pedicle valve interior with short dental plates separated from valve wall by narrow cavities that become filled with shell in old age; muscle field deeply impressed, situated just anterior to ends of dental plates, somewhat cordate in outline. Brachial valve with undivided but medially in- dented hinge plate; crura curved, concave toward midvalve; inner hinge plates united. Median ridge thick, supporting hinge plate and extended ante- rior to posterior side of rounded adductor impres- sion which occupies midvalve. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) AMNH 591 152854a 152854b 152854c 152854d (holotype) 15.0 12.8 18.1 13.7 100 14.6 12.5 17.5 11.7 100 13.2 10.9 15.0 9.5 90 12.8 10.5 15.8 10.5 90 STRATIGRAPHIC OCCURRENCE.—Bone Spring For- mation (lower). LOCALITY.—AMNH 591. DIAGNOSIS.—Large, triangular Antronaria with conspicuously flattened median region on brachial valve and thick median ridge. TYPES.—Holotype: USNM 152854d. Figured par- atypes: USNM 152854b,c,i,k. Measured paratypes: USNM 152854a-c. Unfigured paratypes: USNM 152854a,e-h,j. COMPARISON.—This species is distinctive in hav- ing a strongly triangular lateral profile, strongly truncated and broad front, and the depressed me- dian costae in the fold. It suggests Antronaria dis- ■sona, A. speciosa, A. spectabilis, and A. specialis, all new, but differs from them in its shape and espe- cially in the broadly flattened to slightly emarginate anterior. Antronaria speciosa is often flattened ante- riorly from rapid growth at the anterior margin but it is ornamented so differently from A. pluri- costa that no confusion between them is likely. DISCUSSION.—Antronaria pluricosta has a thick shell, with the result that the musculature is well impressed. The pedicle valve has a narrowly cor- date muscle field with the diductor scars crescentic in outline and wrapped around the adductor scars. In the brachial valve the adductor scars make, at the anterior end of the median ridge, a rounded patch, which does not completely bisect the scar. The median ridge is also distinctive, being low and rounded and swelling somewhat under the hinge plate. It cannot be construed to be a median sep- tum and is entirely typical of Antronaria. The crura are slender for such a thick shell but have the form usual in the genus. Antronaria specialis, new species PLATE 532: FIGURES 1-23 Moderately large, broadly subtrigonal to subellip- tical in outline with narrowly rounded sides and truncated anterior margin. Apical angle varying from 80° to about 110°. Anterior commissure uni- plicate. Maximum width near midvalve. Beak some- what elongated, narrow; deltidial plates conjunct. Surface about two-thirds costate, costae subangular, usually 4 on fold, occasionally 3 or 5; one less in sulcus; flanks usually with 4 costae. Pedicle valve gently convex in lateral profile, broadly flattened to slightly concave in anterior profile. Beak and umbonal region narrowly, gently 2042 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY inflated. Sulcus originating at midvalve moderately broad, shallow, forming short tongue; flanks gently concave, slightly deflected. Brachial valve gently convex in lateral profile, broadly domed in anterior profile with short, abrupt, and steep sides. Umbonal region faintly sulcate, sulcus continuing to anterior margin, slightly depressing median costa. Fold usually low; flanks moderately swollen, moderately depressed below fold. Pedicle valve interior with short and erect dental plates; muscle field lightly impressed. Brachial valve interior with short and narrow hinge plate fairly deeply indented medially; outer hinge plates broad; inner hinge plates small; crura fairly broad, strongly curved toward pedicle valve, concave inward. Median ridge low and inconspicuous. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness <°> AMNH 492 152856a 9.0 7.9 9.5 3.7 80 152856b 11.5 9.7 13.9 6.0 90 152856c 12.2 10.0 14.7 7.3 90 152856d 12.7 10.6 16.0 10.0 100 152856e 14.5 12.0 17.0 10.5 95 152856f 15.2 13.3 19.7 11.4 105 (holotype) 152856g 16.7 13.8 21.2 11.2 105 STRATIGRAPHIC OCCURRENCE.—Bone Spring For- mation (lower). LOCALITIES.—AMNH 492, 591, 624; USNM 728g. DIAGNOSIS.—Medium-sized to large Antronaria with 4 or 5 costae on the fold. TYPES.—Holotype: USNM 152856f. Figured par- atypes: USNM 152856d,g; I54843a-c; 154844b-g; 154845f. Measured paratypes: USNM 152856a-e,g. Unfigured paratypes: USNM 152856a-c,e; 154844a; 154845a-e. COMPARISON.—This species suggests several of the larger new species of Antronaria such as A. titania and A. voluminosa, both new, but it is readily distinguished from them by their lesser size and more especially by the greater width of these two species. In size and general form it is most like A. spectabilis, new species, of the Sierra Diablo and A. dissona, new species, of the Glass Moun- tains. It differs from the former in having finer costae and in having 4 or 5 costae on the fold rather than 3 strong angular ones as in A. spectabilis. Antronaria dissona is about the same size as A. specialis but has only 3 costae on the fold and is usually somewhat narrower than A. specialis. Occa- sional aberrancies of these species may cause con- fusion, but A. specialis with 3 costae on the fold are as rare as are specimens of the other two species with 4 or 5 on the fold. DISCUSSION.—This species is fairly common in Apache Canyon of the Sierra Diablo, where it occurs in a dolomitic rock near the bottom of the Bone Spring Formation with species of Antronaria and Stenoscisma. Typically it is widely triangular and has a narrow hinge plate. This is, however, entirely characteristic of Antronaria, as it is unsup- ported by a septum or even a swelling of the me- dian part of the valve. Full growth stages of the species are available. As usual with these rhynchonellids the young have a concave brachial valve and are completely smooth. Costation starts at the 5-6 mm stage with the appearance of costae in the median region. Costae appear on the flanks in the next stage, at about 7 or 8 mm. During these stages the brachial valve changes to gently convex and the shell is essentially adult. Antronaria speciosa, new species PLATE 532: FIGURES 24-61 Pugnoides elegans [part] R. E. King [not Girty], 1931:106, pi. 34: figs. 2, 3 [not pi. 33: figs. 12-13, or pi. 34: fig. 4 (= Pontisia stehlii Cooper and Grant)]. Wellerella elegans Stehli [not Girty], 1954:355, pi. 25: figs. 13-17. Large for genus, biconvex; outline triangular, slightly bilobate, normally wider than long; sides diverging between 90° and 120°, averaging about 110°; profile subtrigonal; anterior commissure uni- plicate; fold very high, beginning 5-7 mm anterior to brachial beak, anterior margin sharply bent toward commissure; sulcus deep, beginning 7-9 mm anterior to pedicle beak, rather evenly convex from beak to anterior commissure. Costae strong, crests normally blunt, beginning 2-5 mm anterior to beaks, numbering 3 on fold, rarely 4 or 5, one less in sulcus, 3-6 on flanks; middle costa on fold nor- mally depressed, producing indentation of anterior margin. Concentric ornamentation faint; growth lines rare except near margins. Pedicle valve relatively flat; profile broadly sig- NUMBER 21 2043 moidal, with ends of costae on flanks reflexed; beak sharp, somewhat attenuate, straight to slightly curved dorsally; beak ridges poorly to fairly well developed; lateral pseudointerareas normally ab- sent, very narrow where present. Delthyrium tri- angular, base covered by two flat to slightly arched trapezoidal deltidial plates; apex open, forming elongate oval foramen. Brachial valve slightly to moderately convex along median line, strongly con- vex from beak to flanks and transversely; smooth part of umbo flattened or slightly indented; apex of valve within pedicle valve, covered by deltidial plates. Pedicle valve interior with delthyrium open an- terior to deltidial plates, sides moderately to strongly divergent, each with a hinge tooth, elon- gated parallel to delthyrial edge; teeth supported by strong vertical dental plates extending to floor of valve. Muscle area heart-shaped, lying anterior to side of dental plates; adductor impression heart- shaped, indented at posterior midline, pointing anteriorly; diductor scars wider, lying lateral and anterior to adductors, indented at anterior midline. Brachial valve interior with undivided triangu- lar hinge plate, bounded laterally by deep, elon- gate, anteriorly expanding, finely corrugated sockets; crura projecting forward from edge of hinge plate, diverging anteriorly and curving strongly ventrally, maybe twisted, dorsal edge carinate; median ridge low, thick-rounded, higher under hinge plate, providing support, anterior end within oval muscle area. Posterior adductor scars elongate, curved around posterolateral borders of anterior scars, posterior ends separated by median ridge; anterior adductor scars semicircular to semi- ovate. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 702d 148682a 5.8 5.1 5.7 2.6 c.103 148682b 8.5 7.7 9.6 4.0 99 148682c 10.9 8.7 10.0 5.9 90 148682d 12.2 10.5 13.9 5.5 101 148682e 11.7 10.1 15.4 8.7 105 148682f 12.0 10.0 14.4 11.0 103 I48682g 14.0 11.4 16.0 12.0 105 148682h 15.5 13.2 19.4 12.0 112 152847d 13.4 11.4 18.0 12.6 109 (holotype) STRATIGRAPHIC OCCURRENCE.—Skinner Ranch For- mation (Sullivan Peak Member); Hess Formation (Taylor Ranch Member); Cathedral Mountain For- mation. LOCALITIES.—Sullivan Peak: USNM 729h. Taylor Ranch: AMNH 501; USNM 702d, 702e, 702f, 702m, 716n, 716o, 722p. Cathedral Mountain: AMNH 500M; USNM 702, 702ent, 702-low, 702un, 703b. DIAGNOSIS.—Large Antronaria with strong, thick costae, deeply depressed median costa in fold, and strong anterior emargination. TYPES.—Holotype: USNM 154847d. Figured par- atypes: USNM 148682d,f; 148686; 148688; 154846; 154847a-c,e,f,h. Measured paratypes: USNM 148682a-h. Unfigured paratypes: USNM 148682a-c, e,g,h; 154847b,g. COMPARISON.—Antronaria speciosa is character- ized by its moderately large size, rather few and large costae, with the middle one on the fold deeply depressed, and the lateral ones on the flanks of the pedicle valve normally slightly reflexed, its flat- tened dorsal umbonal area, only slight convexity along the midline from brachial beak to anterior margin, and by the low median ridge in its dorsal interior. It differs from A. mesicostalis (Girty), which also has a depressed median costa, by its less widely divergent sides, fewer and broader costae on fold and flanks, less convex pedicle umbonal area, and normally larger size. Its depressed median costa, more transverse and less bulbous shape, reflexed pedicle flanks, and only slightly convex dorsal pro- file (along the crest of the fold) distinguish it from Pontisia stehlii Cooper and Grant. A similar appearing species is Tautosia elegans (Girty), from the Guadalupian Capitan Formation of the Guadalupe Mountains. From it A. speciosa differs in its stronger and more numerous costae on the flanks, deeper indentation of the anterior mar- gin, larger size, and low median ridge instead of the high median septum present in T. elegans. Among foreign species only Rhynchonella (Pug- nax) edelsteini Tschernyschew bears strong resem- blance to A. speciosa, which, however, is larger, more transverse, more strongly costate, especially on the flanks, and has a sharper beak. The interior of P. edelsteini is not known, so internal comparisons cannot be made. DISCUSSION.—This species is one of the most dis- tinctive in the Glass Mountains but it has only a limited distribution. It is moderately variable, some 2044 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY variation taking place in the costation, with the inevitable development of a few specimens with more or fewer costae on the fold and sulcus. Varia- tion in width is also fairly common but in most of the narrower forms relationship to the wider ones remains clear. Some specimens revealing the interior have the muscle scars fairly well preserved. The ventral muscle field is fairly large and the outline of the scar is somewhat rectangular, with the margins nearly straight and the anterior margin somewhat truncated. The diductors enclose the adductor scars. The dorsal adductor scars lie anterior to the front end of the median ridge. The ridge is moderately well formed in some specimens but in others not a vestige may be seen. This suggests the secondary nature of the structure, dependent on age and, perhaps, other physiological characters. Antronaria speciosa is fairly common in the Tay- lor Ranch Member of the Hess Formation, where it occurs in two types of lithology. Most specimens are found in the fairly pure limestones of sponge bioherms but some were taken from silty muds sur- rounding the bioherms. Probably the true habitat was the bioherm, living on and among the sponges and other solid skeletons. The ones found in the silty limestone may have drifted into their environ- ment after death. Antronaria spectabilis, new species PLATE 533: FIGURES 1-38 Wellerella elegans Stehli [not Girty], 1954:335, pi. 25: figs. 13-17. Large for genus, with highly exaggerated costae and anterolateral projections on pedicle valve; transversely pentagonal in outline in adults, more trigonal in young. Maximum width at midvalve. Anterior margin gently rounded to sharply trun- cated. Anterior commissure strongly and narrowly uniplicate. Beak moderately long, generally erect. Foramen small; deltidial plates conjunct. Surface coarsely costate, costae of fold and sulcus extending posterior to those of flanks; beaks and umbonal regions of both valves smooth; costae strongly angular except on flanks of brachial valve, there being rather subangular. Costae usually numbering 3 on fold, median one slightly depressed, 2 in sulcus, and usually 3 on each flank. Pedicle valve gently convex in lateral profile, but with anterolateral areas strongly projecting in ven- tral direction. Anterior profile deeply concave. Um- bonal region narrow, slightly convex; sulcus orig- inating at midvalve, narrow, deepening rapidly and forming strongly geniculated narrow tongue. Flanks gently concave. Brachial valve moderately and evenly convex in lateral profile but broadly domed and steep-sided in anterior profile. Median region slightly swollen; fold originating at midvalve, heightening fairly strongly anteriorly and projecting well beyond de- pressed flanks; median line marked by shallow, barely perceptible sulcus extending from umbo to anterior margin, depressing median costa of fold slightly. Pedicle valve interior with small teeth suported by strong, short dental plates. Muscle field some- what elongated, located just anterior to delthyrial cavity and usually lightly impressed. Brachial valve interior with narrow hinge plate, deeply indented medially and supported by low median ridge; socket ridges thin; outer hinge plates fairly broad; inner hinge plates narrow and medially united; crura long, concave toward midvalve. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 728g 152857a 17.4 15.1 22.7 17.8 115 152857b 16.9 14.7 20.5 15.5 110 152857c 15.8 13.7 21.0 13.8 110 152857c! 14.7 12.8 19.7 13.1 115 152857e 14.7 12.4 18.9 13.7 105 152857f 13.4 11.7 17.7 11.0 100 152857g 12.8 11.0 15.8 9.8 100 152857h 11.8 10.0 13.8 8.7 90 152857i 10.5 8.8 12.2 9.1 90 (holotype) USNM 728f 152858a 15.2 13.3 19.5 11.0 110 152858b 15.0 13.0 19.2 12.0 110 STRATIGRAPHIC OCCURRENCE.—Bone Spring For- mation. LOCALITIES.—AMNH 492, 497, 591, 629; USNM 728e, 728f, 728g, 728h, 745, 746. DIAGNOSIS.—Large, widely sulcate, robust Antro- naria with median costa of fold very slightly depressed. TYPES.—USNM 152857i. Figured paratypes: USNM 152853a-d; 152857d,g; 152858b; 154854a-e. NUMBER 21 2045 Measured paratypes: USNM 152857a-h, 152858a,b. Unfigured paratypes: USNM 152857a-c,e,f; 152858a. COMPARISON.—This species has the depressed median costa characteristic of several species. An- tronaria spectabilis does not attain the great size or great width that is seen in A. titania and A. volu- minosa, new species, but it is similar to A. dissona, A. specialis, and A. speciosa, new species. It is dis- tinguished from the last by its completely different costation and the exaggerated anterior emargina- tion of A. speciosa. It is easily separated from A. specialis by the more numerous costae on the fold and in the sulcus of that species. It is most like A. dissona, from which it differs in having stronger costae, larger size, longer beak, more protuberant anteromedian extremities at sides of the sulcus, and a deeper brachial valve. DISCUSSION.—This species is based primarily on specimens from USNM 728g that are large and robust. With it have been placed specimens from several other localities. Those from AMNH 492 and 497 are identical, but the specimens from USNM 728f are somewhat variable. On the brachial valve the costae do not extend so far onto the umbonal region as is those on the specimens from Apache Canyon. Antronaria titania, new species PLATE 538: FIGURES 12-37 Large for genus, adults transversely elliptical but young forms elliptical; sides narrowly rounded; apical angle variable, 100° to 130°. Anterior mar- gin generally flatly truncated, seldom emarginate. Anterior commissure widely uniplicate. Beak short and narrow, straight to suberect. Foramen small; deltidial plates small, conjunct. Surface costate, ex- cept for beaks of both valves; costae usually strong and angular; costae on brachial valve flanks larger than others; costae well separated, numbering from 4-9 but usually 5 or 7 on fold, median one always depressed, median 3 often depressed; costae on flanks 4-8. Width of sulcus greater than half valve width. Pedicle valve gently convex in lateral profile, greatest convexity just anterior to beak; anterior profile varying from nearly flat to broadly concave. Region anterior to umbo moderately swollen. Sul- cus originating at midvalve, wide, variable in depth; tongue short. Flanks flattened to gently concave, with gentle slope. Brachial valve evenly and moderately convex in lateral profile but broadly and steeply domed in anterior profile, top flattened by fold. Umbonal region with shallow sulcus extending through fold to anterior margin. Fold flat-topped, wide, fairly elevated to midvalve where it originates. Flanks depressed below fold, swollen and with long steep, slopes. Pedicle valve interior with short but strong dental plates. Brachial valve interior with small hinge plate, medially deeply indented; median ridge thick. MEASUREMENTS (in mm).— brachial apical valve sulcus thick- angle length length width width ness n SNM 707a 148660a 10.6 9.2 13.5 8.8 6.5 100 148660b 13.3? 11.2 18.5 11.6 9.4 130 148660c 12.8? 11.8 18.0 10.5 10.6 130 148660d 14.4 12.8 20.0 13.0 8.5 120 148660e 14.9 12.8 21.7 13.6? 12.0 120 148660f 15.8 13.7 23.7 14.4? 11.0 120 148660g 16.2 14.3 23.8 15.0 12.4 130 148660h 17.6 15.2 23.6 15.5 17.7 120 148660i 17.4 15.2 26.8 18.9 14.2 130 148660J 17.4 14.7 26.8 18.0 13.9 130 (holotype) STRATIGRAPHIC OCCURRENCE.—Skinner Ranch For- mation (Decie Ranch and Sullivan Peak members). Hess Formation. LOCALITIES.—Decie Ranch: USNM 707a, 715a, 727u, 733h. Sullivan Peak: USNM 715f. Skinner Ranch (base): USNM 705a, 707w, 708q, 71 Id, 712p, 716p, 719y, 720e, 726j. Skinner Ranch: USNM 723s. Hess: USNM 723b. DIAGNOSIS.—Exceptionally large, transverse An- tronaria with wide fold and sulcus. TYPES.—Holotype: USNM 148660J. Figured par- atypes: USNM 154871; I54872a,b; 154873; 154874. Measured paratypes: USNM 148660a-i. COMPARISON.—This is one of three species of Antronaria that attains an unusually large size. The other two are A. transversa (R. E. King) and A. voluminosa, new species. It is not likely to be con- fused with the former because that species is much more finely costate on both fold, sulcus, and the flanks. Antronaria transversa is commonly somewhat emarginate and usually has a shallower sulcus than A. titania. It also has the median costae of the 2046 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY sulcus, which has as many as 7 costae, medially depressed as is common in A. mesicostalis (Girty). Antronaria voluminosa is very much like A. titania and the two are not always easy to separate. The latter usually has more costae in the fold and sulcus than A. voluminosa, but variants of both species may look alike, although A. titania is usually more transverse. DISCUSSION.—Like their associates in the Decie Ranch Member, A. titania is a giant of its kind. It is probably the largest of the species of Antro- naria. Like most other species of the genus it is quite variable, often having costae numerous enough to make it look like A. transversa, but often sparsely costate and suggesting A. voluminosa. Few interiors of the species were obtained, but these do not have a septum, and examination of the dorsal beaks of unsilicified specimens confirms this fact. Antronaria transversa (R. E. King) PLATE 536: FIGURES 1-27; PLATE 538: FICURES 38-52 Pugnoides transversus R. E. King, 1931:108, pi. 33: figs. 14-17. Unusually large for genus, variable, transversely subelliptical to broadly subtrigonal in outline; apical angle varying in adult from about 100° to 135°. Sides narrowly rounded, maximum width near midvalve; anterior margin truncated to slightly emarginate. Anterior commissure moderately uni- plicate. Beak short, suberect; deltidial plates small, conjunct. Surface costate except for umbonal re- gions of both valves which are smooth; costae nu- merous, narrowly rounded, crowded, and of fairly uniform size; fold with 4-7 costae, median one strongly depressed but some specimens with costa on each side of median one also depressed; flanks with 5-8 costae. Width of sulcus about half valve width. Pedicle valve gently convex in lateral profile but broadly and gently concave in anterior profile; um- bonal region gently swollen, costae of sulcus con- tinued onto anterior part of umbonal region; sulcus originating near midvalve or slightly posterior, broad, shallow, and extended with moderate genicu- lation as blunt, short tongue. Flanks slightly con- vex, not strongly deflected. Brachial valve moderately convex in lateral pro- file, broadly and strongly convex in anterior profile, with median region somewhat elevated and flat- tened by broad fold, extending to anterior margin and including 1-3 depressed costae. Fold moderately well defined and moderately elevated; flanks swol- len, depressed below fold, with steep slopes. Pedicle valve interior with strong dental plates. Brachial valve interior with narrow cardinalia; hinge plate deeply emarginate, with fairly wide outer hinge plates but small inner plates. Crura long and slender, strongly keeled. MEASUREMENTS (in mm).— brachial apical valve sulcus thick- angle length length width width ness (°) USNM 702d 16.2 14.1 22.0 7.2 12.9 120 15.8 12.4 19.7 ? 9.7 110 12.6? 11.5 17.8 9.6 10.0 110 13.4 11.4 15.9 10.6 10.0 95 10.5 9.3 11.2 11.2 6.0 90 9.1 8.3 11.2 12.8 4.8 90 12.8 11.4 17.9 10.5 9.8 120 14.4 12.7 18.2 8.0 10.5 100 13.8? 12.0 19.4 10.0 10.8 120 148645a 148645b 148645c 148645d 148645e 148645f USNM 702e 148651a 148651b 148651c USNM 7l6n 16.0 17.6? 15.6 28.5 15.2 133 154932 USNM 716o 16.7 14.4 24.3 11.9 13.0 120 16.5 + 15.0 24.9 13.6 15.8 120 17.9 16.0 26.1 12.5 14.5 130 15.5 13.0 23.4 12.4 11.2 120 14.8 13.3 22.4 10.3 10.8 120 ? 14.3 24.6 12.3 10.0 p 148668a 148668b 148668c 148668d 148668e YPM 12518 (holotype) STRATIGRAPHIC OCCURRENCE.—Hess Formation (Taylor Ranch Member); Skinner Ranch Forma- tion (Sullivan Peak Member). LOCALITIES.—Taylor Ranch: USNM 702d, 702e, 702f, 713x, 716n, 716o, 722p; King 222. Sullivan Peak: USNM 707. Skinner Ranch: USNM 705r, 714p, 715v. DIAGNOSIS.—Large, transverse Antronaria with numerous fine costae, 5 or more costae on the fold, and 6 on the flanks. TYPES.—Holotype: YPM 12518. Paratypes: YPM 10674, 12519. Figured hypotypes: USNM 148645a,e; 148651a; 148668a; 154865a,b; 154932. Measured hypotypes: USNM 148645a-f; 148651a-c; 148668a-e; 154932. COMPARISON.—This species, with its depressed median costae in the fold and its great width sug- gests Antronaria mesicostalis (Girty), but the two are so different in size and ornament that no con NUMBER 21 2047 fusion between them should result. This species approaches some specimens of Antronaria titania, new species, which also is very large and includes specimens with a large number of costae on the fold and sulcus. That species, however, has a wider sulcus than Antronaria transversa, usually equaling more than half the width of the valve, whereas the sulcus of A. transversa is about equal to half the width. The nature of the ribbing of the two species is different, the costae of A. titania generally is stronger and more angular. Variants of the latter also tend toward stronger and more angular costae. DISCUSSION.—This species is fairly common in silty limestone of the Taylor Ranch Member but is rare in the associated bioherms. It is seldom well preserved, being often crushed, deformed, or broken. To obtain a perfect beak is difficult. We believe that its environment was that of the silty muds. Because of the difficult nature of the matrix few interiors have been obtained; the dorsal valve has a low median ridge. Variations occur in details of the costation and in the width, some specimens never attaining the great width of the normal specimens. Antronaria voluminosa, new species PLATE 537: FICURES 1-51 Large for genus, biconvex, normally somewhat inflated; outline transversely subelliptical to trans- versely and nearly equilaterally triangular, sides diverging between 105° and 125° degrees, averaging about 115°; profile subtrigonal; anterior commis- sure uniplicate; fold high, beginning posterior to midvalve, 7-9 mm anterior to brachial beak; abruptly flexed at anterior end, just behind com- missure; sulcus moderately deep, beginning 10-12 mm anterior to pedicle beak, strongly bent near anterior end, meeting edge of fold at commissure, making straight angle in adults. Costae strong, crests angular, beginning 4-6 mm anterior to beaks, numbering 3-5 on fold, one less in sulcus, 2-5 on flanks, with 5 most common; relative height of crests of costae variable. Concentric ornamentation and growth lines obscure, not appreciably better developed near margins. Pedicle valve somewhat inflated anterior to beak, strongly convex along median line, weakly convex toward flanks, with costae on flanks gently reflexed: profile of pedicle valve broadly sigmoidal; beak' sharp, attenuate, normally slightly curved dorsally, beak ridges absent or poorly defined; lateral pseu- dointerareas narrow, normally completed covered by overlapping brachial valve. Delthyrium triangu- lar on dorsal side of beak, base covered by trape- zoidal deltidial plates, conjunct, curved to form low arch; apical part open forming elongate oval foramen. Brachial valve moderately strongly convex longi- tudinally and strongly domed transversely; smooth part of umbo flattened or slightly indented, and laterally producing gently rounded beak ridges; apex of valve within pedicle valve, covered by del- tidial plates. Pedicle valve interior with delthyrium open an- terior to deltidial plates, teeth slightly elongate parallel to edge of delthyrium, supported by strong vertical dental plates reaching valve floor. Muscle area broadly bilobed, lying anterior to forward ends of dental plates; adductor scars elongate, nar- row, lying along median line, together forming oval mark, shorter than surrounding broadly lobate diductor scars. Brachial valve interior with undivided triangular hinge plate, bounded laterally by deep, elongate, finely corrugated sockets; crura projecting forward from hinge plate, diverging anteriorly, curving strongly toward pedicle valve, dorsal edge carinate; median ridge low, crest rounded, extending only to posterior edge of anterior adductor scar. Muscle area nearly circular, posterior adductor scars elon- gate, anteriorly diverging, posterior ends adjacent to median ridge, anterior ends continuous with larger, oval anterior adductor scar. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 708e 148736a 7.2 6.4 6.9 2.8 95 148736b 8.8 7.4 8.4 3.0 93 148736c 9.0 7.9 9.0 4.0 101 148736d 10.8 9.5 11.6 3.9 92 I48736e 11.5 10.4 12.5 5.3 97 148736f 12.2 10.5 12.7 7.7 108 148736g 13.8 11.8 15.9 8.5 108 148736h 14.9 13.0 18.0 8.0 114 148736i 19.0 16.5 22.3 14.4 110 148736J 20.2 17.7 26.4 13.5 124 148736k 21.5 18.1 29.0 16.0 119 148736-1 22.0 19.8 33.0 19.5 120 (holotype) 2048 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY STRATIGRAPHIC OCCURRENCE.—Skinner Ranch For- mation, Decie Ranch, (Poplar Tank and Sullivan Peak members); Bone Spring Formation. LOCALITIES.—Skinner Ranch (undifferentiated): USNM 715n. Decie Ranch: USNM 707a, 715a. Pop- lar Tank: USNM 718v. Sullivan Peak: USNM 707, 707d, 707g, 707-1, 707v, 708e, 715f, 722-1. Skinner Ranch (top): USNM 705n, 710r, 722m, 723-1, 723o. Bone Spring: AMNH 497. DIAGNOSIS.—Very large, transverse Antronaria with 5 costae on the fold but none of them depressed. TYPES.—Holotype: USNM 148736-1. Figured par- atypes: USNM 148736b,d,f,g,i; 148742; 154868a,b; 154869a-d; 154870. Measured paratypes: USNM 148736a-k. Unfigured paratypes: USNM 148736a,c, e,h,j,k. COMPARISON.—Antronaria voluminosa is charac- terized by its large size, transverse outline, inflated pedicle beak area, reflexed costae on the pedicle flanks, nearly geniculate fold and sulcus that meet to form a straight angle in adults, high, strong, broad costae, and low, short median ridge in the brachial interior. In size and exterior features it most nearly resembles Tautosia fastigiata Cooper and Grant, differing primarily in the height and number of costae whose crests are not necessarily concordant, blunt or absent pedicle beak ridges, curved pedicle beak with arching deltidial plates, and its low median ridge instead of a high septum in the brachial interior. Both fold and sulcus are flexed in A. voluminosa, and strong growth lam- inae are rare, whereas in T. fastigiata they are more uniformly convex and the costae of the fold ter- minate in sharp points at the line of commissure, or at the first prominent growth lamina. Antronaria mesicostalis (Girty), A. transversa. (R.E. King), and A. titania, new species, are large, but the average size of the former is less than that of A. voluminosa. It is more transverse, and more finely costate, with more costae on the fold and flanks. Juveniles of A. voluminosa most nearly re- semble adults of Tautosia shumardiana (Girty), but have more widely divergent sides, more strongly costate flanks, and a flattened brachial beak area. Antronaria voluminosa is also readily distinguished from A. titania by its less numerous and stronger costae on fold and flanks. No other large species of Antronaria is similar enough to be confused with A. voluminosa. Aphaurosia, new genus [Greek aphauros (feeble)] Small to medium rhynchonellids, transversely elliptical to subtrigonal in outline with valves of subequal depth, brachial valves somewhat deeper. Sides widely divergent. Anterior commissure uni- plicate. Beak short, nearly straight; deltidial plates conjunct; foramen small, submesothyridid. Surface irregularly and weakly costate, costae low, rounded, fine to coarse, often faint, and usually with smooth posterior half. Pedicle valve interior with small teeth supported by short, stout dental plates. Muscle area occupying region in front of dental plates nearly to midvalve. Brachial valve with undivided but notched hinge plate. Socket ridges stout; sockets uncorrugated. Outer hinge plates thin and broad; crural bases keeled; inner hinge plates coalesced medially, thin and usually notched along anterior. Crura modified falcifer, long and slender, concave toward mid- valve. Median septum absent or vestige at apex, usually visible only on broken valves. TYPE-SPECIES.—Aphaurosia scutata, new species. DIAGNOSIS.—Rhynchonellacea having irregular radial ornament, rounded outline, generally smooth posterior halves, dental plates in the pedicle valve, and an undivided hinge plate but no septum in the brachial valve. COMPARISON.—This genus has the general ap- pearance of some of the leiorhynchids and of the genera with fine radial ornament and partly smooth posteriors. The absence of a median septum sep- arates it from leiorhynchids. It suggests some species of Cenorhynchia, new genus, but differs in having more costae on the flanks and in lacking a median septum. It suggests some species of Phrenophoria Cooper and Grant, but that genus is supplied with a strong median septum. From species of Pontisia Cooper and Grant it may be separated by its strongly notched hinge plate and generally more irregular and weaker ornament. It differs from Hemileurus, new genus, in its rounded subpen- tagonal rather than trigonal outline and its undi- vided hinge plate. DISCUSSION.—Aphaurosia has a fairly distinctive exterior with its smooth umbones and costellate to costate anterior; the costae are best developed along the margin. Inside the pedicle valve the teeth are small but are supported by long and stout dental NUMBER 21 2049 plates. The musculature in these thin shells is not well impressed on the surface and the different scars have not been distinguished. Inside the brachial valve the cardinalia are deli- cate, the hinge plate undivided, and with strong socket ridges. The outer hinge plates are broad and the same is true of the inner hinge plates, which are well developed and unite medially but have an anterior notch. The crura are long, keeled, stout, concave medially and thus crescentic in cross section. No median septum is formed but a short, thick buttress underlies the inner hinge plates as in Wellerella. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 728p 154509c 8.5 7.3 10.3 8.2 90 154509d 9.1 7.9 10.0 7.5 92 (holotype) USNM 738 152806a 9.0 7.8 9.3 5.5 95 152806b 9.2 7.8 8.4 6.6 90 USNM 725e 152807a 11.3 9.8 11.4 7.8 90 152807b 9.0 7.7 8.7 6.9 90 USNM 403 152808 10.3 9.2 10.8 6.9 95 Aphaurosia rotundata, new species PLATE 504: FIGURES 37-54; PLATE 511: FIGURES 26-64; PLATE 521: FIGURES 32-41 Usual size for genus, usually slightly wider than long, maximum width just anterior to midvalve; posterolateral margins diverging at about 90°. Sides well rounded; anterior margin broadly rounded. Anterior commissure uniplicate. Beak moderately long, suberect. Surface weakly costate, costae var- iable in length and usually beginning beyond mid- valve; posterior parts smooth. Pedicle valve evenly and moderately convex in lateral profile; broadly and gently convex in ante- rior profile; umbonal region swollen; sulcus orig- inating anterior to midvalve, short, narrow, moder- ately deep and extended anteriorly as fairly long narrow tongue. Flanks swollen and gently convex not strongly demarcated. Brachial valve gently and evenly convex in lat- eral profile but strongly domed and with steep slopes in anterior profile. Umbonal region moder- ately convex but median region strongly swollen. Fold low and narrow, marked by 4 or 5 weak costae, originating well anterior to midvalve and well differentiated only near anterior margin. Flanks swollen and steep. Pedicle valve interior with small teeth but stout dental plates. Muscle area somewhat heart-shaped, diductor scars surrounding adductor scars. Brachial valve interior with long laterally com- pressed crura, and complete hinge plate. Socket ridges short but stout. Outer hinge plates broad; inner hinge plates forming narrow fold and ante- rior notch. STRATIGRAPHIC OCCURRENCE.—Bell Canyon For- mation (Lamar and Rader members). LOCALITIES.—Lamar: AMNH 37, 347, 430; USNM 725e, 728p, 738. Rader: AMNH 403. DIAGNOSIS.—Medium size Aphaurosia with length and width nearly equal and numerous fine costae. TYPE.—Holotype: USNM 154509d. Figured par- atypes: USNM 152806a,b; 152807b; 152808; 154509a-c,e-j; 154694b; 154695a-c,e; 154927. Mea- sured paratypes: USNM 152806a,b; 152807a,b; 152808; 154509c. Unfigured paratypes: USNM 154509d, 154694a, 154695d. COMPARISON.—This species differs from A. scu- tata, new species, in its more nearly circular out- line, the length and width being nearly equal, in the finer ornament, and the narrower fold and sulcus. DISCUSSION.—An uncommon species in the Gua- dalupe Mountains, it is thin shelled and is often crushed. Nevertheless, several excellent specimens showing the interiors were obtained. The interiors show no rudiments of a median septum. Aphaurosia scutata, new species PLATE 515: FIGURES 12-25; PLATE 552: FIGURES 1-5 Average size for genus, flatly biconvex; outline transversely ovoid to bluntly triangular, sides diverging between 90° and 130°; profile lenticular; anterior commissure uniplicate, fold low, broad, convexity slight, beginning 5-7 mm anterior to brachial beak; sulcus shallow, strongest between ends of flanks, bent to form right angle with plane of commissure. Costae low, rounded, faint, begin- 2050 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY ning 5-8 mm anterior to beaks, numbering 3-5 on fold, normally 5, one less in sulcus, 3-7, very ob- scure, on flanks. Concentric ornamentation absent; growth lines few and indistinct. Pedicle valve slightly inflated near beak, flatly convex toward flanks; beak sharp, suberect, not attenuate; beak ridges sharp, making beak look flat; lateral pseudointerareas absent: no overlap of valves. Delthyrium triangular, base narrowed by disjunct deltidial plates, apical portion forming elongate oval foramen. Brachial valve nearly flat along fold, more strongly convex toward flanks and transversely; apex within pedicle valve, beneath rudimentary deltidial plates. Pedicle valve interior with sides of delthyrium widely diverging, teeth small, supported by short vertical dental plates reaching floor of valve. Mus- cle area small, subtriangular, slightly excavate, lying just anterior and between edges of dental plates; adductor scars median and posterior, sub- circular, surrounded by larger, anteriorly widening diductor scars. Brachial valve interior with undivided triangular hinge plate, bounded laterally by narrow, elongate, anteriorly widening, finely corrugated sockets. Crura divergent, slender, flattened, joined to socket ridges by narrow outer hinge plates. Inner hinge plates narrow, attached to median ridge. Thick median ridge short, supporting hinge plate, ex- tending anteriorly as low median ridge bisecting posterior half of muscle area. Posterior adductor scars narrow, elongate, diverging anteriorly, flank- ing larger, oval, anteriorly expanding anterior ad- ductor scars. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 738 152809 9.1 8.2 12.0 5.5 120 154727 8.8 7.2 12.2 5.4 117 154726 9.9 8.7 12.0 7.1 100 (holotype) AMNH 430 152810 10.3 9.0 12.8 4.5 120 USNM 738b 152811a 10.8 9.6 13.0 6.7 115 152811b 13.8 11.7 16.6 6.5 115 USNM 725e 152812 9.7 8.5 11.9 6.5 100 STRATIGRAPHIC OCCURRENCE.—Bell Canyon For- mation (Hegler, Pinery, Rader, and Lamar members). LOCALITIES.—Hegler: USNM 731. Pinery: USNM 725n. Rader: USNM 725e. Lamar: AMNH 430; USNM 728i, 728p, 738, 738b. DIAGNOSIS.—Transverse Aphaurosia with numer- ous costae and shallow valves. TYPES.—Holotype: USNM 154726. Figured para- types: USNM 154724a,b; 154725b; 154727; 154913. Measured paratypes: USNM 152809; 152810; 15281 la,b; 152812, 154727. Unfigured paratype: USNM 154725a. COMPARISON.—Aphaurosia scutata is character- ized by its moderate size, low convexity, transverse outline, numerous but low and fine costae that begin far forward, its sharp beak ridges, and its median ridge in the brachial valve. It is about the same size as Anteridocus sivallovianus (Shumard), but is distinguished by its lower convexity, much finer costae, and nonreflexed flanks. The widely triangular outline of some specimens is similar to that of Tautosia shumardiana (Girty), but Aphau- rosia scutata attains a smaller size, is normally much less convex and more transverse, has sharp beak ridges, more and finer costae, and has a median ridge instead of a median septum. This species resembles Bryorhynchus? nitidum (Girty, 1909) from the Bone Spring Formation of the Guadalupe Mountains but differs in its more rounded triangular outline, rather than the sharply pentagonal outline of B. nitidum; it has weak costae on the flanks, whereas B. nitidum has none, and stronger costae on the fold. The profile of the fold of A. scutata is more convex than that of B. nitidum, and it has sharp beak ridges. Acolosia, new genus [Greek akolos (morsel)] Minute to moderate size, elongate oval outline; biconvex but brachial valve deeper than pedicle valve. Anterior commissure broadly uniplicate. Beak short; delthyrium open; no deltidial plates. Surface smooth except for incipient anterior costa- tion developed at front margin and strongest on fold and sulcus. Pedicle valve interior with small teeth supported by strong dental plates. Brachial valve interior with undivided but NUMBER 21 2051 notched hinge plate; socket ridges stout; outer hinge plates fairly wide and attaching to laterally compressed but inwardly concave, short crura, falci- fer; inner hinge plates united but leaving anterior notch. Median septum absent, but threadlike ridge serving as myophragm. TYPE-SPECIES.—Acolosia glabra, new species. DIAGNOSIS.—Small, mostly smooth Rhynchonella- cea having an undivided hinge plate without me- dian septum. COMPARISON.—This genus resembles some small stocks of Cenorhynchia, new genus, but differs in lacking a median septum. It differs from Aphau- rosia, new genus, in size, outline, and lack of anterior costae. DISCUSSION.—Some species of this genus, with their smooth shell and small size, suggest at first glance that they are juveniles. This is denied, how- ever, by their folding and the interior development, which is truly adult. Like several other larger genera in the Permian, these species have no del- tidial plates. Whether this is a primitive or an advanced character is not easily decided. Inside the pedicle valve the teeth are small and supported by strong dental plates that have a fair amount of callus thickening on the delthyrial cav- ity floor. Musculature in these small and thin shells cannot be resolved. In the brachial valve the hinge plate is angularly notched and has strong socket ridges with wide outer hinge plates attaching the keeled crural bases to them. Inner hinge plates are thin and delicate and usually united posteriorly but form a notch anteriorly. Neither a median septum nor a median ridge is developed. The crura are keeled and lat- erally compressed. These small shells are uncommon and some details of their anatomy will have to await the collecting of more specimens. We have not found them abundant or even common at any locality. Acolosia? anomala, new species PLATE 512: FIGURES 50-56 Small, widely triangular, maximum width ante- rior to midvalve; posterolateral margins long and straight, forming angle of 80°. Sides narrowly rounded and anterior margin broadly truncated. Anterior commissure broadly uniplicate. Beak short, sharp, narrow, with small delthyrium and no deltidial plates, point of beak partly resorbed by pedicle pressure. Surface nearly smooth but with anterior costation, 5 costae on fold and 2 on each flank, median 3 costae of fold depressed into broad sulcus. Pedicle valve moderately and evenly convex in lateral profile, broadly and fairly strongly convex in anterior profile, depth and convexity greater than brachial valve. Umbonal and median regions moderately swollen; sulcus originating at midvalve by appearance of 2 bounding costae, but costae corresponding to those of fold obscure. Flanks very narrow and rounded, scarcely differentiated from rest of valve. Brachial valve less deep than pedicle valve, gently convex in lateral profile, broadly and gently con- vex in anterior profile. Umbonal region narrowly swollen, swelling extending into moderately inflated median region. Fold defined by two prominent costae appearing at midvalve and extending to an- terior margin. Sulcus within fold broad and shallow. Flanks very narrow and abruptly rounded, slopes steep. Pedicle valve interior with small teeth but strong dental plates with narrow, slitlike umbonal cavities. Brachial valve interior with narrow undivided hinge plate having narrow outer hinge plates, mod- erately long, broad-bladed moderately curved crura, concave toward midvalve. Inner hinge plates short but strongly coalesced. No trace of median septum. MEASUREMENTS (in mm).—Holotype USNM 152799a: length 7.2, brachial valve length 6.6, width 8.2, thickness 4.8, apical angle 80°. STRATIGRAPHIC OCCURRENCE.—Word Formation (Willis Ranch Member). LOCALITY.—USNM 706e. DIAGNOSIS.—Triangular Acolosia of large size with depressed, broad sulcus in fold. TYPE.—Holotype: USNM 152799a. Unfigured paratype: USNM 152799b. COMPARISON.—This is the largest species assigned to this genus; it is distinguished from others by its broadly triangular form and the peculiar sulcation in the brachial valve fold. DISCUSSION.—This species is assigned with a query to Acolosia. Similarities to Acolosia are in its pedi- cle valve beak and its lack of a median septum supporting the hinge plate. It is unlike most Aco- losia, however, in its large size and transversely 2052 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY triangular outline. The holotype is a unique com- plete shell but another pedicle valve furnished some details of the teeth and dental plates. A hole was broken into the pedicle valve of the holotype to show details of the interior. Acolosia elliptica, new species PLATE 513: FIGURES 30-38 Small for genus, elongate oval in outline with gently rounded sides and rounded anterior margin. Posterolateral extremities converging to acute angle. Anterior commissure faintly uniplicate in adults. Beak moderately long, nearly straight. Surface smooth with no trace of costation. Pedicle valve moderately and evenly convex in lateral profile; broadly and moderately convex in anterior profile. Umbonal and median regions mod- erately swollen. Anterior flattened but no sulcus developed. Brachial valve moderately convex in lateral pro- file and gently domed with moderately steep sides in anterior profile. Umbonal and median regions moderately swollen; anterior gently swollen with no development of fold visible except at com- missure. Pedicle valve interior with short dental plates. Brachial valve interior with well-developed hinge plate with strong socket ridges but very reduced outer hinge plates. Crura laterally compressed, mod- erately long, and slightly curved. Inner hinge plates membranous, strongly developed but with deep angular anterior notch. MEASUREMENTS (in mm).—Holotype USNM 148203a: length 3.4, brachial valve length 2.9, width 2.5, thickness 1.7, apical angle 55°. STRATIGRAPHIC OCCURRENCE.—Hess Formation (Taylor Ranch Member). LOCALITY.—USNM 702d. DIAGNOSIS.—Small Acolosia with incipient fold and long slender outline. TYPES.—Holotype: USNM 148203a. Figured par- atype: USNM 148203b. Unfigured paratype: USNM 148203c. COMPARISON.—The nearly rectimarginate ante- rior commissure of this species separates it from other members of the genus. The somewhat ellip- tical outline and small size also help to distinguish A. elliptica. On the interior the membranous inner hinge plates and the poorly developed outer hinge plates are unlike the hinge plates of the other species. DISCUSSION.—This species is very rare and may be easily overlooked because of its small size. Its most remarkable feature is the large development of the inner hinge plates in the brachial valve. These unite posteriorly but leave a deep and angu- lar notch anteriorly. The crura are short and stout. Acolosia? exasperata, new species PLATE 515: FIGURES 8-11 Large for genus, elongate triangular in outline, maximum width toward anterior; posterolateral margins long and straight, forming angle of 65°. Anterolateral margins narrowly rounded. Anterior margin truncated. Anterior commissure uniplicate. Beak narrow, incurved, erect, with small narrow delthyrium unmodified by deltidial plates. Valves unequal in depth, brachial valve deeper. Surface of posterior two-thirds smooth; anterior incipient co- stae, 3 on fold, 1 on each flank. Pedicle valve evenly and gently convex in lateral profile; anterior profile gently convex with nar- rowly rounded flanks. Umbonal region narrowly convex; median region gently convex; sulcus orig- inating posterior to midvalve, broad and shallow but with moderately long tongue. Flanks narrowly and abruptly rounded and very steep. Brachial valve evenly and moderately convex, slightly more so than pedicle valve in lateral pro- file; anterior profile narrowly and strongly domed with steep sides. Umbonal and median regions swollen. Fold originating near midvalve, low, de- fined only in anterior part. Flanks inflated, sharply deflected and precipitous. Pedicle valve interior with strong dental plates. Brachial valve interior with undivided hinge plate and no median septum. MEASUREMENTS (in mm). Specimens 152800a (holotype) and b, respectively: length 9.0, 8.1; bra- chial valve length 8.2, 7.4, width 8.2, 6.9; thickness 6.3, 5.2; apical angle 65°, 60°. STRATIGRAPHIC OCCURRENCE.—Skinner Ranch For- mation (base). LOCALITY.—USNM 720e. DIAGNOSIS.—Large Acolosia with elongate triang- ular outline. NUMBER 21 2053 TYPES.—Holotype: USNM 152800a. Unfigured paratype: USNM 152800b. COMPARISON.—The only large Acolosia to which this one can be compared is A.? anomala from the Word Formation (Willis Ranch Member). The two are not likely to be confused because the Word species is transversely triangular whereas this one is longer than wide. Other differences appear in the fold and sulcus, the fold of A.? anomala being com- plicated by a broad sulcus and five costae in the fold, while the fold of A.? exasperata has only three costae and none of these is conspicuously depressed. DISCUSSION.—Only two specimens of this unusual species were taken and neither is well preserved. The paratype was opened from the ventral side but the cardinalia are partly covered by siliceous mate- rial. Although it was possible to see the hinge plate, no median septum could be found. Acolosia glabra, new species PLATE 513: FIGURES 42-56 Small, elongate oval to elongate subpentagonal in outline, maximum width anterior to midvalve; posterolateral margins diverging at less than 90°; anterolateral margins narrowly rounded; anterior margin truncated. Anterior commissure uniplicate. Beak moderately long, with large delthyrium, strong, incurving, generally suberect. Surface smooth in young adults but with 3 incipient costae on fold, 1 on each flank of old shells. Pedicle valve evenly and moderately convex in lateral profile but flatly and broadly convex, with narrowly deflected flanks in anterior profile. Um- bonal and median regions gently swollen. Sulcus originating anterior to midvalve, inconspicuous, broad and shallow but with strongly geniculated, short tongue. Flanks convex, abruptly deflected and steep. Brachial valve moderately and evenly convex in lateral profile; strongly and evenly domed in ante- rior profile, with smooth lines and steep sides. Umbonal and median regions swollen. Fold incon- spicuous, best defined at commissure, originating anterior to midvalve and only slightly elevated at margin. Flanks moderately swollen but steep. Pedicle valve interior with strong and stout den- tal plates. Muscle region not defined. Brachial valve interior with small hinge plate not supported by median septum, with wide outer hinge plates and short, stout, laterally compressed crura. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness <") SNM 706c 148173a 6.2 5.5 5.7 4.3 85 148173b 6.1 5.5 5.1 3.8 80 148173c 5.7 5.0 4.9 3.9 80 148173d 5.4 4.8 4.5 3.4 75 148l73e 5.1 4.6 4.4 3.4 80 (holotype) STRATIGRAPHIC OCCURRENCE.—Word Formation (China Tank Member). LOCALITY.—USNM 706c. DIAGNOSIS.—Large Acolosia with anterior costa- tion. TYPES.—Holotype: USNM 148173c Figured par- atypes: USNM 148173a,b,d; 154715c-e. Measured paratypes: USNM 148173a-d. Unfigured paratypes: USNM 148173c; 154715a,b. COMPARISON.—The large size of this species sug- gests A. magna, new species, and the strongly in- flated valves suggests A. recepta, new species, but the incipient costae on the fold and sulcus sep- arate A. glabra from the others. Acolosia magna, new species PLATE 525: FICURES 52-55 Large for genus, elongate oval in outline; postero- lateral margins meeting at less than right angle; maximum width near midvalve; sides broadly rounded; anterior margin truncated. Anterior com- missure strongly uniplicate. Beak moderately long, suberect. Surface smooth but with faint trace of costation at midvalve and on anterolateral extremities. Pedicle valve gently convex in lateral profile and very faintly convex in anterior profile. Umbonal region moderately convex. Sulcus broad and shal- low, originating near midvalve and forming mod- erately long tongue. Flanks narrow, flattened and gently sloping. Brachial valve deeper than pedicle valve, mod- erately convex in lateral profile, greatest curvature at umbo; anterior profile strongly and evenly domed and with steep lateral slopes. Umbonal and median regions swollen. Fold poorly formed, incon- 2054 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY spicuous, originating anterior to midvalve. Flanks swollen and steep. Brachial valve interior, as seen through decorti- cated shell, lacking median septum. MEASUREMENTS (in mm).—Holotype USNM 148207: length 6.0, brachial valve length 5.4, width 5.2, thickness 3.3, apical angle 75°. STRATIGRAPHIC OCCURRENCE.—Skinner Ranch For- mation (Decie Ranch Member). LOCALITY.—USNM 714t. DIAGNOSIS.—Large Acolosia with poorly defined fold and sulcus originating at midvalve. TYPES.—Holotype: USNM 148207. COMPARISON.—This is the largest of the known species of this genus, but it is easily separated from the others on characters other than size. It is the most strongly folded of the species and has a visible sulcus on the pedicle valve, a feature not shared by the other species. The valves of A. magna are not so swollen as those of A. recepta or A. glabra, both new. Acolosia recepta, new species PLATE 513: FIGURES 57-64 Usual size for genus, valves subequal in depth and convexity, longer than wide, oval outline, maximum width anterior to midvalve. Divergence of posterolateral margins less than a right angle. Sides broadly rounded; anterior margin gently rounded. Anterior commissure broadly uniplicate. Beak short, slightly incurved, with large delthyrium; surface smooth. Pedicle valve evenly and moderately convex in lateral profile; moderately domed in anterior pro- file. Umbonal and median regions swollen; sulcus scarcely formed, showing chiefly as wave in com- missure and short, wide, tongue. Flanks swollen and steep. Brachial valve moderately strongly convex in lateral profile, moderately domed in anterior pro- file, and with fairly steep sides. Umbonal, median, and anterior regions fairly strongly swollen; fold scarcely discernible, originating near anterior mar- gin, best defined at commissure. Flanks swollen. Pedicle valve interior with strong dental plates plastered against valve wall. Brachial valve interior with stout socket plates and narrow outer hinge plates supporting long narrow crura. Inner hinge plates uniting posteriorly and deeply notched. Median region of valve marked by low thick ridge. MEASUREMENTS (in mm).—Holotype USNM 152801a: length 4.5, brachial valve length 4.0, width 3.4, thickness 2.7, apical angle 80°. STRATIGRAPHIC OCCURRENCE.—Skinner Ranch For- mation (Poplar Tank Member?). LOCALITY.—USNM 707h. DIAGNOSIS.—Strongly biconvex Acolosia with broad, simple fold of the anterior commissure and slender crura. TYPES.—Holotype: USNM 152801a. Figured par- atypes: USNM 152801b,c. COMPARISON.—This species is about average in size for the genus, but its valves are fairly deep and their depth is about equal. It can be distin- guished readily from the other species of Acolosia by its broad and uncomplicated fold, which is lower than that of A. magna, new species, stronger than that of A. elliptica, new species, and not ser- rated by costae like that of A. glabra, new species. Other characters separate it from the other species: it is wider than A. elliptica and more strongly con- vex; it is smaller than A. magna and does not have a sulcus on the pedicle valve; it is not incipiently costate as is A. glabra, and is much smaller. Anteridocus, new genus [Greek anteridos (braced) + dokos (beam)] Small, rhynchonelliform, biconvex, uniplicate; outline bluntly trigonal to transversely subpentag- onal; anterior commissure uniplicate, fold and sulcus weakly to strongly semicostate; flanks smooth to weakly costate. Concentric ornamentation and growth lines weak. Pedicle valve moderately con- vex; beak short, sharp, usually suberect; beak ridges short, sharp to blunt; delythrium triangular, open, base of triangle slightly constricted by rudimentary, disjunct deltidial plates; valves meeting without overlap, hence no lateral pseudointerareas. Brachial valve strongly convex; beak bluntly pointed, not strongly incurved. Pedicle valve interior with knoblike teeth sup- ported by vertical dental plates reaching valve floor. Muscle area heart-shaped, pointing poste- riorly, beginning between ends of dental plates; adductor marks small, forming subelliptical scar along median line in posterior part of muscle area; NUMBER 21 2055 diductor scars large, widening anteriorly, surround- ing adductor scars laterally and anteriorly. Brachial valve interior with undivided hinge plate deeply and widely notched, forming narrow platform under beak, sockets deep, anteriorly widening, finely corrugated; socket ridges narrow; outer hinge plates and crural bases narrow; crura falcifer, diverging anteriorly, strongly curving dor- sally, strong, wide, with carinate dorsal edge and extending beneath hinge plate as keel; hinge plate supported by short inner hinge plates uniting me- dially to form shallow trough, hinge plate sup- ported by short median septal brace reaching valve floor, normally not extending forward but rarely continuing for short distance as low, narrow me- dian ridge. Muscle area not clearly observed. TYPE-SPECIES.—Anteridocusgongylus, new species. DIAGNOSIS.—Small triangular semicostate rhyn- chonellids having rudimentary deltidial plates and an undivided hinge plate supported by a short brace. COMPARISON.—Anteridocus is characterized by its small size, rotund shape, rudimentary deltidial plates, lack of lateral pseudointerareas, broadly notched but undivided hinge plate that is sup- ported by a short brace instead of a high septum, and its strong, curved crura. Its tiny deltidial plates and lack of a septum distisguish it from Cenorhyn- chia, new genus; its broad notched hinge plate and disjunct deltidial plates distinguish it from Welle- rella Dunbar and Condra; the disjunct deltidial plates, and lack of a median septum and lateral pseudointerareas distinguish it from Phrenophoria Cooper and Grant. From Acolosia, new genus, it is distinguished by its rotund form and round outlines. DISCUSSION.—Features to be remarked in this genus are the deltidial plates of the pedicle valve and the cardinalia of the brachial valve. The del- tidial plates are small, triangular barbs at the ante- rolateral angles of the delthyrium. They are very small and usually difficult to see. They are not always flush with the delthyrial edge but extend in a dorsomedial direction. The dental plates are usually somewhat receding but define fairly large umbonal chambers. The cardinalia are fairly distinctive and fairly complex. The diductor muscles were attached in a pit under the obtuse beak of the brachial valve. Probably the posterior rim shared in this duty. The socket ridges are thick and hang over the wide sockets, which are minutely and closely corrugated. The long narrow crural bases are attached to the socket ridge by a variable but usually narrow outer hinge plate. The inner hinge plate is shallow and gently con- cave, attached to the inner edges of the crural base, usually deeply indented medially and with its mar- gins extending as a small shelf along the inside of the crura. The median part of the inner hinge plate is supported below by a thin and short me- dian ridge. In young shells this slight septal brace does not extend anterior to the distal margin of the inner hinge plate. In old shells and in some aberrant ones, however, the brace is extended ante- riorly for some distance along the valve floor, but is usually thin and inconspicuous. In old specimens the inner hinge plate is built anteriorly for some distance and strongly over- hangs the septal brace underneath. The lateral margins of this plate, in at least one specimen, are built anterolaterally across the outer hinge plate as a ridge. The median part of the hinge plate varies from nearly flat to fairly deeply concave; it never forms a chamber and is always strongly in- dented medially. The hinge plate ensemble thus has the appearance of being divided but actually is complete. The crura are broad-bladed, convex outward, and lie slightly obliquely, the posterior edge toward the interior and the anterior edge toward the out- side. The thin, sharp underside, or dorsal edge, extends as a sharp keel under the edge of the outer hinge plate. The crus is expanded distally and truncated obliquely to leave the ventral edge the longer, and usually ending in a point. Anteridocus bicostatus, new species PLATE 510: FIGURES 44-47; PLATE 520: FIGURES 45-48; PLATE 529: FIGURES 1-7 Small, subpentagonal outline, sides rounded, di- verging from beak at about 100°. Anterior margin broadly rounded. Anterior commissure uniplicate. Beak small, foramen small, and small conjunct deltidial plates. Surface paucicostate, costae occupy- ing anterior half, broad and rounded to subangular, 2 on fold, 1, 2, or 3 on each flank. Pedicle valve gently convex in lateral profile, maximum curvature anterior to umbo; anterior 2056 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY profile broadly and gently concave to flat. Umbonal region slightly swollen; sulcus broad and shallow, originating anterior to midvalve; flanks flattened to slightly concave, anterolateral extremities pro- truding moderately. Brachial valve deeper than pedicle valve, mod- erately convex in lateral profile; moderately domed in anterior profile. Umbonal region swollen. Fold fairly prominent, originating anterior to midvalve, moderately elevated. Flanks swollen, depressed below fold. Pedicle valve interior with strong, short dental plates. Brachial valve interior with undivided but strongly indented hinge plate, not supported by median septum. MEASUREMENTS (in mm).—From locality AMNH 417 specimen USNM 152841 and from USNM 738b specimen 152842a (holotype), respectively: length 8.3, 8.6; brachial valve length 7.5, 7.6; width 9.2, 10.3; thickness 5.5, 5.7; apical angle 100°, 100°. STRATIGRAPHIC OCCURRENCE.—Carlsbad Forma- tion; Bell Canyon Formation (Hegler and Lamar members); Bone Spring Formation (Cutoff Member). LOCALITIES.—Carlsbad: AMNH 417. Hegler: USNM 731, 732a. Lamar: AMNH 40, 347 (-L-2), 401. USNM 725e, 738b. Cutoff: AMNH 678. DIAGNOSIS.—Anteridocus with two costae on the fold and one in the sulcus. TYPES.—Holotype: USNM 152842a. Figured par- atypes: USNM 152841, 154685, 154813, 154814, 152842a. Unfigured paratypes: USNM 152842b-d. COMPARISON.—Anteridocus with only two costae on the fold is rare indeed and comparison with only three other presently described species is per- tinent, since two of the species to be compared are bicostate as an aberration rather than a normal character. One of these is Anteridocus seminudus, new species, which is distinguished by its very small size and subtriangular shape. The other species is Anteridocus swallovianus (Shumard) which is more triangular, narrower, and has a strong depression in the dorsal umbo, one of the chief marks of the species. Anteridocus subcarina- tus, new species, is prominently bicostate but its small size, globular outline, and subcarinate bra- chial valve umbo distinguish it without difficulty. Pugnax bidentata (Girty) is another species hav- ing two costae on the fold but it is very narrowly triangular and is not likely to be confused with A. bicostatus. DISCUSSION.—This is a rare species and, because of its rarity, it might be suggested that it is an aberration of some normally tricostate or multico- state species. The distribution of specimens sug- gests to us that this is not true; we have it from eight different localities and three different strati- graphic levels. Anteridocus erugatus, new species PLATE 539: FIGURES 9-39 Average size for genus, moderately strongly bi- convex; outline transversely subelliptical to sub- pentagonal, sides diverging between 80° and 110°; commissure uniplicate, fold low, convex longitu- dinally, arched transversely, beginning 4-5 mm anterior to pedicle beak. Costae weak, low, rounded, beginning about 5 mm anterior to beaks, number- ing 1 or 2 on fold, one less in sulcus, flanks nor- mally smooth, may have 1 or 2 weak short costae. Concentric striae faint, closely crowded; growth laminae weak, normally visible only near anterior margins. Pedicle valve moderately and smoothly convex, flanks not reflexed; beak short, sharp, straight, or slightly curved; beak ridges sharp, short, promi- nent; delthyrium triangular, base slightly narrowed by minute disjunct remnants of deltidial plates; no overlap of valves, no lateral pseudointerareas. Bra- chial valve more strongly convex; umbonal area normally evenly convex transversely, may be slightly flattened in profile; beak bluntly pointed, not strongly incurved. Pedicle valve interior with sides widely diverging anterior to delthyrium, each side with one elongate knoblike hinge tooth supported by nearly vertical dental plate reaching floor of valve. Muscle area bilobed, heart-shaped, pointing posteriorly; adduc- tor scars small, forming subelliptical to pear-shaped mark along midline of valve in posterior part of muscle area; diductor scars larger, surrounding adductors laterally and anteriorly. Brachial valve interior with small deeply and widely notched hinge plate not completely divided; hinge sockets elongate, anteriorly widening, denticu- late; beak of valve curved up over hinge plate, forming small recess for attachment of diductor muscles; crura diverging slightly anteriorly from forward edge of hinge plate; crural bases extending NUMBER 21 2057 from underside of hinge plate, forming keel along dorsal edges of crura; hinge plate supported by short median brace that may extend forward as short, low median ridge; no true median septum. Muscle area not clearly observed: probably consist- ing of posterior and anterior adductor marks arranged as in Wellerella. MEASUREMENTS (in mm).— brachial apical valve mid- thick- angle length length width width ness (°) USNM 702c 148118a 1.0 0.8 0.9 1.0 0.6 148118b 1.9 1.7 1.5 1.7 1.1 148118c 2.8 2.5 2.1 2.3 1.5 148118d 3.9 3.6 3.2 3.5 2.4 84 148118e 4.9 4.2 4.2 4.5 2.9 87 148118f 5.7 5.0 5.5 5.8 3.7 92 148118g 6.8 5.9 6.0 6.8 4.4 97 148118h 7.9 6.8 7.5 8.1 5.5 102 148118i 8.2 7.2 8.6 9.2 5.1 103 154878b 6.8 5.8 6.9 7.0 5.4 100 (holotype) 154878c 7.3 8.1 7.5 7.8 5.0 100 STRATIGRAPHIC OCCURRENCE.—Cathedral Moun- tain and Road Canyon formations. LOCALITIES.—Cathedral Mountain: AMNH 500N; USNM 702, 702a, 702ent, 708. Road Canyon: USNM 702c, 709c, 710u, 716x, 719x. DIAGNOSIS.—Nearly smooth Anteridocus with co- stae confined to fold and sulcus. TYPES.—Holotype: USNM 154878b. Figured paratypes: USNM 148123a; 154685; 154877a-n; 15487a,c. Measured paratypes: USNM 148118a-i, 154878c. Unfigured paratypes: USNM 148122b-d, 154878d. COMPARISON.—Anteridocus erugatus is character- ized by its nearly smooth shell with few low costae on the fold and normally smooth flanks. It differs from A. gongylus, new species, in its more trans- verse outline, somewhat larger average and maxi- mum size, much weaker and more rounded costae, and less bulbous form. It is smaller than A. eximius, new species, and differs in its weak or absent costae. Anteridocus eximius, new species PLATE 540: FICURES 1-3 Large for genus, unequally biconvex; pedicle valve deeper, outline transversely subelliptical to subpentagonal, sides diverging between 95° and 120°; commissure uniplicate; fold high, narrow, standing high above flanks only at anterior, begin- ning about 5 mm anterior to brachial beak; sulcus moderately deep, deepest near anterior, beginning 4-6 mm anterior to pedicle beak. Costae strong on fold, weak on flanks, crests rounded, beginning 4-5 mm anterior to beaks, numbering 2 or 3 on fold, one less in sulcus, 1-3 on each flank. Growth lines and concentric ornamentation not preserved; shell with faint radial fibers. Pedicle valve flatly convex to slightly concave transversely, moderately convex longitudinally through sulcus; smooth region of umbo slightly swollen; beak short, blunt, suberect beak ridges blunt, obscure; lateral pseudointerareas absent, edges of valves butting; delthyrium broadly tri- angular, sides constricted by small, widely disjunct deltidial plates, leaving elongate, slotlike or slightly triangular foramen. Brachial valve strongly convex transversely and longitudinally; smooth region of umbo swollen, evenly rounded or slightly flattened along midline, crest nearly flat in profile; beak bluntly pointed, apex within pedicle valve. Pedicle valve interior with strong hinge teeth supported by short vertical dental plates reaching valve floor, each plate fused to side of valve toward posterior. Muscle area subtrigonal, apex be- tween dental plates; individual muscle marks not observed. Brachial valve interior with broad, crescentic, medially notched but undivided hinge plate; sock- ets elongate, anteriorly widening, deep, finely cor- rugate; crura diverging and strongly curved dor- sally; median ridge low, rounded, slightly higher just beneath hinge plate forming small supporting brace. Muscle area on floor of valve, near anterior end of median ridge; anterior adductor scars form- ing rounded mark with posterior half divided by median ridge; posterior adductor marks small, widely separated, one on each side of anterior mark, converging slightly posteriorly. STRATIGRAPHIC OCCURRENCE.—Bone Spring For- mation (Cutoff Member). LOCALITY.—AMNH 678. DIAGNOSIS.—Large Anteridocus with broad out- line, costate fold and sulcus, and nearly smooth flanks. TYPES.—Holotype: USNM 154880d. Figured par- atypes: USNM 154880f,g. Measured paratypes: 2058 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (") AMNH 678 154880a 8.4 7.5 8.5 5.0 104 154880b 9.0 8.0 10.3 5.9 106 154880c 9.7 8.8 11.0 7.8 105 154880d 10.5 9.4 10.0 6.6 100 (holotype) 154880e 9.7 8.8 10.5 7.2 100 154880f 9.2 8.3 9.5 0.1 86 USNM 154880a-c,e,f. Unfigured paratypes: USNM 154880a-c,e. COMPARISON.—Anteridocus eximius is character- ized by its relatively large size, broad outline, high fold with strong costae, nearly smooth flanks, and swollen brachial umbonal region. Its average size is about twice that of A. gongylus, new species, and its nearly smooth flanks contrast with the abun- dantly costate flanks of that species. A. erugatus, new species, is similar in shape, but smaller, and its nearly smooth shell with costae normally absent or obscure, even on the fold, distinguishes it from A. eximius. The posterolateral edges of the valves of species of Cenorhynchia abut instead of overlap, a feature that links them to Anteridocus and contrasts them to most other Permian rhynchonellids; how- ever, only C. fracida, new species, becomes as large as A. eximius, and its narrow outline, hooked pedi- cle beak, and high median septum distinguish it clearly from A. eximius. Anteridocus gongylus, new species PLATE 538: FICURES 53-58; PLATE 539: FICURES 40-59 Average size for genus, strongly biconvex; outline subcircular to roundly subpentagonal, sides diverg- ing between 90° and 110°; anterior commissure uniplicate; fold low, beginning 3-4 mm anterior to brachial beak, profile strongly and evenly convex, slightly arched transversely; sulcus shallow, begin- ning 4-5 mm anterior to pedicle beak. Costae rather strong, beginning 3-5 mm anterior to beaks, nor- mally numbering 3, rarely 2 or 4 on fold, one less in sulcus, normally 3 or 4, rarely 2 or 5 on flanks. Concentric ornamentation consisting of faint rounded, closely spaced striae; growth laminae sporadically present, most frequent near anterior margins. Pedicle valve moderately convex, flanks not re- flexed; beak sharp, short, slightly curved dorsally; beak ridges sharp to blunt, prominent; delthyrium triangular, base normally slightly constricted by minute rudimentary deltidial plates; lateral pseudo- interareas absent, no overlapping of valves. Brachial valve strongly convex longitudinally and trans- versely; umbonal area evenly convex to slightly flattened transversely or in profile; beak bluntly pointed, not strongly incurved. Pedicle valve interior with sides diverging widely anterior to deltidial plates; teeth supported by ver- tical dental plates reaching valve floor. Muscle area heart-shaped, with point between anterior edges of dental plates; adductor scars small, forming ellip- tical mark along midline of valve in posterior part of muscle field; diductor scars larger, surrounding adductor scars laterally and anteriorly, widening greatly anteriorly and meeting at midline of valve to form anterior part of muscle area. Brachial valve interior with hinge plate small, deeply and widely notched but undivided; beak curved over hinge plate and forming small recess for attachment of diductor muscles; sockets elon- gate, anteriorly widening, corrugated; crura strong, slightly diverging anteriorly from forward edge of outer hinge plate, braced along dorsal edges by keels extending under hinge plate, making crura concave dorsally and proximally; hinge plate sup ported by short median septal brace to floor of valve, rarely extending forward as low median ridge. Muscle pattern not clearly observed. MEASUREMENTS (in mm).— brachial maxi- apical valve mid- mum thick- angle length length width width ness (°) USNM 702a 148105a 2.5 2.0 2.4 2.6 1.0 - 148105b 3.0 2.5 3.0 3.0 1.3 - 148105c 5.5 4.6 5.1 5.3 4.5 95 148105d 6.0 5.0 5.8 6.3 4.6 105 USNM 702 148103a 3.8 3.2 3.2 3.5 1.7 86 148103b 4.7 4.0 3.9 4.2 2.1 88 148103c 5.0 4.3 4.5 4.9 3.0 89 148103d 6.6 5.6 6.1 6.4 4.8 97 148103e 7.0 6.4 6.8 7.6 4.9 109 148103f 7.3 6.4 7.3 7.7 6.0 98 148103g 6.9 6.3 7.1 7.3 5.1 100 USNM 702a 154875k 7.2 6.3 7.6 7.8 6.0 97 (holotype) NUMBER 21 2059 STRATIGRAPHIC OCCURRENCE.—Cathedral Moun- tain Formation. LOCALITIES.—AMNH 500, 504; USNM 702, 702a, 702b, 702ent, 702-low, 702un; 703a1, 703b, 703bs, 708. DIAGNOSIS.—Rotund Anteridocus with moderately strong costae. TYPES.—Holotype: USNM 154875k. Figured par- atypes: USNM 148105f,g; 154875a-f,i,j,l; 154879a,b. Measured paratypes: USNM 148103a-g, I48105a-d. Unfigured paratypes: USNM 148103a-g; 148105a-e; 154875g,h,m. COMPARISON.—Anteridocus gongylus is character- ized by its bulbous form, moderately strong costae on the flanks as well as on fold and sulcus, and the slightly flattened profile of its brachial umbonal area. It is distinguished from A. erugatus, new species, by its sharper, stronger and more numer- ous costae, more nearly circular outline, more bul- bous form, somewhat smaller maximum size, and strong costae on fold and flanks. Anteridocus paucicostatus, new species PLATE 515: FIGURES 5-7; PLATE 535: FIGURES 1-6 Small, subtrigonal outline, length and width about equal; posterolateral margins straight, form- ing angle about 90°. Sides rounded; maximum width near midvalve; anterior margin truncated. Beak short, foramen elongate oval, deltidial plates small, disjunct. Surface with anterior half costate but posterior half smooth. Costae broad and rounded, three on fold, two on each flank. Pedicle valve gently convex in lateral profile, maximum curvature anterior to umbo; anterior profile broadly and gently concave. Umbonal region convex; sulcus originating at midvalve broad and shallow and with short tongue. Flanks narrowly rounded and steep. Brachial valve evenly and moderately convex in lateral profile but broadly and moderately domed in anterior profile. Umbonal region swollen; fold originating at midvalve, defined by costae, only slightly elevated. Flanks moderately depressed and fairly swollen. Pedicle valve interior with stout dental plates having wide umbonal chambers. Brachial valve interior with undivided hinge plate having narrow outer hinge plates, coalesced inner hinge plates, stout crura concave inward, and no median septum. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 7l4y 148590a 2.6 2.1 2.5 1.4 - 148590b 3.0 2.6 3.0 1.5 88 148590c 3.2 2.7 2.9 1.7 80 148590d 3.5 2.8 3.0 1.8 73 148590e 4.2 3.5 4.0 2.2 82 148590f 4.9 4.2 4.7 2.7 75 148590g 5.9 5.0 5.7 3.7 92 148590h 6.0 5.1 6.0 3.5 87 148590i 6.4 5.5 6.9 3.9 94 USNM 707h 148615a 5.8 5.1 5.4 3.6 90 USNM 733j 154723b 5.1 4.2 4.8 3.2 83 (holotype) STRATIGRAPHIC OCCURRENCE.—Skinner Ranch For- mation (Poplar Tank and Sullivan Peak members). LOCALITIES.—Poplar Tank: USNM 707h. Sulli- van Peak: 714y, 733j. DIAGNOSIS.—Small, anteriorly costate Anteridocus usually with two costae on flanks and low fold. TYPES.—Holotype: USNM 154723b. Figured par- atypes: USNM 148590a,b,e; 154723a-c. Measured paratypes: USNM 148590a-i, 148615a. Unfigured paratypes: USNM 148590c,d,f-i; 148615a-k. COMPARISON.—The only species suggesting this one are Pontisia nanas (Stehli) which is much larger and with stronger, longer costae, and Anteridocus seminudus, new species, in which the costae are only noticeable along the margins but there are more of them on the flanks of A. seminudus and the latter has a longer and sharper beak which makes the posterolateral margins gently concave. Furthermore, the young of A. seminudus are long and slender and quite differently shaped from the wider A. paucicostatus. DISCUSSION.—This is a rare species, having been found only in two localities but at two different stratigraphic levels. The species includes a few specimens that are wider than usual, as might be expected in a rhynchonellid species. No trace of a septum was seen in any of the brachial valve interiors. 2060 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY Anteridocus seminudus, new species PLATE 517: FIGURES 18-20; PLATE 535: FIGURES 26-51 Usual size for genus, wider than long in adults, but longer than wide at youth; outline subtrigonal; profile unequally biconvex, brachial valve deeper and more convex. Sides rounded; maximum width slightly anterior to midvalve; anterior margin truncated. Anterior commissure uniplicate. Beak short, pointed acutely, straight; deltidial plates rudimentary, disjunct. Surface paucicostate, costae confined to marginal region, 2 or 3 on fold, one less in sulcus, and 1-3 on each flank. Pedicle valve unevenly convex in lateral profile, maximum curvature anterior to umbonal region and just posterior to midvalve; anterior profile faintly convex. Umbonal and median region some- what narrowly swollen; sulcus originating at mid- valve, shallow, forming short tongue; flanks slightly inflated and slightly deflected. Brachial valve fairly strongly convex, maximum curvature in umbonal region; anterior profile broadly and evenly domed, sides sloping moderately to steeply. Umbonal and median regions fairly strongly inflated; fold, low, inconspicuous, orig- inating anterior to midvalve, slightly elevated anteriorly. Flanks swollen and slightly depressed. Pedicle valve interior with small knoblike teeth and delicate, slightly divergent dental plates. Bra- chial valve interior with strong, elevated socket ridges hanging over smooth sockets; hinge plate undivided, with variable anterior margin; outer hinge plates narrow; inner hinge plates variable, united, convex, flat or moderately deeply concave; median septum obsolete, remnant, not reaching floor, occasionally attached to underside of hinge plate. Median ridge small and threadlike, extending to about midvalve, but variably preserved. STRATIGRAPHIC OCCURRENCE.—Road Canyon For- mation. LdcALiTiEs.—USNM 709c, 721t, 721x, 721y, 722f, 724b, 726c, 726d. DIAGNOSIS.—Small, paucicostate Anteridocus with the costae confined to the margins. TYPES.—Holotype: USNM 152855h. Figured par- atypes: USNM 152855f,h; 154746a-c; 154863a-e; 154864a-c. Measured paratypes: USNM 152855a-g. Unfigured paratypes: USNM 152855a-e, 154746a. COMPARISON.—This species has a triangular form, MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 722f 152855a 7.2 6.1 7.5 3.8 90 152855b 5.9 5.0 6.0 3.4 90 152855c 5.5 4.7 5.8 3.2 90 152855d 5.4 5.0 4.9 2.8 80 152855e 4.3 3.5 4.0 2.4 70 152855f 3.8 3.1 3.2 1.9 60 152855g 3.3 2.7 3.0 1.4 60 152855h 3.6 2.5 2.6 1.4 60 (holotype) USNM 724b 154746a 6.2 5.3 6.7 3.5 100 fairly wide at the front but the posterior three- fourths of the valve are smooth. The species need be compared only to the smaller species of Pontisia. It is unlike P. franklinensis, new species, and P. nanas (Stehli) because it has a less thick shell, finer costae, and has more of the surface noncostate than either of these species. In size and shape it is most like Anteridocus paucicostatus, new species, but has shorter costae, has a somewhat larger maximum size, and a narrower, shallower sulcus on the pedicle valve. DISCUSSION.—This species proved to be common at USNM 722f where young as well as mature specimens were found. The young are smooth and strongly triangular and do not become costate until they attain about half their adult size. The beak is long and the delthyrium is constricted only slightly at its lateral extremities by rudimentary deltidial plates that are, in some specimens, elevated for a short distance on the delthyrial edge. The crura are fairly wide and stout for a small shell. The median septum is not formed but may appear as a minute ridge scarcely meeting the floor on the underside of coalesced inner hinge plates. Exter- nally the species has a tendency to bicostation. Anteridocus subcarinatus, new species PLATE 551: FIGURES 43-46 Medium size for genus, length slightly greater than width; pentagonal in outline; maximum width slightly anterior to midvalve. Posterolateral mar- gins slightly less than 90°; sides narrowly rounded; NUMBER 21 2061 anterior margin subnasute. Anterior commissure uniplicate. Beak moderately long, incurved, erect. Delthyrium open; deltidial plates absent. Surface paucicostate, umbones with 2 costae on pedicle valve and 1 on brachial valve, 2 on fold, and 1 in sulcus, and 2 on each flank. Costae, broad, low and rounded. Pedicle valve strongly convex in lateral profile; broadly but flatly convex in anterior profile. Umbo narrowly swollen; sulcus originating on anterior side of umbo, widening and deepening slightly to anterior margin. Sulcus occupied by median costa originating about 3 mm anterior to beak and ex- tending to anterior margin. Tongue moderately long and wide. Flanks rounded, narrow. Brachial valve strongly convex in lateral profile, maximum curvature near umbo. Anterior profile narrowly domed, fold slightly protuberant in mid- dle. Umbo narrowly carinated by median costa which is divided just posterior to midvalve to pro- duce narrow strongly elevated fold, strongly convex longitudinally. Flanks swollen and considerably depressed below fold. Pedicle valve interior with deeply entrenched, long diductors scars and dental plates obsolete. Brachial valve interior without median septum and with strongly divided hinge plate having fairly wide outer hinge plates. MEASUREMENTS (in mm).—Holotype USNM 152980: length 8.3, brachial valve length 7.3, width 8.1, thickness 6.9, apical angle 85° STRATIGRAPHIC OCCURRENCE.—Bell Canyon For- mation (Pinery and Hegler members). LOCALITIES.—Hegler: USNM 731. Pinery: 725n. DIAGNOSIS.—Anteridocus with bicostate fold, ro- tund appearance, and few costae. TYPES.—Holotype: USNM 152980. COMPARISON.—This species is most similar to Anteridocus bicostatus, new species, but differs in having deeper valves, more rotund appearance, a keeled umbo, narrower fold and sulcus, more strongly incurved beak, and the costae appear in the posterior half of the shell. DISCUSSION.—This is an extremely rare species, known from only four specimens, but the charac- ters are so strongly marked that we do not hesitate to propose it as a new species. Anteridocus swallovianus (Shumard) PLATE 534: FICURES 50-64; PLATE 538: FIGURES 1-11 Camerophoria swalloviana B. F. Shumard, 1860:394, pi. 11: figs. la-e. Pugnax swalloviana (Shumard) Schuchert, 1897:336.—Girty [part], 1909:314, pi. 15: figs. 8-1 lb [not figs. 12-12d ( = Tautosia elegans (Girty)]. [Not of Hall and Clarke, 1894:240, pi. 60: figs. 27-32 (= Wellerella).] Not Pugnoides swalloviana (Shumard) King, 1931:107, pi. 34: figs. 10 [= Wellerella girtyi girtyi], 11, 12 [= ?]. Small for genus, biconvex; both valves strongly inflated; outline bluntly triangular to pentagonal, sides diverging between 75° and 105°; profile sub- trigonal to elongate oval; anterior commissure uniplicate; fold low to moderately high, beginning 5-7 mm anterior to brachial beak, terminating abruptly anteriorly, profile of fold only slightly convex; sulcus rather shallow, beginning 5-7 mm anterior to pedicle beak, evenly convex longitudi- nally, or flexed dorsally near anterior margin. Costae low, sharp on fold and pedicle flanks, blunt on brachial flanks and in sulcus, beginning 4-6 mm anterior to beaks, numbering 3 or rarely 2 on fold, one less in sulcus, 2-4 on flanks. Concentric orna- mentation faint or absent; growth lines present but weak. Pedicle valve strongly inflated in smooth area near beak, gently convex toward flanks or with ends of costae on flanks slightly reflexed; beak short, curved, sharp, with obscure beak ridges; lateral pseudointerareas absent, valves meeting with- out overlap. Delthyrium in adults partly or com- pletely covered by small deltidial plates, apical part open forming elongate oval foramen. Brachial valve strongly inflated in smooth area near beak, may be flattened or indented there, or evenly convex trans- versely; apex of valve within pedicle valve. Pedicle valve interior with sides of delthyrium widely diverging anterior to deltidial plates, teeth parallel and supported by vertical dental plates reaching floor of valve. Muscle area elongate oval, lying just anterior to edges of dental plates; adduc- tor scars median, small, surrounded laterally and anteriorly by larger diductor scars. Brachial valve interior with triangular, anteriorly notched hinge plate, laterally bounded by deep, anteriorly expanding, finely corrugated sockets; crura projecting forward from anterior edges of hinge plate, anteriorly diverging, strongly curved 2062 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY ventrally, dorsal edge carinate; median ridge greatly reduced or absent. Muscle area in smooth part of beak area, faintly impressed, details unknown. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 740 152859a 6.1 5.7 5.5 3.4 85 152859b 6.6 5.9 6.6 5.5 80 152859c 7.9 7.3 7.8 6.8 79 152859d 8.4 7.7 9.0 6.5 92 USGS 2926 (green) 118562a 8.8 8.1 10.5 6.0 98 118562b 9.3 8.2 10.0 6.2 100 118562c 9.9 8.8 11.7 7.1 104 STRATIGRAPHIC OCCURRENCE.—Capitan Formation; Bell Canyon Formation (Hegler, Pinery, Rader, and Lamar Members). LOCALITIES.—Capitan: AMNH 801, 804, 840, 847; USGS 2926; USNM 725j, 725k, 725-1, 728u, 732q, 735j, 738a, 739, 740, 740-1, 740m, 740n, 740o, 748a, 750a. Hegler: USNM 731, 732a, 740c. Pinery: AMNH 33, 398, 524; USNM 725h, 725n, 733. Rader: USNM 725g, 740a, 740h, 740i, 740j. Lamar: AMNH 37, 40, 347, 401; USNM 725e, 725f, 728p, 728q, 728r, 738, 738b. DIAGNOSIS.—Semicostate Anteridocus, small and triangular, with swollen valves but flattened and concave umbonal region on the brachial valve. TYPES.—Figured hypotypes: USNM 154855a-d; 154856; 154857; 154858; 154859d; 154860a,b,d; 154861a; 154929. Measured hypotypes: USNM 152859a-d, 118562a-c. COMPARISON.—Anteridocus swallovianus is char- acterized by its small size, inflated umbones, with depression in dorsal one, prominent anterior end of fold, short beak with dental plates small or absent, low costae that extend only about half valve length, and the reduced or absent median septum. Similar species are Tautosia elegans (Girty) and T. shumardiana (Girty). Each of these species becomes larger than A. swallovianus, lacks the in- flated umbones, and has a high, bladelike median septum in the brachial valve. "Pugnoides osagensis var. occidentalis" (Girty) is somewhat inflated and to that extent resembles A. swallovianus, but its flanks have stronger and more numerous costae, and the longitudinal profile of its fold is more strongly convex. This variety was considered by King (1931:107) to be a synonym of A. swallo- vianus, but his interpretation was based on com- parison with his specimens, not any of which are A. swallovianus (see synonymy). Fredericks (1932a, pi. 1: figs. 2a-d) figured the exterior of a specimen similar to ours as A. swallo- vianus. To judge by his illustrations, his identifi- cation of A. swallovianus in the "Upper Carboni- ferous" of Pechora-land is correct. However, the interior is not exhibited, consequently the identifi- cation must be held uncertain. DISCUSSION.—Girty's illustrated (1909) specimens of Pugnax swalloviana and P. bidentata represent forms that differ considerably in outline and stratigraphic level. They are similar in profile, however, and both have the specific characters of swollen umbones and weakly costate brachial flanks. The latter does not have the umbonal pit so characteristic of A. swallovianus. The National Museum collections contain specimens of A. swallo- vianus with two costae on the fold intermediate between the narrow extreme of P. bidentata, and the transverse extreme of Girty's A. swallovianus. Shumard's (1860, pi. 11: figs, lc-d) illustrations of the holotype show a specimen that is intermediate in width. We have been unsuccessful in attempts to separate the two forms into two consistently differing groups of specimens. The number of co- stae on the fold is reliable for distinction of species only in a broad way, and the difference between specimens with 2 and those with 3 is insignificant. In fact, Girty (1909, pi. 15: fig. 12) illustrated a specimen with 2 costae on the fold, assigning it to A. swallovianus (although we now consider that specimen to belong to Tautosia elegans). The specimen illustrated by Girty (1909, pi. 21: fig. 19) as an interior of Pugnax swalloviana has a short but well developed low median ridge. Most of the Museum specimens from the Guadalupe Mountains have no median septum. We believe that Girty's specimen represents a different species. An interesting feature of this species, unlike that in any other species of Anteridocus, is the deep depression of the umbonal region of the brachial valve. Other species from the Capitan Limestone and its equivalents have the same sort of concave umbo, such as Strigirhynchia and Ptilotorhynchus, new genera. This suggests the possibility that A. swallovianus may be related to some other generic stock rather than to Anteridocus. NUMBER 21 2063 Anteridocus triangulatus, new species PLATE 521: FIGURES 58-61 Usual size for genus, roundly triangular outline, length and maximum width nearly equal. Antero- lateral extremities rounded; posterolateral margins forming angle of 78°. Anterior commissure unipli- cate. Beak strongly curved and closely appressed to brachial valve umbo; surface paucicostate, posterior half smooth; anterior with costae, four on fold, flanks with one indistinct costa. Pedicle valve fairly strongly and evenly convex in lateral profile, anterior profile broadly domed, only slightly convex on top and with short steep sides. Sulcus originating near midvalve, wide and shallow; umbonal region swollen; flanks convex and steep. Brachial valve slightly deeper, moderately con- vex in lateral profile but narrowly domed and with steep sides in anterior profile; umbonal region swollen; fold beginning at midvalve, poorly defined throughout length; flanks swollen and rounded. Brachial valve interior with undivided hinge plate but no median septum. MEASUREMENTS (in mm).—Holotype USNM 154768a: length 7.8, brachial valve length 7.0, width 7.5, thickness 6.4, apical angle 78°. STRATIGRAPHIC OCCURRENCE.—Road Canyon For- mation. LOCALITY.—USNM 732j. DIAGNOSIS.—Triangular Anteridocus with 4 co- stae on the fold. TYPES.—Holotype: USNM 154768a. COMPARISON AND DISCUSSION.—The subtriangular outline and the 4 costae on the fold distinguish this species from all others of Anteridocus. Paratype USNM 154768b is a smaller individual of which the valves have been separated. The dorsal valve preserves the hinge plate which is without a median septum. The crural bases of this hinge plate extend unusually far below the undersurface of the hinge plate. Family CAMAROTOECHIIDAE Schuchert and LeVene, 1929 Subfamily CAMAROTOECHIINAE Schuchert and LeVene, 1929 Rhynchonellacea with valves partly to completely costate, the costae often dividing. Pedicle valve usually with open delthyrium and short, often obsolescent, dental plates; brachial valve with hinge plate divided; small apical chamber thickened and obsolescent in old shells. Crura mucrifer. Genera in West Texas: Bryorhynchus Cooper and Grant, 1969; Leiorhynchoidea Cloud, 1944. Bryorhynchus has not been found outside of the Guadalupe and Delaware Mountain areas except for one rare occurrence in the Glass Mountains. It is abundant in the black limestones of the Hegler and Pinery members of the Bell Canyon Formation. Like most camarotoechiids, it favored an environment dominated by dark or black muds. Hence, its rarity from the Glass Mountains where black limestones are few. Genus Bryorhynchus Cooper and Grant, 1969 Bryorhynchus Cooper and Grant, 1969:11. Medium size, strongly biconvex, brachial valve inflated near umbo; outline transversely to longi- tudinally subovate or roundly trigonal; commissure uniplicate, height of fold increasing with size of shell; costae weak or absent, normally present only near anterior margins of fold and sulcus, without bifurcation or intercalation. Concentric ornamen- tation weak or absent; growth lines widely spaced over most of shell, more closely crowded toward anterior margins. Pedicle beak short, erect to in- curved; delthyrium triangular, open, with obscure deltidial plates, rarely with conjunct plates; beak ridges long, bordering long, narrow, lateral pseudo- interareas; slight overlapping of lateral pseudoin- terareas by edge of brachial valve; umbonal area somewhat inflated, with blunt median longitudinal crest. Brachial beak blunt, apex within pedicle valve; fold may have flat crest or slight longitudinal median indentation extending into umbonal area. Pedicle valve interior with sides widely diverging anterior to delthyrium, each side with one knoblike elongate tooth parallel to it; dental plates converg- ing toward valve floor often fused to sides of valve. Muscle area narrowly triangular, expanding ante- riorly, sides straight or curving laterally just an- terior to dental plates; adductor scars small, median, posterior, lying just anterior to dental plates, each broadly rounded posteriorly, narrowed to a point anteriorly, together forming heart-shaped 2064 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY scar; diductor scars larger, beginning posteriorly as narrow lines in beak area, posterior and lateral to adductor marks, widening anteriorly, curving around adductor marks, contacting one another at median line of valve, anteriorly surrounding ad- ductor marks. Brachial valve interior with short, wide, hinge plate, partly divided by narrow, wedge-shaped notch; sockets wide, deep, anteriorly expanding, strongly corrugated, bounded laterally by slight thickening along posterior margins; crura mucrifer, long, fragile, projecting from hinge plate, one on each side of median notch, slightly diverging ante- riorly, curved strongly toward pedicle valve; median septum low, normally present just below hinge plate, attached to it with shallow crural cavity that may be filled with callus, simulating an undivided hinge plate; anteriorly, septum continuing low and thin to near midline of valve, or may be low, rounded median ridge, or may be absent. Posterior adductor muscle marks very long, posterior ends touching median septum or ridge, diverging slightly anteriorly, with anterior ends contacting small, elliptical to nearly circular anterior adductor scars. TYPE-SPECIES.—Camarophoria? bisulcata Shu- mard (1859:296). COMPARISON.—Bryorhynchus is characterized by its nearly smooth shell, rotund outline, bulbous brachial valve, short, hooked pedicle beak, divided hinge plate with shallow crural cavity, low median septum or median ridge, and strongly denticulate hinge sockets. It is related to Leiorhynchus Hall and Leiorhynchoidea Cloud, as evidenced by its similar muscle pattern and external shape. It dif- fers from Leiorhynchus in its low, often obsolete median septum, or ridge, and strongly denticulate hinge sockets. The low median ridge also distin- guishes it from Leiorhynchoidea, as do its divided hinge plate and crural cavity. DISCUSSION.—Specimens of Bryorhynchus occur in countless numbers in the dark limestone members of the Bell Canyon Formation (Hegler through Rader members). In many places these specimens are well silicified, consequently it is possible to obtain an abundant supply of fine specimens that give nearly all the details of the shell anatomy. The specimens in the National Museum collection show to perfection the considerable variation of the interior consequent to deposition of callus shell, a phenomenon that may cause the oblitera- tion of generic characters such as the brachial valve septum. Bryorhynchus is usually very unevenly calcified, the posterior ends being thick and heavy but the anterior very thin and fragile. This results in some distortion of specimens and, in many specimens, loss of the anterior part. Nevertheless these poste- rior parts are superb study materials for all details of the cardinalia and delthyrial region. The deltidial plates are so small and fragile that they are not preserved in all specimens. The indi- viduals that do show good development of these structures indicate that the deltidial plates are usually disjunct. The beak is usually strongly in- curved and in B. bisulcatum (Shumard) is pressed tightly to the dorsal umbo, suggesting that the pedicle was no longer functional and that the shell lived loose on the sea bottom. The heavily weighted posterior would tend to hold that part down and permit the anterior end to extend obliquely upward out of the mud. The teeth of the pedicle valve are often very large and consist of several parts. In old specimens they are broadly triangular and protrude into the interior. They are attached to the valve wall by a thin plate lying just under the margin, suggesting the fulcral plate of the opposite valve. Indeed its function is essentially the same as that of the ful- cral plate, because it defines the elongate trough, or socket, separating the shell edge from the outer side of the tooth. Thus the tooth is hook-shaped in section and the dental plate is welded to the inner sloping face of the tooth. In some specimens the cavities between the dental plates and shell wall are filled with tissue and the tooth appears to be unsupported. The dental plates are short and usually strongly recessive. They extend forward to the inside of the tooth but then recede posteriorly to line the wall of the delthyrial cavity. Anterior to the anterior ends of the dental plates the narrowly triangular muscle field is usually strongly impressed. In old shells this is deeply etched into the valve floor, but in the young it is not usually easily seen. At the posterior, or apical, end of the triangle two thick- ened patches extend anteriorly. These fill in the spaces between the posterior ends of the centrally placed adductor scars, which are anteriorly sur- rounded by the diductors. The cardinalia are distinctive but vary with age. NUMBER 21 2065 The socket ridges are conspicuous parts of the car- dinalia as they form a ridge around the posterior margin of the hinge plate. In many specimens the ridge is somewhat alate and elevated at its distal end. The socket ridges define deep, corrugated sockets which at their distal end are generally floored by a well-defined fulcral plate. The outer hinge plates are broad and are usually concave. They are bounded externally by the socket ridge and on their inside by the thickened and elevated crural base. Inner hinge plates were not seen. Attached to the somewhat rounded, narrow and thick crural base is a long crus, rodlike proximally but flattened to somewhat spatulate distally, the flattening taking place in an anteroposterior direc- tion. Proximally, the rounded but slender crus is laterally expanded to form a long crural keel that unites with the median septum to produce a V- shaped chamber. The hinge plate is thus divided by a narrow slit bounded by the crural bases and forming a narrow apical cavity. Some specimens appear to have an undivided hinge plate because the apical chamber is progressively filled from the apex anteriorly by adventitious shell. In such speci- mens the hinge plate is variously notched; the notches are broad in some but narrowly slitlike in others. Deposition of the tertiary shell layer affects other structures as well as the cardinalia. The entire apical region of the brachial valve is often covered by shell tissue that buries all or part of the median ridge. In some specimens the septum is moderately long, high, and slender but in the majority it is merely a myophragm separating the lateral halves of the adductor field, which is a narrowly elongate oval scar usually fairly well defined. Bryorhynchus bisulcatum (Shumard) PLATE 508: FIGURES 40-47; PLATE 546: FIGURE 25; PLATE 547: FIGURES 6-79; PLATE 548: FIGURES 6-17 Camarophoria? bisulcata Shumard, 1859:296; 1860:394, pi. 11: ng. 2. Pugnax? bisulcata (Shumard) Girty, 1909:310, pi. 21: figs. 11-12. Bryorhynchus bisulcatum (Shumard) Cooper and Grant, 1969:11. Average size for genus; outline transversely sub- elliptical; anterior commissure uniplicate, fold moderately high at anterior margin of adults, beginning 8-12 mm anterior to brachial beak; sulcus shallow; costae normally weak, rarely absent on adults, present near anterior margins of fold and sulcus, rarely on flanks, numbering 3 to 5 on fold, one less on sulcus. Concentric ornamentation not visible; growth lines widely spaced over most of shell, crowded near anterior margins. Pedicle valve moderately convex, umbonal area with bluntly rounded longitudinal median crest, giving way anteriorly to shallow sulcus; beak short, abruptly tapered, oblique to erect, not tightly hooked, not in contact with brachial umbo; del- thyrium triangular, open, perforating apex of beak; beak ridges long, bordering exposed narrow pseudo- interareas; slight overlapping of pseudointerareas by edge of brachial valve. Brachial valve strongly convex, umbonal area inflated; fold often with flat to slightly indented crest extending into umbonal area. Pedicle valve interior with hinge teeth forming elongate knobs parallel to sides of valve, supported by dental plates reaching valve floor; dental plates converging but not meeting, partly or completely fused to sides of valve. Muscle area triangular; ad- ductors forming small, median, bilobed, heart- shaped scar, with apex pointing anteriorly; diductors beginning between dental plates as narrow lines, widening anteriorly to form heart- shaped area with apex pointing posteriorly. Brachial valve interior with short, wide, divided hinge plate, bounded laterally by deep, elongate, anteriorly expanding, strongly corrugated sockets; crura projecting from hinge plate, slightly diverg- ing anteriorly, strongly curved ventrally; median ridge low, rounded, rarely high enough to be con- sidered a septum; crural cavity small, formed by convergent plates beneath notch in hinge plate, meeting on crest of median ridge, often filled with callus. Posterior adductor muscle scars long, nar- row, slightly curved, diverging anteriorly, meeting posterior edges of larger, elongate elliptical to nearly circular anterior adductor marks. STRATIGRAPHIC OCCURRENCE.—Cherry Canyon For- mation (Getaway Member); Bell Canyon Formation (Hegler, Pinery, Rader, and Lamar members); Cap- itan Formation. LOCALITIES.—Getaway: Moore 31; USNM 732. Hegler: USNM 731, 732a, 740c, 740d. Pinery: AMNH 33, 524, 537, 435; USNM 725h, 725n, 733. Rader: AMNH 388, 397, 403, 410; USNM 725f, 2066 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 731 148132a c.5.5 ? 6.0 } ? 148132b c.7.0 ? 8.9 ? ? 148132c 9.5 ? 9.5 ? ? 148132d 18.4 16.1 21.0 8.0? 120 USNM 733 148130a 11.5 10.8 11.6 8.9 110 148130b 13.9 12.9 13.9 9.8 110 Moore 31 148128 13.0 12.0 12.9 9.8 123 USGS 2930 (green) 118558a 14.1 13.2 15.8 10.8 110 (neotype) AMNH 33 148135a 14.3 12.0 15.5 9.6 110 148135b 12.6 11.5 13.0 8.7 95 148135c 11.0 10.0 11.3 8.2 90 148135d 9.6 8.6 9.7 5.4 90 725g, 725o, 740a, 740i, 740j. Lamar: AMNH 40; USNM 728p. Capitan: USNM 748a; USGS 2930. DIAGNOSIS.—Bryorhynchus with fold and sulcus anteriorly plicated and beak not in contact with the brachial valve umbo. TYPES.—Neotype: USNM 118558a. Paratype: USNM 118558b. Figured hypotypes: USNM 154905a-c; 154906a-e; 154907; 154908a-d,f,g,i,j; 154909a-d,h-k,m,o; 154910a,b; 154931a,b. Measured hypotypes: USNM 148128; 148130a,b; 148132a-d; 148135a-d. COMPARISON.—Bryorhynchus bisulcatum is char- acterized by its transversely subelliptical outline, moderately high fold that normally has a few weak costae near the anterior margin, low median ridge, rarely a median septum, short curved beak that is not in contact with the brachial umbo, and lateral pseudointerareas that are exposed, not completely covered by overlapping of the edge of the brachial valve. These features distinguish the species from B. graliosum (Girty). DISCUSSION.—R. E. King (1931:105, pi. 33: figs. 1-8) assigned several specimens to "Leiorhynchus" bisulcatum (Shumard). Shumard's (1860: pi. 11: fig. 2) illustrations are not strictly accurate, but they show a specimen that differs from King's in several important features. King's specimens are more strongly costate, with costae on the flanks as well as the fold and sulcus, and they have the sulcus beginning far back on the umbo to where Shu- mard's specimen has a ridge instead of a trough. Shumard illustrates the profile (fig. 2d) of the shell, showing the beak to be nearly straight. His descrip- tion (1859:296) portrays the beak, as, "incurved nearly in contact with the opposite valve," which is true of B. bisulcatum, but not of King's speci- mens. We believe that King's are specimens of Leiorhynchoidea amygdaloidea, new species. Bryorhynchus gratiosum (Girty) PLATE 548: FIGURES 1-5 Pugnax? bisulcata (Shumard) var. gratiosa Girty, 1909:312, pi. 21: figs. 10-lOc. Pugnax? bisulcata (Shumard) var. seminuloides Girty, 1909: 312, pi. 21: figs. 13-16, pi. 29: fig. 9. Average size for genus; outline subelliptical to bluntly subtrigonal; anterior commissure unipli- cate; fold normally low at anterior margin of adults, beginning 8-12 mm anterior to brachial beak, sulcus shallow; costae normally absent, rarely faintly present at anterior end of fold or sulcus. Concentric ornamentation not visible; growth lines closely spaced, stronger near anterior margins. Pedicle valve moderately convex, umbonal area somewhat inflated, with bluntly rounded longitu- dinal median crest giving way anteriorly to shallow sulcus; beak moderately long, abruptly tapered, strongly curved, normally erect and in tight con- tact with brachial umbo except at posterior ex- tremity; delthyrium triangular, open, producing minute perforation at apex of beak; beak ridges short, rounded; lateral pseudointerareas narrow, obscurely delimited, mostly covered by edge of brachial valve. Brachial valve strongly convex, um- bonal area strongly inflated; fold often with slight longitudinal indentation along crest, extending into umbonal area. Pedicle valve interior with narrow elongate knob- like hinge teeth, dental plates reaching floor of valve, converging but not meeting, normally not fused or cemented to sides of valve. Muscle area elongate triangular, sides straight; adductors form- ing small, median heart-shaped scar with apex for- ward; diductors beginning between dental plates as narrow lines, proceeding forward, lateral to adductors, there expanding slightly, each forming small triangle with apex posterior. Brachial valve interior with short wide hinge NUMBER 21 2067 plate, divided by narrow wedge-shaped notch, bounded laterally by deep, narrow, moderately strongly denticulate hinge sockets; crura projecting forward from edges of hinge plate, slightly diverg- ing anteriorly, strongly curved ventrally, converg- ing posteriorly beneath hinge plate to form small crural cavity; median septum low, long, thin, rarely low enough to be median ridge, posterior end in contact with crural cavity. Posterior adduc- tor muscle scars long, narrow, slightly diverging anteriorly, extending forward to small subcircular anterior adductor marks. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 736 148148a 148148b 148148c USNM 735 148153a 148153b 148153c 148153d 148153e 6.8 6.1 6.5 2.6 ? 7.7 7.0 8.0 2.9 95 9.6 8.8 10.9 5.6 ? 10.5? 10.0 11.7 6.3 ? 11.2 10.2 12.4 7.6 110 13.4 11.9 14.0 8.2 105 15.0 13.9 15.0 10.6 105 15.4 13.8 16.8 9.7 110 15.6 12.3 110 USGS 2930 (green) 118559 15.6 14. (holotype) STRATIGRAPHIC OCCURRENCE.—Cherry Canyon For- mation (Getaway Member); Bell Canyon Formation (Hegler, Pinery, and Rader members). LOCALITIES.—Getaway: AMNH 512. Hegler: USNM 731. Pinery: USGS 2930 (green); USNM 736. Rader: USNM 735. DIAGNOSIS.—Usually noncostate Bryorhynchus with pedicle valve beak closely appressed on the umbo of the brachial valve. TYPES.—Holotype: USNM 118559. Measured hy- potypes: USNM 148l48a-c, 148l53a-e. COMPARISON.—Bryorhynchus gratiosum is distin- guished from B. bisulcatum (Shumard) by its more triangular outline, low fold, normally noncostate shell, low thin median septum, strongly hooked pedicle beak that normally is in close contact with the brachial umbo, obscure lateral pseudointerareas, normally straight-sided brachial muscle area, and its pedicle dental plates that are not fused to the sides of the valve. DISCUSSION.—Girty (1909:312) distinguished Pug- nax? bisulcata vars. gratiosa and seminuloides from P.? bisulcata on the basis of the number and strength of costae on the fold. He admitted that such a criterion left some specimens intermediate between two varieties. We believe that the length and curvature of the pedicle beak, plus the other distinguishing characters mentioned above, are more useful as criteria for separating the two kinds of shells. However, this formula still offers no valid method for distinguishing Girty's variety seminu- loides, and we have accordingly included it with B. gratiosum. Bryorhynchus? nitidum (Girty) PLATE 510: FICURES 39-43 Pugnax nitida Girty, 1909:313, pi. 24: figs. 15-15c. We have found only one specimen referable to this species in all the residues from the Guadalupe Mountain region in the collections of the National Museum of Natural History and the American Museum of Natural History. The type specimen is small, measuring 9 mm in length, 10.6 mm in width and 6.0 mm in thickness. The specimen is characterized by its wide fold and shallow sulcus, with no ornament except on the margin of the pedicle valve tongue where 5 indistinct costae appear. The exterior features thus suggest Bryo- rhynchus, which is so common in the upper parts of the Guadalupe Permian. This suspicion is con- firmed by the presence of a long median septum, visible from the exterior when the shell is moist- ened. Two somewhat closely spaced and convergent dental plates are also visible under the same conditions. The location and horizon from which B? nitidum was taken have been a matter of speculation. Girty's map (1909, pi. 1) shows the location of this species, USGS 2920 (green), as west of the big bend of the highway in the pass, and it is stated that the location is in a small canyon in the foothills 2 miles south of Guadalupe Peak. This places the locality, within the mapped band of Bone Spring Formation, which is confirmed by P. B. King in his Guadalupe studies ( 1948:21, 22). The strati- graphic level of this species and its associates "Pugnax" bidentata Girty and "P." osagensis Girty (not Swallow) is from the black Bone Spring Formation. TYPES.—Holotype: USNM 118563. 2068 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY Bryorhynchus plicatum, new species PLATE 550: FIGURES 8-19 Usual size for genus, subcircular in outline with well rounded sides and truncated anterior margin; maximum width at midvalve. Valves unequally convex, brachial valve much deeper than pedicle valve. Anterior commissure strongly uniplicate. Maximum width slightly anterior to midvalve. Sur- face smooth in posterior third to half, marked by low, broad plicae in anterior half, 3 on fold, each flank marked by 2 to 3. Pedicle valve gently convex in lateral profile, maximum convexity in median region; anterior profile unevenly and flatly convex, narrow median elevation flanked by slightly concave to flat flanks. Umbonal region narrowly convex, convexity ex- tending and increasing to midvalve, there merging onto tongue. Flanks narrowly concave with margins slightly reflected in ventral direction. Sulcus broad and shallow, defined only at anterior and extending onto long, rounded tongue. Brachial valve strongly convex in lateral profile, umbonal region flattened, maximum swelling in anterior half; anterior profile strongly rounded with long, steep sides. Umbonal region flattened to slightly concave; fold originating near midvalve, low and spreading, and not strongly differentiated. Interior with long, thin median septum in bra- chial valve reaching to midvalve. Dental plates of pedicle valve short. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (*) USNM 731z 153484a 16.3 15.4 17.3 12.7 112 (holotype) 153484b 17.5 15.4 17.6 10.5 112 153484c 15.0 14.8 16.5 11.3 beak missim STRATIGRAPHIC OCCURRENCE.—Word Formation (Appel Ranch Member). LOCALITY.—USNM 73lz. DIAGNOSIS.—Bryorhynchus of usual size with smooth posterior and broadly plicated anterior. TYPES.—Holotype: USNM 153484a. Figured par- atypes: USNM 153484b,d. Measured paratypes: USNM 153484b,c. Unfigured paratypes: USNM 153484c,e-i. COMPARISON AND DISCUSSION.—This species is un- like any of those from the Bell Canyon Formation of the Guadalupe Mountains in which the costation is usually less coarse when present and which are usually more nearly smooth. It is also unlike species of Leiorhynchoidea which all have a more pro- nounced sulcus and have more costae. This species has been placed in Bryorhynchus because of its rounded and compact outline, its strongly swollen brachial valve, and the abruptly geniculated tongue of the pedicle valve. It is rare in the Glass Mountains. Genus Leiorhynchoidea Cloud, 1944 Leiorhynchoidea Cloud, 1944:57.—Williams et al., 1965:H581. Interior details of Leiorhynchoidea are different from those of Bryorhynchus. Although some speci- mens attain large size, the teeth of the pedicle valve are small and knoblike and the deltidial plates when present are conjunct. These plates are small and the junction is very narrow, consequently many specimens do not preserve thern. The dental plates are commonly obsolete because of filling in of the umbonal chambers. The construction of the cardinalia of the bra- chial valve is much like that of Bryorhynchus, but the median septum is much stronger and the V- shaped chamber is small and commonly filled in to create a solid plate across the septum. The mucri- fer crura are very long, slender, and have horizon- tally flattened distal extremities. Members of this genus are rare at most places in the Glass Mountains and, when silicified, are extremely fragile. It is thus difficult to obtain com- plete and perfectly preserved specimens. The genus appears also to be rare in the lower Guadalupian rocks in the Guadalupe Mountains, except in the black limestone of the South Wells Member, where thickened posterior parts of both valves yielded good details of the interior. TYPE-SPECIES.—L. schucherti Cloud (1944:58, pi. 18: figs. 28-31, pi. 19: figs. 2-4, 6-8). DIAGNOSIS.—Large, often coarsely costate Cama- rotoechiinae with undivided hinge plate, conjunct deltidial plates, and a high, slender median septum in the brachial valve. NUMBER 21 2069 Leiorhynchoidea amygdaloidea, new species PLATE 548: FIGURES 19-38 Leiorhynchus bisulcatum R. E. King [not Shumard], 1931:105, pi. 33: figs. 1-8. L. weeksi nobilis R. E. King [not Girty], 1931:105, pi. 33: figs. 9-11. Small for genus, biconvex; outline transversely subelliptical to elongate oval; anterior commissure uniplicate, fold low, broadly arched, beginning 8- 10 mm anterior to brachial beak, profile gently convex, maximum convexity near beak, anterior half nearly straight; sulcus shallow, longitudinal convexity nearly uniform; costae low, crests rounded, beginning 3-6 mm anterior to beaks, numbering 3 on fold, 2 in sulcus, 3 or rarely 4 on flanks, strongest on fold and sulcus, low and obscure on flanks; costellae fine, converging toward crests of costae, increasing anteriorly in troughs. Concentric ornamentation absent; growth lines weak, widely spaced. Pedicle valve moderately convex longitudinally through sulcus, flatly convex transversely, with slight median longitudinal crest giving way ante- riorly to sulcus; beak curved, oblique to erect; beak ridges sharp, long, bordering long narrow lateral pseudointerareas partly covered by edge of brachial valve; delthyrium triangular, base covered or con- stricted by small, disjunct deltidial plates. Brachial valve nearly flat along fold, strongly convex trans- versely, 3 costae of fold extending farther back toward umbo than lateral costae. Pedicle valve interior with sides abruptly wid- ened anterior to deltidial plates; teeth small, elon- gate denticulate knobs, supported by slightly convergent dental plates reaching floor of valve, not fused to sides of valve; edges of valve anterior to hinge teeth with small flaps forming internal extensions of lateral pseudointerareas. Muscle area elongate triangular; adductor scars small, elongate, one on each side of median line, located anterior to ends of dental plates; diductors large, lobate, each beginning as narrow line near edge of dental plate, expanding slightly around small adductor scar, widening abruptly anterior to adductor, di- ductors meeting at median line. Brachial valve interior with undivided triangular hinge plate, medially notched, with small crural depression or cavity often filled with adventitious material; median septum high, thin, long, joined to small plates forming crural cavity; hinge sockets long, narrow, finely denticulate, bounded internally by socket ridges from hinge plate; crura long, flat, narrowly diverging from anterior of hinge plate, gently curved ventrally and expanding distally. Posterior adductor muscle scars long, narrow, closely adjacent to median septum on each side; anterior adductor scars not observed. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 706 148264a 7.3 6.6 7.4 2.8 90 148264b 14.4 13.2 13.7 9.2 90 148264c 18.0 16.6 16.0 11.5 100 USNM 706b 148268a 15.0 13.8 15.7 8.4 110 148268b 17.2 ? 19.8 ? 110 King 144 YPM 12552 18.9 17.4 18.0 11.1 95 (holotype) USNM 721p 148282 14.2 13.0 13.2 7.5 90 STRATIGRAPHIC OCCURRENCE.—Word Formation (China Tank, Willis Ranch members, and lens just above Willis Ranch Member). LOCALITIES.—China Tank: USNM 721p. Willis Ranch: USNM 706, 706e; King 144. Lens: USNM 706b. DIAGNOSIS.—Small Leiorhynchoidea with fairly strong costae and delicate interior structures. TYPES.—Holotype: YPM 12552. Figured para- types: USNM 148263a, 148265, 148268a, 148282. Measured paratypes: USNM 148264a-c; 148268a,b; 148282. Unfigured paratypes: USNM 148263b, 148268b. COMPARISON.—Leiorhynchoidea amygdaloidea is characterized by its relatively small size, narrow outline, strong convexity but nearly flat profile of the fold, strongly curved pedicle beak, normally 3 costae on the fold and 2 in the sulcus, and low rounded, weak costae on the flanks. It differs from L. schucherti Cloud in its flatter fold profile and correspondingly higher fold, 3 costae on the fold instead of 4, and its stronger costae on fold and sulcus and on the flanks. Its normally narrower outline and its costae distinguish L. amygdaloidea from L. laevis Cloud. It differs from L. cloudi Cooper in its smaller size, weaker and more rounded 2070 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY costae, lower convexity, and less strongly curved pedicle beak. It differs from L. scelesta, new species, in its smaller size, weaker, more rounded costae, narrower outline, weaker growth lines, greater con- vexity of both valves, and higher fold. Leiorhynchoidea rotundidorsa, new species PLATE 550: FIGURES 20-37 Average size for genus, moderately biconvex; out- line transversely and roundly elliptical; wider than long; maximum width at midvalve; anterior com- missure uniplicate; fold low, broadly arched, de- fined best at commissure beginning about slightly anterior to midvalve; profile evenly convex, with- out strongly convex umbonal area; sulcus shallow; costae low, beginning 3-5 mm anterior to beaks, crests rounded, numbering 3 or 4 on fold, 2 or 3 in sulcus, 4 or 5 on each flank. Concentric ornament absent; growth lines widely spaced over most of shell, more closely crowded and stronger toward anterior margins. Pedicle valve gently convex longitudinally and transversely; umbonal area with low, blunt median crest giving way anteriorly to sulcus near midvalve; beak moderately curved, normally oblique; beak ridges sharp, long bordering narrow anteriorly expanding lateral pseudointerareas; delthyrium triangular, wide, perforated at apex, base con- stricted or closed by disjunct small deltidial plates (?). Brachial valve moderately convex longitudi- nally, strongly convex transversely; edges of valve overlapping lateral pseudointerareas of pedicle valve. Pedicle valve interior with sides abruptly widen- ing anterior to deltidial plates, each side with small knoblike tooth; dental plates converging toward valve floor, diverging anteriorly, normally not fused to sides of valve. Muscle area small, sub- circular; adductor scars small, elongate, one on each side of median line; diductor scars beginning between edges of dental plates as narrow lines, widening anteriorly, surrounding adductor scars laterally and anteriorly. Brachial valve interior with short, wide grooved hinge plates; outer hinge plates small; inner hinge plates uniting with median septum to form nar- row groove; median septum high, strong, long, posterior end joining plates of crural cavity; crura with stout bases, but distal extremities broken; sockets elongate, narrow, finely denticulate, bounded internally by narrow socket ridges; muscle marks faint; posterior adductor scars long, narrow, out- wardly slightly bowed; anterior adductor scars not clearly observed, probably small, subcircular, as in other camarotoechiids. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 728 148285a 11.0 10.0 12.0 4.7 110 148285b 18.8 ? 22.7 } 120 (holotype) 148285c 5 16.0 21.0 8.5 ? 148285d 19.4 ? 21.6 ? 120 148285e ? 16.3 21.4 9.8 ? STRATIGRAPHIC OCCURRENCE.—Cherry Canyon For- mation (Getaway Member). LOCALITY.—USNM 728. DIAGNOSIS.—Leiorhynchoidea of medium size with strongly convex and swollen brachial valve and delicate cardinalia. TYPES.—Holotype: USNM 148285b. Figured par- atypes: USNM 148285a,c,d,f. Measured paratypes: USNM 148285a,c-e. Unfigured paratypes: USNM 148285e. COMPARISON.—Leiorhynchoidea rotundidorsa is characterized by its many low costae, transverse out- line, low fold, strongly and uniformly convex bra- chial valve, grooved hinge plate, and relatively large crural cavity. It differs from L. schucherti Cloud in its more strongly costate flanks and more transverse outline. Presence of costae distinguishes it from L. laevis Cloud; its larger size more numer- ous costae on fold and flanks, more transverse out- line, lower fold, fused dental plates, and slightly excavated umbonal area in the pedicle interior dis- tinguish it from L. mexicana (Cloud). It is smaller and less strongly costate than L. nobilis (Girty), L. cloudi Cooper, or L. scelesta, new species. In addition, its beak is less strongly curved, fold lower, and costae more numerous (although weak) than in L. cloudi, and it is much more strongly convex than L. scelesta. NUMBER 21 2071 Leiorhynchoidea scelesta, new species PLATE 549: FIGURES 1-28; PLATE 550: FIGURES 38-53 Unusually large for genus, flatly biconvex; out- line transversely subelliptical to bluntly trigonal, anterior commissure uniplicate; fold low, begin- ning about 10 mm anterior to brachial beak, profile nearly flat, height increasing only slightly ante- riorly, increase due to convexity of flanks; sulcus shallow; costae broad and angular, low, except at margins of large adults, beginning 3-5 mm ante- rior to brachial beak, 5-7 mm anterior to pedicle beak, numbering 3 on fold, 2 in sulcus, 3-5 on each flank; costellae very fine, crowded, converging toward crests of costae. Concentric ornamentation absent; growth lines inconspicuous and widely spaced over most of shell, strong and closely crowded near anterior margins. Pedicle valve moderately convex longitudinally and nearly flat to slightly concave transversely; um- bonal area with blunt longitudinal crest, giving way anteriorly to sulcus, slightly posterior to mid- valve; beak short, blunt, strongly curved, oblique to erect; delthyrium wide, triangular, apex may perforate beak, base closed or constricted by small, conjunct deltidial plates; beak ridges moderately sharp, well marked, bordering long narrow lateral pseudointerareas. Brachial valve flatly convex longi- tudinally, slightly more strongly convex trans- versely; posterior lateral edges of valve slightly overlapping lateral pseudointerareas of pedicle valve; apex of valve within pedicle valve, covered by deltidial plates. Pedicle valve interior with sides of delthyrium abruptly widening, teeth small and narrow; sup- ported by short convergent dental plates reaching valve floor but not meeting, not fused to sides of valve in young but obsolete in old specimens. Muscle area elongate, bluntly subtrigonal; adduc- tors elongate, median, extending about three-fourths of muscle area, along median line; diductor scars lateral to adductors, anteriorly widening, meeting at median line anterior to adductors. Brachial valve interior with large, triangular un- divided hinge plate, with shallow crural cavity usually filled with adventitious material; hinge sockets narrow, elongate, strongly corrugated, me- dian septum high, thin, base may be thickened near posterior end, edge meeting convergent plates of crural cavity. Muscle pattern not clearly ob- served, apparently camarotoechiid, with greatly elongate, narrow, outwardly bowed posterior ad- ductor scars, one on each side of septum, meeting small, subcircular anterior adductor scars near middle of valve. MEASUREMENTS (in mm).— brachial apical valve thick- angle USNM 715i length length width ness C) 148277 20.4 18.7 22.3 8.8 90 148276a 20.2 18.4 23.7 8.3 110 148276b USNM 719z 33.7 29.6 36.1 16.0 110 152882a 38.4 36.0 48.4 14.0 115 152882b 33.7 35.2 40.2 15.6 110 152882c 30.3 22.7 33.7 13.0 110 152882d 25.1 22.2 30.3 9.0 110 (holotype) 152882e 22.3 19.5 22.5 9.7 110 STRATIGRAPHIC OCCURRENCE.—Word Formation (Appel Ranch Member); Cherry Canyon Formation (Getaway Member). LOCALITIES.—Appel Ranch: USNM 715i, 719z, 722t, 727j, 731z. Getaway: AMNH 496, 512, 600; USNM 728, 730. DIAGNOSIS.—Unusually large Leiorhynchoidea with broad angular costae. TYPES.—Holotype: USNM I52882d. Figured par- atypes: USNM 148276a,c; 152882a-h,k,l,o-q,t,w; 15491 la,b. Measured paratypes: USNM 148276a,b, 148277, 152882a-c,e. Unfigured paratypes: USNM 148276b, 152882i,j,m,n,r,s,u,v. COMPARISON.—Leiorhynchoidea scelesta is charac- terized by its broad costae, strongly curved pedicle beak, undivided hinge plate with shallow crural cavity commonly filled, and its strong, high median septum. It differs from L. laevis Cloud and L. schu- cherti Cloud in its much stronger costae that are present on the flanks as well as on the fold and sulcus. Internally the muscle patterns of all three species appear to be similar, but it is not certainly known whether the hinge sockets of L. scelesta are denticulate as in L. laevis and L. schucherti. L. sce- lesta differs from L. mexicana (Cloud) in its larger size, wider, more elliptical outline, less strongly curved pedicle beak, much lower convexity, and lower fold. Leiorhynchoidea cloudi Cooper from the Monos Formation of Sonora, Mexico, is a similar appear- 2072 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY ing, nearly completely costate species but is much smaller, with costae less broad and less angular, and much thicker in youthful forms, than L. scelesta. Pugnax weeksi nobilis Girty is the same type of shell as our L. scelesta but it is a much smaller species, with strong rounded ribs rather than angu- lar ones as in the Word species. DISCUSSION.—Fragmentary specimens of a Leio- rhynchoidea from AMNH 512 ( = USNM 728) are referred to this species tentatively. Only the poste- rior part is preserved, but this indicates a species with strong costae that begin near the beaks on both valves. The apical angle of the pedicle valves is 120°, suggesting that the species was large. No complete adult specimens appear in the collection, consequently a closer comparison or a positive identification cannot be made. Leiorhynchoidea sulcata, new species PLATE 504: FIGURES 34-36; PLATE 550: FIGURES 1-7 Medium size for genus; roundly subpentagonal in outline, maximum width near midvalve; sides somewhat narrowly rounded; anterior margin trun- cated; valves of unequal depth, brachial valve deeper; anterior commissure strongly uniplicate; apical angle varying between 100° and 120°. Sur- face variable, costae originating on umbo and ex- tending to anterior margin; 1-3 costae in sulcus and 3 or 4 on the fold; flanks varying from smooth to having occasional indistinct costae. Pedicle valve moderately convex in lateral pro- file, broadly and gently convex in anterior profile, middle slightly depressed; beak small, closely ap- pressed to dorsal umbo; sulcus originating at umbo and deepening anteriorly to form long subacumi- nate tongue; flanks flattened but with gentle slopes. Brachial valve moderately convex in lateral pro- file but strongly domed and with steep sides in anterior profile. Fold originating between umbo and midvalve, low, not strongly defined anteriorly but forming deep slightly angulated reentrant. Flanks moderately swollen. Interior not seen. STRATIGRAPHIC OCCURRENCE.—Cherry Canyon For- mation (South Wells Member). LOCALITIES—AMNH 414; USGS 7641, 7649. DIAGNOSIS.—Anteriorly deeply sulcate Leiorhyn- choidea. MEASUREMENTS (in mm).— brachial apical valve thick- angle, length length width ness (°) AMNH 414 155054 20.0 18.4 21.4 14.0 109 (holotype) USGS 7649 155056a 19.1 17.3 21.9 13.6 116 155056b 20.0 17.8 19.1 13.6 112 155056c 18.7 16.9 21.0 13.4 114 155056e 16.9 15.5 18.4 10.5 108 155056g 11.7 10.7 12.8 5.7 123 TYPES.—Holotype: USNM 155054. Figured par- atypes: USNM 154619b, 155056b. Unfigured para- types: USNM 155056a,c-g. Measured paratypes: USNM 155056a-c,e,g. COMPARISON.—This species is most like L. schu- cherti Cloud from the Permian at Las Delicias, Mexico, but is smaller, more deeply sulcate at the anterior, and with a longer, more carinate tongue. It is a more pentagonal, more deeply sulcate, and differently proportioned species than L. amygdaloi- dea, new species, from the Glass Mountains. Leiorhynchoidea sulcata is common in parts of the South Wells Member, where it occurs with Paranorella Cloud and Glossothyropsis Girty. Leio- rhynchoidea is associated with Paranorella in the black nodules and shales of the Permian in Las Delicias. Leiorhynchoidea species unidentified PLATE 520: FICURES 19-22 Specimens of Leiorhynchoidea are extremely rare in the residues from the Glass Mountains and Sierra Diablo partly because they are not abundant but also because they are extremely fragile. If the shells have survived the rigors of transport and burial they may not withstand the still harsher treatment received in the acid tubs. Some of the specimens are extremely thin-shelled, a few so thin that they are translucent. Specimens are listed below by formation. BONE SPRING FORMATION (Plate 520: figures 19- 22).-—From the lower Bone Spring in the Sierra Diablo, 4 specimens have been taken, 2 pedicle valves and 2 brachial valves, each from a different locality. The specimens, however, suggest the same species. The larger pedicle valve is 15 mm long by NUMBER 21 2073 16.7 mm wide, and has a short beak, strongly rounded sides, and small delthyrium. On the exte- rior, the posterior half is smooth; the sulcus orig- inates not far anterior to midvalve and is broad and shallow but is produced into a long tongue. The sulcus is marked by 4 costae. The dental plates are short and delicate. The brachial valve is small and delicate, with a low fold that posteriorly becomes a shallow, narrow sulcus extending to the umbonal region, similar in some respects to L. mexicana (Cloud). The hinge plates are fairly wide, the crura narrow and thin at their bases but not preserved in entirety. The outer hinge plates are wider than usual but the median groove is completely filled and only a trace of it is left. The median septum is long and delicate. Pedicle valve USNM 152883 comes from USNM 728e and USNM 152867 from 728f; the brachial valves were taken at USNM 728h (USNM 152868) and AMNH 632. Figured specimens: USNM 152867, 152868. GAPTANK FORMATION.—One crushed pedicle valve from USNM 701 p. ROAD CANYON FORMATION.—All the specimens from this formation are very fragmentary and it is impossible to get a good idea of the exterior of the species. In most of the pedicle valves the dental plates are fused to the valve wall and in some specimens are obsolete. The muscle region is tri- angular. The exterior is smooth. The one brachial valve has a thick median septum solidly fused with the hinge plate but still exhibiting the median groove. The crura are thick and rounded. Two localities are represented; USNM 720d and 721j. Described specimens: USNM 152870, 152869. WORD FORMATION (CHINA TANK MEMBER).—A single fragment (USNM 148269) of a pedicle valve was found at USNM 706c. WORD FORMATION (WILLIS RANCH MEMBER).—A single fragment of a pedicle valve (USNM 148279a) and one dorsal valve (USNM 148279b) were taken from USNM 706e. No dental plates appear in the fragment of pedicle valve. The ornament of the brachial valve is most un- usual because the posterior half which is fairly convex and swollen is marked by numerous narrow costae, but the fold originates near midvalve and is marked by 4 thick angular costae, and the flanks by a few large costae. All costae are a sudden expansion in size and angularity of the finer costae of the posterior, the change taking place at mid- valve. The specimen is 23 mm long and somewhat wider at midvalve. PARANORELLINAE, new subfamily Smooth, sulcate Camarotoechiidae. Genus in West Texas: Paranorella Cloud. This is an excessively rare shell but it has been found in many of the formations. A trace of it was found in the Sierra Diablo at the base of the Bone Spring Formation and in equivalent beds of the Skinner Ranch Formation in the Glass Mountains. In the latter area it was also seen in the Cathedral Mountain (lower) and Road Canyon formations. In the Word Formation it was found in the China Tank and Willis Ranch members and in the lens between the latter and the Appel Ranch Member (USNM 706b). In the Guadalupe Mountains only two specimens were taken from the Getaway Member of the Cherry Canyon Formation. It is fairly common in the black limestone of the South Wells Member of the Cherry Canyon Formation, but is not well pre- served. It occurs in Permian black limestone and shale at Las Delicias, Coahuila, Mexico. Genus Paranorella Cloud, 1944 Paranorella Cloud 1944:59.—Williams et al., 1965: H 582. This is a poorly known genus which, for a time, had not been found outside of Mexico. It is now known from the Guadalupe and Glass Mountains but in both places it is extremely rare. Several speci- mens preserving the interior confirm Cloud's view (1944:60) that this peculiar genus is similar inter- nally to Leiorhynchus and Camarotoechia (sensu Sartenaer, 1961b). The feature that gives Paranorella its distinctive character is the reversed fold and sulcus from that usual in the rhynchonellids. In Paranorella the pedicle valve is the larger, more bulbous, and has an anterior median fold. The brachial valve is shal- lower, but convex, and bears a fairly strong median sulcus. Paranorella is thus like some other genera that have this reversal of fold and sulcus such as the Triassic rhynchonellid Norella, the Mississip- pian rhynchonellid Sanjuania, the Permian stenos- 2074 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY cismatacean Camarophorina, and the Recent rhyn- chonellid Neorhynchia. The last is very thin-shelled and is a deep-water species. The pedicle valve interior of Paranorella has receding dental plates that are often rendered obso- lete by filling in of the umbonal cavities. As in Leiorhynchoidea the teeth are small for so large a shell. The pedicle valves of all available specimens are too badly damaged to determine the nature of the deltidial plates, if any. The muscle field is small and oval with the diductor scars surrounding nearly central adductor scars. The interior of the brachial valve of Paranorella has a deeply notched undivided hinge plate which has strong socket ridges bounding corrugated sock- ets. The outer hinge plates are much reduced but the crural bases are stout. Their keels unite with the median septum which is strong and thick, to form a narrow V-shaped chamber that is not closed by adventitious shell in any of the specimens. Crura thickened, mucrifer?. The adductor field is small and is located near midvalve and is divided by the median septum. Paranorella has a fairly long range as indicated by spasmodically occurring isolated valves of great rarity. It occurs in the Poplar Tank Member of the Skinner Ranch Formation and in the Road Canyon Formation below the Word. It is more common in the Word Formation where it has been taken from the China Tank and Willis Ranch members. In the Sierra Diablo and Guadalupe Mountains it is known from the Bone Spring Formation at USNM 728f, the Getaway Member of the Cherry Canyon Formation at AMNH 600, and the South Wells Member at AMNH 414. TYPE-SPECIES.—Paranorella imperialis Cloud (1944:60, pi. 19: figs. 5, 9-16, 20). Paranorella aquilonia, new species PLATE 551: FICURES 6-12 Large but average size for genus, moderately bi- convex; outline subelliptical, widest slightly ante- rior to midline; anterior commissure broadly sul- cate, fold low, weak, beginning about 15 mm ante- rior to pedicle beak, profile of fold flatly convex; greatest convexity of valve posterior to fold; bra- chial valve with shallow sulcus originating at mid- valve; costation absent; growth lines irregularly spaced, stronger, and more closely crowded near anterior margins; growth lamellae strong and dis- tant. Pedicle valve moderately convex longitudinally and transversely; beak blunt, suberect; apex per- forated by foramen; delthyrium small, open, with- out deltidial plates; beak ridges blunt, inconspicu- ous, nearly coincident with valve edge. Brachial valve gently convex in anterior and lateral profiles, slightly inflated near umbo. Pedicle valve interior with sides of delthyrium widely diverging; each with one large knoblike, weakly corrugated hinge tooth, elongated; dental plates supporting hinge teeth, widely divergent anteriorly and dorsally, firmly fused to sides of valve or partly buried. Muscle area cordate, small; adductor scars small, elongate, forming subelliptical mark along median line; diductor scars larger, sur- rounding adductor mark and forming two lobes anteriorly, narrowed to fine lines posteriorly; pos- terior part of muscle area bisected by low, rounded myophragm. Brachial valve interior with small, deeply di- vided hinge plate, reduced to two rounded, ante- riorly projecting crural bases; sockets narrow, deep, elongate, corrugated, formed between edge of shell and thick, high, curved socket ridges; crura diverg- ing anteriorly, length and shape unknown; median septum low, short, thickened posteriorly, joining plates of narrow crural cavity beneath notch in hinge plate. Adductor field elongate oval; scars long, narrow, distally bowed, one on each side of median septum, converging on midline of valve anterior to end of septum; posterior and anterior adductor scars probably continuous with one another. MEASUREMENTS (in mm).—From locality AMNH 600 specimen 148296 (holotype) and from AMNH 347, 148298 (paratype), respectively: length 25.0, (?); brachial valve length 23.6, 24.7; width 28.0, 27.6; thickness 10.5, 6.4; apical angle 115°, (?). STRATIGRAPHIC OCCURRENCE.—Cherry Canyon For- mation (Getaway Member); Bell Canyon Forma- tion (Lamar Member). LOCALITIES.—Getaway: AMNH 600. Lamar: AMNH 347( = L-2). DIAGNOSIS.—Paranorella of average size having a broad shallow sulcus originating at midvalve. TYPES.—Holotype: USNM 148296. Figured and measured paratype: USNM 148298. NUMBER 21 2075 COMPARISON.—Paranorella aquilonia is character- ized by its shallow valves, low, noncostate fold and sulcus, median septum without any knob on the crest, nonraised dorsal muscle area with posterior and anterior adductor scars not distinctly discon- tinuous. These features distinguish it from P. comp- tula, new species, which occurs in the Word For- mation (China Tank Member). This species is distinguished from P. imperialis Cloud by its lesser convexity and shallower sulcus that does not extend past midvalve as it does so conspicuously in the Mexican species. It also has a less prolonged beak and much less swollen median region on the pedicle valve than the Mexican species. It also differs from Paranorella species 1 from the Glass Mountains in having a smaller size, shorter, narrower median septum in the brachial valve, and in not having the conspicuous sulcus in the median and posterior parts of the pedicle valve. Paranorella comptula, new species PLATE 551: FIGURES 13-18 Average size for genus, flatly biconvex; outline transversely subelliptical, widest near midline; ante- rior commissure broadly and shallowly sulcate; fold low, beginning far forward about 20 mm anterior to pedicle beak, profile nearly flat; sulcus shallow; costae low, weak, rounded, present only on fold and sulcus, numbering about 5 or 6 on fold, one less in sulcus; growth lines faint, most closely spaced near anterior margins. Pedicle valve most strongly convex in umbonal region; beak blunt, oblique to erect, apex perfo- rated by foramen; delthyrium small, open, without deltidial plates; beak ridges absent. Brachial valve nearly flat except for slight swelling of umbonal area. Pedicle valve interior with wide delthyrium, teeth knoblike, elongate, supported by dental plates, tightly fused to sides of valve, or buried in adventitious shell. Muscle area lobate; adductor scars small, elongate, lying along median line, to- gether forming elliptical mark; diductor scars larger, beginning near edges of dental plates, sur- rounding adductor marks, greatly widening ante- riorly, meeting at median line forward of adductor scars; posterior part of muscle bisected by low, faint median ridge. Brachial valve interior with small, deeply divided hinge plate, reduced to a pair of anteriorly pro- jecting crural bases and a part of high socket ridges; sockets deep, elongate, anteriorly widening, faintly corrugated; crura diverging anteriorly, length and anterior course unknown; median sep- tum moderately high, thickened along base and at posterior end, joining plates of crural cavity be- neath median notch of hinge plate; small knob projecting from crest of septum near posterior end of muscle area which is greatly elongated, subellip- tical, slightly thickened and with edges somewhat raised; posterior adductor scars elongate, one on each side of median septum; anterior adductor scars somewhat larger, more nearly circular. MEASUREMENTS (in mm).—Specimen USNM 148293 (holotype): length 28.0, brachial valve length 27.0, width 33.2, thickness (crushed), apical angle 127°. STRATIGRAPHIC OCCURRENCE.—Word Formation (China Tank Member). LOCALITY.—USNM 706c. DIAGNOSIS.—Paranorella with anterior end of fold and sulcus costate. TYPES.—Holotype: USNM 148293. Figured para- types: USNM 148292a,b,c. COMPARISON.—Paranorella comptula is character- ized by its relatively flat shell, elliptical outline widest at the midline, costate fold and sulcus, non- indented pedicle umbonal area, small hinge teeth, moderately high median septum with a small boss on the crest, raised edges of the brachial muscle area, and fairly large posterior adductor muscle marks. It differs from P imperialis Cloud (1944) in most of these features, but most conspicuously in the lower convexity, costation of fold and sulcus, and raised edges of the brachial muscle area. The little knob on the crest of the septum is at the posterior end of the muscle area and probably is part of its raised edge. Paranorella imperialis Cloud PLATE 551: FIGURES 1-5 Paranorella imperialis Cloud, 1944:60, pi. 19: figs. 5, 9-16, 20. Illustrations of Paranorella imperialis Cloud have been introduced for comparison with the mostly fragmentary specimens from the Glass Mountains. TYPES.—Figured specimen: USNM 148295a. 2076 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY Paranorella species 1 PLATE 551: FIGURES 19-30 Large for genus, wider than long, roundly ellip- tical outline; sides broadly rounded; anterior mar- gin truncated. Anterior commissure broadly sulcate; beak short, suberect; delthyrium open. Surface marked by concentric lamellae of growth, distantly placed; no costae. Pedicle valve fairly evenly and gently convex in lateral profile; broadly domed in anterior profile; umbonal region swollen; median region moder- ately inflated and usually marked by shallow sul- cus. Fold low and inconspicuous usually marked only at anterior. Flanks generally inflated. Brachial valve known only from incomplete speci- mens, flatly convex, sulcus confined to anterior part. Pedicle valve interior with elongated teeth lo- cated just inside lateral margin and supported by short, insignificant dental plates lying against valve wall with very narrow cavities. Muscle field unusu- ally small for large shell, somewhat cordate with narrow tear-shaped diductor scars wrapping around central elongate, elliptical adductor field. Brachial valve interior with narrow sockets bounded by short socket ridges; outer hinge plates small, attaching stout crural bases to socket ridges. Crura rounded in section, moderately stout and bounding small apical chamber. No inner hinge plates. Median ridge stout proximally, tapering an- teriorly and dying out before midvalve but forming low myophragm that divides the posteriorly sit- uated, elongated elliptical adductor patch. MEASUREMENTS (in mm).—From locality USNM 706b specimens 148290a and b, respectively: length 26.6, 28.6; brachial valve length (?); width 26.0, 32.8; thickness 9.6, 9.8; apical angle 110°, 120°. STRATIGRAPHIC OCCURRENCE.—Word Formation (Willis Ranch Member; lens between Willis Ranch and Appel Ranch members). LOCALITIES.—Willis Ranch: USNM 706e, lens: USNM 706b. DIAGNOSIS.—Large Paranorella with shallow sul- cus on pedicle valve in addition to fold. TYPES.—Figured specimens: USNM 148290a-c, 148297, 154912a-c. COMPARISON.—The few specimens of this species indicate the largest species known, but one that was probably not so robust as P. imperialis Cloud from Mexico. The most distinctive feature of the species is the sulcus on the pedicle valve, but indi- cations point to the sulcus having been wide and the fold low and inconspicuous. Unfortunately no good brachial valves have yet been taken of this very rare fossil. DISCUSSION.—The muscle field of the pedicle valve seems unusually small for such a large shell. It is only 9 mm wide in the largest specimen and has a length of about 8 mm. The cardinalia of the brachial valve appear to have been correspondingly small but no complete specimens are known. Paranorella species 2 PLATE 510: FIGURES 13-20; PLATE 551: FIGURES 31-34, 47 Another species besides those suggested herein and P. imperialis Cloud is indicated by several fragmentary specimens from the Sierra Diablo and one from the Glass Mountains. This may be re- garded as average for the genus. It is subcircular in outline, with the pedicle valve fairly convex in lateral profile and moderately convex in anterior profile. The fold and sulcus are not strongly marked and are not costate. Inside the pedicle valve the teeth are small and the dental plates are readily visible and have nar- row but fairly strong umbonal cavities. The muscle field is strongly impressed, elongate oval in outline and small for the size of the shell. The brachial valve interior is represented only by small parts of the posterior end, but they show delicate structures. The socket ridges are strong; outer hinge plates are narrow and recessed, and the crural bases are stout and slender but none of the specimens has complete crura. The median septum is long, low, and stout and extends to about midvalve and divides the adductor field, which is located at about midvalve and is small. STRATIGRAPHIC OCCURRENCE.—Bone Spring For- mation (lower); Skinner Ranch Formation (Poplar Tank Member, lower). LOCALITIES.—Bone Spring; USNM 728f. Poplar Tank: USNM 729f. DIAGNOSIS.—Medium-sized Paranorella with nar- row, elongate, small muscle area in the pedicle valve. TYPES.—Figured specimens: USNM I54690a-c; 152874a,c,d; 152875. DISCUSSION.—This is a very rare species of which NUMBER 21 2077 only fragmentary specimens have been taken from the Bone Spring Formation. Not enough specimens have been found to give a proper idea of the exte- rior of the species, although the interior with its elongate muscle field in the pedicle valve and the long median septum and median adductor field in the brachial valve are fairly distinctive. The single brachial valve known from the Glass Mountains has features such as the long septum and size that suggest relationship to the Sierra Diablo speci- mens. The association is tentative. Paranorella species 3 A single specimen of a fine pedicle valve measur- ing 11.5 mm long by 12.5 mm wide indicates a new species or a young individual, possibly of P. aqui- lonia, new species, from the Cherry Canyon Forma- tion (Getaway Member) at AMNH 512. TYPES.—Described specimen: USNM 155053. Paranorella species 4 PLATE 183: FIGURES 18-21 (in volume 2) The lots on which this description is based con- sist of the two figured specimens and another lot of five fragments of the posterior showing cardi- nalia and dental plates. The largest specimen (USNM 153565a) is a pedicle valve, subpentagonal in outline with rounded anterolateral extremities but a truncated anterior. It is fairly strongly con- vex in both profiles but the medial region is mod- erately swollen. There is no marked fold, but the anterior margin has a broad wave toward the ven- tral side that would have accommodated a small tongue from the opposite valve. On the inside the dental plates are short and inconspicuous and the muscle field is very small for such a large shell. The brachial valve (USNM 153565b) is fragmen- tary but it shows the presence of a sulcus originat- ing near midvalve. The median ridge is thick and the notothyrial cavity is a slit between the crural bases. One of the fragmentary specimens in lot USNM 152873 has a thick socket ridge but a nar- row, rounded crural base. In a still younger speci- men the outer hinge plate is visible and there is evidence of a small V-shaped chamber. STRATIGRAPHIC OCCURRENCE.—Cathedral Moun- tain Formation. LOCALITY.—USNM 721u. TYPE:.—Figured specimens: USNM I53565a,b. Paranorella species 5 PLATE 504: FIGURES 55-60 This lot consists of seven specimens, all frag- mentary, four of them adult but the others juvenile. The two largest and most complete specimens are in matrix and the details of the exterior cannot be seen. The pedicle valve is deep and appears to be somewhat swollen on the exterior. The fold is not clearly discernible. The dental plates are plastered against the inner wall of the shell with the merest slit between them and the wall. The brachial valve is less deep and shows evidence of an anterior tongue. The median septum is thin and delicate and forms an obscure shallow V-shaped chamber. The socket ridges are rounded and slender and separated by a deep indentation from the crural bases, which are rounded and delicate for such a large shell and which unite at their proximal ex- tremity. The interior is unlike any other species except Paranorella species 2. Two pedicle valves from USNM 72lj (USNM 152871) and five pedicle valves from USNM 732j (USNM 155055) are also referred here, but they are not well preserved. STRATIGRAPHIC OCCURRENCE.—Road Canyon For- mation. LOCALITIES.—USNM 72lj, 726d, 732j. TYPES.—Figured specimens: USNM 152872a-e. Paranorella species 6 PLATE 510: FICURES 21-26 Three very poorly preserved valves, two pedicle and one brachial valve, indicate the presence of a species in the Skinner Ranch Formation (Dugout Mountain Member, at USNM 732e). The pedicle valves are moderately convex but the brachial valve seems more convex than usual. The cardinalia are incomplete, with only the outer hinge plates re- vealed. TYPES.—Figured specimens: USNM 154689a,b. TROPHISININAE, new subfamily Camarotoechiinae with finely costellate shells. 2078 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY Genera in West Texas: Trophisina, new genus. This very rare genus is known only from the lower Cathedral Mountain Formation in the vicin- ity of Split Tank. Trophisina, new genus [Greek trophis (well fed)] Small to medium size, strongly biconvex in pro- file, subcircular to longitudinally suboval in out- line. Valves unequal in depth, brachial valve deeper; sides rounded, greatest width near midvalve; ante- rior commissure uniplicate, folding usually best defined at anterior. Beak suberect; foramen large, elongate oval; deltidial plates small and disjunct. Dorsal umbo swollen. Surface multicostellate. Pedicle valve interior with small teeth supported by strong convergent dental plates; muscle field lightly impressed, elongate rectangular in outline; adductor scars medial, posterior; diductors sub- flabellate. Brachial valve interior with divided hinge plate in young but with complete, undivided hinge plate in adults; sockets defined by concave socket plates; inner socket ridge strongly overhanging sockets; outer hinge plates broad; crural bases narrow and forming keels along dorsal edge of crura; crura mucrifer, moderately long and curved toward ven- tral valve; inner hinge plates uniting medially along median suture line, outer edge attached to the sloping edge of outer hinge plate. Median sep- tum very short, attached to midline of inner hinge plates and extended anteriorly to midvalve or beyond as threadlike elevated line. TYPE-SPECIES.—Trophisina fenaria, new species. DIAGNOSIS.—Strongly biconvex and rotund rhyn- chonellids having disjunct deltidial plates, multi- costellate exterior, and undivided hinge plate in the adult supported by a very short median septum. COMPARISON.—Costellate rhynchonellids are suf- ficiently rare that comparison of Trophisina is not difficult. Trophisina may be confused with three genera— Strigirhynchia Cooper and Grant, and Lirellaria and Chaeniorhynchus, both new. Strigirhynchia is generally much larger and has a long, thin, and high median septum that contrasts with the short one in Trophisina. Its dental plates in adults tend to fuse with the sides of the valve and it has a deeply concave umbonal region on the brachial valve. This is one of the most conspicuous fea- tures of Strigirhynchia, which is not shared by Trophisina. Lirellaria is not difficult to separate from Tro- phisina because it has no median septum in the brachial valve and has small, but conjunct deltidial plates in the pedicle valve. Chaeniorhynchus is like Trophisina because its exterior is very similar, although it usually is more strongly ornamented and has no trace of deltidial plates as presently known. Inside the brachial valve the hinge plate is undivided and is supported by a long, strong median septum, whereas in Trophisina the hinge plate becomes a solid piece only in the older adults, and the median septum is usually short and stout and, in some specimens, much reduced. DISCUSSION.—Costellate rhynchonellids are rare in all eras and especially so in the Paleozoic. The general aspect of this unusual genus suggests Hypo- thyridina of the Devonian in the rotundity of the valves and the strongly convex profiles. They are, however, not flattened anteriorly, as are species of Hypothyridina, and they have a median septum, which is lacking from the Devonian genus. Tro- phisina is thus a very distinctve shell in the Permian and one that is recognized readily. The costellae are variable, in some specimens being fairly narrow but in others approaching costae in width, espe- cially in the fold and sulcus. The costellae increase by bifurcation and intercalation. The adult is not flattened in the umbonal region of the brachial valve as in Ptilotorhynchus, another costellate new genus from the Guadalupe Mountains. A fair abundance of specimens of all sizes per- mits a view of the shell development from speci- mens about 1.5 mm long to fully grown adults. In the youngest stages the pedicle valve is the deeper and is nearly flat, with a long beak that is inclined ventrally. The brachial valve is flat in profile except for the umbonal region, and is marked me- dially by a sulcus. This valve is less deep than the pedicle valve. The valves become about equal in depth when a length of 7.5 mm is attained. After that the brachial valve in the larger specimens becomes slightly to markedly deeper than the pedicle valve. The smallest specimens are smooth in the posterior half or more and have costellae developed at the margin only. The beak attitude NUMBER 21 2079 changes from fairly strongly ventrad (apsacline) to suberect (anacline). At 4-5 mm from the beak, the sulcus of the brachial valve flattens, and usually cannot be detected in an adult. The reversion of the anterior commissure from a broadly sulcate condition in the young to uniplicate in the adult is gradual. Specimens about 7 mm long are usually rectimarginate or nearly so. The delthyrium of the youngest specimens is elongate triangular and its margin is unmodified. At a length of approximately 2 mm the margin of the delthyrium is thickened by addition of small deltidial plates, thickest and widest along the basal part of the delthyrium. In somewhat larger speci- mens these have a rounded, concave margin against the pedicle. These deltidial plates are fairly con- spicuous in young and youthful individuals; in fully grown adults they are wider and have a flat surface, but never unite. The interior of the pedicle valve does not exhibit the muscle region well because of the unusual deli- cacy of the shell. The teeth are small and narrow, but fairly protrusive. They lie oblique to the me- dian line of the valve, with a northwest-southeast slant essentially parallel to the shell margin. The posterior side of the tooth bears a small notch. The dental plates are stout and have fairly deep um- bonal chambers setting them off from the valve wall. They are somewhat receding in a posteroven- tral direction and are moderately convergent ven- trally but remain well separated. The muscle area is not well impressed and lies anterior to the del- thyrial cavity. It is trapezoidal in outline but the individual scars cannot be resolved. Interior details of the brachial valve, especially the hinge plate, are variable in the adult. The smallest brachial valve interior is 1.5 mm in length. Its crura are closely tied to the strong elevated socket ridges, and descend to the valve floor with a slight anterior excavation beneath. A strong, thick, median ridge formed by the sulcus of the exterior divides the narrow but deep pits of the adductor scars. Essentially the same arrangement appears in specimens 2.5 mm long, but in these the inner hinge plates are concave and are supported by the median ridge, at this stage somewhat narrowed. In succeeding stages up to 5 mm long the inner hinge plates in their forward growth tend to flatten and the median ridge becomes a slender but short septum supporting them. A chamber is not devel- oped, but the median line of attachment of inner hinge plates and median septum is usually de- pressed and forms a narrow groove. The socket ridges are strong plates throughout the development of the cardinalia and strongly overhang the sockets, locking into the grooves on the outer faces of the teeth. The socket is floored by a curved fulcral plate that grows obliquely forward with advancing age. This appears to be corrugated in some adults, but it is not possible to make certain of this feature in all specimens. In adults the fulcral plate is deep and moderately thick. Outer hinge plates between the socket and the crus appear not to exist in the very young but can be detected at a length of 5 mm. These become more prominent with advancing age. The crus of the young is a simple blade, with its inner edge approximately parallel to the median line of the shell. With advancing age the crus is much elon- gated, becomes fairly deeply curved with the con- cavity toward the pedicle valve. The crus is con- cave in cross section, the concavity facing medially. It is strongly keeled on the dorsal side, the keel extending under the hinge plate to form the crural base. The distal end of the crus is oblique, with a sharp point on the ventrad end. The crus thus proves to be of the mucrifer type. As indicated above, the median ridge in septal development goes from a broad ridge in the young- est specimens, to a short septum and ridge, finally to a very short septum. The length and develop- ment of the septum in the adult are variable. In some specimens the septum extends from inner hinge plate to valve floor but is confined to the apex. This kind of septum is usually extended anteriorly as a fine elevated thread to the adductor field or beyond. In some specimens, however, no septum supports the hinge plate. In these the sep- tum has probably been resorbed or may not have been well silicified. In old specimens the adductor scars are narrow, deeply entrenched, separated by a median thread or secondary ridge (myophragm) and are arranged in anterior and posterior pairs, the former slightly the longer and the latter slightly oblique and out- side the former. 2080 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY Trophisina fenaria, new species PLATE 506: FIGURES 1-42 Average size for rhynchonellids, juveniles flatly biconvex, adults globose; outline tear-shaped to nearly circular, sides diverging between 70° and 110°; commissure uniplicate, fold low, indistinct except at commissure; sulcus shallow but extending forward as moderately long broad tongue, flat on top. Costae fine, low, rounded, beginning at beaks, number increasing anteriorly by bifurcation, num- bering 15-45 along anterior margins, averaging about 30. Concentric striae absent; growth lines weak, normally visible only near anterior margins. Pedicle valve nearly flat in juvenile, strongly con- vex in adults; beak sharp, straight to nearly erect; delthyrium wide, triangular, sides narrowed by rudimentary, disjunct deltidial plates that tend to coverge only in largest shells; lateral pseudointer- areas absent: no overlap of valves. Brachial valve strongly convex transversely, mod- erately convex along crest of fold; beak bluntly pointed, slightly curved into pedicle valve. Interior as described for genus. MEASUREMENTS (in mm).— brachial apical valve mid- thick- angle length length width width ness (°) USNM 703b 148236a 1.9 1.5 1.7 1.7 0.8 p 148236b 2.7 2.1 2.1 2.1 1.0 88 148236c 3.2 2.8 2.8 2.8 1.1 94 148236d 3.7 3.0 3.0 3.0 1.5 97 148236e 4.8 4.0 3.7 4.0 1.8 80 148236f 5.8 5.0 4.7 4.9 2.1 78 148236g 6.7 5.6 5.5 5.8 3.0 78 148236h 8.2 7.2 7.3 7.4 5.5 93 148236i 8.9 7.9 8.0 8.0 6.9 95 USNM 702un 148224a 7.6 6.6 6.9 6.9 4.7 90 148224b 10.5 9.2 8.6 8.6 7.9 89 USNM 702-low 148242a 9.0 8.2 8.3 8.4 8.0 98 USNM 702 148231 9.6 8.3 9.0 9.0 8.6 94 USNM 702un 148225 10.0 8.8 9.6 9.6 8.4 88 (holotype) STRATIGRAPHIC OCCURRENCE.—Cathedral Moun- tain Formation. (Institella-Torynechus Zone). LOCALITIES.—AMNH 500B; USNM 702, 702-low, 702un, 703b, 735b. TYPES.—Holotype: USNM 148225. Figured para- types: USNM 148224a; 148236f,g,i-q,s,t; 148238a-f; 148242a,b; 154640a-o. Measured paratypes; USNM 148224a,b; 148231; 148236a-i; 148242a. Unfigured paratypes: USNM 148224b; 148236a-e,h,r. DIAGNOSIS.—Globular rhynchonellacea with co- stellate exterior, short median septum, and with the adult hinge plate undivided. COMPARISON.—Trophisina fenaria is characterized by its flat juveniles and globose adults, its low, flat-topped fold usually expressed only at the line of commissure and rarely posteriorly on the shell, its rudimentary disjunct deltidial plates that begin to constrict base of delthyrium only in largest adults, its large, normally not divided but deeply notched adult hinge plate, and especially by its very fine, low, numerous and bifurcating costae. It is about the same size as Fascicosta longaeva (Girty), but is more globose, and its costae are much finer, lower, and more numerous. In its globose shape and its normal size T. fenaria resembles Chaeniorhynchus inauris, new species, differing primarily in its bifurcating costae, dis- junct deltidial plates, and lack of a high median septum in the brachial valve. DISCUSSION.—Inasmuch as only the type species of this genus is known the development of the hinge plate and other generic details are discussed under the genus heading. The species is rare and is confined, so far as known, to the Institella Zone in the Split Tank and Word Ranch areas. Superfamily STENOSCISMATACEA Oehlert, 1887 Aberrant Rhynchonellacea having spondylium in pedicle valve and camarophorium in brachial valve. Deltidial plates conjunct. Family STENOSCISMATIDAE Oehlert, 1887 Stenoscismatacea with stolidium in some stage of development. Subfamily STENOSCISMATINAE Oehlert, 1887 Stenoscismatidae with costae beginning anterior to beaks. Genera in West Texas: Stenoscisma Conrad, 1839. This is an abundant genus in the Glass Moun- NUMBER 21 2081 tains, less abundant in the Guadalupe Mountains and Sierra Diablo. It occurs sparingly in Wolfcam- pian rocks of the Glass Mountains but is common in the Hueco Formation of the Hueco Mountains. It becomes common in Leonardian rocks but tapers off to rarity in the Guadalupian rocks of West Texas. Genus Stenoscisma Conrad, 1839 Stenoscisma Conrad, 1839:59.—Cooper, 1944:315.—Grant, 1965a: 138 [for synonymy and discussion]. Stenocisma Conrad, Dall, 1877:65.—Cooper, 1942:229.—Shaw, 1962:633. [Not of Hall, 1847:142; 1867:335.] Stenoschisma Conrad, Oehlert, 1887:1309. [Not of Hall and Clarke, 1894:187]. Camerophoria W. King, 1844:313; 1845:254; 1846:89. Camarophoria W. King, Herrmannsen, 1846:161.—W. King, 1850:113. Not Stenochisma Conrad, Grabau, and Shimer, 1907:288.— Kozlowski, 1929:146. A more complete synonymy and a discussion of use of the name Stenoscisma, its various spellings and type species, and the extended competition between it and the name Camerophoria can be found in Grant (1965a: 138-143). Shell rhynchonelliform, biconvex; small to large; outline subtrigonal to elongate or transversely sub- elliptical; commissure uniplicate, lateral and ante- rior margins of either or both valves typically extended to form large or small "'stolidium"; co- stae beginning at or considerably anterior to beaks, normally stronger on fold and sulcus than on flanks, simple, anteriorly bifurcating, or intercalated; ra- dial striae absent; concentric ornament consisting only of fine, closely spaced growth lines and occa- sional stronger growth laminae. Pedicle valve normally gently convex transversely, strongly convex through sulcus; beak blunt or slightly attenuate, nearly straight to strongly in- curved against brachial umbo; beak ridges blunt, short, ill-defined; delthyrium small, triangular, nor- mally nearly completely filled by small deltidial plates or by umbo of brachial valve; foramen nar- row, elongate oval; lateral pseudointerareas elon- gate, narrow, normally covered by overlapping edge of opposite valve. Brachial valve strongly convex transversely, gently convex along crest of fold; beak blunt to slightly attenuate, apex within pedicle valve, hidden by deltidial plates or by strongly hooked pedicle beak. Pedicle valve interior with small blunt teeth elongate parallel to sides of valve; dental plates converging in gentle curve, fused along median line, forming deep, scoop-shaped spondylium, supported by low median septum. Muscle marks in spondy- lium weak and undifferentiated; transverse pallial troughs (vascula media) sporadically present on floor of valve, diverging nearly at straight angle immediately anterior to end of median septum. Brachial valve interior with subtrigonal hinge plate greatly thickened at apex to form knoblike or lobate cardinal process; sockets elongate, narrow, finely corrugated, formed between socket ridges of hinge plate and valve margins; brachial processes elongate, slender, outwardly bowed and ventrally curved; median septum high, capped by anteriorly expanding, spoon-shaped camarophorium; short and low intercamarophorial plate supporting hinge plate along median line. Muscle marks in camaro- phorium faint; posterior adductor scars apparently subelliptical, one on each side of intercamaropho- rial plate; anterior adductor pattern uncertain, apparently consisting of several narrow, elongate, anteriorly diverging and widening scars on anterior portion of camarophorium. TYPE-SPECIES.—Terebratula schlotheimi Buch (1835:59-60, pi. 2: figs. 32a-c), by monotypy in Conrad (1839:59). COMPARISON.—Stenoscisma is characterized by its normally subtrigonal outline, prominent pedicle beak with small foramen, more strongly convex brachial valve, and, normally, by the presence of a stolidium around the margins. Internally the genus is distinguished by its large spondylium and short septum in the pedicle valve, and the high median septum, large spoon-shaped camarophorium, long, gracefully curved brachial processes, and prominent cardinal process of the brachial valve. It most nearly resembles Psilocamara Cooper, differing in its costate shell; Nantanella Grabau, differing in its lack of a brachial umbonal sinus; and Camaropho- rinella Licharew, differing in its undivided hinge plate and presence of an intercamarophorial plate. Externally it resembles some of the larger species of Wellerella Dunbar and Condra and Phreno- phoria Cooper and Grant; but normally its pedicle umbonal region is thicker, its brachial valve less bulbous, and its margins bear the characteristic stolidium. Internally Stenoscisma bears little resem- blance to those two genera. 2082 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY The interior of Stenoscisma is similar to that of Torynechus Cooper and Grant (1962), except for its shallower camarophorium and shorter intercam- arophorial plate. Externally Stenoscisma differs in its fewer and coarser costae, higher fold, less inflated and attenuate brachial beak, and absence of ante- rior levigate surfaces. DISCUSSION.—The spondylium in Stenoscisma is supported by a median septum, even in the smallest and youngest specimens that were studied. How- ever, as the shell increases in size, the more the apical area along the septum in some individuals becomes filled with adventitious shelly material, making it appear that the spondylium had been sessile in the earlier growth stages. The spoon-shaped structure in the brachial valve of this genus has received several names given by various authors. W. King (1850:114) referred to it simply as a "large spatula-shaped process," and Waagen (1883) followed that usage. Tschernyschew (1902) called it a dorsal spondylium, but Weller (1914) and R. E. King (1931) used the term "crura- lium." Kozlowski called the structure simply a plate or a small tongue in his 1914 paper on the Bolivian fauna; in 1929 (p. 1-3), however, he pro- posed the term "camarophorium'' for the so-called "cruralium" of the genus Camarophoria ( = Steno- scisma), pointing out that it bears no genetic or structural relation to the cruralian of genera of the Pentameracea. Subsequently, Stehli (1954:338) combined the previous nomenclature in referring to the, "spoon-shaped cruralium (camarophorium)," and Cooper (1956a:521) coined the new term "tory- nidium" for the same plate. The ambiguity in this sequence arises from Kozlowski's (1929) use of the generic names Camarophoria King and Stenos- chisma (sic) Conrad for separate and distinct genera. It is apparent from the serial sections of Stenos- chisma Conrad is based upon Hall's (1869:335, pi. 54) interpretation of the genus, and in fact is Machaeraria Cooper. This application of the name is entirely different from the present usage that equates Camarophoria with Stenoscisma. Strong dental plates are present in the pedicle valve of .S. althi, and they do not join to form a spondylium; the brachial valve there has a slender cardinal proc- ess, no median septum, and no camarophorium. However, Kozlowski's idea of Camarophoria is clearly presented in his 1914 paper and agrees precisely with the modern concept of Stenoscisma. His discussion (1929) of the internal structures of Camarophoria also indicates that he means the genus that now is called Stenoscisma. Grant (1965a: 14) in an extended discussion of Stenoscisma recommended adoption of Kozlowski's name camarophorium because this is the earliest name and was based on a clear and unambiguous definition. Kozlowski (1929:131) and Licharew (1936:60) studied the construction of the small septum within the camarophorium and concluded that it was not a continuation of the medium septum from the floor of the valve. Licharew proposed a distinguish- ing term, the "intercamarophorial plate." Study of silicified specimens leads us to the same conclusion, on the grounds of the shape and length of the two septa. Grant (1965a,b) made serial sections of shells in most of the stenoscismatacean genera and con- firmed Licharew's idea of the intercamarophorial plate. Despite the median position of the intercam- arophorial plate, it is normally not as thick as the median septum. The anterior edges of the two plates coincide only fortuitously: normally the edge of the median septum is much farther anterior. The hinge plate of Stenoscisma bears an apical thickening of varying shape. It is rounded on some species and polylobate on others, but its form is not consistent within a species. Its surface normally is striated as a result of the attachment of muscles. The form, function, and position of this protuber- ance is that of a cardinal process, and we agree with Kozlowski (1914) and Licharew (1936) that that is what it should be called. The lateral and anterior margins of many species of Stenoscisma bear the thin shelly expansion or skirt for which Grant (1965a) proposed the term "stolidium." Stehli (1954:338) speculated that the stolidium enabled the shell to rest lightly on the surface of a soft sea bottom, thus keeping the gape above the sediment. We consider this to be a rea- sonable and likely explanation of the function of the stolidium. The pedicle foramen in many species is rather small, postulating a pedicle that was thin and perhaps nonfunctional in the same species. A trend in the evolution of the genus is toward reduc- tion of the pedicle opening, and in the most abun- dant species of the Word Formation (5. renode, new species) the pedicle beak is pressed tightly to the brachial umbonal region without any room for a pedicle in most individuals. Perhaps in earlier NUMBER 21 2083 species also the small size of the pedicle opening provided only for a vestigial pedicle that was not used for attachment, and the animal lay free on the sea floor (Grant, 1965a: 9). Stenoscisma abbreviatum, new species PLATE 553: FIGURES 10-27 Shell somewhat small for genus; outline trans- versely elliptical, greatest width near midlength; profile not strongly biconvex, pedicle valve rather flat; fold broad, low, somewhat flattened across top; costae beginning far forward, normally about 7 mm anterior to brachial beak, numbering 2 or 3 on fold in juveniles, normally 4 in adults, 2 or 3 weak costae on each flank beginning still farther forward; stolidium broad, wavy, apparently equally devel- oped on both valves and on fold as well as on flanks, and continuous between. Pedicle valve with sharp beak only moderately curved; foramen small, but apparently remaining open in adults; deltidial plates very small, con- stricting only anterior part of foramen, sporadically present; sulcus beginning far forward, but strongly depressed below flanks toward anterior, and con- tinuing as broad tongue into fold. Brachial valve more strongly convex, both transversely as well as along crest of fold; zone of overlap of valves very short because of extensive stolidium beginning nearly as far back as hinge teeth. Pedicle valve interior with broad, flat-bottomed spondylium on low and occasionally somewhat thick median septum; hinge teeth blunt; pallial lines weakly impressed. Brachial valve interior with small and proportionately short camarophorium; median septum very short, supporting only poste- rior part of camarophorium, then continuing as keel along underside; cardinal process knoblike; intercamarophorial plate somewhat thick. MEASUREMENTS (in mm).— length width thickness AMNH 347 154917a 12.2 13.5 7.0 AMNH 728p 154918a (holotype) 13.2 16.7 8.8 154918g 13.4 17.6 9.5 154918b 14.0 19.0 11.9 STRATIGRAPHIC OCCURRENCE.—Bell Canyon Forma- tion (Lamar Limestone Member). LOCALITIES.—AMNH 347; USNM 728p. DIAGNOSIS.—Small, transverse, few costae, broad continuous stolidium; interior structures short. TYPES.—Holotype: USNM 154918a. Figured par- atypes: USNM 154917a, 154918b-f. Unfigured para- type: USNM 154918g. COMPARISON.—Stenoscisma abbreviatum is charac- terized by rather small size, transverse outline of adults, few costae on fold and flanks, and broad, continuous stolidium. Internally, the short, broad spondylium and short camarophorium on a high but longitudinally abbreviated median septum are distinguishing features. It most nearly resembles S. doricranum, new species, from the lower part of the Cathedral Mountain Formation, differing in its wider and elliptical, rather than triangular, outline, its stronger and more numerous costae, and inter- nally by its shorter spondylium and camaropho- rium. It also may be compared to the unnamed species, illustrated on figures 1-7 of plate 583, which also occurs in the Lamar Member. Stenoscisma abbreviatum, new species, differs from that species in its 3 costae on the fold, costate flanks, and much less inflated profile, especially of the brachial valve. It resembles S. aberrans, new species, which occurs in the Rader Member of the Bell Canyon Forma- tion in its very short internal structures, but differs externally in its more normally stenoscismatacean shape and its somewhat stronger but fewer costae on both fold and flanks. Stenoscisma aberrans, new species PLATE 554: FIGURES 23-32 Medium size for genus, subrectangular to ellip- tical in outline; valves unequally deep, brachial valve deeper; sides strongly rounded; widest near midvalve. Anterior margin truncated. Beak very short and inconspicuous, without deltidial plates. Sides diverging at wide angle, near 140°. Surface sparsely and irregularly costate, costae of pedicle valve poorly developed, conspicuous only at front part of sulcus. Fold with 4 costae at front, produced by bifurcation of 2 farther back, costae strong and rounded and with narrow interspaces. Flanks of pedicle valve smooth or indistinctly costate, those of brachial valve with few strong costae. Stolidium vestigial. Pedicle valve flatly convex or slightly concave in 2084 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY lateral profile and nearly flat in anterior profile. Umbonal region narrowly swollen; sulcus beginning near midvalve, deepening abruptly, generally flat transversely, extended into long truncated tongue with vestigial stolidium. Flanks broad, extended laterally, slightly concave and prominent. Brachial valve unevenly convex in lateral profile, posterior region moderately curved but anterior flattened; anterior profile broadly domed and with long steeply sloping sides. Fold prominent, origi- nating posterior to midvalve, widening and height- ening anteriorly, there strongly elevated above flanks. Anterior margin of fold strongly deflected dorsally. Flanks strongly descending and moderately swollen, forming strong contrast to flattened and elevated fold. Pedicle valve interior with very short, wide, shal- low spondylium occupying a quarter to a fifth valve length. Median septum moderately high and ex- tending anteriorly to front of spondylium. Inner margin of tongue of sulcus with 5 prominent, coni- cal projections or spines. Camarophorium longer than spondylium but relatively short nevertheless, widening abruptly anteriorly and with moderately long median pro- jection. Crura slender. Intercamarophorial plate long and slender. Inner margin with thick conical spines. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness C) USNM 725f 152876a 17.9 ? 25.0 ? 146 (holotype) 152876b 20.4 ? 27.0 ? 146 152876c 16.4 ? 23.1 ? 140 152876d 23.6 22.4 29.8 13.0 138 STRATIGRAPHIC OCCURRENCE.—Cherry Canyon For- mation (Getaway Member); Bell Canyon Formation (Hegler and Rader members). LOCALITIES.—Getaway: USNM 728. Hegler: USNM 731. Rader: USNM 725f. DIAGNOSIS.—Stenoscisma with strong, unequally costated valves, rectangular to elliptical outline, and vestigial stolidium. TYPES.—Holotype: USNM 152876a. Figured par- atype: USNM 152876b. Measured paratypes: USNM 152876b-d. Unfigured paratypes: USNM I52876c,d. COMPARISON.—The exterior form with its rec- tangular outline and nearly flat pedicle valve is unlike that of any other Stenoscisma described herein. The brevity of the spondylium and cardi- nalia for such a large shell is also a distinctive fea- ture. The only species remotely like this one is S. fabarium, new species, from the upper Cathedral Mountain Formation. This has somewhat the same configuration but it is costated differently, is much smaller, and has a large stolidium as well as many minor differences of configuration. DISCUSSION.—This species is represented by few specimens, consisting of three pedicle valves, a complete shell, and a few scraps that preserve parts of the interior of both valves. Ordinarily we would not propose a specific name for fragmentary mate- rial of this sort but this is a unique species and very rare. In spite of the meager material, all of the essentials of the interior and exterior are pre- served so that an accurate picture can be given of all but the variation of the species, which is prob- ably considerable. Two fragmentary specimens, both parts of pedicle valves indicate the same or a sim- ilar species at other localities; one is from the Hegler Limestone at USNM 731 and the other from the Cherry Canyon Formation (Getaway Member) at USNM 728. The exterior details of this species suggest those of the Devonian Leiorhynchus Hall. The short beak, strong fold and sulcus and the irregularity of the ornament are all reminiscent of this similarity. Stenoscisma fabarium is also similar in this respect and may be related to 5. aberrans. Stenoscisma amoenum, new species PLATE 554: FIGURES 1-14 Small for genus, subtriangular in outline, maxi- mum width just anterior to midvalve; sides nar- rowly rounded; anterior margin broadly curved; apical angle about 95°; valves subequal in depth. Beak moderately long, suberect; no deltidial plates (?). Surface costate except for smooth um- bones, costae fairly uniform in size on flanks, fold, and sulcus, 4 or 5 on fold with outer 2 usually depressed below median 2 or 3; costae on each flank numbering 4 or 5, outer one indistinct. Sto- lidium not seen. Pedicle valve in anterior profile broadly concave but moderately convex in lateral profile; umbonal NUMBER 21 2085 region narrow; sulcus moderately wide, shallow, originating posterior to midvalve and forming mod- erately long tongue. Flank narrow, gently convex. Brachial valve evenly and gently convex in lat- eral profile, fairly strongly domed in anterior pro- file with fold slightly protuberant medially and sides sloping steeply. Fold originating posterior to midvalve, elevating above flanks slightly in anterior direction; flanks moderately broad and gently convex. Interior not known, except for presence of spon- dylium and septum seen on broken specimens. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 708q 152271a 12.8 11.0 14.3 8.9 95 (holotype) 152271b 11.9 10.6 12.4 8.4 89 152271c 13.3 11.3 15.6 9.2 94 STRATIGRAPHIC OCCURRENCE.—Skinner Ranch (De- cie Ranch Member). LOCALITY.—USNM 708q. DIAGNOSIS.—Small nearly completely costate Sten- oscisma with strongly costate flanks. TYPES.—Holotype: USNM 152271a. Figured par- atype: USNM 152271b. Unfigured paratype: USNM 152217c. COMPARISON.—This small Stenoscisma differs from all other Glass Mountains and Guadalupe Mountains species of comparable size in having the surface nearly completely costate. In this respect it suggests S. mutabile oregonense Cooper from the Coyote Butte Formation of central Oregon. It dif- fers, however, in being more completely costate than that species, in having more costae on the fold, and in having less clearly defined and differ- ently arranged intercalations and bifurcations. DISCUSSION.—This is a very rare species; only six specimens were collected. It was not found in any of the siliceous residues but was recovered in break- ing up Decie Ranch limestone. Stenoscisma aptatum, new species PLATE 555: FIGURES 1-50 Average size for genus; outline broadly subtrig- onal or subelliptical, sides diverging between 70° and 105°, maximum width located near midlength; profile moderately strongly biconvex; commissure uniplicate, fold low to moderately high, standing increasingly high above flanks anteriorly, beginning 5-7 mm anterior to brachial beak; sulcus shallow, becoming moderately deep anteriorly, beginning 7- 10 mm anterior to pedicle beak. Costae moderately strong on fold and sulcus, weaker on flanks, blunt crested, normally not bifurcating, beginning 5-7 mm anterior to beaks, numbering 3 or 4 on fold, one less in sulcus, normally 3 on each flank; sto- lidium well developed, better formed on brachial flanks, but on both valves at fold; growth lines fine and closely spaced, with irregularly spaced stronger laminae. Pedicle valve moderately strongly convex trans- versely and longitudinally, umbonal region some- what swollen; beak relatively short but strongly hooked and erect, not pressed against umbonal region of brachial valve; lateral pseudointerareas elongate, narrow, covered by edge of brachial valve; delthyrium triangular, normally constricted by small, disjunct deltidial plates, but entirely open in specimens with strongly hooked beaks; foramen small, slit-shaped, opening directly ventrally. Bra- chial valve strongly convex transversely, less convex longitudinally along crest of fold; beak bluntly pointed, slightly swollen, apex within pedicle valve, beneath deltidial plates. Pedicle valve interior with small hinge teeth fused to sides of valve; dental plates converging just above floor to form boat-shaped spondylium, continuing to floor as low median septum. Muscle marks faint in anterior two-thirds of spondylium, set off by sharp line from posterior portion; vascula media diverging at straight angle to cross valve just anterior to median septum; gonocoel impressions posterior, lateral to spondylium. Brachial valve interior with semicircular to cres- centic hinge plate, thickened at apex of valve to form cardinal process, fibrilate for muscle attach- ment; hinge sockets located at lateral extremes of hinge plate, details not observed; crural bases ex- tending forward from base of cardinal process, con- tinuing free as slender brachial processes, outwardly bowed, ventrally bent, conforming to outline of camarophorium; intercamarophorial plate support- ing hinge plate by contact with small, short crural plates between crural bases; camarophorium spoon- shaped, with broad, short anterior median projec- 2086 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY tion; median septum short on valve floor, length increasing greatly with height. Muscle marks weak in camarophorium; pallial marks not observed. MEASUREMENTS (in mm).— brachial apical USNM 702c length valve length width thick- ness angle (°) 152241a 152241b 1.0 1.7 1.0 1.6 0.8 1.3 0.6 0.8 ? } 152241c 3.3 3.1 2.7 1.6 70? 152241d 4.0 3.7 3.0 1.9 72? 152241e 15224H 5.3 7.2 5.0 6.5 4.8 6.4 2.8 3.3 78 78 152241g 152241h 9.8 13.0 8.3 10.9 9.4 12.9 5.0 7.6 83 84 15224H 14.6 12.7 14.7 8.3 86 152241J USNM 702 16.5 14.6 18.6 10.2 98 152239 USNM 703bs 18.4 16.4 21.4 15.0 89 152244 20.0? 18.4 25.0 15.4 99 USNM 702c 152240 17.5 15.0 18.2 11.4 95 (holotype) STRATIGRAPHIC OCCURRENCE.—Cathedral Moun- tain Formation; Road Canyon Formation. LOCALITIES.—Cathedral Mountain: USNM 702, 702un, 703b, 703bs. Road Canyon: AMNH 501; USNM 702c, 716x. DIAGNOSIS.—Medium-sized Stenoscisma with erect beak and moderately inflated brachial valve. TYPES.—Holotype: USNM 152240. Figured para- types: USNM 152239, 152241a-g. Measured para- types: USNM 152239, 152241a-j, 152244. Unfigured paratypes: USNM 152241h-j. COMPARISON.—Stenoscisma aptatum is charac- terized by its subelliptical to broadly trigonal out- line, rather weak costae with rounded crests, hooked beak, and well-developed stolidium. It most nearly resembles a large version of S. doricranum, new species, but differs in its larger size, more numerous costae on fold and flanks, more consistently hooked pedicle beak, and different pattern of pallial marks, at least in the pedicle valve. The pattern of develop- ment of the stolidium indicates that it probably belongs to the group of species that includes S. venustum (Girty) and S. triquetrum, new species. It differs from both of those species in its smaller size, fewer and weaker costae, less strongly triangu- lar outline, and more strongly hooked pedicle beak with disjunct deltidial plates. Some specimens of 5. renode, new species, are similar in their blunt costation, but differ in their more triangular out- lines, more numerous costae, and especially in their beaks that are pressed against the brachial umbo, eliminating the foramen. Among foreign species S. mutabile (Tscherny- schew 1902), also illustrated by Grabau (1931a, pi. 4), appears to have the strongest similarity to S. aptatum. It differs in its stronger costae and more closely hooked pedicle beak, and Tschernyschew's specimens differ additionally in their normally bifurcating costae on the fold. Stenoscisma biplica- tum (Stuckenberg) as shown by Tschernyschew (1902) also is very similar, but S. aptatum is not as swollen in the pedicle umbonal region, its costae begin farther forward, is not as strongly triangular, and its fold does not stand as prominently above the flanks. Stuckenberg's (1898) illustrations of S. biplicatum do not closely resemble S. aptatum. The same species illustrated by Reed (1944, pi. 24: figs. 10-10b) is much more attenuate and more strongly triangular than S. aptatum. Another similar species is S. pingue (Waagen), which differs in its narrower outline, more numerous costae, and more strongly biconvex profile. Stenoscisma bellatulum, new species PLATE 556: FIGURES 34-54 Small for genus; outline subtrigonal, sides diverg- ing about 100°, widest anterior to midlength; pro- file narrowly convex in youth, curvature of valves increasing with growth; uniplicate commissure bear- ing 3 costae on fold in early stages, adding 2 more by lateral branching in adults, 3 or 4 costae on each flank, beginning farther forward than costae on fold; stolidium rather narrow, apparently best de- veloped on fold of pedicle valve and flanks of brachial valve. Pedicle valve with moderately curved beak; for- amen reduced in adults but nevertheless remaining open and without deltidial plates in all specimens; sulcus beginning about 2 mm anterior to beak. Brachial valve more strongly convex; fold broad and transversely flat across crests of costae; postero- lateral edges lapping over flattened flange of pedi- cle valve edges. Pedicle valve interior with proportionately short spondylium elevated on thin median septum; hinge NUMBER 21 2087 teeth short, supported by central plates that con- verge to form spondylium; pallial trunks dichoto- mous, full course not observed. Brachial valve interior with proportionately small and delicate camarophorium, trough-shaped, and moderately curved ventrally; cardinal process small and narrow; pallial marks not observed. MEASUREMENTS (in mm).— apical thick- angle length width ness (°) USNM 727e 154574a 9.0 11.0 5.5 100 154574d 11.0 13.0 7.0 98 154574f 11.8 13.8 7.2 100 154574g 12.5 15.0 9.8 105 154574e (holotype) 14.4 15.6 10.9 101 STRATIGRAPHIC OCCURRENCE.—Neal Ranch For- mation. LOCALITY.—USNM 727e. DIAGNOSIS.—Small, 3 costae on fold in juveniles, 2 added by bifurcation in adults, costae of moder- ate strength. TYPES.—Holotype: USNM 154574e. Figured par- atypes: USNM 154574a-d. COMPARISON.—Stenoscisma bellatulum resembles a few of the other Wolfcampian species that are not strongly costate. It is smaller and narrower than S. levicostum, new species, of the Bone Spring For- mation, and its costae begin farther forward, with the lateral 2 of the fold being added by bifurcation at a considerable distance from the beak. It is larger and more strongly costate than S. myioides, new species, of the Skinner Ranch Formation, is more highly convex, has a better developed stoli- dium, and its beak is more strongly curved. Its size and convexity recall S. hueconianum (Girty) of the Hueco Formation, but S. bellatulum is proportion- ately narrower, the pedicle valve is flatter, and its costae are fewer on both fold and flanks. Stenoscisma bonum, new species PLATE 556: FIGURES 1-33 Small for genus, wider than long, maximum width near midvalve; subpentagonal in outline; sides narrowly rounded; beak short, strongly in- curved; deltidial plates absent or vestigial; pauci- costate, costae short, low, rounded, confined to anterior third or half, strongest on fold and sulcus, 2 or 3 on fold (usually 3) and one less in sulcus; flanks with 1 or 2 costae, outside one indistinct. Stolidium usually narrow, shared by both valves, tongue of pedicle valve and flanks of brachial valve. Pedicle valve with moderately convex lateral pro- file, maximum curvature in umbonal region; ante- rior profile very gently convex; umbo and posterior moderately swollen; sulcus originating near mid- valve, widening and deepening abruptly and form- ing short tongue. Flanks moderately broad and nearly flat. Brachial valve evenly and moderately convex in lateral profile but strongly domed in anterior pro- file; sides sloping steeply to precipitously. Median region and umbo swollen. Fold originating near midvalve, steepening abruptly and moderately strongly elevated at anterior. Flanks gently swollen, sweeping strongly away from fold. Pedicle valve interior with short, anteriorly rounded and moderately deep spondylium sup- ported on low septum extending short distance anterior to anterior margin of spondylium. Brachial valve interior with long camarophorium, delicate intercamarophorial plate, and high median septum. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (") USNM 724j 152877a 4.1 3.7 3.8 2.2 60 152877b 4.9 4.3 4.3 2.7 66 152877c 5.9 5.2 5.2 3.2 77 152877d 6.2 5.9 6.1 3.4 77 152877e 6.7 6.0 6.7 3.8 82 152877f 8.2 7.3 8.8 4.8 92 I52877g 8.2 7.3 9.7 5.6 96 152877h 9.7 8.7 10.8 5.9 104 152877i 10.0 8.7 11.9 7.0 97 152877J 8.5 7.5 9.8 6.2 100 152877s 8.5 8.0 9.5 5.5 95 (holotype) STRATIGRAPHIC OCCURRENCE.—Road Canyon For- mation. LOCALITIES.—USNM 707e, 720d, 721j, 721o, 721t, 721y, 722e, 722g, 724a, 724b, 724j. DIAGNOSIS.—Small, delicate, nearly nude Stenos- cisma with 3 short costae on the fold. TYPES.—Holotype: USNM 152877s. Figured par- atypes: USNM 152877j,k,m-r; 154575a. Measured and unfigured paratypes: USNM 152877a—i. Unfig- ured paratype: USNM 152877-1. 2088 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY COMPARISON.—This species belongs to a group of semismooth stenoscismas and need be compared only to them. It is smaller than all of those named here but has other differences as well. It differs from 5. doricranum and peneleve, both new, in having more subdued costae on both flanks and fold. It differs from S. calvatum, new species, in having a less robust brachial valve, less strong costae on the fold and sulcus, and a shorter beak. It is completely unlike 5. fabarium, new species, which is strongly convex, variably ornamented, and, for its size, has a more prominent sulcus and shorter beak. Stenoscisma calvatum, new species PLATE 557: FIGURES 1-60 Small for genus, length and width nearly equal; outline subtrigonal, posterolateral margins some- what pinched and sides narrowly rounded; greatest width just anterior to midvalve; anterior margin broadly and gently curved. Sides diverging between 75° and 100°, depending on age. Beak suberect, not pressed onto brachial umbo; deltidial plates ves- tigial. Surface nearly smooth except for anterior third where low rounded costae appear, 2-4, usually 3 at margin but become obsolete posteriorly in short distance; flanks with 1 or 2 costae distinct only at margin. No stolidium seen and no traces along margin. Pedicle valve moderately convex in lateral view, not as deep as brachial valve; anterior profile vary- ing from slightly and broadly convex to slightly and broadly concave. Umbonal region narrowly swol- len. Sulcus originating abruptly at midvalve, occupying about half valve width, shallow, and developing into fairly long tongue. Flanks narrow, moderately steep, and nearly flat. Brachial valve evenly and fairly strongly convex in lateral profile, anterior profile narrowly domed and with very steep lateral slopes. Umbonal and median regions inflated; fold originating slightly posterior to midvalve, best defined at margin, there slightly elevated. Flanks moderately depressed below the fold, convex, and inflated. Pedicle valve interior with deep spondylium slightly less than a third valve length, wide and deep with broadly rounded anterior, attached to low median septum protruding short distance ante- rior to front of spondylium. Brachial valve interior with strongly elevated camarophorium attached to short septum. Hinge plate broad and flattened, with thick striated cardinal process. Intercamarophorial plate short. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 721t 152340a 7.4 6.4 7.3 4.1 87 152340b 8.5 7.4 8.6 5.3 85 152340c 9.5 8.1 10.0 5.4 85 152340d 11.2 9.4 12.2 8.2 83 152340e 12.3 10.3 12.5 8.2 83 152340f 11.7 10.0 13.0 8.5 87 152340g 12.4 10.6 12.6 7.8 87 152340n 10.5 10.0 13.0 8.5 96 (holotype) USNM 721x 152341a 6.0 5.0 5.6 3.1 76 152341b 8.1 6.7 7.7 4.8 77 152341c 9.2 8.0 9.0 5.5 69 152341d 10.4 8.8 10.9 6.5 86 152341e 10.5 8.9 12.0 6.5 89 STRATIGRAPHIC OCCURRENCE.—Cathedral Moun- tain Formation; Road Canyon Formation. LOCALITIES.—Cathedral Mountain: USNM 702, 702un, 735b. Road Canyon: USNM 702c, 703a, 703c, 706f, 709c, 710u, 719x, 721t, 721x, 721y, 726z. DIAGNOSIS.—Small, nearly smooth Stenoscisma with a few subdued costae. TYPES.—Holotype: USNM 152340n. Figured par- atypes: USNM 152340h-k,m-q; 152341f-h. Meas- ured paratypes: USNM 152340a-g, 152341 a-e. Un- figured paratypes: USNM 152340b-g,l; 152341a-c. COMPARISON.—The paucicostate exterior of this species limits comparison to other paucicostate spe- cies such as S. doricranum, new species, and S. bonum, new species. Stenoscisma calvatum differs from the first in having less prominent costae on both valves, in being generally not so large or thick, in having a more elongated beak, and in showing no trace of a stolidium. S. calvatum differs from S. bonum in its larger size, its lack of a stoli- dium, and in having a more erect beak not curved over the umbo of the opposite valve and stronger costae. Stenoscisma camurum, new species PLATE 558: FIGURES 1-42 Shell about normal size for genus; outline trans- NUMBER 21 2089 versely subelliptical to subpentagonal, sides diverg- ing between 85° and 115°, maximum width slightly anterior to midlength; profile moderately to strongly biconvex; commissure uniplicate, fold moderately high, broad, beginning 7-9 mm anterior to brachial beak; sulcus shallow, beginning 7-10 mm anterior to pedicle beak. Costae strong, blunt crested, nor- mally not bifurcating nor intercalating, beginning 5-7 mm anterior to beaks, numbering 3-6 on fold, one less in sulcus, 4-6 on each flank, weaker on flanks; stolidium well developed on brachial flanks and pedicle sulcus; growth lines fine, with occa- sional stronger laminae. Pedicle valve moderately strongly convex trans- versely, more strongly convex longitudinally through sulcus; umbonal region rather swollen; beak rela- tively short, erect to strongly hooked, usually pressed tightly against brachial umbo; lateral pseu- dointerareas comparatively short and wide, mostly covered by edges of brachial valve; delthyrium wide, triangular, rarely with small deltidial plates, nor- mally completely filled by brachial beak, without external foramen. Brachial valve strongly convex transversely and longitudinally; beak bluntly pointed, with apex in pedicle valve. Pedicle valve interior with elongate, knoblike teeth; dental plates continuous with hinge teeth, converging just above floor of valve to form large, boat-shaped spondylium, fused beneath spondylium to form low median septum reaching floor of valve. Muscle marks faint and undifferentiated in anterior two-thirds of spondylium; pallial marks moderately strongly impressed: vascular media forming troughs diverging nearly at straight angle from point just anterior to median septum, marks of gonocoels faintly visible posterior to transverse pallial troughs, on floor of valve beside spondylium. Brachial valve interior with large, laterally attenuate hinge plate, greatly thickened at apex of valve to form large, knoblike cardinal process striated for muscle attach- ment; hinge sockets short, relatively wide, denticu- late, located at extremities of hinge plate; crural bases diverging anteriorly from near base of cardi- nal process, space between them filled for short distance by small crural plates attaching them to top of intercamarophorial plate; camarophorium long, spoon-shaped, widest toward anterior end, with short, wide projection at anterior median line; intercamarophorial plate short, supporting floor of camarophorium to underside of hinge plate; median septum high, thin, length increasing with height. Muscle marks in spondylium faint; pallial marks on valve floor consisting of two thin trunks diverg- ing from near sides of median septum, branching near midlength of valve, sending branches to ante- rior and lateral edges. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) SNM 707e 152238a 12.3 11.6 15.0? 8.4 90 152238b 17.0 15.2 20.6 11.3 104 152238c 18.4 16.2 23.0 14.5 97 152238c! 21.4 20.0 27.9 19.0 98 152238e 22.0 20.5 30.4 16.5 111 152238f 29.5 17.0 24.0 13.9 106 152238g 19.7 18.2 23.0 14.5 90 152878 17.3 15.8 19.2 13.1 99 (holotype) STRATIGRAPHIC OCCURRENCE.—Road Canyon For- mation; Cherry Canyon Formation (Getaway Member). LOCALITIES.—Road Canyon: AMNH 503; USNM 702c, 703d, 706f, 707e, 710z, 716x, 721s, 719x, 721x, 721y, 721z, 722g, 724a, 726z. Getaway: AMNH 585. DIAGNOSIS.—Fairly large, strongly convex, and widely frilled; strongly hooked beak pressed against dorsal umbo. TYPES.—Holotype: USNM 152878. Figured para- types: USNM 152237a-d, 154573a-f. Measured par- atypes: USNM 152238a-g. COMPARISON.—Stenoscisma camurum is character- ized by its strong convexity, strongly hooked pedicle beak that normally presses against the brachial beak so that the foramen is nearly completely filled, moderately strong and simple costae, and its well- developed, broad and somewhat wrinkled stolidium. Its nearest relative is S. renode, new species, which probably is a descendant; it differs from S. renode in its wider outline with more strongly diverging sides, greater convexity, especially of the brachial valve, and its pedicle beak that is not as consistently pressed tightly against the brachial umbo. It is more inflated and narrower than S. repigratum, new spe- cies, and its beak is more strongly hooked. The hooked beak, absent deltidial plates, and the arrangement of the stolidium on the brachial flanks and pedicle sulcus distinguishes S. camurum from 5. venustum (Girty) and S. triquetrum, new species. The only other comparable Texas species is S. 2090 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY aptatum, new species, which is less convex, has fewer and weaker costae on fold as well as flanks, and has the stolidium better developed on the brachial valve, as in S. triquetrum. Several foreign species must be compared to S. camurum, most notably S. mutabile (Tschernyschew, 1902). The Texas species differs in its somewhat less inflated brachial valve, and its simple, nonbifur- cating costae. Stenoscisma purdoni (Davidson) as shown in Waagen (1883, pi. 3) also is similar, but differs in its more numerous and stronger costae on the flanks, and its somewhat narrower outline. Stenoscisma pingue (Waagen) has the costae begin- ning closer to the beaks, and also is narrower, characters that it shares with S. biplicatum (Stuck- enberg, 1898). Stenoscisma "deloi" (R. E. King) Camarophoria deloi R. E. King, 1931:110, pi. 34: figs. 24-27. DISCUSSION.—As originally constituted, this spe- cies includes forms from the "Gym" (Hueco) For- mation as well as from the Word Formation and from an unnamed formation in the Santa Rita Mountains of Arizona. An editor's footnote by Dunbar in R. E. King (1931:110) warns that this species is in part preempted by "Camarophoria" hueconiana Girty (see under Stenoscisma hueconia- num). The holotype, not illustrated here, has proved to be among the specimens anticipated by the lat- ter species, so "deloi" is effectively nullified. The Word specimens of King are reillustrated herein under the new species, Stenoscisma maniculum (see Plate 565: figures 11-15) and as far as can be ascer- tained, the specimens identified by Stainbrook and Madera (1941, pi. 55: fig. 15-27) also belong to S. maniculum. The Arizona specimens lack the internal features of Stenoscisma, and probably represent a species of Pontisia (Plate 565: figures 1-10). TYPES.—Figured specimens: YPM 12694a,b. Stenoscisma doricranum, new species PLATE 559: FICURES 1-55 Camarophoria thevenini R. E. King [not Kozlowski, 1914], 1931:110, pi. 34: figs. 28a-c. Small for genus; outline subtrigonal to trans- versely subpentagonal, sides diverging between 75° and 110°, most juveniles narrower than most adults, maximum width anterior to midlength; profile moderately biconvex to subtrigonal; commissure uniplicate, fold moderately high, not standing sharply above flanks, broad to narrowly arched, beginning 4-9 mm anterior to brachial beak; sulcus shallow but extended forward into brachial valve as short tongue, beginning 7-10 mm anterior to pedicle beak, no emargination of anterior. Costae low, weak, round crested, simple, beginning 5-10 mm anterior to beaks, numbering 1-3 on fold, one less in sulcus, 1 or 2 on each flank; stolidium mod- erately developed on both valves, normally continu- ous from flanks to fold. Pedicle valve moderately convex transversely, more strongly convex longitudinally through sulcus; beak near average length for genus, erect, hooked on some specimens but not pressed against brachial valve; umbonal region moderately swollen; beak ridges short, sharp on some specimens; lateral pseudointerareas narrow, short, or absent, normally covered by edge of brachial valve; delthyrium small, triangular, constricted by small, disjunct deltidial plates. Brachial valve strongly convex transversely, with swollen umbonal area, moderately convex longitudinally along crest of fold; apex of beak within pedicle valve beneath deltidial plates. Pedicle valve interior with small elongate teeth, parallel to and fused to sides of valve; dental plates fused just above valve floor, forming normal size, boat-shaped spondylium, supported by low, short median septum. Muscle marks faintly impressed in anterior half of spondylium; pallial trunks fine, narrowly diverging from near sides of median septum, bifurcating twice to send branches to lat- eral and anterior margins. Brachial valve interior with broadly triangular hinge plate, swollen or transversely ridged at pos- terior apex to form cardinal process; hinge sockets short, narrow, finely denticulate, located at lateral extremes of hinge plate; crural bases diverging nar- rowly from anterior base of cardinal process, space between them filled by crural plates uniting them to top of intercamarophorial plate; brachial proc- esses free, outwardly bowed and ventrally bent, conforming roughly to outline of camarophorium; median septum moderately long, length increasing with height; camarophorium elongate, spoon- shaped, with toothlike process extending anteriorly at median line; intercamarophorial plate short, NUMBER 21 2091 sturdy; muscle marks faint, in anterior part of camarophorium; pallial marks not completely ob- served: posterior parts of vascula media seen diverg- ing anteriorly on floor of valve near median septum, anterior portions not observed. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 702a 152287a 2.9 2.6 2.4 1.3 ? 152287b 3.7 3.3 3.3 1.8 90? 152287c 4.7 4.3 4.0 2.6 80? 152287d 5.3 4.8 4.7 2.6 78 152287e 6.2 5.6 5.4 2.9 77 152287f 7.7 6.7 6.9 3.6 77 152287g 8.6 7.5 8.9 4.9 85 152287h 9.7 8.6 9.0 5.6 77 152287i 10.3 8.8 11.0 6.5 87 I52287J 12.3 11.0 13.0 7.0 88 152287k 12.5 11.7 14.0 9.0 92 152287-1 14.0 12.4 15.5 10.0 90 152286h 13.0 13.5 14.0 9.0 104 (holotype) STRATIGRAPHIC OCCURRENCE.—Cathedral Moun- tain Formation; Hess Formation (Taylor Ranch Member); Skinner Ranch Formation. LOCALITIES.—Cathedral Mountain: AMNH 500; USNM 702, 702a, 702ent, 702-low, 702un, 703b, 714w, 735b. Taylor Ranch: USNM ?702e. Skinner Ranch: USNM ?705a. DIAGNOSIS.—Small, pauciplicate Stenoscisma with long beak and small, narrow stolidium. TYPES.—Holotype: USNM 152286h. Figured par- atypes: USNM 152285; 152286a-g,i-k; 152291a. Measured paratypes: USNM 152287a-l. COMPARISON.—Stenoscisma doricranum is charac- terized by its small size, triangular outline, few and weak costae that begin far forward and do not bifurcate, moderately long pedicle beak with only rudimentary plates that leave a relatively large foramen, and its moderately well-developed stoli- dium that is equally developed on both valves and normally continuous. It is about the same average size as 5. fabarium, new species, differing in its more triangular outline, less strongly costate fold, more consistently present stolidium, narrower di- vergence of sides, longer pedicle beak and spondy- lium, and present although disjunct deltidial plates. 5. aptatum, new species, is most nearly similar in shape, but is about twice the size, has stronger and more numerous costae on fold and flanks, a more strongly swollen and hooked pedicle beak, and a better developed stolidium. S. camurum and S. tri- quelrum, both new, and S. venuslum (Girty) differ in most of these same characters, and also are broader in outline. King (1931) assigned this species to S. thevenini (Kozlowski), but our more abundant collections show several differences from that species that are consistent and significant. Stenoscisma doricranum is less elliptical in outline, has broader, lower and normally fewer costae on the fold, the costae begin farther forward, the brachial umbonal region is swollen, and the pedicle beak is longer, leaving room for a larger foramen. Among other foreign species that resemble S. doricranum is the type spe- cies S. schlotheimi (von Buch), figured by W. King (1850, pi. 7: figs. 10-21) and Grant (1965a, pi. 21: figs. 1-12). It attains a larger size than S. doricra- num, has more and sharper costae, and its stolidium is more complete than on any known specimen of the Texas species. Juvenile shells of S. mutabile (Tschernyschew, 1902) also are similar to S. dori- cranum in some features; however, they are more strongly convex, more costate on the flanks, and have the beak normally pressed tightly against the brachial umbonal region. Stenoscisma meyeri (Ozaki, 1931) is small like S. doricranum, but its costae are higher, more numer- ous and sharper on the fold, and they begin farther back, although the flanks are nearly smooth as in S. doricranum. Stenoscisma biplicatum (Stucken- berg) as shown not by Stuckenberg (1898) but by Tschernyschew (1902, pi. 50) and Reed (1944, pis. 22, 24) also is similar, but has the costae more numerous and beginning farther back, and that species is more convex and its pedicle umbonal area somewhat more swollen. Reed's specimens have the pedicle beak rather long and attenuate, but in Tschernyschew's it is shorter and more strongly hooked toward the brachial valve. Stenoscisma semiplicata (Gemmellaro, 1899 )is comparable to S. doricranum, but differs in its stronger, sharper, more numerous costae on fold and flanks, and its somewhat more strongly hooked pedicle beak. Stenoscisma exutum, new species PLATE 560: FIGURES 1-38 Adult moderately large for genus; outline trans- 2092 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY versely subelliptical, sides diverging between 75° and 135°, in most adults over 100°, maximum width of shell near midlength or slightly anterior thereto; profile strongly biconvex to subtrigonal; commissure uniplicate, fold low to moderately high, beginning 6-10 mm anterior to brachial beak; sulcus relatively shallow, beginning 10-15 mm an- terior to pedicle beak. Costae fairly strong on fold and sulcus, weaker on flanks, crests sharp to slightly rounded, beginning 1-2 mm anterior to apexes of beaks, normally simple but occasionally bifurcated or intercalated, numbering 5-7 (normally 6) on fold, one less in sulcus, 6-11 (normally 7 or 8) on each flank; stolidium poorly developed, rudimen- tary or missing on most specimens. Fine radial ornamentation absent; growth lines fine, closely spaced, with occasional strong laminae. Pedicle valve moderately convex transversely, strongly convex through sulcus, with somewhat inflated umbonal area; beak short to moderately long for genus, suberect or rather strongly hooked; beak ridges short, blunt; lateral pseudointerareas elongate, narrow, mostly covered by overlapping edge of brachial valve; delthyrium small, sides con- stricted by small and normally disjunct deltidial plates, conjunct only on large adults; foramen small, elongate oval, opening directly ventrally. Brachial valve strongly convex transversely and longitudinally, umbonal region somewhat swollen; beak bluntly pointed, apex within pedicle valve, beneath deltidial plates. Pedicle valve interior with 2 blunt, finely den- ticulate elongate teeth, fused to sides of valve, parallel to sides of valve; dental plates continuous with and supporting hinge teeth, converging just above valve floor to form boat-shaped spondylium by fusing into low median septum bracing spondy- lium to floor of valve; pallial troughs (vascula media) diverging nearly at straight angle from ante- rior end of median septum, deeply indenting floor of some valves; muscle marks faint, undifferentiated, on floor and sides of spondylium. Brachial valve interior with broadly triangular to nearly semicircular hinge plate; cardinal process at apex of hinge plate just under apex of valve, striated radially for muscle attachment, normally knob-shaped; hinge sockets narrow, short, finely corrugate; crural bases extending forward from base of cardinal process, fused to hinge plate, fused to top of intercamarophorial plate by short crural plates; camarophorium long, spoon-shaped, widest near anterior end, median line extended anteriorly as short, toothlike projection; intercamarophorial plate short; median septum high, thin, length in- creasing with height; muscle marks in camaropho- rium faint, anteriorly widening and diverging slightly. MEASUREMENTS (in mm).— apical angle ness (°) brachial valve thick length length width 4.0 3.8 11.0 9.6 12.4 10.3 14.4 12.6 3.5 11.0 12.4 17.8 20.4 28.0 2.5 6.5 8.7 10.8 13.1 13.4 14.8 19.0 15.8 85 79 78 98 101 106 116 123 94 16.6 14.3 21.6 19.4 USNM 702 152296a 152296b 152296c 152296d 152296e (holotype) 152296f 22.3 20.3 28.3 28.0? 26.4 35.7 USNM 702b 152298a 152298b USNM 703b 152301a 22.0 26.7 20.1 STRATIGRAPHIC OCCURRENCE.—Cathedral Moun- tain Formation. LOCALITIES.—USNM 702, 702b, 702-low, 703b, 727p, 731t. DIAGNOSIS.—Subelliptical Stenoscisma strongly and completely costate but with poorly developed stolidium. TYPES.—Holotype: USNM 152296e. Figured par- atypes: USNM 152296c,g-j; 152301a,b. Measured paratypes: USNM 152296a-d,f; 152298a,b; 152301a. Unfigured paratypes: USNM 152296a,b,d,f. COMPARISON.—Stenoscisma exutum is character- ized by its subelliptical outline, strong convexity, rather swollen pedicle beak, numerous costae begin- ning near the beaks, and its absent or stunted stoli- dium. These features distinguish it from its nearest relatives in the Glass Mountains, S. venustum (Girty) and S. triquetrum, new species. It most nearly resembles S. inaequale (Girty) from the Sierra Diablo, differing in its less swollen brachial valve, stronger costae, larger maximum size, and reduced or absent stolidium. Stenoscisma renode, new species, from the Word Formation has fewer and coarser costae and its beak is pressed against the umbonal region of the brachial valve. Stenos- cisma pyraustoides, new species, has many costae, but is much wider, strongly emarginate, and nor- NUMBER 21 2093 mally has a well-developed stolidium. Stenoscisma camurum, new species, has many costae on the flanks, but fewer on the fold. Furthermore it is much less bulbous, has a well-developed stolidium, and normally has the pedicle beak pressed against the brachial umbonal region. Stenoscisma repigra- tum, new species, is similar in outline, but much less convex and has fewer and coarser costae, well- developed deltidial plates, and normal stolidium. Among European species the closest resemblance to S. exutum is in S. latissimum (Schellwien, 1892: 53, pi. 8: figs. 3a-d), the outline and costation of which are similar; however, S. exutum is more con- vex and its flanks normally have more costae; nor can its beaks and stolidium be compared, inasmuch as Schellwien's specimen is an internal mold. Stenos- cisma sanctispiritus (Schellwien, 1892) also is multi- costate, but its maximum width is far posterior to the midlength, its fold and sulcus begin farther back, and its brachial valve is extremely convex longitudinally, resembling more nearly species of Rhynchopora. Stenoscisma applanata (Tschernyschew, 1902:87, 497, pi. 46: fig. 1) is similar in outline to S. exutum, but differs in its weaker and fewer costae. Stenos- cisma mutabile (Tschernyschew, 1902:81, 491: pi. 45) has some individuals that are similar in costa- tion to S. exutum, but must have fewer, stronger costae, more triangular outlines, and have the beak tightly pressed against the brachial umbonal region, more like S. renode than S. exutum. Of Salt Range species identified by Waagen (1883), only S. purdoni (Davidson) is sufficiently similar to S. exutum to warrant comparison. S. pur- doni is narrower in outline, its costae are stronger and fewer, and its pedicle beak is shorter and closely hooked over the brachial umbonal region. DISCUSSION.—No specimen of Stenoscisma exutum in our collections has a well-developed stolidium; most have no stolidium. This absence is not an accident of preservation, because otherwise com- plete and well-preserved specimens have the stoli- dium lacking. Perhaps its absence in this species is a reflection of necessities of habitat, just as we have speculated for certain individuals of other species (e.g., S. fabarium, new species). The pedicle opening in S. exutum is of about normal size for the size of shell, perhaps to accommodate a functional pedicle, whereas in species with the stolidium well devel- oped the pedicle foramen normally is small or completely blocked (e.g., S. renode, new species). For a species of Stenoscisma, exutum is relatively wide, and possibly the width of the shell served the same supporting function as the stolidium of other species. Stenoscisma fabarium, new species PLATE 561: FIGURE 1-67 Small for genus; outline subelliptical to subpen- tagonal, sides diverging between 75° and 125°, over 100° in most adults, maximum width slightly ante- rior to midlength; profile biconvex, normally sub- trigonal; commissure uniplicate, fold moderately high, broad, evenly arched transversely, not stand- ing sharply above flanks, beginning approximately 5-7 mm anterior to brachial beak; sulcus broad, shallow, beginning 5-7 mm anterior to pedicle beak, extending forward as broad tongue, producing slight emargination in some shells. Costae relatively weak, low, round crested, normally not intercalating or bifurcating, beginning 3-5 mm anterior to beaks, stronger on fold and sulcus than on flanks, number- ing 2-6 (normally about 3) on fold, one less in sulcus, 0-4 (normally 1 or 2) on each flank, stoli- dium present or absent, equally well developed on both valves, occasionally continuous from flanks to fold. Pedicle valve moderately convex transversely, somewhat more strongly convex longitudinally through sulcus; beak very short, erect, normally strongly hooked, umbonal region somewhat swol- len; lateral pseudointerareas absent; delthyrium small, triangular, without deltidial plates. Brachial valve strongly convex transversely, moderately con- vex along crest of fold, umbonal area swollen, strongly convex, slightly attenuate, apex of beak slightly within pedicle valve. Pedicle valve interior with small, finely denticu- late teeth, elongated parallel to sides of valve and fused to edge; dental plates converging just above valve floor, forming proportionately short, boat- shaped spondylium, supported by low to moderately high, short median septum; muscle marks in ante- rior half of spondylium, set off from beak portion by plainly visible dividing line; pallial marks of vascula media diverging narrowly anteriorly, each lateral trunk normally bifurcating once near valve midlength, gonadal marks on posterior floor of 2094 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY valve surrounding septum and spondylium. Brachial valve interior with small, crescentic hinge plate, greatly thickened at apex to form knoblike cardinal process, radially striated for mus- cle attachment; sockets short, finely corrugated, located at lateral extreme of hinge plate; crural bases diverging anteriorly from base of cardinal process, space between them filled by crural plates, one on each side, dipping to unite crura with top of intercamarophorial plate; brachial processes curved ventrally, not outwardly bowed; median sep- tum very short on floor of valve, length greatly increasing with height; camarophorium spoon- shaped, anteriorly widening, not joined to hinge plate except by short, relatively high intercamaro- phorial plate, anterior midline with short, toothlike process. Muscle marks faintly impressed, undiffer- entiated, in anterior half of camarophorium; pallial trunks (vascula media) on floor of valve, one on each side, diverging anteriorly from forward edge of medium septum, bifurcating near midlength of valve. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 708u 152234-1 11.0 10.3 12.3 7.5 106 (holotype) 152235a 1.7 1.6? 1.6 0.8 ? 152235b 2.6 2.4 2.4 1.2 76? 152235c 3.7 3.3 3.1 1.8 91 152235d 4.3 3.9 3.9 1.9 96 152235e 4.8 4.3 4.3 2.6 94 152235f 5.3 4.8 5.0 2.8 100 152235g 7.0 6.4 6.9 4.0 88 152235h 7.7 6.7 7.0 4.4 85 152235i 8.2 7.5 8.4 4.8 90 152235J 10.0 9.3 10.9 7.0 101 152235k 11.1 11.1 14.3 8.0 117 152235-1 13.6 13.0 17.4 8.9 113 152235m 15.7 14.9 20.0 11.4 112 STRATIGRAPHIC OCCURRENCE.—Cathedral Moun- tain (base). LOCALITIES.—USNM 702, 702-low, 708u. DIAGNOSIS.—Small, pentagonal Stenoscisma with subdued costae, nearly smooth flanks, and unusually short beak without deltidial plates. TYPES.—Holotype: USNM 152234-1. Figured par- atypes: USNM 152233; 152234a-k,m-q. Measured paratypes: USNM 152235a-m. Unfigured paratypes: USNM 152234a-k. COMPARISON.—Stenoscisma fabarium is character- ized by its small size, widely elliptical or pentagonal outline with widely diverging sides, low and rounded costae on the fold and in the sulcus, and nearly smooth flanks, absent lateral pseudointer- areas (see discussion, below), short beak without deltidial plates, short spondylium, short brachial median septum, and its characteristic pallial mark- ings. Among Texas species it most nearly resembles S. doricranum, new species, differing in its wider outline, more strongly costate fold, shorter beak, absent deltidial plates, and proportionately shorter spondylium. Stenoscisma hueconianum (Girty) is similar in size, but is much more bulbous, more strongly costate, and more nearly triangular in outline. Among foreign species the closest resemblance is in some specimens of S. globulina (Phillips) illus- trated by Tschernyschew (1902, pi. 50: fig. 16). Stenoscisma fabarium differs in its larger size, less bulbous profile, normally broader fold, and more numerous costae on the fold. Stenoscisma sella (Ku- torga) of Schellwien (1900, pi. 15: figs. 1^) and Ozaki (1931, pi. 13: figs. 18-18d) is similar in out- line, but has no costae, only a sharp fold and groovelike sulcus. Stenoscisma tanakouense, (Ozaki, 1931, pi. 14: figs. 13a-b) is somewhat narrower in outline, and has a low, transversely flat fold with costae that begin rather abruptly, more like a species of Wellerella than like S. fabarium. Stenos- cisma superstes inornatum (Merla, 1934, pi. 23: figs. 3-19) also is similar in outline, but differs in its lack of costation, and if Merla's illustrations are correct, also differs in its round foramen. Stenos- cisma thevenini (Kozlowski, 1914, pi. 9: figs. 71-76, pi. 10: figs. 15a-d) is similarly costate, but not as wide as S. fabarium, its beak is longer, pedicle um- bonal area not as swollen, and its brachial proc- esses are strongly bowed laterally. DISCUSSION.—Stenoscisma fabarium has a pattern of pallial markings different from typical species of the species of the genus such as S. triquetrum, new species. Instead of the strong and deep trunks that diverge almost at a straight angle, the marks of the vascula media of S. fabarium diverge more nar- rowly, extend forward about to midlength, there bifurcate, and disappear near the anterior and lat- eral margins. Some specimens have the position of the gonocoels indicated by markings on the floor of the pedicle valve near the apex. This may be a NUMBER 21 2095 clue to their position in species of Stenoscisma where the marks are not visible. The stolidium is developed on some individuals of S. fabarium, but absent from others. Perhaps this sporadic development is linked to the lack of del- tidial plates in the foramen, which provides a rela- tively large opening for a functional pedicle. If the pedicle served for attachment of most individuals, a broad stolidium would have been unnecessary. S. fabarium lacks lateral pseudointerareas. Instead its pedicle valve has a flange around the entire margin, against which the ede of the brachial valve can bear, so that instead of meeting edge-to-edge, the valves meet in a kind of shallow tongue-and- groove joint, or in effect, overlap, thus providing more surface of contact than would be obtained by having the edges butt directly. This feature is pres- ent in other of the small species of Stenoscisma. Stenoscisma hadrum, new species PLATE 562, FIGURES 1-40 Camarophoria venusta [part] R. E. King [not Girty], 1931:110 pi. 34: figs. 29a, b, ?30a, b, 31a, b; pi. 35: fig. 5. Large for genus; outline broadly subtrigonal to subpentagonal, sides diverging between 70° and 120°, maximum width slightly anterior to mid- length; profile strongly biconvex; commissure unip- licate, fold moderately high, gently arched trans- versely, beginning 5-8 mm anterior to brachial beak; sulcus rather deep, broad, beginning 5-7 mm anterior to pedicle beak. Costae strong, rather sharp crested, added distally on fold and sulcus by bifur- cation, beginning 3-5 mm anterior to beaks, num- bering 3-6 (normally 5 or 6) on fold, one less in sulcus, 3-6 on each flank, becoming weaker later- ally; stolidium well developed, discontinuous be- tween fold and flanks, probably better developed on brachial valve; growth lines fine, closely spaced, with sporadic stronger laminae. Pedicle valve flatly convex transversely, strongly convex longitudinally through sulcus; beak short, erect, but not hooked; lateral pseudointerareas elon- gate, covered by edge of brachial valve; delthyrium triangular, constricted by large conjunct deltidial plates, leaving small eye-shaped foramen opening ventrally. Brachial valve strongly convex trans- versely, moderately convex longitudinally along crest of fold; beak blunt, now swollen nor atten- uate, apex within pedicle valve. Pedicle valve interior with teeth supported by large dental plates that fuse just above floor of valve to form boat-shaped spondylium, plates con- tinuing to valve floor as low median septum; muscle marks not observed; pallial marks shallow, trunks of vascula media diverging nearly at straight angle, crossing valve, one on each side, beginning just anterior to median septum. Brachial valve interior with crescentic hinge plate, greatly thickened at apex of valve to form large, striated, commonly polylobate cardinal proc- ess; hinge sockets at lateral extremes of hinge plate, details not seen; crural bases diverging slightly an- teriorly, space between them filled by short crural plates joining to top of intercamarophorial plate; brachial processes continuing free into valve, out- wardly bowed and ventrally bent, conforming to outline of camarophorium, spoon-shaped, with rather long median projection at anterior edge; median septum high, short on floor of valve, but length increasing with height; muscle marks not observed; intercamarophorial plate thin, low, rela- tively long; pallial marks on floor of valve not observed. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness o USNM 710r 152274a 21.0? 18.6 22.5 11.7 92 152274b 21.6 20.3 25.2 15.2 88 152274c 23.6 21.2 29.0 18.5 90 152274d 27.0? 24.2 34.0? 18.2 95 152274e 27.4 25.4 40.2 22.7 101 (holotype) USNM 707w 152283 32.3 27.2 44.6» 23.8 102 USNM 702e 152267a 26.1 23.1 33.7 15.7 93 152267b 28.5 25.4 38.0 19.6 109 STRATIGRAPHIC OCCURRENCE.—Skinner Ranch For- mation (Decie Ranch and Sullivan Peak members); Hess Formation (Taylor Ranch Member). LOCALITIES.—Decie Ranch: USNM 715a. Sullivan Peak: USNM 707, 707b, 707d, 707v, 708e, 713d, 713m, 722h. Skinner Ranch (low): USNM 707w, 708q, 709u, 711k, 720f, 720j. Skinner Ranch (top): USNM 705r, 710r, 715v, 722m, 723h, 723-1, 723s, 724p, 726h, 729p. Skinner Ranch: USNM 705n, 2096 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY 727m. Taylor Ranch: USNM 702d, 702e. Hess: USNM 726n. DIAGNOSIS.—Large Stenoscisma, strongly costate with well-developed stolidium and short beak. TYPES.—Holotype: USNM 152274e. Figured par- atypes: USNM 152267a-c, 152272, 152274a-d, 152275, 154576a, 154577a. Measured paratypes: USNM 152267a,b; 152274a-d; 152283. Unfigured paratype: USNM 152274c. COMPARISON.—Stenoscisma hadrum is character- ized by its large size, strong convexity, strong costae that begin near the beaks and normally bifurcate at the sides of the fold and sulcus, well- developed stolidium, and short beak. It occurs at some localities with S. pansum, new species, from which it differs by its less triangular outline, stronger, sharper, and more numerous costae that begin farther back, shorter beak without attenua- tion, proportionately greater thickness and convex- ity, and its greater frequency of bifurcating costae. It most nearly resembles S. venustum, differing pri- marily in its broader, less markedly triangular out- line, somewhat greater convexity, fold and sulcus that start farther posteriorly, lateral costae that tend to begin farther forward on the beak, and sharper costae on fold and sulcus. It also is similar to S. triquetrum, new species, differing in its less swollen pedicle umbonal region, without pinched-appearing sides, normally nonbifurcating costae that begin far- ther from the beaks, broader and less strongly trigonal outline, and its proportionately longer pedicle beak. Stenoscisma hadrum is more strongly and abundantly costate than S. pansum, and also attains larger size, is more convex, less triangular, and has shorter, less attenuate beaks on both valves. Stenoscisma exutum, new species, also is similar in some features, but is more nearly elliptical in out- line, has more numerous costae, many extending nearly to the apexes of the beaks, and it lacks a stolidium. Several species illustrated by Tschernyschew (1902) are superficially similar to S. hadrum. These are S. kutorgae (Tschernyschew), S. crumenum (Martin), and S. mutabile (Tscherynschew), all of which are easily distinguishable by their costae that begin at or near the beaks and are strong on the flanks. Waagen (1883) illustrated specimens of S. purdoni (Davidson) from the Salt Range that are similar to S. hadrum, but differ in their more nu- merous lateral costae, lower brachial convexity, stronger pedicle convexity, and more strongly hooked pedicle beak. His figured specimens of S. humbletonense (Howse) also differ in their stronger and more numerous lateral costae, and more strongly hooked beak, as well as in their weaker costae that begin farther forward on the fold. Stenoscisma pingue (Waagen) is smaller than S. hadrum, and also narrower and more strongly con- vex transversely. Stenoscisma alpinum (Schellwien, 1892) appears to be similar to S. hadrum, but its fold begins farther posterior and its longitudinal convexity is such that the anterior margin is nearly straight rather than somewhat emarginate as in S. hadrum. Stenoscisma hueconianum (Girty) PLATE 563: FIGURES 1-54 Camarophoria hueconiana Girty 1929:412, 414, figs. 41-21. Camarophoria deloi [part] R. E. King, 1931:110, pi. 34: fig. 24 [holotype]. Stenoscisma hueconiana (Girty) Stehli, 1954:340, pi. 24: figs. 14-17. Stenoscisma hueconianum (Girty) Grant, 1965a: 147, pi. 19: figs. 1-lb. Small for genus; outline transversely subelliptical to subpentagonal or trigonal, sides diverging be- tween 70° and 105°, maximum width located ante- rior to midlength; profile strongly biconvex; com- missure uniplicate; fold low to moderately high, broad, beginning about 5 mm anterior to brachial beak; sulcus very shallow, beginning 5-7 mm ante- rior to pedicle beak. Costae strong, sharp to blunt, commonly bifurcating on fold or sulcus, beginning 3-5 mm anterior to beaks, numbering 3-5 (nor- mally 5) on fold, one less in sulcus, 3-5 on each flank; stolidium rudimentary or absent; growth lines faint. Pedicle valve moderately convex transversely, strongly convex longitudinally through sulcus; beak relatively long, moderately strongly hooked but not normally pressed against brachial umbonal region; lateral pseudointerareas large, covered by edge of brachial valve; delthyrium broadly triangular, nor- mally without deltidial plates, leaving large open foramen. Brachial valve strongly convex trans- versely, less strongly convex longitudinally along crest of fold; beak bluntly pointed, apex within pedicle valve. Pedicle valve interior with hinge teeth fused to NUMBER 21 2097 sides of valve; dental plates converging just above floor of valve to form boat-shaped spondylium, fused together beneath spondylium and forming low median septum extending slightly anterior to spondylium; apical region between spondylium and side of valve often filled with shell material. Muscle marks in anterior two-thirds of spondylium, faint and undifferentiated, set off from posterior third by sharp line; pallial marks on valve floor, vascula media diverging at straight angle from forward edge of median septum, crossing valve to sides; marks of gonocoels posterior to transverse vascula, on floor of valve beside spondylium. Brachial valve interior with broadly triangular to crescentic hinge plate, thickened at apex to form cardinal process; hinge sockets short, located at lat- eral extremities of hinge plate; crural bases extend- ing forward from base of cardinal process, space between them filled by crural plates, joining them to top of intercamarophorial plate; brachial proc- esses continuing free beyond crural bases, outwardly bowed and ventrally bent, conforming to shape of edge of camarophorium; median septum high, thin, relatively short on floor but length increasing with height, capped by spoon-shaped camarophorium with unusually broad median projection at anterior edge; intercamarophorial plate short, buried in callus in some specimens. Muscle marks in spondy- lium and pallial marks on floor of valve not observed. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 712e 142508 9.2 7.5 10.5 7.4 81 0 10.2 8.8 12.0 9.3 84 1 10.5 8.8 13.6 9.5 92 2 11.1 9.9 14.7 10.7 93 3 12.5 10.8 15.8 12.0 97 155137 11.0 9.5 15.0 9.0 90 (lectotype) STRATIGRAPHIC OCCURRENCE.—Alacran Mountain Formation. LOCALITIES.—USNM 712e, 712m, 741h. DIAGNOSIS.—Small, transverse Stenoscisma with swollen pedicle valve umbo and wide fold and sulcus. TYPES.—Lectotype (herein designated): USNM 155137. Figured hypotypes: USNM 152247a-d, 154578a-g. COMPARISON.—Stenoscisma hueconianum is char- acterized by its small size, bulbous shape, sharp costae, open delthyrium without deltidial plates, and its absent or rudimentary stolidium. Its near- est relative in West Texas is S. maniculum, new species, from the Word Formation of the Glass Mountains, but it is normally about twice as big as the latter, and attains a maximum size about three times as big. In addition its costae are stronger and sharper and begin farther back, its pedicle valve is more strongly convex, and its maximum width is located farther forward. No other Texas species is closely similar to 5. hueconianum. Among foreign species S. karpinskii (Tscherny- schew, 1902, pi. 60) is most similar to S. hueconia- num. It differs in its more globose profile, costae that begin farther back, and more numerous costae on the large specimens. S. globosum (Tscherny- schew, 1902, pi. 46) is much more rotund, also differ- ing in its lower and broader costae, and more nearly circular outline. S. hueconianum differs from S. nuculum (Schellwien, 1900b) also illustrated by Hamlet (1928, pi. 9), in its larger size, more nu- merous and stronger costae,, and more strongly inflated pedicle valve. S. meyeri (Ozaki, 1931) is similar in outline, but differs in its less globose shape, stronger costae, and more attenuate pedicle beak. Stenoscisma acuminatum and S. peronae (Gemmellaro, 1899) both are more finely costate that S. hueconianum, and have the pedicle beak more strongly incurved against the brachial um- bonal area. DISCUSSION.—An editor's footnote in King (1931: 110) points out that the species Camarophoria deloi King was partly anticipated by C. hueconiana Girty (1929). Unfortunately, it is the holotype from the Hueco Formation that belongs to Girty's species, thus nullifying "deloi" as a taxon. This is discussed further under Stenoscisma "deloi" King (see above). Stenoscisma inaequale (Girty) PLATE 557: FIGURES 61-67 Camarophoria inaequalis Girty, 1929:411, pi. [p. 414]: figs. 10-13. This species from the Bone Spring Formation in North Apache Canyon in the Diablo Plateau was not recovered in our collecting nor in the work done in this region by members of the American 2098 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY Museum parties. The species strongly suggests S. kalum Stehli in general aspect and in the costation of the fold and sulcus, but S. kalum has finely costate flanks unlike the coarsely costate flanks of Girty's species. TYPES.—Holotype: USNM 155138. STRATIGRAPHIC OCCURRENCE.—Bone Spring For- mation. LOCALITY.—USGS 4643: Apache Canyon, Sierra Diablo, Van Horn (30') quadrangle, Texas. Stenoscisma kalum Stehli PLATE 565: FIGURES 24-32 Stenoscisma kala Stehli, 1954:339, pi. 25: figs. 1-6.—Grant, 1965a, pi. 19: fig. 4. This is one of the rarest species in the Sierra Diablo. Stehli figured 2 specimens and we recov- ered an additional 2 from the same place. The pedicle valve in the Museum collection is much larger than Stehli's and preserves its stolidium, which is confined to the tongue of the sulcus. A battery of 10 small conical spines guards the gape at the anterior of the tongue. The anterior margin of the flanks is similarly guarded. Unusually broad beveled areas over which the brachial valve laps make a shelf along the posterior margin lateral to the small teeth. The brachial valve preserves the stolidium, which is narrow and has obscure costae corresponding to those of the flanks. The inner margin of this valve is guarded by spines that dovetail with those of the pedicle valve. MEASUREMENTS (in mm).—From locality USNM 728f specimens 142519b and 142520b, respectively: length 18.0, (?); brachial valve length (?), 12.2; width 26.4, 19.0; thickness 8.0?, 8.3; apical angle 109°, 124°. STRATIGRAPHIC OCCURRENCE.—Bone Spring For- mation (lower). LOCALITIES.—AMNH 629; USNM 728f. TYPES.—Lectotype: AMNH 27315/1:1. Figured paratypes: AMNH 27315/1:2. Figured hypotypes: USNM 142519a-d; 142520a,b. Stenoscisma levicostum, new species PLATE 564: FIGURES \-i\ Camarophoria venusta [part] R. E. King [not Girty], 1931: 110, pi. 35: figs, la-c, 4. Average size, or slightly larger for genus; outline broadly subtrigonal to subpentagonal, sides diverg- ing between 85° and 130°, averaging more than 90°; profile moderately biconvex; commissure uniplicate, fold moderately high, slightly arched across crest, beginning about 6 mm anterior to brachial beak; sulcus shallow to moderately deep, beginning 8-10 mm anterior to pedicle beak. Costae moderately strong on fold, crests sharp to blunt, low and weak on flanks, beginning 5-7 mm anterior to beaks, numbering 4-6 on fold, one less in sulcus, 3-5 weak and low on flanks, bifurcations occurring only rarely, at sides of fold; stolidium better devel- oped on brachial valve, present on flanks and fold but not continuous. Growth lines weak, irregularly spaced; other ornamentation absent. Pedicle valve flatly concave transversely, moder- ately convex along sulcus; umbonal region slightly swollen; beak short, moderately hooked; beak ridges blunt, short; lateral pseudointerareas elongate, flat, normally covered by edge of brachial valve; del- thyrium triangular; deltidial plates small, only barely conjunct in adults, leaving narrowly elon- gate, oval foramen. Brachial valve rather strongly convex transversely, somewhat less longitudinally; umbonal region evenly convex, not strongly swol- len or flattened; beak bluntly pointed, apex within pedicle valve, beneath deltidial plates. Pedicle valve interior with blunt, knoblike hinge teeth; dental plates supporting hinge teeth, converg- ing toward floor of valve; joining just above floor to form large, boat-shaped spondylium, fusing and continuing to floor as low median septum, support- ing spondylium. Transverse pallial troughs shal- lowly impressed, diverging from anterior edge of median septum; anteriorly directed pallial marks making thin lines, diverging from near anterior edge of median septum, each trunk bifurcating toward edge of valve, making dendritic pattern; muscle marks faint striations in anterior part of spondylium. Brachial valve interior with broadly triangular hinge plate, apex greatly thickened and roughened to form large knoblike cardinal process; sockets elongate, narrow; crura diverging from anterior of hinge plate, continuing free, bowed and bent to conform to outline of camarophorium; intercamaro- phorial plate thickened at posterior end, descending to merge with floor of camarophorium; median NUMBER 21 2099 septum high, moderately long, length slightly in- creasing with height, capped by large, spoon-shaped spondylium with prominent, toothlike projection at anterior midline; muscle and pallial marks not observed. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness C) USNM 728g 152879a 7.2 6.4 6.5 3.6 65 152879b 8.9 8.1 8,5 4.0 75 152879c 10.8 9.6 11.0 5.2 82 152879d 12.4 10.7 13.9 6.9 87 152879e 16.6 14.6 17.0? 9.0 82 152879f 17.7 15.2 22.4 10.3 95 152879g 18.5 15.3 23.0 12.3 93 AMNH 591 154579b 22.3 18.9 28.4 16.1 100 (holotype) STRATIGRAPHIC OCCURRENCE.—Bone Spring For- mation (lower). LOCALITIES.—AMNH 492, 497, 591; USNM 728g. DIAGNOSIS.—Large, triangular Stenoscisma with strong and prominent costae on the fold but sub- dued costae on the flanks and posterior. TYPES.—Holotype: USNM 154579b. Figured par- atypes: USNM 152879a,i-m; 154579a-c. Measured paratypes: USNM 152879a-g. Unfigured paratypes: USNM 152879c-g. COMPARISON.—This species is most like S. hadrum and S. aptatum, both new. It differs from S. hadrum in being much smaller, in having much less promi- nent costae on the flanks, in having the shell more completely costate, and in having the fold originate farther anteriorly than in S. hadrum. The fold and sulcus of S. aptatum are less numerously costated than those of S. levicostum, the flanks are more strongly costate, it has a narrower outline, and S. levicostum is more spreading laterally than S. aptatum. It differs from S. triquetrum, new species, in its less inflated pedicle umbonal region, without the pinched appearance of the sides, as well as its fewer and weaker costae, wider outline, and smaller size. Its wide outline is similar to that of S. exutum, new species, but it is readily distinguished from that species by its fewer and weaker costae that begin far forward of the beaks. Stenoscisma maniculum, new species PLATE 565: FIGURES 16-23 Camarophoria deloi R. E. King, 1931:110, pi. 34: figs. 25a-c [not fig. 24 = S. hueconianum (Girty)].—Stainbrook and Madera, 1941:378, pi. 55: figs. 15-27. Small for genus; outline broadly subelliptical to subpentagonal, sides diverging nearly 100°, maxi- mum width located near midlength; profile mod- erately strongly biconvex; commissure uniplicate, fold moderately high, transversely flat, beginning about 6 mm anterior to brachial beak; sulcus rather shallow, beginning 5-6 mm anterior to pedicle beak. Costae low, rounded, bifurcating at sides of fold, weak on flanks, numbering 5 or 6 on fold, one less in sulcus, about 5 on each flank; growth lines faint, sporadic laminae slightly stronger. Pedicle valve moderately convex transversely, somewhat more convex longitudinally through sul- cus; beak short, stubby, fairly strong, hooked but not pressed against brachial umbo; lateral pseudo- interareas narrow, short, overlapped by edge of brachial valve; delthyrium triangular, open, with- out deltidial plates, partly filled by brachial beak. Brachial valve moderately and evenly convex trans- versely and longitudinally; apex of beak within pedicle valve. Pedicle valve interior with small hinge tooth fused to each side of valve, supported by strong dental plates that meet just above floor to form boat-shaped spondylium, continue to floor as low median septum; marks of vascula media shallow, diverging at straight angle just anterior to median septum; other pallial marks and muscle marks not observed. Brachial valve interior with triangular hinge plate, thickened at apex to form cardinal process; hinge sockets short, located at lateral extremes of hinge plate; crural bases diverging forward from near base, continuing free as brachial processes, outwardly and ventrally bending to conform to outline of camarophorium; space between crural bases and around intercamarophorial plate filled by callus; median septum high, rather long on floor of valve, length increasing slightly with height. Muscle and pallial marks not observed. STRATIGRAPHIC OCCURRENCE.—Road Canyon For- mation. 2100 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (c) 8.6 7.3 11.4 7.0 99 10.7 8.7 12.0? 9.5 85? 9.5 105 USNM 706£ 152305a (holotype) 152305b King 241 YPM 12693 12.0? ? 13.! LOCALITIES.—King 241; USNM 706f. DIAGNOSIS.—Small, widely elliptical Stenoscisma, resembling H. hueconianum (Girty). TYPES.—Holotype: USNM 152305a. Figured par- atype: USNM 152305b. COMPARISON.—Stenoscisma maniculum is charac- terized by its small size, broad outline, short hooked beak without deltidial plates, and its weak costae that are bifurcated only at the sides of the fold. It most nearly resembles S. hueconianum (Girty) from the Leonardian of the Hueco Mountains. Stenos- cisma maniculum differs in its smaller size, weaker costae, less tightly hooked beak, and much lower convexity, especially of the pedicle valve. It differs from other small species from Texas, S. doricranum and S. fabarium, both new, in its broader outline and especially by its finer and more abundant costae, especially on the flanks. Compared to foreign species, S. maniculum has fewer and weaker costae than S. acuminatum (Gem- mellaro, 1899) or S. karpinskii (Tschernyschew, 1902), and is broader and less bulbous. It is more costate on the flanks than S. thevenini (Kozlowski, 1914), and also is smaller and proportionately broader. Stenoscisma multicostum Stehli PLATE 553: FIGURES 28-32; PLATE 565: FIGURES 33-45 Stenoscisma multicosla Stehli 1954:339, pi. 25: figs. 7-9.— Crant, 1965a, 148, pi. 19: figs. 3-3a. Large for genus, wider than long, widely trigonal outline; widest anterior to midvalve; sides narrowly rounded; divergence of sides about 100°. Beak short, straight, smooth, with vestigial deltidial plates. Foramen elongate, elliptical. Surface multicostate, costae narrowly rounded, moderately strong, occa- sionally bifurcated or implanted on flanks but with several bifurcations near 10 mm anterior to beak. Fold with 4 or 5 costae at origin but 9 or 10 at anterior margin. Lateral costae of fold or sulcus disappearing near midvalve. Flanks with 5-7 costae. Stolidium narrow. Pedicle valve less deep than brachial valve, gently convex in lateral profile but broadly concave in anterior view. Sulcus originating about 7 mm ante- rior to beak, shallow to midvalve, widening rapidly and forming long moderately strongly geniculated tongue. Flanks moderately wide, gently convex, fairly strongly elevated above sulcus anteriorly. Brachial valve strongly and evenly curved in lat- eral profile, broadly domed in anterior profile, with long steeply sloping sides. Umbonal and median regions swollen; fold originating about 7 mm ante- rior to beak, low and rounded, widening rapidly anteriorly to occupy about half valve width; flanks narrow and moderately swollen and steeply descend- ing anterolaterally. Pedicle valve interior 9 mm long, tapering slightly anteriorly, narrowly rounded at front, suported on short low septum slightly extended anterior to end of spondylium. Vascula media transverse, strongly impressed. Teeth small. Brachial valve incomplete but with small hinge plate, ponderous cardinal process and short stout intercamarophorial plate. Septum high but short; camarophorium not fully preserved. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 728f 142515a 28.4 ? 37.8 ? 100 142518b ? 22.4 34.0*? 12.6 100 USNM 738h 154919a 29.6 27.0 39.0 21.3 89 USNM 728m 152880 29.8 27.5 43.04- 20.0 107 STRATIGRAPHIC OCCURRENCE.—Cibolo Formation, Bone Spring Formation. LOCALITIES.—Cibolo: USNM 728m, 738c, 738h, 738t. Bone Spring: AMNH 629; USNM 728f, 728h, 728e. DIAGNOSIS.—Large, nearly completely costate Stenoscisma with bifurcation and intercalation of costae at the inception of the fold and sulcus. TYPES.—Lectotype (herein designated): AMNH 27316/1:3. Figured paratypes: AMNH 27316/1, 2. Figured hypotypes: USNM 142515a,b; 142518a,b; 152880; 154919a. NUMBER 21 2101 COMPARISON.—Stenoscisma multicostum is most like S. pyraustoides, new species, in size and out- line, but its costae are wider and more closely crowded, their increase is more concentrated than in the Glass Mountains species, the flanks are nar- rower and less strongly costate, and the lateral extremities are more flaring. This species differs from S. problematicum, new species, in having more numerous costae on the fold, broader flanks, and more flaring anterolateral regions. The fold and sulcus generally have more costae which are finer than those of either S. triquetrum, new species, or S. venustum (Girty). DISCUSSION.—Stehli (1954) figured three fragmen- tary specimens of this species. We obtained only two specimens from the Sierra Diablo: a complete pedicle valve and a nearly complete brachial valve with parts of the stolidium preserved. The species is thus exceedingly rare and even with the addi- tional information given herein can hardly be said to be properly described. In addition to the two specimens from the Sierra Diablo, we refer here another large, poorly preserved but nearly com- plete specimen from the Cibolo Formation in the Chinati Mountains. This specimen (USNM 152880) differs somewhat from the others, especially in the form and costation of the flanks; nevertheless, it is so close that we have furnished its measurements. The peculiar development of the costae bifurcat- ing near the initiation of the fold and sulcus is the feature that makes this species unique. This may ultimately prove to be an evanescent feature when a large series of this species is found. The speci- mens in the collection certainly do not constitute satisfactory comparative material. It is also possible that, when more and better material is obtained, S. pyraustoides, new species, will prove synonymous. At present the differences between the two species seem distinct, although there is no question as to their similar appearance and probable contempo- raneity. Stenoscisma myioides, new species PLATE 566: FIGURES 1-57 Small for genus; outline subtrigonal to subpen- tagonal, sides diverging between 70° and 90°, max- imum width located anterior to midlength; com- missure uniplicate, fold low to moderately high, beginning 4-7 mm anterior to brachial beak, broadly to narrowly arched transversely, sulcus shallow, be- ginning 5-8 mm anterior to pedicle beak. Costae low, rounded, without bifurcation or intercalations, beginning 1-6 mm anterior to beaks, numbering 2-4 (averaging 3) on fold, one less in sulcus, 2 or 3 on each flank. Concentric ornament and growth lines faint; stolidium absent. Pedicle valve moderately strongly convex trans- versely and longitudinally; umbonal region some- what swollen; beak somewhat short, slightly atten- uate, normally rather strongly hooked, may press against brachial umbo; beak ridges undefined; lat- eral pseudointerareas long, narrow, normally cov- ered by edge of brachial valve; delthyrium triangu- lar, wide; deltidial plates absent in individuals with strongly hooked beaks, small and disjunct in others. Brachial valve moderately strongly convex transversely, less convex along crest of fold; um- bonal region slightly swollen, may be slightly atten- uate; apex of beak within pedicle valve, normally covered by overhanging pedicle beak. Pedicle valve interior with small, denticulate, knoblike teeth, dental plates large, converging just above floor to form boat-shaped spondylium, con- tinuing to floor as low median septum. Muscle marks faintly impressed in anterior half of spon- dylium; troughs of vascula media diverging nearly at straight angle from anterior edge of median septum, extending across floor to sides of valve; other pallial marks thin, anteriorly diverging from edge of median septum. Brachial valve interior with triangular hinge plate greatly thickened at apex to form cardinal process; sockets wide, rather long, corrugated, lo- cated along posterolateral edges of hinge plate; crural bases diverging from forward edge of hinge plate; brachial processes extending free, outwardly and ventrally bent, conforming to outline of cama- rophorium; median septum short, relatively thick, length increasing slightly with height; camaropho- rium short, wide, with wide, blunt, anterior mar- ginal projection; intercamarophorial plate propor- tionately long, thick, low, supporting hinge plate by means of short, connecting crural plates. Muscle marks not observed: presumably in camarophorium; pallial marks on floor of valve, vascula media diverging from anterior edge of median septum, bifurcating about three times on course toward valve edge. 2102 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (") USNM 705a 152218a 7.6 6.4 7.4 4.1 86 152218b 9.0 7.8 10.0 5.8 89 152218c 10.0 8.4 10.0 6.4 78 152218d 10.7 8.7 12.1 7.0 92 (holotype) STRATIGRAPHIC OCCURRENCE.—Skinner Ranch For- mation (base). LOCALITIES—USNM 705a, 716q, 720e. DIAGNOSIS.—Small, paucicostate Stenoscisma with- out stolidium. TYPES.—Holotype: USNM 152218d. Figured par- atypes: USNM 152217a,b; 152218b,c; 154580a-e. Measured paratypes: USNM 152218a-c. Unfigured paratype: USNM 152218a. COMPARISON.—Stenoscisma myioides is character- ized by its small size, rather weak costae that begin near the beaks, normally somewhat hooked pedicle beak, and absent stolidium. Among Texas species it most nearly resembles S. doricranum, new species, differing in its slightly smaller average size, more narrowly triangular outline, more numerous costae beginning farther back, and absence of a stolidium. S. aptatum, new species, also is similar in form, but is about three times as big, has a stolidium, a wider outline, proportionately shorter and more consist- ently hooked beak, and stronger growth lines. Sten- oscisma myioides occurs in the same beds as S. py- raustoides, new species, but differs from that species in its much smaller size, narrower outline, fewer costae which do not begin at the beaks and do not bifurcate, and absence of a stolidium. Stenoscisma fabarium, new species, is another small species, although larger than S. myioides, and is easily dis- tinguishable by its wide outline, bifurcating costae, very short beak, and normally well developed stolidium. Stenoscisma Ihevenini (Kozlowski, 1914) from the Copacabana Formation of Bolivia is similar to S. myioides, differing primarily in its stronger costae on the fold which begin farther back and tend to bifurcate anteriorly, weaker costae on the flanks, wider outline, and less attenuate beak. S. biplica- tum (Stuckenberg) as figured by Reed (1944, pi. 22) also is similar, differing in its much stronger costae that begin nearly at the beaks. Stenoscisma biplicatum (Stuckenberg, 1898, pi. 3) is entirely dissimilar, probably more closely related to S. renode, new species. Stenoscisma oblisum, new species PLATE 567: FICURES 1-68 Average size for genus; outline subtrigonal with protruding anterior margin and attenuate beak, sides diverging between 50° and 100°, maximum width normally located slightly anterior to mid- length; profile slightly to moderately biconvex; commissure uniplicate, fold high, broad, standing high above flanks at anterior, beginning 7-10 mm anterior to brachial beak; sulcus rather shallow, broad, beginning 9-12 mm anterior to pedicle beak. Costae moderately strong, sharp to blunt crested, rarely bifurcating, beginning 6-8 mm anterior to beaks, numbering 4-7 on fold, one less in sulcus, 6-8 on each flank; stolidium present, but full ex- tent and pattern of development not observed. Pedicle valve nearly flat transversely, moderately convex longitudinally through sulcus; beak long and attenuate, sides pinched, umbonal area may appear swollen due to pinching of sides, apex erect, not hooked; deltidial plates not observed, but prob- ably present; lateral pseudointerareas present, cov- ered by edge of brachial valve, hence dimensions unknown. Brachial valve strongly convex trans- versely, moderately convex longitudinally along fold; beak only slightly swollen, attenuate, apex within pedicle valve. Pedicle valve interior with boat-shaped spon- dylium supported above floor by low median sep- tum; other interior details unknown. Brachial interior with thin median septum, and camaropho- rium; other internal details unknown. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (') USNM 739 152284a 6.0 5.7 5.5 3.0 65 152284b 9.0 8.4 8.6 4.0 75 152284c 11.0 10.2 13.0? 5.3 87 152284d 19.0 17.1 18.7 12.0 78 152284e 22.0 20.0 27.0? 14.0 96 (holotype) USNM 740 152264a 10.4 10.4 7.7 4.3 66NUMBER 21 2103 STRATIGRAPHIC OCCURRENCE.—Capitan Limestone. LOCALITIES.—USNM 725-1, 739, 740. DIAGNOSIS.—Stenoscisma having low convexity and narrow pedicle valve beak. TYPES.—Holotype: USNM 152284e. Figured par- atypes: USNM 152263a,b; 152264a-c; 152284a-d. Measured paratypes: USNM 152264a, 152284a-d. COMPARISON.—Stenoscisma oblisum is character- ized by its attenuate beak with pinched sides, rela- tively low convexity, numerous and normally non- bifurcating costae, and its fold that stands high at the anterior margin and causes protrusion of the anterior outline. In its numerous costae it resem- bles S. trabeatum, new species, which also occurs in the Guadalupian of the Guadalupe Mountains. It differs from that species in its normally non- bifurcating costae that begin much farther forward, pinched posterolateral outline, attenuate beaks, and normally narrower, more strongly triangular outline. It is smaller and less convex than S. venus- tum (Girty) or S. triquetrum, new species, has its sides more strongly pinched, and has more numer- ous costae on the flanks. It is much smaller and narrower than S. pyraustoides, new species, and its costae start much farther forward and rarely bifur- cate. It differs from S. renode, new species, from the Word Formation of the Glass Mountains in its lower convexity, more numerous costae that start farther forward, and especially in its attenuate pedicle beak that is not hooked against the umbonal region of the brachial valve. It is smaller, more attenuate and narrower than S. multicostum Stehli, and its nonbifurcating costae do not begin as far back on the beaks. Stenoscisma pansum, new species PLATE 568: FIGURES 1-42 Average size for genus; outline narrowly to broadly trigonal, sides diverging between 70° and 105°; profile flatly to moderately biconvex; com- missure uniplicate; fold low to moderately high, gently arched transversely beginning 6-10 mm an- terior to brachial beak; sulcus moderately deep beginning 6-12 mm anterior to pedicle beak. Co- stae moderately strong on fold and sulcus, weak on flanks, subangular, rarely bifurcating, beginning 6- 12 mm anterior to beaks, numbering 3-5 on fold, one less in sulcus, 2-5 on each flank, becoming weaker laterally; stolidium well developed on fold and flanks of brachial valve, presumably less strong on pedicle valve; growth lines faint, closely spaced, with irregularly spaced stronger laminae. Pedicle valve flatly convex transversely and longi- tudinally; umbonal region slightly swollen, with pinched sides; lateral pseudointerareas elongate, narrow, covered by edge of brachial valve; beak moderately long, erect, slightly hooked; deltidial plates small, disjunct, leaving narrow foramen. Bra- chial valve moderately convex transversely, less convex longitudinally along crest of fold; beak slightly swollen, normally rather attenuate, apex within pedicle valve. Pedicle valve interior with boat-shaped spon- dylium supported by low median septum; brachial interior with high median septum and camaropho- rium; other internal features not observed. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 7l2p 152259 18.2 15.9 23.7 103 11.5 USNM 711d 152257a 22.0 20.0 28.4 16.0 97 152257b 25.8 23.0 31.0? 16.2 100? 152258d 17.0 15.0 24.0 11.3 114 (holotype) STRATIGRAPHIC OCCURRENCE.—Skinner Ranch For- mation (Decie Ranch and Poplar Tank members); Skinner Ranch Formation (lower). LOCALITIES.—Decie Ranch: USNM 707w. Poplar Tank: USNM 708e. Skinner Ranch (low): USNM 71 Id, 712p. Skinner Ranch (undifferentiated): USNM 730v. DIAGNOSIS.—Large, sparsely costate Stenoscisma of low convexity. TYPES.—Holotype: USNM 152258d. Figured par- atypes: USNM 152254; 152255; 152257a,b,; 152258a-c. Measured paratypes: USNM 152257a,b; 152259. Unfigured paratype: USNM I52258d. COMPARISON.—Stenoscisma pansum is character- ized by its trigonal outline, low convexity, weak costae that start far forward and may be nearly absent from the flanks, and by its rather pinched- appearing sides with attenuate pedicle and brachial beaks. It occurs at a few localities with S. hadrum, new species, from which it differs in its smaller maximum size, fewer costae, lower convexity, longer 2104 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY and more attenuate beaks, and more distinctly trigonal outline. Among Texas species it suggests S. venustum (Girty) and S. triquetrum, new species, although the resemblance is not close. Stenoscisma pansum is smaller, flatter, less completely costate and has the costae beginning farther forward, leav- ing the umbonal region smooth. Its juveniles are similar to adults of S. thevenini (Kozlowski, 1914) but S. pansum is larger, more trigonal, less convex, and has longer more attenuate beaks. Stenoscisma biplicatum (Stuckenberg) illustrated by Reed (1944, pi. 22: fig. 11) is somewhat similar to S. pansum, although its costae appear to be stronger, especially on the fold, and normally fewer, beginning farther back toward the beaks. Stenoscisma peneleve, new species PLATE 569: FIGURES 1-44 Medium size for genus, subtrigonal in outline, wider than long, maximum width near midvalve. Sides somewhat narrowly rounded; anterior margin broadly rounded. Divergence of sides nearly right angle. Beak short, suberect, not pressed onto umbo of opposite valve. Surface posteriorly smooth, ante- rior half sparsely costate, generally with 3 costae in fold, 2 in sulcus continued onto umbo and 1 indis- tinct costa on each flank. Stolidium present, but shape not known. Pedicle valve fairly evenly and gently convex in lateral profile but broadly and gently concave in anterior profile. Umbonal region narrowly swollen; sulcus originating posterior to midvalve, shallow and wide, not deeply depressed; flanks narrow, slightly convex to slightly concave. Brachial valve evenly and gently convex in lat- eral profile, strongly domed with steeply dipping sides in anterior profile. Median region and umbo swollen; fold originating slightly posterior to mid- valve, only moderately elevated anteriorly; flanks moderately depressed but convex and swollen. Interior unknown except for generic characters. STRATIGRAPHIC OCCURRENCE.—Neal Ranch Forma- tion; Lenox Hills Formation. LOCALITIES.—Neal Ranch: USNM 715b. Lenox Hills: USNM 709t. DIAGNOSIS.—Medium-size Stenoscisma with smooth posterior and flanks but fold with three costae. TYPES.—Holotype: USNM 152261a. Figured par- MEASUREMENTS (in mm).— brachial apical valve thick- angle length le7igth width ness (°) USNM 715b 152261a 8.8 7.9 8.9 4.4 76 (holotype) 152261b 12.4 11.0 12.7 7.3 86 152261c 13.0? 11.2 14.0 8.8 92 152261d 14.0 12.3 16.6 ? 86 atypes: USNM 152256a-c, 152261b. Measured para- types: USNM 152261b-d. Unfigured paratypes: USNM 152261c,d. COMPARISON.—The lack of costae on the posterior part and the sparseness of the costae on the anterior part of this species suggests S. bonum, S. doricra- num, and S. calvatum, all new. Stenoscisma pene- leve differs from the first in its larger size and much stronger costae in the adult. While S. doricranum attains about the same size as S. peneleve, it differs in having much stronger costation and deep spaces between the costae. In S. calvatum the costation is not uniform, there often being 3 on the fold, the flanks are more costate, and the brachial valve more strongly convex. Furthermore, in these species the costae in the sulcus do not begin as far back as the umbonal slope, as they do in S. peneleve. Stenoscisma problematicum, new species PLATE 570: FIGURES 1-44 Large for genus, widely triangular in outline with narrowly rounded sides, widest part well ante- rior to midvalve; anterior margin nearly straight; sides diverging about 90° in adult, less in younger specimens but slightly more in old ones. Brachial valve deeper than pedicle valve. Beak short, nearly straight; deltidial plates small. Surface costate ex- cept for smooth beaks; costae usually direct, fold with 5-9 costae, usually 6 or 7, outside costa often appearing on lateral slope; sulcus with one less; flanks with 6-9, usually 6, outside 1 or 2 indistinct. Stolidium narrow. Pedicle valve gently convex in lateral profile but broadly concave when viewed from anterior; um- bonal region narrow and flatly convex; sulcus orig- inating near beak (5-7 mm anterior), widening rapidly, moderately geniculated with moderately long tongue. Flanks moderately elevated, narrowly rounded, slopes steep. NUMBER 21 2105 Brachial valve strongly and evenly convex in lat- eral profile, broadly domed in anterior view; fold slightly elevated, umbonal region moderately swol- len; fold originating on umbonal slope about 7 mm anterior to beak, low with rounded profile and not strongly elevated, forming about 45 percent of the valve width. Flanks somewhat transverse, with swollen, steep sides. Details of spondylium and camarophorium not known. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length ividth ness (°) USNM 727u 154581a 11.0 10.0 11.0 5.2 74 154581b 18.0 16.8 22.6 8.8 86 154581c 23.5 21.1 27.2 ? 84 154581d 21.1 18.9 27.9 16.1 82 154581c 23.4 21.1 30.7 17.0 93 154581f c.23.0 21.2 32.6 18.3 100 154581g 23.2 21.8 24.6 19.0 102 (holotype) USNM 707a 152197a 25.0 22.4 28.7 16.4 86 152197b 21.0 18.2 22.9 12.9 78 STRATIGRAPHIC OCCURRENCE.—Lenox Hills Forma- tion; Cibolo Formation (Breccia Zone of Udden); Skinner Ranch Formation (Decie Ranch Member). LOCALITIES.—Lenox Hills: USNM ?705k, ?707n. Cibolo Formation: USNM 728-1. Decie Ranch: USNM 707a, 715a, 715f, 719y, 727u, 729i. Skinner Ranch (low): USNM 720g; (upper): USNM 730r. DIAGNOSIS.—Widely triangular Stenoscisma usu- ally with 6 or 7 costae on the fold and numerous costae on the flanks. TYPES.—Holotype: USNM 154581g. Figured par- atypes: USNM 152197b,c; 154581a-f; 154582. Mea- sured paratypes: USNM 152197a,b; 154581a-f. Un- figured paratype: USNM 152197a. COMPARISON.—This species belongs to the stock of large stenoscismas characterized by S. venustum (Girty) and S. triquetrum, new species. Conse- quently, resemblance is strong to a number of the larger species. It differs from S. pansum and S. ap- tatum, both new, in having a much larger size and more numerous costae on both flanks and on fold and sulcus. Stenoscisma problematicum differs from S. ha- drum, new species, in its more numerously costate flanks, smooth umbonal regions, and more closely crowded costae. It differs from S. triquetrum and S. venustum in the same respects. Its shape and costation are completely different from those of S. exutum, new species. Stenoscisma multicostum Stehli and S. pyraustoi- des, new species, are large forms occurring near the same level as S. problematicum but their much larg- er size, greater lateral spread, and very numerous costae make separation easy even in young forms. DISCUSSION.—This species is fairly common in the Decie Ranch Member in the Lenox Hills area but was not seen at the same level to the east where .the more numerously costate and larger stenoscis- matids predominate. We have placed a number of specimens from the Cibolo Formation of the Chinati Mountains (USNM 728-1), dated by fusulinids as Wolfcampian, with this Glass Mountains species. These Chinati specimens occur with large Scacchinella in an asso- ciation strongly suggesting the Decie Ranch Mem- ber of the Glass Mountains. These may be a facies type adapted to biohermal conditions, or they may indicate contemporaneity. Stenoscisma pyraustoides, new species PLATE 571: FIGURES 1-37; PLATE 572: FIGURES 1-17 Large for genus; outline broadly subelliptical to subtrigonal, sides diverging between 80° and 125°, normally over 100° in adults, maximum width near midlength, normally slightly farther toward the anterior; profile strongly biconvex to subtrigonal; commissure uniplicate, fold moderately high, standing increasingly high anteriorly, beginning 1-5 mm anterior to brachial beak; sulcus rather shal- low, but dipping steeply at anterior, extending forward as broad tongue, producing emargination of anterior. Costae strong and sharp crested on fold and in sulcus, lower, broader, and rounder on flanks, beginning at beaks, frequently bifurcated, especially on fold and sulcus, numbering 6-10 on fold (normally 9), one less in sulcus, 4-9 on each flank, number not necessarily equal on both sides; stolidium better developed on brachial valve, vary- ing from broad and fanlike to nearly absent. Pedicle valve flatly convex transversely and from beak to flanks, strongly convex longitudinally through sulcus; beak short, only moderately thick, suberect to erect but not hooked; beak ridges gen- 2106 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY tly curved, ill-defined; lateral pseudointerareas elon- gate, narrow, normally covered by edge of brachial valve; delthyrium moderately large, sides only slightly constricted by small, normally widely dis- junct deltidial plates; foramen large for genus, nevertheless small, opening ventrally. Brachial valve strongly convex transversely, only moderately convex along crest of fold due to ante- rior increase in height of fold, convexity uniform without swelling in umbonal region; beak bluntly pointed, apex only slightly inside pedicle valve. Pedicle valve interior with small teeth, continu- ous with dental plates that form short, boat-shaped spondylium just above floor of valve; median sep- tum low, extending slightly forward of spondylium; troughs of vascula media diverging from midline of valve just anterior to median septum, extending directly across floor of valve; muscle marks in spondylium faint and undifferentiated. Brachial valve interior with short, broad hinge plate, semicircular to crescentic; cardinal process at apex of hinge plate, located just beneath apex of valve, low or rather high, knoblike, normally not polylobate, shallowly striate for muscle attachment; hinge sockets short, narrow, at lateral extremes of hinge plate, finely corrugated; crural bases slightly diverging anterior to cardinal process, space be- tween filled by narrow crural plates dipping along center line attaching crural bases to top of inter- camarophorial plate; brachial processes not ob- served, presumed to be normal for genus; median septum high, thin, exceptionally short, length increasing greatly with height; camarophorium nar- row, relatively short, anteriorly widening; inter- camarophorial plate low, thick, relatively long; muscle marks not observed. STRATIGRAPHIC OCCURRENCE.—Skinner Ranch For- mation (base); Hess Formation (Taylor Ranch Member); Cibolo Formation. LOCALITIES.—Skinner Ranch: USNM 705a, 705b, ?709a, 71 lo, 71 Iz, 715c, 716p, 720e, 726j, 729j. Tay- lor Ranch: USNM 716o. Cibolo: USNM 739-1. DIAGNOSIS.—Exceptionally large and wide Stenos- cisma with numerous bifurcations of costae on pos- terior of fold and flanks. TYPES.—Holotype: USNM 152220L Figured par- atypes: USNM 152219a-d; 152220b,c,k; 152221a,b; 152225. Measured paratypes: USNM 152220a-h,j; 152225. Unfigured paratypes: USNM 152220a,d-h,j. COMPARISONS.—Stenoscisma pyraustoides is char- -Measurements exclude MEASUREMENTS (in mm), stolidium. brachial apical valve thick- angle length length width ness n USNM 705a 152220a 13.0 10.7 14.5 c.6.0 95 152220b 15.0? 13.0 16.7 10.3 89 152220c 13.5 12.8 18.4 11.0 104 152220d 18.2 16.2 23.5 14.0 103 152220e 19.0 16.8 26.0 + 14.0 107 152220f 23.7 22.4 28.0 16.0 93 152220g 26.0 25.2 35.9 21.3 116 152220h 28.3 26.6 45.1 22.7 104 152220i 32.5 30.5 50.0 26.6 114 (holotype) 152220J 34.7 32.5 56.0? 21.0? 118 USNM 716o 152225 35.5 33.5 50.5 23.2 109 acterized by its exceptional width, large maximum size, numerous and frequently bifurcating costae on fold and sulcus, lower and fewer costae on flanks, short beak with small disjunct deltidial plates, rela- tively short spondylium and camarophorium. The only known species that is closely related to S. pyraustoides is S. midticostum Stehli (1954) from the Sierra Diablo. Stenoscisma pyraustoides is larg- er, wider, and less strongly costate, especially on the flanks where the costae are lower, broader, and fewer. The species bears superficial resemblance to S. Irabcatum, new species, which is smaller, more triangular in outline, less strongly convex, has a longer beak, and a stolidium that is continuous from flanks to fold. DISCUSSION.—Stenoscisma pyraustoides, with its great width and many bifurcating costae that begin at the beaks, is the most distinctive species of the genus in the Glass Mountains. Its only close rela- tive is S. mullicoslum Stehli, from the Sierra Diablo, and the Chinati Mountains with which it shares the characteristics of the multicostate fold and sul- cus, open delthyrium with disjunct deltidial plates, and short spondylium and camarophorium. Stenos- cisma pyraustoides is rather variable, however, with respect to development of the stolidium; it is broad on some specimens and nearly absent on others. Perhaps the great width of the largest specimens reduced the need for extra surface area to be added by means of a stolidium. On the other hand, pos- sibly the relatively large foramen, unrestricted by large deltidial plates, was present to provide for NUMBER 21 2107 egress of a functional pedicle, thus reducing the necessity for the supporting surface provided by a broad stolidium. In our collections it is a fact that the few specimens with well-developed stolidia have the beak unusually short and nearly pressed against the brachial umbo. Apparently the genetic poten- tial for development of a stolidium was consistently present in this species, as in others, but the actual growth of the stolidium depended on its use to the organism; the stolidium developing if the pedicle failed to function in attachment. Stenoscisma renode, new species PLATE 573: FICURES 1-48; PLATE 574: FIGURES 1-22; PLATE 575: FIGURES 1-19 Normal size for genus; outline subtrigonal, sides diverging between 50° and 100°, maximum width just posterior to anterior margin; profile moderately strongly biconvex; commissure uniplicate, fold rather low, not standing high above flanks, begin- ning about 7 mm anterior to brachial beak; sulcus shallow, relatively flat transversely, beginning 7-10 mm anterior to pedicle beak. Costae strong on fold and sulcus, weaker on flanks, rounded, normally not bifurcating, beginning 3-7 mm anterior to beaks, numbering 4-7 on fold (normally 5), one less in sulcus, 4-7 on each flank (normally 5 or 6); stolidium moderately broad, best developed on flanks of brachial valve and in sulcus of pedicle valve, frequently double, with two flaps on one valve rather than one flap on each valve; growth lines fine, occasional stronger laminae present. Pedicle valve moderately strongly convex trans- versely and longitudinally through sulcus, some- what swollen in umbonal region; beak strongly hooked, pressed against brachial umbo in adults; lateral pseudointerareas proportionately broad, short, partly covered by edge of brachial valve; del- thyrium wide, triangular, without deltidial plates, normally competely occupied by brachial beak, with foramen visible only in juveniles. Brachial valve strongly convex transversely, moderately con- vex longitudinally along crest of fold; umbonal region only slightly swollen; beak bluntly pointed, entirely within pedicle valve. Pedicle valve interior with small but prominent teeth, fused to valve, supported by strong dental plates that form relatively long, boatlike spondy- lium; median septum low, slightly longer than spondylium, formed by union of dental plates be- neath spondylium. Muscle marks faint in anterior two-thirds of spondylium; pallial troughs deep on floor of valve, vascula media diverging at straight angle from center line of valve just anterior to median septum. Marks of gonocoels posterior to transverse marks, on floor of valve on either side of septum and spondylium. Brachial valve interior with large, subelliptical, laterally attentuate hinge plate, swollen at apex to form large, knoblike, frequently polylobate cardinal process, striated for muscle attachment; hinge sock- ets short, deep, finely denticulate, located at lateral extremities of hinge plate; crural bases extending forward from base of cardinal processs, continuing anteriorly as free, outwardly bowed and ventrally bent brachial processes; crural plates between crural bases very short, attaching to top of short and rather low intercamarophorial plate; camaropho- rium long, spoon-shaped, widest near anterior, with only short projection on anterior median line; mus- cle marks faint and undifferentiated in camaropho- rium; median septum high, relatively long, length increasing with height. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness C) USNM 706b 152210a 5.8 5.4 4.8 3.3 51 152210b 9.7 ? 8.3 - 53 152210c 12.7 10.9 11.0 8.3 60 152210d 17.2 14.9 16.6 9.9 72 152210e 18.0 15.5 18.4 12.0 82 152210f 20.0 17.9 22.8 13.8 85 152210g 22.0 20.0 23.9 17.0 84 152210h 23.8 19.8 25.0 18.4 94 152210i 25.0 25.8 28.0 19.9 88 (holotype) 152210J 26.8 23.7 29.6 18.8 91 USNM 706c 152212 28.0 24.8 29.6 18.8 91 STRATIGRAPHIC OCCURRENCE.—Word Formation (China Tank, Willis Ranch, Appel Ranch mem- bers, and lens between the last two); Cherry Can- yon Formation (Getaway Member). LOCALITIES.—Word: USNM 731u. China Tank: USNM 726r, 726s, 706c. Willis Ranch: USNM 706, 706e. Appel Ranch: USNM 704, 715i, 716v, 719z. Lens: USNM 706b, 732c, 742b. Getaway: USNM 728. 2108 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY DIAGNOSIS.—Robust Stenoscisma with pedicle valve beak pressed tightly onto the umbo of the brachial valve and with a prominent stolidium. TYPES.—Holotype: USNM 152210L Figured par- atypes: USNM 152209a-o; 152210c,e; 15221 la-d. Measured paratypes: USNM 152210a-i,j; 152212. Unfigured paratypes: USNM 152210a,b,d,f-h,j. COMPARISON.—Stenoscisma renode is characterized by its triangular outline, strong but blunt costae that begin near the beaks, a stolidium that develops on the brachial flanks and pedicle sulcus, its long spondylium, camarophorium and brachial median septum, and especially by its strongly hooked pedi- cle beak that is pressed so tightly against the bra- chial umbo as to close completely the delthyrium and external opening of the foramen. In its shape and costation it resembles S. venustum (Girty) and S. triquetrum, new species, but differs in its hooked beak and arrangement of its stolidium. Its closest relative in the Glass Mountains is S. camurum, new species, which is wider, has more bifurcating costae, and has the pedicle beak not as tightly pressed against the brachial umbo. S. repigratum, new species, occurs in the same beds with S. renode, but is wider, less convex in profile, has the costae beginning farther back, has an erect pedicle beak with well-developed deltidial plates and rather large foramen, and rudimentary or absent stolidium. Other Texas species are easily distinguished from S. renode by the characters listed above. The most common foreign species that resembles .S'. renode is S. mutabile (Tscherynschew) as illus- trated by himself (1902, pis. 22, 23, 45, 46) and by Merla (1934, pi. 22). Stenoscisma renode differs in its less bulbous profile, fewer bifurcating costae, and normally narrower outline. Stenoscisma bipli- catum (Stuckenberg, 1898) also has the beak pressed against the brachial umbo, but it differs from S. renode in its more pentagonal outline, and stronger, sharper costae that begin at the apexes of the beaks. Another species with the beak strongly hooked is S. pingue (Waagen) of Rothpletz (1892, pi. 10), but that species, which undoubtedly differs from Waagen's (1893) species, is much wider than S. renode, less strongly costate, and has the costae beginning farther forward, near the midlength of the shell. Several of Waagen's (1893) species from the Salt Range, namely, S. purdoni (Davidson), ■V. humblelonensis (Howe), and S. pingue (Waagen), have the beak strongly hooked or pressed against the brachial umbo as in S. renode. All three of these species differ from S. renode in their more numerous costae, and wider, less strongly trigonal outlines. DISCUSSION.—Stenoscisma renode occurs in the Word Formation of the Glass Mountains, and rep- resents an ultimate in the trend that we believe characterizes Texas Permian species of Stenoscisma. This species has the pedicle beak so tightly pressed against the brachial umbo in most individuals that a functional pedicle was impossible. The animal probably lived unattached, lying on the sea floor, supported by the added shell surface of the stolidium. Stenoscisma repigratum, new species PLATE 554: FIGURES 15-22 Average size for genus; outline moderately to broadly subelliptical, sides diverging between 80° and 120°, maximum width located slightly anterior to midlength; commissure uniplicate; fold low at commissure, but standing moderately high above flanks, slightly arched transversely; beginning 8-10 mm anterior to brachial beak; sulcus rather deep, broad, beginning 10-12 mm anterior to pedicle beak. Costae moderately strong, blunt to sharp, normally not bifurcating, beginning 2-5 mm ante- rior to beaks, numbering about 6 on fold, one less in sulcus, 5-8 on each flank; stolidium not present on observed specimens, presumably absent from species. Pedicle valve nearly flat transversely, rather con- vex longitudinally along sulcus, beak short, blunt, not hooked; lateral pseudointerareas elongate, somewhat broad, overlapped by edge of brachial valve; delthyrium triangular, constricted by well- developed, conjunct or disjunct deltidial plates, leaving relatively large foramen opening ventrally. Brachial valve moderately to strongly convex trans- versely, flatly convex along crest of fold, with maxi- mum convexity in umbonal region and just behind margin; beak blunt, apex within pedicle valve. Pedicle valve interior with dental plates converg- ing just above floor to form elongate boat-shaped spondylium, supported by low median septum. Space between spondylium and apical region partly filled by callus. Brachial valve interior with trigo- nal to crescent-shaped hinge plate, greatly thick- ened at apex of valve to form large, knoblike or NUMBER 21 2109 polylobate cardinal process with thickened base extending along midline of hinge plate; crural bases diverging from thickened base of cardinal process, continuing free into valve as brachial proc- esses bending ventrally; camarophorium large, with prominent anterior median extension; intercamaro- phorial plate long, space around it filled with cal- lus, obscuring any crural plates; median septum high, long, length only slightly increasing with height. MEASUREMENTS (in mm).—From locality USNM 706c specimen 152281: length 23.2, brachial valve length 23.2, width 33.6*, thickness 21.9, apical angle 116°. STRATIGRAPHIC OCCURRENCE.—Word Formation (China Tank Member); Cherry Canyon Formation (Getaway Member). LOCALITIES.—China Tank: USNM 706c. Getaway: 728w. DIAGNOSIS.—Large Stenoscisma with costate um- bones but lacking a stolidium. TYPES.—Holotype: USNM 152281. COMPARISON.—Stenoscisma repigratum is charac- terized by its many costae that begin near the beaks, its fold and sulcus that begin far from the beaks, its short beak with deltidial plates, broad outline, and flatly convex pedicle valve. It occurs with S. renode and S. camurum, both new, from which it differs in its nonhooked beak, many costae on the umbonal regions, broader outline, and absence of a stolidium. It differs from S. venustum (Girty) and S. triquetrum, new species, in the absence of a stolidium, a flatter pedicle valve, brachial umbo and anterior part of fold more swollen, and, on the flanks, more numerous costae that continue farther toward the beaks. Stenoscisma hadrum, new species, has a thicker pedicle valve, more strongly longitu- dinally convex brachial valve, bifurcating costae, fewer costae on the flanks, and a fold and sulcus that begin nearer the beaks. Among foreign species it most nearly resembles S. sanctispiritus (Schellwien, 1892), differing in its less widely divergent sides and fewer, nonbifurcat- ing costae. Stenoscisma thevenini (of R. E. King) PLATE 569: FIGURES 45-52 Camarophoria thevenini R. E. King [not Kozlowski], 1931: 110, pi. 34: figs. 28a-c. DISCUSSION.—King identified specimens from the Wolfcamp, Gym, and Leonard Formations with Kozlowski's Bolivian species. The single illustrated specimen is a juvenile shell from the Leonard that could be referred to any one of several species. The unillustrated specimens from the Hueco Formation resemble the Bolivian species, but most likely be- long to S. hueconianum (Girty). There is a strong resemblance between the fauna of part of the Hueco Group and that described by Kozlowski from Bolivia, but careful study normally shows specific differences. TYPES.—Figured specimen: YPMM 12695. Stenoscisma trabeatum, new species PLATE 576: FIGURES 1-31; PLATE 577: FIGURES 9-24 Stenoscisma venustum Newell et al. [not Girty], 1953, pi. 21: fig. 31. Average size for genus; outline transversely sub- elliptical to subtrigonal, sides diverging between 70° and 120°, maximum width located near mid- length; profile moderately strongly biconvex; com- missure uniplicate, fold moderately high, broad, rather flat transversely, beginning 10-12 mm ante- rior to pedicle beak. Costae moderately strong, sharp crested, added anteriorly by bifurcation and intercalation, beginning 3-6 mm anterior to beaks, numbering 5-10 on fold, one less in sulcus, 5-6 on each flank; stolidium well developed on brachial valve, broad, continuous from flanks to fold, short or missing from pedicle valve. Pedicle valve flatly concave transversely and mod- erately convex longitudinally; umbonal region slightly swollen; beak rather long, attenuate or with pinched sides, erect but not hooked; lateral pseudointerareas wide or narrow, spread into inte- rior, detached from side of shell along margin, forming elongate, shallow pocket along insides of posterolateral slopes; delthyrium triangular, con- stricted by well-developed, conjunct deltidial plates; foramen small, eye-shaped, opening directly ven- trally. Brachial valve moderately strongly convex transversely and longitudinally, with maximum convexity in umbonal region; beak somewhat at- tenuate, apex in pedicle valve beneath deltidial plates. Pedicle valve interior with strong hinge teeth, one on each side, fused to side of valve or to 2110 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY inwardly bowed part of lateral pseudointerareas; dental plates with forward edges sloping posteriorly, then curved strongly anteriorly to form edges of boat-shaped spondylium, plates fused beneath spon- dylium to form low median septum, slightly longer than spondylium. Muscle marks in anterior half of spondylium, set off from posterior half by sharp line; pallial marks distinct, troughs of vascula media beginning at edge of median septum, one crossing each side of valve, directly or slanting slightly toward posterior; gonocoel markings on floor of valve beside spondylium and behind pallial troughs. Brachial valve interior with small, crescentic hinge plate, greatly thickened at apex of valve to form knoblike cardinal process; crural bases extend- ing forward from near base of cardinal process, space between them filled by forward extension of process and by rather long crural plates attaching to top of intercamarophorial plate; brachial proc- esses continuing free into living chamber, outwardly bowed and ventrally bent; camarophorium elon- gate, narrow, with broad projection at anterior midline giving trilobate appearance to anterior edge; median septum high, thin, short on floor but length increasing with height. Muscle marks faint in camarophorium; pallial marks plain on floor of valve: two fine trunks diverging anteriorly, one from each side of median septum (on floor of valve), bifurcating at regular intervals, finally branching near margin, producing one trunk for each costa. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 737a 152230a 10.0 9.0 8.9 4.7 82 152230b 12.3 11.1 10.6 6.3 70 (holotype) 152230c 18.0? 15.3? 22.0 10.1 88 USNM 738 152231a 20.6 18.8 26.4 13.0 103 152231b 23.7 21.0 31.8 14.0 114 152231c 22.5 19.8 28.3 14.5 118 USNM 750a 152202a 24.4 21.3 29.4 15.2 95 STRATIGRAPHIC OCCURRENCE.—Bell Canyon For- mation (Rader and Lamar members); Capitan Formation. LOCALITIES.—Rader: USNM 725f. Lamar: AMNH 37, 40, 347 ( = L-2), 384, 430; USNM 725e, 728p, 728s, 738, 738b. Capitan: AMNH 475, 847; USNM 725p, 732q, 737a, 740-1, 740m, 740n, 750a, 750b. DIAGNOSIS.—Broad Stenoscisma with well- developed stolidium, bifurcating and intercalated costae that begin near the beaks. TYPES.—Holotype: USNM 152230b. Figured par- atypes: USNM 152230a,c,d; 152231a-c; 154585a; 154586; 154587; 154588. Measured paratypes: USNM 152202a; 152230a,c; 152231a-c. COMPARISON.—Stenoscisma trabeatum is charac- terized by its relatively broad outline, numerous bifurcating and intercalating costae that begin near the beaks, well-developed stolidium that is continu- ous, pedicle beak with conjunct deltidial plates, and its peculiar, externally opening pockets that are formed by partial detachment of the marginal por- tion of the lateral pseudointerareas. Externally it resembles 5. oblisum, new species, differing in its wider outline, less attenuate and pinched beak, and its more numerous costae that frequently branch or intercalate. S. pyraustoides, new species, from the Wolfcamp of the Glass Mountains is similar in its costation, but S. trabeatum differs in its narrower outline, more numerous costae on the flanks, and its continuous stolidium and lateral pockets. Stenos- cisma multicostum Stehli also is similar, but differs in its greater convexity, discontinuous stolidium, disjunct deltidial plates, and well-developed, nor- mal lateral pseudointerareas without pockets. No foreign species that are familiar to us have the numerous and bifurcating costae or continuous sto- lidium of S. trabeatum, therefore detailed compari- sons are not necessary. Stenoscisma triquetrum, new species PLATE 578: FIGURES 1-79; PLATE 579: FIGURES 1-32; PLATE 580; FIGURES 1-36; PLATE 581: FIGURES 1-19; PLATE 582: FIGURES 1-22 Camarophoria venusta R. E. King [not Girty], 1931:110, pi. 34: figs. 29a, b, 31a, b [not figs. 30a, b (= .S\ hadrum, new spe- cies)], pi. 35; figs. 3a-d, 5 [not figs, la-c, 4( = S. levicostum, new species), fig. 2(= ?)]. Stenoscisma venusta Cooper [not Girty], 1944:315, pi. 120: figs. 38-40. Stenoscisma venustum Cooper [not Girty], 1956a:522, text fig. la—Grant, 1965a:150, pi. 21; figs. 13, pi. 22: figs. 1-10, pi. 23: figs. 1-5; 1965b:H629, fig. 515:4f-i. Adult large for genus; outline broadly subtrigo- NUMBER 21 2111 nal, sides diverging between 65° and 115°, averag- ing about 90°, divergence typically increasing with shell size; young longer than wide; length and width becoming approximately equal at about 20 mm. Profile moderately biconvex; commissure unipli- cate; fold high, broad, and only gently arched over crest, beginning about 8-15 mm anterior to brachial valve beak; sulcus shallow except at anterior, begin- ning 12-18 mm anterior to pedicle valve beak. Costae moderately strong, blunt-crested, beginning 1-5 mm anterior to beaks, numbering 5-8, nor- mally 5 or 6 on fold, one less in sulcus, 4-6 on flanks, becoming lower and weaker laterally, rarely 1 or 2 on fold or sulcus bifurcating anteriorly; sto- lidium broad, fanlike, with fine concentric orna- ment, beginning just behind widest part of shell, not continuous from flanks to fold, better devel- oped on brachial valve, occasionally reduced or absent from pedicle valve. Radial and concentric ornamentation absent (except on stolidium); growth lines fine and closely spaced, with a few stronger laminae at irregular intervals. Pedicle valve gently convex transversely and from beak to flanks, more strongly convex through sul- cus; umbonal region relatively low to somewhat swollen; beak about normal length for genus, sub- erect to erect varying from not strongly to moder- ately hooked; beak ridges short, blunt; delthyrium triangular, small, constricted along sides and at anterior by conjunct deltidial plates, leaving nar- row, slitlike foramen normally opening directly dorsally; lateral pseudointerareas elongate, narrow, normally covered by overlapping edge of opposite valve. Brachial valve strongly convex transversely, mod- erately strongly convex along crest of fold, convex- ity rather uniform, valve nowhere strongly swollen or flattened; beak bluntly pointed, apex within pedicle valve, hidden by deltidial plates. Pedicle valve interior with blunt teeth, elongate, parallel to sides of valve; dental plates continuous with teeth, slightly convergent toward floor of valve, more abruptly curved immediately above floor, joining one another to form boat-shaped spon- dylium supported by low median septum; space between valve floor and outside of spondylium com- monly filled with callus. Relatively deep, transverse pallial troughs present in some individuals, crossing floor of valve just anterior to end of median sep- tum; muscle marks in spondylium weak. Brachial valve interior with broadly triangular hinge plate having apex thickened to form cardinal process, as a single small node in young individuals and becoming greatly thickened and binodose in adults, surface textured for muscle attachment; sockets elongate, narrow, finely corrugated, laterally bounding anterior third of hinge plate; crural bases fused to hinge plate, extending forward from base of cardinal process to anterior edge of plate, there continuing free as slender brachial processes, out- wardly bowed and gently curved ventrally; median septum high, thin, length increasing with height; camarophorium spoon-shaped, capping septum, wid- est just behind anterior end, slightly produced at anterior apex; intercamarophorial plate somewhat shorter than median septum, forming support be- tween camarophorium and hinge plate, median part of hinge plate frequently extending forward between brachial processes and dipping from sides to top of intercamarophorial plate; space between hinge plate and camarophorium commonly filled with callus, burying intercamarophorial plate. Muscle pattern not observed, presumed to lie in camarophorium. STRATIGRAPHIC OCCURRENCE.—Cathedral Moun- tain and Road Canyon formations. LOCALITIES.—Cathedral Mountain: AMNH 500B, C, J, N; USNM 700-1, 700x, 702, 702a, 702b, 702ent, 702-low, 702un, 703b, 708, 708u, 71 lq, 713t, 713w, 721u, 723y, 724s, 726u, 726y, 727o, 727p, 729z, 731b, 735b, 737v. Road Canyon: AMNH 503, 507; USNM 702c, 703, 703a, 706f, 716x, 719x, 721o, 721s, 726z, 726za. DIAGNOSIS.—Large Stenoscisma with elongate young stage, few bifurcations of costae, and wide stolidium. TYPES.—Holotype: USNM 152191u. Figured par- atypes: USNM 142526; 142528; 142531; 142531-38; 142540-43; 142544; 142547; 152190a-n; I52318a-d; 152320a-c; 152334b,e-g; 154589a-c. Measured para- types: USNM 152191a-t; 152319a-h; 152321a-f,j. Unfigured paratypes: USNM 152191a-t; 152334a,c,d. COMPARISON.—Ste?ioscisma triquetrum is charac- terized by its fairly large size, triangular outline with slightly indented sides just anterior to the beaks, and its usually direct and only occasionally bifurcating costae. Compared to other large stenos- cismas it differs from S. hadrum, new species, in its less robust form of the fully grown adult, its more rounded costae, its less strong costae on the flanks, 2112 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 702c 152191a 1.7 1.5 1.4 0.8 67 152191b 3.5 3.1 2.9 1.6 67 152191c 4.9 4.2 3.9 2,5 74 152191d 5.5 5.0 4.7 2.8 70 152l91e 6.5 5.7 5.2 3.0 68 152191f 7.3 6.5 6.2 3.5 71 152191g 7.8 7.0 6.6 3.5 79 15219lh 9.2 8.2 8.4 3.8 73 15219H 10.8 10.2 10.7 5.4 79 152191J 12.0 10.6 11.3 5.8 83 152191k 14.4 12.8 13.6 6.3 73 152191-1 17.0 15.0 16.4 8.0 82 152191m 19.9 17.8 22.8 10.0 88 152191n 23.9 22.0 27.7 14.7 80 15219lo 5.5 5.0 5.0 2.8 78 152191p 10.5 9.4 10.8 5.2 92 152191q 20.1 19.8 25.3 15.2 92 152191r 24.3 22.6 32.3 17.3 97 152191s 25.0 23.2 31.3 17.7 88 152191t 27.7 24.6 33.5 20.8 85 152191u 28.0 25.4 37.7 22.3 97 (holotype) USNM 702 152319a 2.8 2.4 2.4 1.4 82 152319b 3.2 2.8 2.7 1.3 89 152319c 3.9 3.5 3.2 1.7 91 152319d 4.9 4.3 4.3 2.5 74 152319e 5.5 4.9 4.9 2.8 81 152319f 6.8 6.0 6.0 3.2 85 152319g 8.6 7.3 7.7 4.4 70 152319h 11.2 10.6 10.9 7.7 87 USNM 702b 152321a 15.4 15.0 15.3 6.4 85 152321b 18.6 16.0 16.9 10.3 74 152321c 20.0 17.6 21.3 13.9 74 152321d 22.2 19.4 23.5 15.8 80 152321e 24.5 22.4 30.8 19.6 84 152321f 31.0 28.0 41.0 22.5 101 152321J 28.0 25.0 32.0 19.0 84 its sulcus not extending so far anteriorly, and its generally transverse young. Stenoscisma levicostum, new species, is a smaller, though coarsely costate species, which is wider and shorter than S. trique- trum and with the costae more spread out laterally. Stenoscisma multicostum Stehli is still larger than S. triquetrum, is much wider, and has more nu- merous costae. The same is true of S. problemati- cum, new species, regarding width and has more numerous costae but the two species attain nearly the same adult size. Stenoscisma pyraustoides, new species, is not likely to be confused with S. trique- trum because it is a very large, transverse, and multicostate species. As explained under S. venus- tum (Girty) only remote similarity exists between it and S. triquetrum. Among the foreign species similar enough to S. triquetrum externally to make comparison desir- able are several species illustrated by Tscherny- schew (1902); however, they all seem to differ con- sistently in having the ventral median septum higher and the camarophorium more strongly curved ventrally. Among them, S. crumenum (Mar- tin) is most similar (see Tschernyschew, 1902:489, pi. 22: figs. 2-15), differing in its somewhat smaller size, more strongly hooked pedicle beak, less abun- dantly costate juveniles, and more rounded, less triangular outline. Most of Tschernyschew's illus- trations show specimens that are less strongly co- state and have the costae starting farther forward than in S. triquetrum. However, figure 10 of plate 22 is more similar to the Texas species in its costa- tion. Stenoscisma kutorgae (Tschernyschew, 1902, pi. 22: figs. 16-17) is more remotely related to this species; it is more gibbous, its flanks are more strongly costate, and its costae begin at the beaks. S. mutabile (Tschernyschew, 1902:491, pi. 45) is comparable in size and costation, but it has the pedicle beak tightly pressed against the brachial umbo, as in the West Texas S. renode, new species, in contrast to the more erect beak of S. triquetrum which has the pedicle foramen and deltidial plates visible. The Salt Range of Pakistan contains four species comparable to S. triquetrum. Waagen (1883, pi. 32) illustrated S. purdoni (Davidson), S. humbletonense (Howse), and S. pingue (Waagen), all of which bear superficial resemblance to the Texas species, but differ primarily in the increased longitudinal convexity of brachial valves which results in a much lower crest for the fold. These species also are not as strongly trigonal in outline, and have more strongly hooked and shorter pedicle beaks. Also from the Salt Range, Reed (1944:135, pi. 24: figs. 5-5c) illustrated a specimen of S. cuneiforme (Reed) that resembles the Texas species in outline and strength of costation. It differs in its more strongly hooked beak, smaller size, narrower out- line, and judging by Reed's illustrations, its fora- men that is completely closed by the deltidial plates NUMBER 21 2113 (this last feature may be a feature only of the illus- trated specimen, or of the illustration itself. The European forms of S. humbletonense (Howse) were described and illustrated by W. King (1850) under the name of "Camarophoria" multipli- cata. King's illustrations (1850, pi. 7: figs. 26-32, pi. 8; figs. 1-7) show specimens that are similar in size and strength of costation to S. triquetrum. They differ from the Texas species in their more ellip- tical outlines, smaller and more abundant costae, possibly higher median septum in the pedicle valve, and longer intercamarophorial plate in the brachial valve. They belong to the same general group of species, but seem to resemble more closely S. inae- quale (Girty) than S. triquetrum. Another relatively similar European species is S. affine (Gemmellaro, 1899:128, pi. 27: figs. 1-7) which differs in its weaker costellae, especially on the flanks of the shell. Gemmellaro's specimens are internal molds which do not show the shape and attitude of the beak, so close comparison is impos- sible. Schellwien (1892:51, pi. 8: figs. 4-8) described S. alpinum from the Permian of the Carnic Alps, a species remarkably similar to S. triquetrum. Ap- parently S. alpinum is costate farther back on the pedicle beak, and its sulcus begins farther poste- riorly. Schellwien illustrated only two adult shells, and showed both of them only from the ventral side, so that their beaks do not show. However he states in his description that the pedicle beak is strongly hooked and has a rather wide delthyrium, but makes no mention of deltidial plates. These features stand in contrast to the pedicle umbonal configurations of .S'. triquetrum. DISCUSSION.—Juveniles of S. triquetrum are rather flat and very narrowly lenticular in profile as usual in the young of normally strongly biconvex rhyn- chonellids and stenoscismatids. Furthermore, these young are longer than wide with their sides diverg- ing at an angle less than 90°. With approaching adulthood, length in relation to width lessens until the two are approximately equal. Costae become progressively stronger with growth, giving the im- pression that juvenile shells are more finely costate than the adults. The stolidium does not appear until the shell is about half grown. It may be present, however, on some small specimens that are stunted; their matur- ity can be estimated from the convexity of the brachial valve. A few juveniles in the National Museum collection are larger than some apparently fully grown adults that are complete with stolidium. Such variations in growth and attainment of adult- hood have been noted in many other brachiopods (e.g., Echinosteges). Most large stenoscismas in the Glass Mountains and the Guadalupe Mountains have been referred to S. venustum (Girty) regardless of stratigraphic level. It will be seen below that Girty's species is unlike any others described herein and that the name does not have such wide applicability. Stenoscisma venustum (Girty) PLATE 577: FIGURES 1-8 Camarophoria venusta Girty, 1909:303, pi. 31: figs. 6-6c. Medium size, triangular in outline, length and width about equal, maximum width anterior to midvalve; valves of unequal depth, pedicle valve shallower; posterolateral sides nearly straight; an- terolateral extremities narrowly rounded; anterior margin moderately rounded, beak small, narrow, nearly straight, delthyrium visible. Surface ante- riorly costate, costae numerous, narrowly rounded, interspaces broader than costae; 6 on fold, 5 or possibly 6 on each flank. Posterior half with costae much reduced or missing. Pedicle valve gently convex in lateral profile, maximum convexity just anterior to umbo; anterior profile faintly concave. Umbonal region narrowly rounded; sulcus broad and shallow, originating just anterior to midvalve, occupying about half valve width; flanks somewhat narrowly rounded, short, slopes steep. Brachial valve fairly strongly convex, maximum convexity at midvalve; anterior profile narrow, steep-sided dome. Median region strongly swollen; fold originating just posterior to midvalve, low and gently rounded. Flanks only moderately swollen and with steep slopes. Interior unknown. MEASUREMENTS (in mm).—Specimen USNM 118557 (holotype): length 18.0, brachial valve length 15.5, maximum width 18.6,, thickness 11.0, apical angle 85° STRATIGRAPHIC OCCURRENCE.—"Supposed to repre- sent the Delaware Mountain Formation" (Girty, 1909:512). 2114 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY LOCALITY.—USGS 3763 (green) (essentially an unknown locality). DIAGNOSIS.—Medium size Stenoscisma with short fold and sulcus, fine costae, and nearly straight beak. TYPES.—Holotype: USNM 118557. COMPARISON.—All the large and transverse spe- cies of Stenoscisma are eliminated from comparison. Species of similar size to S. venustum are few and most of them are more strongly costate. Stenoscisma aptatum, new species, is about the same size but it is coarser ribbed and much wider. Stenoscisma exutum, new species, has costae of about the same size as those of S. venustum but the shell is rather elliptical rather than triangular, as in S. venustum. Stenoscisma levicostum, new species, is of about the same size as S. venustum but is very strongly costate and the costae are thick and high. DISCUSSION.—Stenoscisma venustum has proved to be an enigma. We have compared it closely with all the species of the genus in the Glass Mountains and elsewhere and are unable to recognize it any- where in the collection. The specimen is not well preserved and little is revealed on its coarsely silici- fied surface. No details of the interior can be ascer- tained, and the deltidial plates have been destroyed. The specimen is quite clearly an adult as it has a well-formed fold and sulcus, features that are usu- ally not formed in juveniles. Furthermore the un- equal depth of the valves also indicates that the specimen is adult. Valves of young specimens as a rule are nearly equal in depth. The strength of the ribs, which, although narrow, are fairly high and well formed, is another adult character. Stenoscisma venustum is the same type of shell as S. triquetrum, new species, which King and others referred to S. venustum. This type has prominent costae on the fold and sulcus, but those of the flanks are usually somewhat reduced and best formed only anteriorly. Compared to specimens of 5. triquetrum having the same length as S. venustum, the latter proves to be much more convex, with a stronger fold and sulcus, and a much deeper brachial valve. Specimens of S. triquetrum of 18 mm are really still in the youth- ful stage and have the broad low costae and shal- low valves characteristic of the young. Thus S. venustum appears not to be a young form of this large species. In seeking from its stratigraphic level some clue to its relationships we are also baffled. The species is reported from Comanche Canyon in the Glass Mountains. We have been unable to identify this canyon and thus get no help in our effort to locate the species. Species listed by Girty from USGS 3763 appear to include Leonardian as well as Word species but with a predominance of the latter. None of the Word stenoscismas identified and described herein even remotely suggests S. venustum. Further- more, the preservation of the specimen suggests Leonardian rather than Word. The dilemma can- not be resolved by us and this rather widely used name is another that must rest on its type specimen. Stenoscisma species 1 PLATE 583: FICURES 22-42 Medium size for genus, wider than long, valves unequally deep, brachial valve deeper; subtrigonal to subelliptical in outline, widest just anterior to midvalve. Beak smooth, short, suberect but not pressed onto dorsal umbo. Costae strong and sub- angular, 5 on fold, outer two being implanted at inception of fold, and 4 or 5 on each flank. Distal 1 or 2 indistinct. Stolidium not seen. Pedicle valve gently but unevenly convex in lat- eral profile; anterior profile broadly concave. Um- bonal region narrow and convex; sulcus originat- ing posterior to midvalve, 6 or 7 mm anterior to beak, deepening and widening anteriorly, flat in transverse section, produced into fairly long tongue; flanks slightly convex, narrow, and sloping fairly steeply. Brachial valve strongly convex, somewhat more strongly curved in anterior third. Umbonal and median regions swollen; sulcus originating on um- bonal slope posterior to midvalve, occupying about half valve at midwidth, nearly flat in transverse section. Flanks moderately depressed, swollen and steep. Interior details unknown. MEASUREMENTS (in mm).-—From locality USNM 730a specimen 152279a and from USGS 9999, USNM 152280a, respectively: length 17.5, 16.1; brachial valve length 15.2, 13.2; width 21.6, 22.0; thickness 14.2, 10.7; apical angle 103°, 104°. STRATIGRAPHIC OCCURRENCE.—Hueco Formation; Lenox Hills Formation. LOCALITIES.—Hueco: USGS 9999; USNM 720b. Lenox Hills: USNM 730a. NUMBER 21 2115 DIAGNOSIS.—Fairly wide Stenoscisma with strong costae, five on the fold, and strongly costate flanks. TYPES.—Figured specimens: USNM 152279a,b; 152280a,b. COMPARISON.—The general expression of this species is that of S. hueconianum (Girty) but it is larger and much more robust, although the number of costae is in accordance with that of Girty's species. Other differences appear in the generally greater divergence of the sides of Stenoscisma species 1, and in the more strongly inflated brachial valve. DISCUSSION.—This species is represented by a few specimens; the best preserved one was found loose but in a position that made it clear that only the upper part of the Lenox Hills Formation could have produced it. All the specimens have the gen- eral expression of S. hueconianum, a much smaller species that is common in the Hueco Canyon Formation. Stenoscisma species 2 PLATE 583: FIGURES 8-21 Small, widely elliptical in outline, with widely divergent posterolateral margins and narrowly rounded sides; maximum width near midvalve. Beak short, suberect, but pressed onto dorsal umbo. Surface multicostate, 7-9 costae on fold and about 5 on each flank; costae narrow and subangular, sep- arated by spaces of about equal width. Stolidium not seen. Pedicle valve flatly convex in lateral profile and broadly but slightly convex in anterior profile. Umbonal region swollen; sulcus originating slightly posterior to midvalve, wide and shallow, slightly wider than midwidth. Flanks slightly elevated ante- riorly, flat and with gentle slope to margins. Brachial valve fairly strongly convex, greatest convexity in anterior third; anterior profile broadly domed and with steep lateral slopes. Median region swollen; fold originating near midvalve, wide and moderately elevated. Flanks, narrow, swollen, and steep. Interior, except for generic characters, unknown. MEASUREMENTS (in mm).—From locality USNM 716r specimen (USNM 152227b): length 11.5mm (but minus beak, which would add about 1.0 mm), brachial valve length 11.0, width 17.8, thickness 10.0, apical angle 118°. STRATIGRAPHIC OCCURRENCE.—Lenox Hills Forma- tion. LOCALITIES.—USNM 713y, 716r. DIAGNOSIS.—Small widely elliptical, multicostate Stenoscisma. TYPES.—Figured specimens: USNM 152227a,b. COMPARISON.—This species, like Stenoscisma spe- cies 1, has the general expression of S. hueconia- num (Girty) in its elliptical outline and rounded brachial valve in lateral profile but unlike the for- mer, is much more numerously costate than Girty's species, having 7-9 costae on the fold. Despite the numerous costae, the nearly 50 percent ratio be- tween fold and maximum valve width is the same in all three species. DISCUSSION.—Only a single undistorted specimen of this species was found, but it lacks the beak of the pedicle valve; the other 11 specimens are crushed in one or more directions but all reveal the multicostate character of the species. The fact that only 12 specimens were found in the upper part of the Lenox Hills Formation confirms this as a rare species. This species could be the ances- tral form of S. pyraustoides, new species, which it immediately underlies. It could also have been an- cestral to S. kalum and S. multicostum, both of Stehli (1954). Stenoscisma species undetermined PLATE 583: FIGURES 1-7 A single complete shell from the Lamar Lime- stone appears to be unique and cannot be placed in a recognized species. It is small, transverse, and essentiallly smooth, having but 2 costae on the fold and 2 very weak and short costae on each flank. The stolidium is not preserved, and the valve mar- gins indicate that it had not yet developed, so per- haps the specimen is not fully adult. The closest resemblance is to two small and relatively smooth species from low in the Cathedral Mountain Forma- tion, S. doricranum and S. fabarium, both new. The Lamar specimen has a shorter beak than the former, a more rounded outline, and much shorter and weaker costae on fold and flanks; it differs from the latter in having fewer costae on the fold, these beginning much farther forward, and obscure costae on the flanks, and the profile of the Lamar specimen is slightly more inflated than that of the 2116 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY latter, especially in the dorsal umbonal region. MEASUREMENTS (in mm).—Specimen USNM 152317: length 12.5, width 14.9, thickness 9.3. STRATIGRAPHIC OCCURRENCE.—Bell Canyon For- mation (Lamar Limestone Member). LOCALITY.—USNM 738. TYPES.—Figured and measured specimen: USNM 152317. Subfamily TORYNECHINAE Grant, 1965 Completely costate, uncinuliform Stenoscismati- dae with stolidium reduced or absent. Genera in West Texas: Torynechus Cooper and Grant, 1962. Genus Torynechus Cooper and Grant, 1962 Uncinuloides R. E. King, 1931:112. Torynechus Cooper and Grant, 1962:1128.—Grant, 1965a: 152; 1965b:H631. Large, strongly triangular in outline with broadly truncated anterior margin; valves unequally deep, brachial valve deeper. Beak short, pointed, with small disjunct deltidial plates. Surface costellate to finely costate; anterior margin slightly deflected, suggesting rudimentary or vestigial stolidium. Pedicle valve interior with short, deep spondy- lium, anteriorly rounded, attached to low median septum which may be made obsolete by adventi- tious shell. Vascula media deeply impressed, ex- tending laterally from anterior end of spondylium. Brachial valve with narrow, modified hinge plate and massive bosslike cardinal process; camaropho- rium long and deep, extending anterior to end of spondylium; intercamarophorial plate thick. Crura long and slender as in Stenoscisma. TYPE-SPECIES.—Torynechus caelatus Cooper and Grant (1962:1128). DIAGNOSIS.—Internally like Stenoscisma but cos- tellate and with broadly flattened anterior, the exterior like Uncinunellina, with only a trace of a stolidium. COMPARISON.—The interior of this genus is ex- actly like that of Stenoscisma but the distinctive uncinuliform exterior separates it from all other Stenoscisma tidae. DISCUSSION.—This rare genus straddles the boun- dary betweeen the Skinner Ranch and Cathedral Mountain formations. It appears first in the Dug- out Mountain Member of the Skinner Ranch For- mation, and its last known occurrence is in the Wedin Member of the Cathedral Mountain Forma- tion. It is fairly common at a few localities in the Wedin Member, but is generally rather rare. Shells in the detrital upper part of the Skinner Ranch Formation normally are badly damaged, but well- preserved silicified shells can be obtained from the base of the Cathedral Mountain Formation. Despite the stratigraphic equivalence of the Hess Formation to parts of the Skinnner Ranch and Cathedral Mountain formations, Torynechus has not been found in the Hess. Cooper and Grant (1962) and Grant (1965a,b) explained the nomenclatural difficulties with the type species and the necessity for substituting a new name for King's genus Uncinuloides. Torynechus has not yet been found outside of the Glass Moun- tains where it occupies a very thin part of the section. The exterior of Torynechus is unusual not only in the ornament but in the development of the anterior. Costellae cover the entire shell, including the umbones of both valves. Considerable bifurca- tion of the costellae takes place in the posterior but costellae are direct. The anterior margin is sharply geniculate to form a flat base and at this point the costellae of the base develop an impressed line. This feature is characteristic of such similar rhyn- chonellids as Uncinulus Bayle, Hypothyridina Buck- man, and Sphaerirhynchia Cooper and Muir-Wood. The costella on each side of the impressed line is marked by chevron-shaped growth lines. The im- pressed line is produced by the hollow conical spine with which it terminates at the margin. The spines of the two valves interlock when the shells are closed, but form a sieve or screen when they gape, as explained by Schmidt (1937). Another interesting feature, especially of adult shells, is the deflection of the anterior margin of both valves at right angles to the direction of growth. This results in an elevated ridge at the commissure. This suggests the stolidium of Stenos- cisma but in a much aborted condition and cer- tainly without the same function. The interior of the pedicle valve is so like that of Stenoscisma that few additional remarks are necessary. The posterior is often thickened to such an extent that the septum supporting the spondy- lium is completely buried and appears to be sessile. NUMBER 21 2117 The pallial trunks are exceptionally deep in the pedicle valve of this group, a help in understanding their pattern. The brachial valve hinge plate, is much narrowed and confined, and the crural bases are squeezed close together. The camarophorium is long, fairly wide, and extends far beyond the end of the spon- dylium. It is supported by a strongly elevated, stout median septum. The tip of the camarophorium is drawn out into a fairly long blunt subrectangular projection. In our experience Torynechus is confined to the upper part of the Skinner Ranch Formation and the basal part of the Cathedral Mountain Forma- tion. It is found throughout the lateral extent of the Skinner Ranch Formation. It is rare in Lenox Hills but is fairly common in the hills west of Iron Mountain and on Leonard Mountain. It has a somewhat wider range in the Cathedral Mountain Formation where it is found in King's Leonard "Fifth Limestone" on Dugout Mountain, at the same level as in Leonard Mountain, and at a few places east of there in the canyon leading up to the Appel Ranch and Split Tank. R. E. King (1931:113) reports Uncinuloides from the Wolfcamp (—Lenox Hills) on Dugout Moun- tain and from the Word Formation ( = Road Can- yon) southwest of Sullivan Peak. Our extensive col- lections have not yielded this genus from either of these horizons. Torynechus alectorius, new species PLATE 584: FIGURES 1^41 Uncinuloides guadalupae [part] R. E. King [not Shumard], 1931:112, pi. 35: figs. 7a-c. Average size for genus; outline moderately to broadly subtrigonal, sides diverging between 75° and 120°, normally about 100°; profile nearly equi- laterally subtrigonal; commissure uniplicate, fold standing rather high toward anterior, with lower relief posteriorly, beginning 7-10 mm anterior to brachial beak; sulcus shallow, beginning 10-12 mm anterior to pedicle beak. Costae moderately coarse to fine, beginning at beaks, sharp-crested, a few adding toward anterior by bifurcation, more rarely by intercalation, numbering 9-13 on fold, one less in sulcus, 10-12 on each flank; anterior margins abruptly bent to form flattened levigate region, may be slightly concave, extending along sides slightly anterior to widest part of shell, each costa there deeply grooved along crest, slightly extended at margin to form interlocking serrations of com- missure. Concentric ornamentation fine, closely spaced; growth laminae weak, widely spaced. Pedicle valve moderately thick, flatly convex transversely, more strongly convex longitudinally along sulcus; beak moderately long, somewhat attenuate, slightly hooked; lateral pseudointerareas narrow, elongate, covered by edge of brachial valve; delthyrium triangular, constricted by small, dis- junct deltidial plates. Brachial valve rather strongly convex transversely, nearly flat along crest of fold, except for increased convexity in beak region; beak slightly attenuate, not greatly swollen. Pedicle interior with boat-shaped spondylium supported above floor of valve by low median septum; other internal features unknown. Brachial interior with high median septum and deep camaro- phorium; other internal features unknown. MEASUREMENTS (in mm).— brachial apical valve thick- angle length length width ness (°) USNM 710r 154590a 9.0? 8.4 8.9 4.2 77 154590b 11.5 10.6 13.0? 6.0 99 154590c 13.0 12.1 16.5 6.4 106 154590d 17.0 15.1 20.0 11.9 106 154590e 16.3 14.0 20.8 15.9 102 154590f 17.8 15.6 22.0 17.8 108 (holotype) STRATIGRAPHIC OCCURRENCE.—Skinner Ranch For- mation (Dugout Mountain and Sullivan Peak members). LOCALITIES.—Dugout Mountain: USNM 700p, 732e, 733-1. Sullivan Peak: 707b, 729p. Skinnner Ranch (top): 71 Or, 723h, 724-1, 73lo. DIAGNOSIS.—Tor^rag'tVu/.y with strong, angular co- stellae and fairly prominent fold. TYPES.—Holotype: USNM 154590L Figured and measured paratypes: USNM 154590a-e. COMPARISON.—Torynechus alectorius is character- ized by its sharp costae that are not characteris- tically bifurcated or intercalated, its somewhat thick pedicle valve, brachial valve with low longitudinal convexity, and its extensive, somewhat concave levi- gate anterior surface. It differs from the other Texas species, T. caelatus Cooper and Grant (1962), in its sharper, less frequently bifurcating or inter- 2118 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY calating costae, somewhat greater levigate anterior surface, less swollen brachial umbonal region, and fold that stands higher above the flanks at the anterior. DISCUSSION.—This is an uncommon species that seems generally to come from locations west of the Split Tank area which is the locale for T. caelatus. The latter has not been identified in what appar- ently is the same horizon elsewhere. Indeed, the distribution of the genus is peculiar because it has not yet been found in some localities where Insti- tella bioherms are best developed. Torynechus alec- torius is commonest where the upper part of the Skinner Ranch Formation forms the top zone of hill 5280, and very near the top on Leonard Moun- tain. There it occurs in cherts just under the 40- foot calacarenite or calcirudite forming the top beds of the type section of the Skinner Ranch For- mation. It also survives into this upper bed, but is less common. Torynechus caelatus Cooper and Grant PLATE 585: FIGURES 1-33; PLATE 586; FIGURES 15-29 Uncinuloides guadalupae [part] R. E. King [not Shumard], 1931:112, pi. 35, figs. 6a-c—Cooper, 1944:315, pi. 120: figs. 49-51. Torynechus caelatus Cooper and Grant 1962:1128.—Grant, 1965a:154, pi. 24: figs. 1-10; 1965b:H631, figs. 515; la-e. Fairly large, attaining width about 25 mm, sub- triangular to subpentagonal in outline, long sloping posterolateral margins and narrowly rounded sides; anterior margin broadly rounded to abruptly trun- cated. Posterolateral margins forming an angle of 69-96°. Maximum width slightly anterior to mid- length. Beak moderately elongated, nearly erect but slightly incurved; foramen elongate, elliptical; del- tidial plates small and narrowly disjunct. Surface costellate to finely costate, costellae low to moder- ately elevated, narrowly rounded and usually closely crowded, separated by spaces of about equal width; costellae numbering 9-16 on fold and usually occu- pying lateral slopes of fold as well as dorsal sur- face; flanks with 8-15, the outer third or half fine and often indistinct. Bifurcation and intercalation of costellae infrequent. Pedicle valve unevenly and flatly convex in lat- eral profile, most curvature just posterior to mid- valve; anterior profile broadly and fairly evenly shallow; umbonal region gently convex; sulcus originating just posterior to midvalve, broad and shallow, not well defined because of costation of inner slopes; tongue broad and long, fairly rounded, flat or slightly concave in transverse section; flanks poorly defined, narrow, moderately convex but with steep outer posterolateral slopes. Brachial valve much deeper than pedicle valve, gently convex in lateral profile, anterior half flat- tened; anterior profile broadly domed, sides pre- cipitous. Umbonal and median regions moderately swollen; fold slightly elevated, not strongly differ- entiated from flanks, slopes costellate; fold orig- inating just posterior to midvalve and occupying slightly more than half midwidth. Flanks gently swollen, but flattened and dropping off to margins at point of marginal geniculation. Interior as described for genus. MEASUREMENTS (in mm).— brachial apical va Ive thick- angle length length width ness C) USNM 702un 154593a 14.5 12.2 14.5 11.4 75 154593b 15.3 13.1 14.4 11.2 69 154593c 16.8 14.8 18.0 10.3 78 154593d 17.0 15.0 18.2 11.9 87 154593e 17.2 14.6 19.6 15.1 85 154593f 17.2 14.7 18.7 15.0 81 154593g 16.8 14.6 18.9 13.0 90 154593h 17.4 14.9 21.0 15.4 89 154593i 18.7 17.0 23.7 15.0 92 USNM 703b 142555 21.2 18.5 24.6 17.8 96 STRATIGRAPHIC OCCURRENCE.—Cathedral Moun- tain Formation {Institella zone). LOCALITIES.—AMNH 500D, 504; USNM 700-1, 700x, 702, 702un, 703b, 708, 709, 712o, 72lu, 724n, 724r, 724s, 730u, 735b. DIAGNOSIS.—Torynechus with narrowly rounded costellae. TYPES.—Holotype: T10167. Figured paratype (R. E. King, 1931): YPM 12582. Figured hypotypes: USNM 142553; 152594a,b; 152595a; 154591; 154593a-d,f,j-m. Measured hypotypes: USNM 142555, 154593a-i. COMPARISON.—-This species differs from its close relative in the Glass Mountains, T. alectorius, in having finer costellae that are narrowly rounded rather than angular as in T. alectorius, in having the fold less prominent, and in having more nu- merous costellae generally, a smaller angle of diver- NUMBER 21 2119 gence of the posterolateral margins, and a somewhat less levigate anterior surface. DISCUSSION.—This species seems to be confined to the eastern part of the mountains, where it occurs in beds in the vicinity of Split Tank. There it occurs in biohermal limestone and in detrital mate- rial between bioherms. It occurs with Institella and the unusual Niviconia globosa (R. E. King). An interesting feature observed on shells of this species is the borings that penetrate many of them. The elongate forms are evidently of a boring bar- nacle but the circular holes were probably produced by gastropods. These are perfectly round and have even sides, not beveled inward with diminishing diameter as in borings of Tertiary and Recent shells. Family ATRIBONIIDAE, Grant, 1965 Subfamily PSILOCAMARINAE Grant, 1965 Atriboniidae with intercamarophorial plate ab- sent or rudimentary, hinge plate divided or very short. Genus Psilocamara Cooper, 1956 Levicamera Grabau, 1934:18 [nomen nudum, not of Sarycheva and Sokolskaya, 1952:171 (= Camerisma Grant, 1965a)]. Psilocamara Cooper, 1956:523.—Waterhouse, 1964:102.—Grant, 1965a: 77; 1965b:H627. Small, subglobose to subpyramidal; outline sub- trigonal to subpentagonal; anterior commissure strongly uniplicate; fold high, crest blunt to sharp, sloping evenly to flanks, normally smooth, some with few simple or bifurcating costae; sulcus shal- low with weak median groove corresponding to sharp crest of fold; flanks smooth; valve edges butt- ing except for slight overlap at extreme posterior of some shells; stolidium absent; growth lines fine, closely spaced; radial ornament absent. Pedicle valve moderately convex transversely, strongly convex longitudinally; umbonal region swollen, flanks relatively flat; beak short, bluntly pointed, straight to suberect; beak ridges gently rounded; delthyrium small, triangular, constricted by small triangular, disjunct deltidial plates; fora- men small, elongate, slitlike, partly filled by beak of brachial valve. Brachial valve strongly convex transversely, moderately convex longitudinally; beak short, rounded, slightly attenuate, apex within pedicle valve. Pedicle valve interior with hinge tooth on each side of delthyrium, each parallel to valve edge; dental plates large, curved toward floor, meeting to form deep, scoop-shaped spondylium, sessile in apex, anteriorly supported on low median septum duplex; septum thinner and higher toward anterior, extending about a third length of valve. Brachial valve interior with short undivided hinge plate; crura extending from anterior edge of hinge plate, curved dorsally slightly more strongly toward anterior; median septum beginning at beak, ventral edge expanded to form spoon-shaped cam- arophorium, not attached to hinge plate, either directly or by intercamarophorial plate; height of septum increasing anteriorly, curving camaropho- rium ventrally, septum reduced to median keel on convex side of camarophorium at anterior, length about one-fourth length of valve. TYPE-SPECIES.—Psilocamara renfroarum Cooper, by original designation (1956a:524, pi. 61B: figs. 20-32, text-fig. 18, nos. 4-15). COMPARISONS.—Psilocamara is characterized by its smooth shell, high fold that is not distinctly set off from the flanks, lack of an intercamarophorial plate in the camarophorium of the brachial valve, and by its partly sessile spondylium and low median septum in the pedicle valve. The smooth shell dis- tinguishes it from Sedenticellula Cooper, which also has a partly sessile spondylium. The edges of the camarophorium do not touch the hinge plate, distinguishing Psilocamara from Camarophorinella Licharew, which also lacks an intercamarophorial plate. Camarophorina Licharew lacks the intercam- arophorial plate and also is smooth, but its fold is reversed, producing a sulcate rather than uniplicate commissure. The genus Camerisma Grant also is smooth and uniplicate, but is much larger than Psilocamara and has an intercamarophorial plate bracing the midline of the camarophorium to the underside of the hinge plate in the apex of the brachial valve. Psilocamara hesperia, new species PLATE 586: FIGURES 1-14 Small for genus, biconvex; outline heart-shaped or subpentagonal, sides diverging about 90° at 2120 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY posterior; commissure strongly uniplicate, fold high at commissure but not set off distinctly from flanks, crest bluntly ridged, extending to brachial beak; sulcus shallow but with narrow median trough reflecting ridge of fold. Costae and concentric orna- ment absent; growth lines not observed. Pedicle valve moderately convex transversely, more strongly curved along midline through sulcus, somewhat inflated in umbonal region anterior to beak; beak short, sharp, nearly straight; beak ridges short, blunt; delthyrium small, triangular, con- stricted at anterior by beak of brachial valve, at sides by very small deltidial plates; foramen slitlike. Brachial valve moderately strongly convex in pro- file, very strongly convex transversely; beak region inflated; beak slightly incurved, apex within pedicle valve. Pedicle valve interior with dental plates meeting to form proportionately long spondylium, elevated toward anterior on median septum duplex extend- ing about to midlength of valve. Brachial valve interior obscure; median septum apparent, extend- ing anteriorly about a third length of valve; cam- arophorium broken or hidden on specimens avail- able, apparently constructed as described for genus. MEASUREMENTS (in mm).-— brachial apical valve thick- angle length length width ness (°) USNM 701-1 148188a 5.4 4.9 5.0 4.1 90 148188b 5.0 4.6 ? 3.7 90 148188c 5.2 4.9 4.8 4.4 96 (holotype) STRATIGRAPHIC OCCURRENCE.—Neal Ranch For- mation (beds 4 and 9 of P. B. King). LOCALITIES.—USNM 701-1, 701a3. DIAGNOSIS^—Small, beak short, commissure not parasulcate. TYPES.—Holotype: USNM 148188c. Figured par- atypes: USNM 148188a,b; 154590a,b. COMPARISON.—Psilocamara hesperia is smaller than the only other known species, P. renfroarum Cooper, from the Pennsylvanian of north-central Texas. In addition, its beak is shorter and straighter, and the juncture of the valves, viewed in profile, is less sinuous, with less of a dorsal bend near the anterior. DISCUSSION.—The above description is based upon two specimens from USNM 701-1, one nearly com- plete and the other broken so that some internal features can be seen, and six specimens from USNM 701a3. Unfortunately the camarophorium is nearly completely missing from the one from USNM 701-1, with only the extreme posterior part, and the base of the median septum preserved. Externally, the shells have the generic features of Psilocamara. Specimens from USNM 701a3 preserve the cama- rophorium well and it has no intercamarophorial plate and is thus assignable to Psilocamara. Order SPIRIFERIDA Waagen, 1883 Suborder SPIRIFERIDINA Waagen, 1883 Biconvex, usually laterally extended shells having an interarea on both valves and with a delthyrium and notothyrium, the former with or without del- thyrial cover. Internally a laterally directed conical spiralium supported the lophophore. Superfamily CYRTIACEA Fredericks, 1924 Exterior and micro-ornament variable, interior with or without dental plates in the pedicle valve; brachial valve with supporting plates and nonstriate cardinal processs. Impunctate. Family AMBOCOELIIDAE George, 1931 Usually small, smooth or faintly ribbed; spines or papillae on surface; pits or plicae on inner layer. Hinge narrow, ears rounded. Jugum absent. Spire with few whorls. Genera in West Texas: Crurithyris George, 1931; Attenuatella Stehli, 1954. Crurithyris is inherited from the Pennsylvanian and is common in Wolfcampian rocks, rather rare in the Leonardian but well represented by species of large size in the Guadalupian. The genus is present in all West Texas areas covered in this monograph. Attenuatella is a long and harrow aberration of Crurithyris that is rare in the Sierra Diablo but also occurs in Mexico, Australia, New Zealand, New Caledonia, and Siberia. Genus Crurithyris George, 1931 Crurithyris George, 1931, p. 42—Williams et al., 1965:H672. Small to medium size, maximum reaching 24 mm NUMBER 21 2121 in length, planoconvex to unequally biconvex; out- line semielliptical, slightly elongate to rather strongly transverse; hinge narrower than greatest shell width, sides rounded; greatest width near or posterior to midlength; anterior margin evenly curved or slightly emarginate; commissure normally rectimarginate, sporadically folded either dorsally or ventrally in emarginate species; costae absent; some species with narrow median depression of pedicle valve simulating sulcus but normally not expressed as fold in anterior commissure; brachial valve normally not folded, occasionally depressed along midline; surface bearing fine short spines in random distribution (not along concentric or radial lines); spines seldom preserved, usually appearing as minute bumps over surface; growth lines fine, closely spaced, visible only on well-preserved sur- faces; growth laminae weak, irregularly spaced. Pedicle valve strongly convex, especially in um- bonal region; beak prominent, bluntly pointed, normally erect or slightly incurved; delthyrium nar- rowly trigonal, open, on some specimens bounded laterally by narrow flanges (probably incipient or vestigial deltidial plates); interarea proportionately low and very wide, longitudinally rather strongly concave, tapering laterally to hinge ends. Brachial valve less strongly convex, forming low cover on deeply cup-shaped pedicle valve; greatest convexity near beak or slightly farther forward; slight median depression of anterior in emarginate shells; interarea very low, wide, nearly flat, exca- vated medially by shallow, broadly trigonal noto- thyrium with low flanges formed by raised traces of growth of hinge sockets. Pedicle valve interior with knoblike hinge teeth projecting anteriorly; dental ridges low, rounded, little more than thickening of inner portion of traces of hinge teeth; muscle area oval, in beak area, with elongate narrow median diductor marks extending nearly entire length of valve in some species, about half length in others; adductor marks larger, lying one on each side, separated from diduc- tors by pair of low ridges, one ridge on each side of diductors; umbonal region lateral to muscle area with weak radial lirae fading posterior to mid- length of valve. Brachial valve interior with small, deep hinge sockets; socket walls thickened slightly; crural plates extending from underside of socket ridges to floor of valve; crura projecting anteriorly from crural plates near valve floor, rather strong, nearly cylin- drical, cemented to valve floor for short distance anteriorly in some species, gradually rising from floor, bowing distally; flattened ribbonlike spiralia attached to ends of crura, first diverging strongly, then bending medially before forming first loop on each side; axes of coiling directed slightly obliquely posteriorly toward point of greatest shell width, including about 5-7 loops on each side; cardinal process small, knoblike, deeply striate, in apex of notothyrium; muscle area elongate, between crura, extending from concavity between crural plates; pair of small depressions just anterior to muscle area located under crura, probably not muscle marks, but recesses formed where crura nearly touch floor. TYPE-SPECIES.—Spirifer urei Fleming (1828:376) by original designation of George (1931:43). DIAGNOSIS.—Strongly convex pedicle valve, nearly flat brachial valve, spinose shell surface, narrow socket ridges attached or very near floor of valve in posterior, spiralia with S-shaped flexure before first medial loop, rising from brachial valve floor and crura, and axes of coiling normally pointed some- what posteriorly rather than directly transverse to median plane of shell. COMPARISON.—Crurithyris resembles Ambocoelia Hall (1860), differing in its narrower hinge, knob- like and lamellate rather than elongate and bifid cardinal processs, more posteriorly located muscle areas, and spinose outer surface. It differs from Ambothyris George (1931) in its proportionately narrower hinge, lower pedicle interarea, more strongly curved pedicle beak, and spinose surface. The planoconvex form, wide, concave interarea, and lack of strong concentric lamellae are obvious differences from Squamularia Gemmellaro, Neo- phricadothyris Licharew (=Permophricodothyris Pavlova), Phricodothyris George, and Reticularia McCoy; the form of the crural plates and the close adherence of the crura to the brachial valve floor, with the resulting extra curve in the spiralia, are further differences. Except for the concentric lamel- lae, these differences also distinguish Crurithyris from Martinia McCoy and its relatives. The rela- tively short beak, more nearly circular outline, and fully developed spires distinguish it from Attenua- tella Stehli, which also attains a larger maximum length. DISCUSSION.—According to George (1931:42, pi. 5: 2122 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY fig. 4), the cardinal process of Crurithyris is knob- like and tuberculate. Specimens in our collections with cardinal processes large enough to exhibit detail have them deeply scored longitudinally, pro- ducing in effect a closely spaced group of parallel plates in the form typical of most spiriferids. The tuberculate process of C. magnispina George (1931) possibly developed as a further transverse scoring of the typical spiriferid process. In that case it prob- ably is a specific character. Posssibly, however, the tuberculate condition that George illustrated re- sulted from the manner and perfection of preserva- tion of the specimen. Some Texas specimens have the lamellate knoblike cardinal porcess incompletely preserved in such a way that the parallel plates are detached from the apex of the valve, producing a series of tiny rods, or tubercules, much like those of the British shell. These rods project posteriorly, not perpendicularly to the valve wall. This "ero- sion" of the cardinal process may be incomplete silicification, or may have taken place before burial of the shell. Crurithyris guadalupensis (Girty) PLATE 587: FIGURES 41-59 Ambocoelia planoconvexa var. guadalupensis Girty, 1909:370, pi. 14: fig. 12-14. Not Ambocoelia guadalupensis Girty of R. E. King, 1931:119, pi. 41: figs. 1-5 [= Crurithyris species]. Small for genus, nearly planoconvex; outline sub- elliptical to nearly semielliptical, only slightly transverse in juveniles, becoming increasingly trans- verse with growth, greatest width near midlength, curvature of outline slightly flattened at anterior midline, rarely slightly emarginate; pedicle valve without trace of median depression except rarely at extreme anterior of large specimens; brachial valve unfolded, commissure rectimarginate; surface of many specimens rough, where short spines broke off; growth lines fine, visible on few specimens; growth laminae slightly stronger, visible on most specimens, irregularly spaced. Pedicle valve moderately convex for genus; beak low, long, projecting well over interarea, normally incurved; interarea proportionately low, flatly con- cave; delthyrium narrowly triangular, open, lateral flanges low or absent. Brachial valve flatly convex, slightly swollen at beak, interarea very low; noto- thyrium relatively narrow. Pedicle valve interior with small hooked hinge teeth; dental ridges greatly reduced; short apical plates in apex of delthyrium extending down toward valve floor rather than anteriorly along delthyrial sides, thus not constricting delthyrium; muscle area in umbonal region, without median ridge or groove, individual muscle marks not differentiated. Brachial valve interior with deep open hinge sockets with socket ridges; cardinal process forming ridge or brace between socket walls, then small lamellate thickening apically (posteriorly); hinge plates thin, short, joining crura to socket ridges; crura rodlike, rather narrowly spaced, cemented to floor for about 1 mm in posterior, bowed outward only narrowly; spiralia ribbonlike, beginning with S-shaped curve to rise above valve floor; remainder of spiralia not observed; muscle area narrow, be- tween crura. MEASUREMENTS (in mm).— brachial hinge width thick- valve length length width USNM 738b 152430a 2.9 2.4 3.1 2.0 1.9 152430b 3.1 2.8 3.2 2.0 1.8 152430c 3.1 2.9 3.6 2.1 1.8 152430d 3.5 2.8 3.5 2.4 2.3 152430e 3.8 3.0 4.0 3.0 2.5 152430f 4.0 3.3 3.9 2.9 2.7 152430g 4.3 3.8 4.6 3.4 3.1 152430h 5.0 4.4 5.2 3.3 3.6 152430i 5.4 4.6 6.3 5.3 3.9 152430J 5.8 4.9 6.4 4.0 3.8 152430k 6.6 5.4 7.0 4.8 3.9 152430-1 6.8 5.2 6.9 5.0 4.4 152430m 7.0 6.0 7.2 4.8 4.9 152430n 7.2 6.5 9.0 6.2 5.0 152430o 7.4 6.4 7.9 5.9 4.5 152430p 8.0 6.9 9.2 6.6 4.9 152430q 8.1 6.4 8.1 5.9 5.1 152430i 8.3 6.9 9.2 5.8 5.3 152430s 10.7 7.9 11.5 8.4 5.5? USNM 738 152428a 7.6 6.4 8.6 6.0 4.8 152428b 8.7 7.2 9.2 6.0 5.6 152428c 9.4 7.7 9.9. 7.5 5.9 USNM 737a 152426a 7.9 6.7 7.8 4.9 4.1 152426b 8.2 6.7 8.9 6.8 5.0 USGS 2926 118598b 8.2 6.6 9.6 6.9 5.0 118598c 8.5 7.1 8.0 5.3 5.3 118598a 9.9 7.5 10.2 7.3 5.4 (lectotype) AMNH 40 189934 9.4 7.9 10.6 7.0 5.8 NUMBER 21 2123 STRATIGRAPHIC OCCURRENCE.—Bell Canyon For- mation (Pinery, Rader, and Lamar members); Cap- itan Formation. LOCALITIES.—Pinery: AMNH 398. Rader: USNM 725g. Lamar: AMNH 37, 38, 40, 347( = L-2), 351 (=L^6), 430; USNM 725e, 728i, 728p, 738, 738b. Capitan: USGS 2926; USNM 737a. DIAGNOSIS.—Small, transverse Crurithyris with wide cardinal process, low interarea, and narrowly separated crura. TYPES.—Lectotype herein designated (Girty, 1909, pi. 14: fig. 12): USNM 118598a. Figured hypotypes: USNM 152428a,b,d-f; 152430-l,r; 154420a,b. Meas- ured hypotypes: USNM 118598b,c; 152426a,b; 152428a-c; 152430a-s; 189934. COMPARISON.—Crurithyris guadalupensis is char- acterized by its small to medium size, rather flat brachial valve, transverse outline in adults, com- paratively low interarea, narrowly separated crura, and rather wide cardinal process. It most nearly re- sembles C. tumibilis, new species, differing in its larger size, flatter brachial valve, and more strongly curved pedicle beak, with lower interarea. It is much larger and its hinge ends not as sharp as in C. minutalis, new species. It lacks the high interarea and definite sulcus of C. sulcata Stehli; it is some- what smaller and, in adults, wider and less strongly convex in the pedicle valve than C. inflata Stehli. Crurithyris major and C. tholiaphor, both new and both from the Word, are much larger. Girty (1909) considered this species a variety of C. planoconvexa (Shumard), a species that it does resemble strongly. Crurithyris guadalupensis differs, however, in its slightly more convex brachial valve, total lack of fold or sulcus in the pedicle valve, higher interarea, and proportionately wider outline in adults. DISCUSSION.—The above description differs in sev- eral respects from that of Girty (1909), largely be- cause it is based on a larger collection (including Girty's illustrated specimens), mainly of silicified shells. Further differences are due to opportunity for comparison with a larger number of different species. For example, Girty says, "Area . . . strongly concave." The interarea is strongly concave only at the apex where the curvature of the beak takes its effect, nearer the hinge it is nearly flat, and it is flatter than that of most other species examined, hence the description above of the "flatly concave" interarea. The rather strong median groove shown on the pedicle valve of figure 13 on Girty's (1909) plate 14 is not present on the illustrated specimen. No specimen of this species has a clearly defined external pedicle groove except at the extreme ante- rior, and it appears there only in a few specimens. Crurithyris inflata Stehli PLATE 587: FIGURES 60-73 Crurithyris inflata Stehli 1954:342, pi. 26: fig. 7-11. About medium size for genus, nearly planocon- vex; outline subpentagonal, length and width nearly equal, widest near midline, rarely indented; valves normally without fold or sulcus, rare pedicle valves with shallow, indistinct sulcus or median flattening; commissure rectimarginate; surface of many specimens with short spine bases, others ap- parently smooth; radial ornamentation weak, visible on many specimens as faint fibrous texture; growth lines and laminae weak, not visible on many specimens. Pedicle valve strongly and evenly convex; beak short, thick, strongly incurved; interarea high, rela- tively narrow, concave; delthyrium narrowly trian- gular, open; lateral deltidial flanges short or absent. Brachial valve flatly convex; umbonal region slightly swollen, beak obtusely pointed; interarea low, relatively high for genus, flat; notothyrium deep, about equilaterally triangular. Pedicle valve interior with small, knoblike, slightly hooked hinge teeth; dental ridges rounded, thickened, producing very short apical plate in apex; muscle area elongate, fusiform, depressed, bounded on each side by low ridge, ridges converging at anterior of area to form single ridge for short dis- tance, posterior part of area bisected by low median ridge; faint radial pallial marks visible in posterior, lateral to muscle area. Brachial valve interior with strong hinge sockets, socket ridges forming flange along each side of notothyrium, inoperative posterior parts of sockets bridged by thin plates; cardinal process roughly triangular, occupying wedge-shaped space in apex of notothyrium, posterior part finely lamellate, or, where partially eroded or broken, tuberculate; hinge plates thick, convergent toward midline of valve, joining crura to socket ridges; crura rodlike, distally bowed, extending just beyond midlength of valve; 2124 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY spiralia flatter than crura, continuing anterior course just above valve floor for short distance, then becoming flat and broad, forming S-curve to raise spiralium above valve floor; complete spiralium not observed; muscle area between crura, narrow, weakly impressed. MEASUREMENTS (in mm).— brachial valve hinge thick length length width width ness SNM 728f 152433a 2.5 2.0 2.3 1.9 1.8 152433b 2.6 2.1 2.8 1.9 1.5 152433c 2.8 2.4 3.2 2.3 1.8 152433d 3.2 2.9 3.4 2.2 2.1 152433c 3.3 2.8 3.6 2.5 2.2 152433f 3.4 2.9 3.6 2.5 2.3 152433g 3.7 3.1 4.1 2.7 2.5 152433h 4.1 3.3 4.3 3.4 2.7 1524331 4.1 3.9 4.8 3.0 2.6 152433J 4.6 4.3 5.4 3.6 3.1 152433k 4.9 4.4 5.5 3.9 3.0 152433-1 5.1 4.7 5.6 3.7 3.2 152433m 5.3 4.6 5.4 3.8 3.3 152433n 6.2 5.0 6.2 3.9 4.2 152433o 6.5 5.7 7.1 4.5 4.2 152433p 6.6 5.6 7.0 4.9 4.0 152433q 7.5 5.9 8.4 5.9 4.7 152433r 7.7 6.6 9.3 6.4 4.6 152433s 8.0 7.0 8.9 6.3 5.0 152433t 8.9 7.3 9.0 6.0 5.7 152433u 9.0 7.5 10.1 7.9 5.7 152433v 9.7 8.0 11.1 7.9 5.0 152433w 11.1 8.8 10.9 7.9 6.6 152433x 11.8 c.9.0 11.8 8.0 ? 152433y 12.0 9.5? 11.5? 8.5 ? STRATIGRAPHIC OCCURRENCE.—Bone Spring For- mation. LOCALITIES.—AMNH 696, 697; USNM 725c, 728e, 728f. DIAGNOSIS.—Medium size Crurithyris with strongly swollen pedicle valve, narrow interarea, and depressed muscle field in pedicle valve. TYPES.—Holotype: AMNH 27323/1:1. Figured hypotypes: USNM 152433o,q,t,u,w. Measured hypo- types: USNM 152433a-y. COMPARISON.—Crurithyris inflata is characterized by its moderate size, strongly convex pedicle valve, flatly convex brachial valve, comparatively narrow outline, high and narrow interarea, and pedicle muscle area that is bounded laterally by low ridges and is depressed. It most nearly resembles C. sulcata stehli, with which it occurs, differing in its more strongly inflated pedicle valve that lacks a median sulcus, and has the muscle area more deeply im- pressed. It is much larger and not as wide as C. tumibilis or C. minutalis, both new, or C. guada- lupensis (Girty), and somewhat smaller than the Word species C. tholiaphor and C. major, both new. It differs further from the latter two species in its proportionately higher pedicle interarea, less in- flated and less strongly curved beak, and somewhat flatter brachial valve. It is not similar to the small Pennsylvanian species C. planoconvexa (Shumard). Crurithyris longirostris, new species PLATE 588: FIGURES 1-7 Medium size for genus, wider than long; outline subpentagonal to roundly subelliptical; widest at or just posterior to midvalve. Sides rounded; ante- rior margin broadly rounded. Anterior commissure rectimarginate. Cardinal extremities rounded. Beak elongated; interarea long, strongly apsacline. Del- thyrium long and narrow. Surface with fibrous appearance and closely spaced spine bases. Pedicle valve moderately and unevenly convex, maximum convexity between umbonal region and midvalve; anterior profile somewhat narrowly domed. Umbonal region elongated, narrowly in- flated; median region inflated but anterior mod- erately convex to somewhat flattened; sulcus not developed. Flanks convex and steep. Brachial valve evenly and flatly convex in lateral profile, broadly and gently convex in anterior pro- file. Umbonal region moderately swollen, anterior region and flanks gently convex. Posterolateral ex- tremities slightly depressed. Pedicle valve interior with short apical plate. Brachial valve interior with stout, ribbonlike de- scending branches and with strong S-curve ante- riorly. Spire not seen. MEASUREMENTS (in mm).— brachial valve hinge thick- 3.7 3.3 4.3 3.8 3.0 4.5 3.8 5.2 3.9? 3.3 1.7 4.2 5.8 4.0 3.4 6,1 5.1 6.6 5.0 4.2 length length width width ness AMNH 591 152985a 152985b 152985c 152985d (holotype) 152985c 7.4 5.6 8.0 5.7 4.3 NUMBER 21 2125 STRATIGRAPHIC OCCURRENCE.—Bone Spring For- mation. LOCALITY.—AMNH 591. DIAGNOSIS.—Moderate-sized Crurithyris with long beak. TYPE.—Holotype: USNM 152985d. Figured par- atype: USNM 152985L Measured paratypes: USNM 152985a-c,e. COMPARISON.—The long beak and strongly apsa- cline interarea are so distinctive that detailed com- parisons are unnecessary. Crurithyris major, new species PLATE 588: FICURES 8-32 Large for genus, nearly planoconvex; outline subovate, normally somewhat elongate especially in large adults, greatest width near midlength, anterior outline normally evenly arcuate, less commonly flattened, rarely indented; pedicle sulcus weakly defined on some specimens, absent from most; bra- chial fold barely perceptible on most specimens; surface with fine radial fibers, weak growth lines and laminae, roughness possibly due to broken spine bases. Pedicle valve strongly and relatively evenly con- vex; beak long, thick, strongly curved, normally incurved; interarea proportionately low, flatly con- cave near hinge, more deeply concave near beak; delthyrium deeply wedge-shaped, bounded laterally by pair of comparatively large deltidial flanges con- verging toward one another across delthyrium but not meeting. Brachial valve flatly convex, slightly swollen in umbonal region, flattened toward ante- rior, with slightly longitudinal median crest on some specimens; interarea wide, low, nearly flat; notothyrium broadly wedge-shaped with low flanges formed by socket walls. Pedicle valve interior with proportionately small, knoblike hinge teeth; dental ridges low, rounded, converging to form proportionately very small api- cal plate of delthyrium; muscle area elongate, ante- riorly widening, radially striated, median portion depressed, with median ridge in posterior, median groove in anterior. Brachial valve interior with hinge sockets formed by strong socket ridges, bridged by thin plates; cardinal process relatively large, knoblike, filling apex of notothyrium, finely lamellate with numer- ous closely spaced parallel plates; crural plates short, low, joining crura to socket ridges; crura strong, rod-shaped, distally bowed, cemented to valve floor for several millimeters in posterior, cemented for entire length in some specimens, remaining near floor for entire length; spiralia beginning with flat- tened ribbon in S-shaped loop; coiled part of spi- ralia narrower but still flat and ribbonlike, num- ber of loops not observed; muscle area between crura, very weakly impressed, individual marks not distinguishable, entire area weakly striated radially. MEASUREMENTS (in mm).— brachial valve hinge thick- length length width width ness USNM 7l5i 152437a 2.8 2.6 2.8 1.9 1.7 152437b 24.0 16.0? 22.0 15.6 ? 152437c 26.2 19.2 21.6 16.0 12.8 (holotype) USNM 719z 152439a 2.9 2.7 3.0 2.3 1.6 152439b 4.1 3.8 4.0 2.9 2.3 152439c 4.7 3.9 4.6 3.0 2.6 152439d 5.0 4.7 5.4 3.8 3.0 152439e 6.0 5.6 5.5 3.5 c.3.0 152439f 6.6 5.8 6.8 4.3 3.9 152439g 7.5 6.6 8.4 5.9 4.0 152439h 9.0 7.7 9.7 5.7 5.0 1524391 10.0 8.4 11.9 9.0 6.4 152439J 13.6 11.0 14.0 10.5 7.2 152439k 16.1 12.4 c.17.0 13.0 9.0 152439-1 18.7 13.4 18.8 13.9 10.3 152439m 20.6 14.9 19.5 14.0 10.0 152439n 20.4 15.4 19.5 13.9 9.0 152439o 22.7 15.0? 24.5 19.0 ? 152439p 23.0 16.3 21.5 16.0 11.0? 152439q 23.2 16.0? 21.1 15.6 ? STRATIGRAPHIC OCCURRENCE.—Word Formation (Appel Ranch Member). LOCALITIES.—UNSM 715i, 719z, 722t. DIAGNOSIS.—Large (gigantic for the genus) nar- row Crurithyris. TYPES.—Holotype: USNM 152437c. Figured par- atypes: USNM 152439d,e,j,o,p; 154421a,b. Measured paratypes: USNM 152437a,b; 152439a-q. COMPARISON.—Crurithyris major is characterized by its large size, long and thick, strongly curved pedicle beak that results in a proportionately low and concave interarea, large delthyrial flanges, de- pressed pedicle muscle area, and crura that remain close to valve floor, cemented to floor for their entire length in some specimens. It is the largest of the 2126 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY Texas Permian species, with a median size near the maximum size of the next largest species, C. tholia- phor, new species. It is so much larger, and pro- portionately narrower, than the other species of the genus from the area, that other detailed com- parisons are unnecessary. Crurithyris minutalis, new species PLATE 590: FICURES 1-22 Very small for genus, nearly planoconvex; outline subquadrate to semielliptical, widest near mid- length, anterior margin slightly flattened at midline in largest specimens; commissure rectimarginate, pedicle valve with slight flattening or depression near anterior of largest specimens, not folding com- missure; surface spines short, visible on few speci- mens; growth lines also obscured; growth laminae visible on some specimens, weak and intermittently spaced. Pedicle valve strongly and rather evenly convex; beak thick, proportionately high for genus, slightly incurved, bluntly pointed; interarea proportionately high for genus (nevertheless much wider than high) flatly concave; delthyrium narrowly triangular, with very small lateral flanges. Brachial valve flat to flatly convex, slightly swollen at beak; interarea broadly triangular, flat; notothyrium proportion- ately wide, triangular, with low lateral flanges. Pedicle valve interior with hinge teeth short, rel- atively broad; dental ridges rudimentary, converg- ing at apex of delthyrium to form very small apical plate; muscle area proportionately large, ovate, without median ridge or furrow; marks weakly im- pressed, not individually distinguishable. Brachial valve interior with deep, tapered hinge sockets; socket ridges thick, swelling to form small knob at anterior end; cardinal process flat to slightly convex, in apex of notothyrium, finely lam- ellate; crural plates proportionately thick, hardly differentiated from crura proper, fused to valve floor; crura proportionately far apart, fused to floor for short distance anteriorly, rodlike; spiralia flat, ribbonlike, rising above floor by S-shaped fold; com- plete spiralium not observed, hence number of loops unknown; muscle area between cura, elongate, weak, individual marks not apparent. STRATIGRAPHIC OCCURRENCE.—Road Canyon For- mation. MEASUREMENTS (in mm).— brachial valve hinge thick- length length width width ness USNM 703 152415a 1.5 1.2 1.6 1.2 1.1 152415b 1.7 1.5 1.7 1.2 12. 152415c 1.7 1.6 1.8 1.5 1.3 152415d 1.7 1.5 1.9 1.6 1.3 152415c 1.8 1.6 1.9 1.6 1.3 152415f 1.8 1.6 2.0 1.8 1.5 USNM 703c 152416a 1.4 1.2 1.8 1.4 1.1 152416b 2.2 1.7 2.3 1.9 1.6 152416c 2.5 2.1 2.7 2.2 1.8 152416d 3.5 2.8 3.9 3.4 2.7 USNM 703d 152417 4.1 3.4 4.4 3.4 3.2 USNM 709c 152423a 1.2 1.1 1.4 0.9 0.9 152423b 1.9 1.7 2.1 1.6 1.4 USNM 707e 152422 2.8 2.5 3.0 2.5 2.2 USNM 702c 152410a 0.6 0.5 0.8 0.4 0.5 152410b 0.9 0.8 0.9 0.6 0.7 152410c 0.9 0.8 1.1 0.8 0.7 152410d 1.0 0.9 1.3 1.1 0.8 152410e 1.0 0.9 1.3 0.9 0.7 152410f 1.2 1.0 1.4 1.2 0.9 152410g 1.3 1.1 1.5 1.3 1.0 15241 Oh 1.4 1.2 1.6 1.2 1.1 152410i 1.6 1.3 1.8 1.4 1.3 152410J 1.7 1.5 1.9 1.6 1.3 152410k 1.9 1.6 2.1 1.7 1.4 152410-1 2.0 1.7 2.3 1.9 1.5 152410m 2.1 1.8 2.2 1.7 1.6 152410n 2.2 2.0 2.4 1.9 1.6 152410o 2.4 2.1 2.5 1.8 1.9 152410p 2.6 2.1 2.6 2.1 1.9 152410q 2.7 2.2 2.6 2.4 2.0 15241Or 2.7 2.4 2.7 2.1 2.0 152410s 2.9 2.4 2.8 2.5 2.2 154428b 2.5 2.0 2.5 2.2 1.9 (holotype) LOCALITIES.—USNM 702c, 703, 703c, 703d, 706f, 707e, 709c, 719x, 721j, 721o, 721x, 723a, 724j. DIAGNOSIS.—Very small Crurithyris with long ped- icle valve beak and angulated cardinal extremities. TYPES.—Holotype: USNM 154428b. Figured par- atypes: USNM 152417; 152427; 154428a,d,i,j. Meas- ured paratypes: USNM 152410a-s, 152415a-f, 1524I6a-d, 152417; 152422; 152323a,b. COMPARISON.—Crurithyris minutalis is character- ized by its very small size, about half that of the NUMBER 21 2127 next smallest species, C. tumibilis, new species, its proportionately long pedicle beak and high pedicle interarea, and its wide hinge with ends that are sharp for the genus (nearly right angle), and result- ant subquadrate outline. Its brachial valve is flatter, its; interarea higher, and its hinge ends sharper than those of C. tumibilis, the only other species with which it need be compared. The small size might lead to the belief that the collection repre- sents only juveniles of a larger species. The collec- tion contains several hundred specimens, however, and the size range is small; these collections are from samples that contained large specimens of other species in other genera. A few large speci- mens of Crurithyris are known from the Skinner Ranch Formation but they are insufficient in num- ber for description. It is highly probable that C. minutalis is a distinct species of small size. Crurithyris sulcata Stehli PLATE 588: FIGURES 33-54 Crurithyris sulcata Stehli 1954:342, pi. 26: figs. 1-6. Medium size for genus, nearly planoconvex; out- line transversely subquadrate, widest anterior to hinge, posterior to midlength, anterior margin slightly emarginate; fold absent; short depression present at anterior of most brachial valves; sulcus shallow but distinct, beginning at pedicle beak or just anterior to beak, becoming deeper anteriorly, expressed at anterior margin only by shallow inden- tation, not by folding of commissure; surface with short spines or low spine bases preserved on few specimens; radial fibrous effect weak; growth lines closely spaced, indistinct; growth laminae stronger, more frequent near margins. Pedicle valve strongly convex; greatest convexity in umbonal region; beak long, strongly curved, erect to incurved; interarea high, strongly concave; delthyrium narrowly wedge-shaped, bounded later- ally by pair of relatively high deltidial flanges. Bra- chial valve flatly convex transversely, umbonal region slightly swollen, anterior midline slightly flattened or depressed; beak sharp, short; interarea low, wide, height about average for genus; noto- thyrium wide, shallow to moderately deep, bounded laterally by notothyrial flanges produced by exten- sions of socket ridges. Pedicle valve interior with short, knoblike, MEASUREMENTS (in mm).— brachial valve hinge thick- length length width width ness USNM 728f 152435a 1.5 1.4 1.8 1.3 1.0 152435b 1.7 1.5 2.0 1.4 1.1 152435c 1.8 1.5 1.9 1.3 1.1 152435d 1.9 1.7 2.1 1.4 1.2 152435e 2.1 1.8 2.1 1.4 1.3 152435f 2.2 1.8 2.4 1.5 1.5 152435g 2.2 1.9 2.5 1.8 1.5 152435h 2.4 2.2 2.7 1.7 , 1.6 1524351 2.6 2.1 2.6 1.8 1.8 152435J 2.8 2.4 2.9 2.2 2.1 152435k 3.1 2.9 3.8 2.6 2.3 152435-1 3.3 3.1 3.9 2.5 2.1 152435m 3.5 3.0 3.9 2.7 2.5 152435n 3.8 3.2 4.0 2.8 2.5 152435o 4.0 3.4 4.3 3.2 2.6 152435p 4.1 3.6 4.5 3.3 2.6 152435q 4.2 3.6 4.5 3.3 2.8 152435r 4.4 3.9 5.0 3.0 2.9 152435s 4.6 3.9 5.4 3.4 3.0 152435t 4.9 3.9 5.0 3.4 3.5 152435u 5.0 4.3 5.6 3.7 3.3 152435v 5.2 4.4 5.7 3.7 3.1 152435w 5.7 4.6 5.9 4.0 3.6 152435x 5.9 4.8 6.2 4.3 3.9 152435y 6.1 5.0 6.3 4.0 4.2 152435z 6.4 5.3 6.8 4.9 4.0 152435a' 6.4 4.8 6.9 5.2 4.4 152435b" 6.6 5.5 7.9 5.6 4.0 152435c 7.2 5.8 8.0 5.3 4.9 152435d' 7.2 6.1 8.9 6.0 4.5 152435c 7.5 6.4 8.3 5.0 4.8 152435f 7.8 6.0 8.0 5.0 5.0 152435g' 7.9 6.7 8.8 5.9 5.0 152435h' 10.5 8.0 11.1 8.4 6.2 slightly hooked teeth; dental ridges flat, nearly nonexistent, expanded at apex of delthyrium to form short apical plates nearly perpendicular to plane of commissure; muscle area in umbonal re- gion, indistinct, subovate, not depressed, without median or lateral ridges. Brachial valve interior with hinge sockets deep, bridged by thin plates, socket ridges thick; cardinal process small, wedge-shaped, filling extreme apex of notothyrium, finely lamellate longitudinally, with only few parallel plates; crural plates filling space between socket ridges and crura, slightly convergent toward floor; crura rodlike, fused to valve floor at posterior, slightly bowed distally, extending just beyond midlength of valve; spiralia not observed; 2128 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY muscle area located between crura, weakly im- pressed, individual muscle marks not differentiable. STRATIGRAPHIC OCCURRENCE.—Bone Spring For- mation. LOCALITIES.—AMNH 629, 631; USNM 725a, 725c, 728e, 728f, 728h, 728t. DIAGNOSIS.—Moderately large Crurithyris with sulcus on pedicle valve and brachial valve and emar- ginate anterior. TYPES.—Lectotype (herein designated): AMNH 27322/1:4. Figured paratypes: AMNH 27322/1:1-3. Figured hypotypes: USNM 152435d,g',h'; 154422a-d. Measured hypotypes: USNM 152435a-z, a'-h'. COMPARISON.—Crurithyris sulcata is characterized by its transverse outline, consistently sulcate pedi- cle valve, normally sulcate brachial valve, reduced dental ridges, and weakly impressed muscle marks. It occurs with C. inflata Stehli, differing in its somewhat less convex, and less evenly convex pedi- cle valve with sulcus, normally emarginate anterior outline, and weakly impressed muscle marks. It is larger and more nearly plano-convex than C. tumi- bilis, new species, from the Neal Ranch Formation of the Glass Mountains. It is larger and more trans- verse than C. guadalupensis (Girty) from the Bell Canyon Formation (Lamar Member), in the Guada- lupe Mountains. It is much larger than C. minu- talis, new species, and much smaller than either C. tholiaphox or C. major, both new, from the Word Formation. Crurithyris tholiaphor, new species PLATE 589: FIGURES 1-38 Medium to large for genus, moderately biconvex to nearly planoconvex; outline subquadrate, length and width nearly equal, greatest width slightly an- terior to midlength, anterior outline slightly flat- tened, rarely emarginate; pedicle sulcus normally absent, rarely slightly impressed at extreme ante- rior; fold absent; surface of some specimens with patches of fine raised lines, probably spine bases or flat-lying spines fused to shell; fine radial fibrous structure; growth lines indistinct; growth laminae weak. Pedicle valve strongly and evenly convex; beak long, thick, strongly incurved; interarea low, strongly convex; delthyrium wedge-shaped, rela- tively wide, but nevertheless higher than broad; lateral flanges of delthyrium low or absent. Brachial valve flatly convex, slightly swollen in umbonal region; interarea low, wide, flat; notothyrium broadly wedge-shaped, with low lateral flanges. Pedicle valve interior with relatively large, knob- like, slightly hooked teeth; dental ridges thick, low, rounded, meeting at apex of delthyrium to form short apical plate; muscle area large, elongate, de- pressed, with short median septum in umbonal cav- ity; diductor marks narrow, anterior, together form- ing chevron; adductor marks posterior, median, elongate, depressed, separated from remainder of valve by pair of lateral ridges fusing at anterior to form low median ridge for 1-2 mm in center of valve. Brachial valve interior with thick-walled socket ridges each bridged by thin plate; cardinal process, a low boss in apex of notothyrium, more quadrate than wedge-shaped, weakly lamellate; crural plates thick, short, joining crura to socket ridges; crura strong, rodlike, distally bowed; spiralia flat, ribbon- like, beginning with S-shaped curves, then about 5 coils with axes directed posterolaterally; muscle area weakly impressed between crura, consisting of four small quadrate impressions. MEASUREMENTS (in mm).-— brachial valve hinge thick- length length width width ness USNM 706c 152445a 2.8 2.8 3.2 2.4 1.7 152445b 3.9 3.6 4.3 3.1 2.3 152445c 5.9 5.2 6.2 4.4 3.4 152445d 5.9 5.2 6.2 4.1 3.6 152445e 6.5 5.6 7.0 5.0 3.9 152445f 7.4 6.4 8.0 5.8 4.7 152445g 8.7 7.3 9.0 6.5 5.0 152445h 10.0 9.0 11.2 8.5 6.3 152445i 11.3 9.0 11.7 9.1 7.0 152445J 14.4 10.5? 14.2 9.3 9.0? 152445k 15.3 11.4 15.0 11.2 9.5? (holotype) 152445-1 16.8 12.0 15.9 12.3 9.9 USNM 706 152441a 3.0 2.9 3.6 2.0 1.7 152441b 3.4 2.9 3.8 2.9 2.3 152441c 4.4 3.9 5.0 3.9 2.7 152441d 4.8 4.3 5.0 3.0 3.0 152441c 10.6 8.4 10.7 7.8 6.2 152441f 10.8 8.4 11.2 8.2 6.5 USNM 706b 152443 20.0 15.0 19.0? 14.0? ? USNM 728 152449a 23.7 17.0? 23.0? 17.3 ?NUMBER 21 2129 STRATIGRAPHIC OCCURRENCE.—Word Formation (China Tank, Willis Ranch, and Appel Ranch members and lens between the last two). Cherry Canyon Formation (Getaway Member). LOCALITIES.—Word: USNM 737b. China Tank: USNM 706c, 713e, 726r, 726s. Willis Ranch: USNM 706, 706e, 719e, 723w, 724u. Appel Ranch: USNM 727j. Lens: USNM 706b. Getaway: AMNH 46, 496, 512, 600; USNM 728. DIAGNOSIS.—Large Crurithyris with squarish out- line, depressed muscle area bounded by anteriorly coalesced ridges. TYPES.—Holotype: USNM 152445k. Figured par- atypes: USNM 152423; 152440a-c; 152441a,b,; 152445a,d,f,m,n; 152446a; 152449b,c. Measured par- atypes: USNM 152441a-f; 152443; 152445a-j,l; 152449a. COMPARISON.—Crurithyris tholiaphor is charac- terized by its relatively large size (for species from this area), nearly equal length and width, thick and strongly curved pedicle beak producing relatively low and strongly curved interarea, and its de- pressed pedicle muscle area bounded by low ridges that coalesce at the anterior. The only species that is comparable in size that occurs here is C. major, new species, from the Appel Ranch Member of the Word. Crurithyris tholiaphor is slightly smaller in median and maximum size, is slightly thicker shelled, has a lower interarea and shorter beak, and normally less deeply impressed and sharply bounded pedicle muscle area. The two species undoubtedly are related, with external characters of C. tholia- phor somewhat exaggerated in C. major. This species differs from C. sulcata Stehli in its larger size and depressed pedicle muscle area. This latter feature is similar to that in C. inflata Stehli, from which C. tholiaphor differs in its larger size, longer and more strongly curved pedicle beak, more distinct radial fibers (possibly a function of preser- vation), and larger cardinal process that is more quadrate than trigonal. It is much larger and less transverse than C. guadalupensis (Girty). Crurithyris tumibilis, new species PLATE 589: FIGURES 39-58; PLATE 590: FIGURES 40-52 Ambocoelia planoconvexa R. E. King [not Shumard], 1931:120. Small for genus, normally biconvex, less com- monly nearly planoconvex; outline transversely sub- elliptical, less commonly slightly elongate, widest between hinge and midlength, anterior normally evenly arcuate, less commonly slightly emarginate or flattened at midline; commissure rectimarginate; surface appearing smooth, rarely exhibiting irregu- larities of surface spines or growth lines. Pedicle valve strongly convex, especially in um- bonal region; slight median depression in some, producing anterior emargination; beak thick, bluntly pointed, strongly curved; normally erect or slightly incurved; interarea high for genus, trans- versely triangular, longitudinally concave; delthy- rium narrowly to nearly equilaterally triangular, open, bounded laterally by pair of small (yet high for genus) deltidial flanges. Brachial valve flatly to moderately convex, with convexity rather even both longitudinally and transversely; beak slightly pro- jecting, obtusely pointed; interarea high for genus, about a third height of pedicle interarea, flat to slightly concave; notothyrium broadly triangular, bounded by straight flanges formed by socket ridges. Pedicle valve interior with hinge teeth short, slightly flattened and slightly hooked; dental ridges low and rounded, converging at apex of delthyrium and growing forward conjunctly for about 0.3 mm in adults, forming short apical plate; muscle marks weakly impressed in oval area in umbonal region, bisected in apex of some by short, low median ridge. Brachial valve interior with deep, strongly con- structed hinge sockets; cardinal process broad, slightly convex, finely lamellate, consisting of about 8 thin closely spaced parallel plates; hinge plates extending from socket ridges to valve floor, very short, slightly thickened; crura rodlike, cemented to valve floor for short distance in posterior by thin plates, rising slightly from floor toward anterior; spiralia attached to crural ends, flatter and more ribbonlike, broadening to make S-curve raising spiralia above valve floor, then once more narrow- ing to coil in about 5 loops with axes diverging posteriorly; muscle elongate, narrow, weakly im- pressed between crura in posterior half of valve. STRATIGRAPHIC OCCURRENCE.—Gaptank Forma- tion (Uddenites-bearing Shale Member); Neal Ranch Formation. LOCALITIES.—Uddenites: USNM 701e, 701p, 701q. Neal Ranch: USNM 701, 701a, 701a3, 701c, 701d, 701h, 701k, 701-1, 715b, 721g, 727d, 727e, 730c. DIAGNOSIS.—Small Crurithyris with strongly con- vex brachial valve. 2130 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY MEASUREM] ENTS (in mm).— brachial valve hinge thick- length length width width ness USNM 701k 152406a 1.1 0.9 1.2 0.8 0.7 152406b 1.3 1.1 1.5 0.8 1.0 152406c 1.5 1.2 1.6 1.2 1.1 152406d 1.7 1.4 1.7 1.2 1.1 152406e 1.8 1.4 2.0 1.4 1.3 152406f 2.2 1.8 2.3 1.7 1.6 152406g 2.2 1.9 2.5 1.5 1.5 152406h 2.3 1.9 2.6 1.9 1.6 152406i 2.6 2.0 2.6 1.7 1.8 152406J 2.8 2.2 2.8 2.1 1.7 152406k 2.9 2.4 3.3 1.9 1.9 152406-1 3.1 2.6 3.6 2.0 2.1 152406m 3.4 2.8 3.7 2.6 2.0 152406n 3.8 3.3 4.1 3.1 2.6 152406o 3.9 3.1 3.6 2.4 2.6 152406p 4.2 3.6 4.4 3.6 3.0 152406q 5.5 4.4 5.0 3.8 2.9 152406r 5.5 4.7 5.4 3.6 3.8 152406s 5.7 5.0 6.4 4.6 3.8 152406t 5.8 4.5 5.0 4.0 3.9 152406U 6.4 5.6 6.5 4.4 4.6 152406v 6.9 6.0 7.0 4.9 4.7 152406w 6.9 5.9 7.9 5.8 4.8 152406x 7.7 6.8 7.8 5.4 5.0 152406y 7.9 6.6 8.0 6.0 5.4 152406z 8.2 6.9 8.0 5.3 5.6 152406a' 8.5 7.0 8.4 6.0 5.9 152406b' 9.7 8.2 10.1 7.1 6.5 USNM 701d 154425a 7.0 6.7 9.0 6.0 4.7 (holotype) TYPES.—Holotype: USNM 154425a. Figured par- atypes: USNM 154424a-c,e; 154425c; 154426a,b. Measured paratypes: USNM 152406a-z,a',b'. Unfig- ured paratypes: USNM 154424d, 154425b. COMPARISON.—Crurithyris tumibilis is character- ized by its small size, smooth appearing surface, relatively high interarea, and especially by the great number of its individuals whose brachial valve is more strongly convex than normal for the genus. Its median size is much greater than the Leonard- ian C. minutalis, new species, and it differs further in its normally less quadrate outline and narrower, more rounded hinge ends, and in its more tumid brachial valve. Crurithyris inflata Stehli and C. sul- cata Stehli from the Bone Spring Formation are much larger and are planoconvex; the Word species are still larger. Crurithyris guadaluperisis (Girty) is similar in median size, but has a narrower and shorter beak, less convex brachial valve, and more quadrate outline. The species that most nearly resembles C. tumi- bilis is C. planoconvexa (Shumard), widespread in the Pennsylvanian (Dunbar and Condra, 1932:344). It is similar in size and outline, but differs in its less convex brachial valve and more strongly curved pedicle beak that produces a lower interarea. Crurithyris species unidentified Some small lots of Crurithyris from the Skinner Ranch Formation, which are insufficient in number to serve as a basis for species descriptions, but which should be noted are listed below. SPECIES A.—Fairly large, transversely elliptical in outline, greatly swollen pedicle valve, gently con- vex brachial valve. Interarea short, apsacline beak strongly incurved. Neither valve sulcate. A complete specimen (USNM 152987a) from USNM 707a measures (in mm): length 8.2, brachial valve length 7.1, width 9.4; hinge width 7.0, thickness 5.5. This species suggests C. inflata Stehli and C. gua- dalupensis (Girty) but is less inflated and has a shorter, less elongated beak region than the former, and is wider and more robust than the latter. Specimens are from the Skinner Ranch Formation at USNM 707a and 71 lp. Described specimens: USNM 152987a-d, 152988a-d. SPECIES B.—Also moderate size, chiefly distin- guished by very short beak and short interarea, but swollen umbonal region and a fairly convex brachial valve. Neither valve is sulcate. A complete speci- men (USNM 152989a) from USNM 707d measures (in mm): length 6.6, brachial valve length 5.6, width 7.0, hinge width 4.7, thickness 4.0. The shortness of its beak and interarea distin- guishes this species from all others in the collection. Specimens come from the upper part of the Skin- ner Ranch Formation at USNM 707d and 722-1, and from the Hess Formation (Taylor Ranch Mem- ber) at USNM 702d. Describedspecimens:USNM 152989a-c; I52990a-c; 152991a,b. SPECIES C.—We do not have enough specimens to indicate the maximum size of this species, but some incomplete fragments suggest that the size is mod- erate. The outline is roundly elliptical, with width slightly greater than length. The beak is moderately long, interarea moderately long, brachial valve NUMBER 21 2131 fairly strongly convex. The specimens are not fully enough grown to show a sulcation of the pedicle valve, but the brachial valve is anteriorly flattened but swollen posteriorly. The hinge is fairly wide but considerably narrower than the midwidth. Measurements (in mm) are as follows: brachial valve hinge thick- . length length width width ness USNM 702e 152413a 1.9 1.7 2.2 1.8 1.5 152413b 3.8 3.5 4.5 3.1 2.6 152413c 4.0 3.4 4.4 3.1 2.8 152413d 4.4 3.8 4.6 3.1 3.0 152413e 4.8 4.0 5.1 3.4 3.0 152413f 5.4 4.3 6.0? 4.1 3.5? Compared with specimens of C. inflata Stehli of the same size this species proves to have a much more convex pedicle valve. Specimens come from the Hess Formation (Tay- lor Ranch Member) at USNM 702e. Described and measured specimens: USNM 152413a-f. SPECIES D (In Volume 5, Plate 745: figures 40- 44).—This is a large species somewhat larger than C. guadalupensis (Girty) but much smaller than either C. tholiaphor or C. major, both new. It differs from the former in having a broader ventral umbo which does not protrude so far posteriorly and has somewhat narrower shoulders. It also suggests C. sulcata Stehli but lacks the narrow, shallow sulcus on the ventral valve of that species. This is a rare shell in the Cathedral Mountain Formation at USNM 721u. Figured specimen: USNM 154512. Genus Attenuatella Stehli, 1954 Attenuatella Stehli, 1954:343. — Cherniak in Ustritsky and Cherniak, 1963:114. — Waterhouse, 1964:108; 1967:167.— Armstrong, 1968:783. Small, nearly planoconvex; outline narrowly elon- gate subovate, normally flattened or slightly in- dented at anterior margin, greatest width anterior to midlength; commissure rectimarginate; pedicle valve weakly sulcate; brachial valve without fold, accommodating sulcus by anterior emargination; costae absent; shell with fine radial fibers, crowded short spines or spine bases; growth lines and lam- inae weakly visible on some specimens, invisible on others. Pedicle valve elongate, strongly convex; beak very long for genus, slightly attenuate, strongly curved posterior to hinge, apex normally incurved; inter- area proportionately high and narrow, nearly equi- laterally triangular, strongly concave; delthyrium deeply wedge-shaped, bounded laterally by low flange on each side. Brachial valve flatly convex to nearly flat; slightly swollen in beak area; beak pointed, projecting slightly beyond posterior mar- gin; interarea proportionately very low, wide, flat; notothyrium proportionately wide and shallow. Pedicle valve interior with large, transversely elongate, rounded hinge teeth; dental ridges, flat, scarcely identifiable as ridges, coalescing at apex of delthyrium to form very short apical plates; muscle area in umbonal region; adductor marks slightly depressed on floor of valve in posterior lateral parts of area; diductor marks raised on long narrow median ridge with low lateral flanges, ridge con- tinuing anteriorly beyond muscle area, bisecting all but anterior fourth of valve. Brachial valve interior with wide hinge sockets formed by thick socket ridges; cardinal process occu- pying apex of notothyrium, bifid in some species, proportionately thick, convex, finely lamellate; hinge plates very short, nearly parallel to valve walls, joining crura to socket ridges; crura rod- shaped, cemented to valve floor only in extreme posterior part of their length; spiralia absent (fide Armstrong, 1968); muscle area between crura, weakly impressed, subquadrate, individual muscle marks not distinguishable, but pattern apparently as in Crurithyris. TYPE-SPECIES.—Attenuatella texana Stehli (1954: 343, pi. 25: figs. 31-33) (by monotypy). DIAGNOSIS.—Elongate narrow outline, strongly in- curved beak of pedicle valve, raised thickened myo- phragm in pedicle valve, short crural plates lying nearly against posterior walls of brachial valve, brachidia terminating without forming spires. COMPARISON.—Attenuatella is longer and nar- rower than either Ambocoelia or Crurithyris. It dif- fers further in its long and rather thick ventral beak and nearly flat brachial valve. Internally it is distinguished by the prominent median ridge in the pedicle valve that forms a deep groove in decor- ticated and weathered specimens, and by its trun- cated brachidia that begin as in Crurithyris but fail to develop spiralia. DISCUSSION.—Attenuatella was established on a 2132 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY single pedicle valve. Since then it has been described in Permian strata of New Zealand (Waterhouse, 1964), New Caledonia (Waterhouse, 1967), and Australia (Waterhouse, 1967; Armstrong and Brown, 1968; Armstrong, 1968). In addition, it has been recognized in the literature as having been described in other guises in Mexico, Siberia, the Ural Mountains, and Novaya Zemlya (see Arm- strong, 1968:787, fig. 3). Despite such wide recogni- tion the spiralia remained undescribed, a fact usually attributed to rarity and poor preservation. Armstrong (1968) contends that the brachidia of Attenuatella terminate without forming the spiralia that would be expected from its obvious close rela- tionship to Crurithyris. Although such abortive development could well account for the fact that no spiralia were seen in the genus, and for the elongate narrow outline of the shell, initial skepti- cism prompted a second look at specimens of A. attenuata (Cloud) from the Las Delicias area of Mexico (USNM 814). A suite of about 30 specimens was examined: many are internal molds, some re- tain the shell. Several specimens clearly show holes where the initial laminae of the brachidia pene- trated the matrix and were weathered out. None shows any sign of a spiralium although preservation and breakage is such that one would show it if present. Therefore we accept Armstrong's conclu- sion that the brachidium of Attenuatella terminated without development of a spiralium. We agree also that other features require taxonomic placement as a close relative of Crurithyris despite lack of a spire, that the brachidia of Attenuatella are aborted spires rather than some other independent configuration. Attenuatella attenuata (Cloud) PLATE 590: FICURES 32-39 Crurithyris attenuata Cloud 1944:62, pi. 17: figs. 22-25.— Waterhouse, 1964:108. Attenuatella attenuata (Cloud) Stehli, 1954:343.—Waterhouse, 1967:171.—Armstrong, 1968:786. DESCRIPTION.—The description and measurements by Cloud are adequate and need not be repeated. STRATIGRAPHIC OCCURRENCE.—Waagenoceras zone (Word equivalent). LOCALITY.—Palo Quemado, NW end of Las Deli- cias Valley, Coahuila, Mexico, USNM 814. DIAGNOSIS.—Large Attenuatella with unusually long ventral beak and nearly flat brachial valve. TYPES.—Holotype: YPM S-2745. Figured para- types: YPM S-2746. Figured hypotypes: USNM 154429a-c. COMPARISON.—Stehli (1954:343) considered the possibility that additional material might prove A. texana to be synonymous with A. attenuata. New material of both species from their type localities, however, merely confirms their difference. Attenua- tella attenuata is larger, the pedicle valve is more strongly curved, the beak is longer and thicker, and the brachial valve more nearly circular and almost perfectly flat. Many of the specimens are preserved as steinkerns, inviting comparison with the simi- larly preserved Australian species A. multispinosa Waterhouse ( 1967). The Mexican species does not exhibit the ventral sulcus and dorsal costae of the New South Wales species. It is much more elongate and the brachial valve more nearly plane than in A. convexa Armstrong (1968) from the Permian of Queensland. Attenuatella texana Stehli PLATE 590: FIGURES 23-31; PLATE 745: FIGURES 64-68 (in volume 5) Attenuatella texana Stehli, 1954:343, pi. 25, figs. 31-33. Shell smaller than medium size for genus, nearly planoconvex; outline elongate subovate with flat- tened anterior margin, sides subparallel, greatest width about a third distance back from anterior margin; sulcus shallow, barely perceptible on some specimens; brachial valve without fold; radial fibers fine; surface spines or spine bases apparently randomly distributed; growth lines and laminae weak. Pedicle valve long, narrow, strongly convex in both directions; beak long, somewhat attenuate, incurved; interarea comparatively high, narrow (for genus) but wider than high, strongly concave; delthyrium deeply wedge-shaped, lateral bounding flanges low or absent. Brachial valve elongate ellip- tical, nearly flat, slightly swollen in beak area; interarea proportionately very low and wide; noto- thyrium shallow, broad, with low lateral flanges. Pedicle valve interior with large, broad, flat, slightly hooked hinge teeth; dental ridges rudi- mentary; apical plate in apex of delthyrium very short; muscle area in umbonal region; adductor NUMBER 21 2133 marks very weak, barely discernible; diductor marks on narrow median ridge, elongate, one on each side; median ridge extending anteriorly well beyond muscle area. Brachial valve interior known only from imma- ture valve; hinge sockets wide, with strong socket ridges, bridged by thin plates; cardinal process fill- ing apex of notothyrium, finely lamellate; crural plates thick, widely divergent, connecting crura to socket ridges; crura rod-shaped, rather far apart, distally bowed; muscle area between crura about a third distance anterior to beak, small, quadrate, weakly impressed. MEASUREMENTS (in mm).—Brachial valve length, and thickness, unmeasurable. commissure hinge length length width width SNM 728f 152986a 6.0 4.5 4.2 2.9 152986b 7.0 4.8 4.9 3.4 152986c 7.1 4.8 5.1 2.9 152986d 7.4 5.2 5.4 3.5 152986e 7.7 5.3 c.5.5 3.1 152986f 8.0 5.8 5.9 3.7 152986g 9.0? 6.5? 6.2 4.0 152986h 9.0 6.0 6.7 4.3 STRATIGRAPHIC OCCURRENCE.—Bone Spring For- mation. LOCALITY.—USNM 728f. DIAGNOSIS.-—Small, very narrow Attenuatella. TYPES.—Holotype: AMNH 27321. Figured hypo- types: USNM 152986c,d,h-j. Measured hypotypes: USNM 152986a-h. COMPARISON.—Attenuatella texana is character- ized by its small size and narrow outline. It is smaller than the only other American species, A. attenuata (Cloud) from the Las Delicias area of Mexico, and its hinge is narrower, and brachial valve proportionately smaller. The two are difficult to compare further, because the former are silicified free valves, whereas the Mexican ones are internal casts, except for one small complete shell. The Texas specimens are narrower than the Australian species illustrated by Armstrong (1968), and much smaller than A. incurvata Waterhouse (1964) from the Per- mian of New Zealand. Suborder ATHYRIDIDINA Boucot, Johnson and Staton, 1964 Biconvex, generally rounded shells with recti- marginate or uniplicate commissure; interareas obsolete. Pedicle valve with rounded foramen; bra- chial valve with small undivided hingeplate. Spiri- dium with laterally directed cones. Jugum simple to complex. Superfamily ANTHYRIDACEA McCoy, 1844 Family ATHYRIDIDAE McCoy, 1844 Brachial apparatus with complex V-shaped jugum. Subfamily ATHYRIDINAE McCoy, 1844 Smooth, lamellose or spiny, rounded jugal proc- ess confined between primary and secondary whorls of spiral. Genera in West Texas: Cleiothyridina Buckman, 1906; Composita Brown, 1849. Cleiothyridina has seldom been reported in the Permian of the United States but the etching pro- gram has produced rare and mostly small specimens from many parts of the West Texas Permian. The Wolfcampian species is very small. The genus is equally rare in the Road Canyon and the Word formations. One species occurs in the Bell Canyon Formation. The rarity and small size of the genus in the United States is in strong contrast to its abundance and large size in Asia. Composita is one of the commonest genera in all parts of the Permian of West Texas, occurring in all parts of the section. Genus Cleiothyridina Buckman, 1906 Cleiothyridina Buckman, 1906:324. —Hall and Clarke 1893: 90.—Weller 1914:472.—Williams et al., 1965:H662.—Carter 1967:342. Small to medium size, moderately strongly bi- convex to subglobose; outline subcircular to trans- versely subelliptical, greatest width near midlength; hinge narrow, without protruding ends; commis- sure rectimarginate to strongly uniplicate, less commonly weakly sulcate; in some species fold beginning near beak and remaining prominent toward anterior, in other species becoming promi- nent only near anterior, in some species absent; sulcus shallow, gently rounded in most species, sharply outlined in some; radial ornament absent; 2134 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY concentric lamellae bearing short to moderately long, apparently solid, slender spines, density of occurrence varying with species; spines normally broken off, leaving concentric lamellae visible; growth laminae stronger, interrupting more regu- larly spaced lamellae. Pedicle valve moderately to strongly convex, greatest swelling normally just anterior to umbonal region; beak short, blunt to slightly attenuate, nor- mally suberect to erect or slightly recurved; beak ridges curved, obscure; delthyrium large, triangular, fully occupied by brachial beak; deltidial plates absent; foramen small, subcircular, perforating apex of beak. Brachial valve slightly less strongly convex, greatest swelling in umbonal region; beak obtusely pointed, apex within pedicle valve; edges of valve slightly overlapping posterolateral edges of pedicle valves, elsewhere butting directly. Pedicle valve interior with rather large hinge teeth, elongate parallel to sides of delthyrium; den- tal plates short, divergent, meeting valve walls and continuing toward floor either fused to wall or tightly pressed against it, forming small vessel- shaped smooth area in umbonal region posterior to muscle area; muscle marks located anterior to smooth apical area, extending nearly to midlength of some species, nearly to anterior margin of others; large lateral diductor marks separated by obscurely differentiated pair of mesial adductor marks; pallial trunks extending anteriorly nearly parallel to me- dian line of shell, varying in depth with species and with individual, fading just behind valve mar- gins, numbering about 6-8, some bifurcating at anterior extremity. Brachial valve interior with slightly concave semielliptical hinge plate at beak, perforated at apex by small cardinal foramen with small tooth- like cardinal process projecting posteriorly within it (probably for insertion of diductor muscle ten- dons); hinge sockets large, posteriorly tapering, formed between valve walls and socket ridges, mesial parts of socket ridges supporting lateral edges of hinge plate; muscle area elongate elliptical, bisected in posterior half by low flat median ridge; muscle marks deepest at posterior, becoming shal- lower in anterior part, merging and losing distinct boundaries anteriorly; pallial grooves subparallel, slightly radial, widely spaced, similar to those in pedicle valve; crura extending anteriorly from ante- rolateral edges of hinge plate, directed toward floor of valve, then anteriorly above floor; spiralia at- tached to crura, laterally coiled in about 9 loops, axis of coiling nearly directly transverse to median plane of shell. TYPE-SPECIES.—Spirifer de roissyi Leveille" (1835 39=Athyris roysii [sic] Davidson, 1860:84, pi. 18 fig. 8) by original designation of Buckman (1906 324). COMPARISON.—Cleiothyridina is characterized by its concentric lamellae that bear short spines, its pedicle beak without interarea, its subcircular pedi- cle foramen that penetrates the apex of the beak, and by presence of small dental plates in the pedi- cle valve and an apically perforated hinge plate in the brachial valve. The surface spines and concen- tric lamellae resemble those on Permophricadothyris, but differ in their single rather than double bases, and apparent solidity. Cleiothyridina differs further in its lack of interarea, its apical foramen, and pos- session of dental and hinge plates. The absent interarea and subcircular apical foramen resemble similar features of Composita, but Cleiothyridina is distinguished by its concentric spinose lamellae, and internally by its perforated hinge plate. This genus strongly resembles Actinoconchus of the Car- boniferous, differing primarily in its concentric lamellae that bear slender spines. DISCUSSION.—This is the first report of Cleiothyri- dina from the Texas Permian. It is very rare except at a few localities in the Wolfcamp Hills, and was not discovered by previous workers. Apparently, after its abundant development in the Pennsylva- nian, the genus declined in the United States, becoming not only rare but very small in the Texas Permian. R. E. King (1931:41) stated, "The genera Spirigerella and Cliothyridina (sic), which are con- spicuous elements of Eurasian Permian faunas, are quite absent from the Texas Permian. This is the only family in which a common Pennsylvanian genus is unrepresented, for Cliothyridina, an abun- dant fossil in places in the lower and middle Penn- sylvanian, does not occur higher in this country.'' Among the few species of Cleiothyridina in the Texas Permian there is a definite increase in strength of the anterior fold from the rectimarginate Wolf- campian C. rectimarginata, new species, through increasingly strongly folded C. mulsa, new species, from the Late Wolfcampian and C. nana, new spe- cies, from the Road Canyon Formation. Despite increase in strength of folding, all these species are NUMBER 21 2135 very weakly folded compared to most species of the genus. The trend here in Texas culminates in the relatively (for the genus) strongly folded C. pilu- laris, new species, from the Late Guadalupian Lamar Member of the Bell Canyon Formation. This trend, while apparent in our few species, is not a general trend in the more complete history of the genus; there are Mississippian species that are nearly rectimarginate, and others well folded (Weller, 1914). The major difference between Cleiothyridina and Athyris, whose range is earlier in the Paleozoic, is in the presence of spines instead of frills along the concentric lamellae of the shell. These spines appear to be solid rather than tubular, not only on silici- fied Permian specimens, but also on calcareous specimens in tire National Museum collection from the Mississippian and Pennsylvanian. In order for solid spines to be formed, without an inner tube occupied by mantle as in productid spines, they must have been secreted along the mantle edge at the valve edges. Most specimens on which spines are preserved have the longest and most numerous spines at the valve edge near the commissure. From there toward the posterior the number and length of spines decreases irregularly, the decrease prob- ably due simply to the breaking off of earlier sets of spines. If the spines were indeed formed along the valve edge, they are closely related to the frills that formed along the margins of Athyris, and might be considered simply as discontinuous or deeply notched frills. All other features of the two genera also are so similar that Cleiothyridina is undoubt- edly a close phylogenetic relative of Athyris, and descended from that genus. The small perforation in the apex of the dorsal hinge plate normally is described as simple and circular (e.g., Dunbar and Condra, 1932:359). In most of our specimens it is elongate elliptical, and a few exceptionally well preserved specimens show a small toothlike extension projecting posteriorly into the perforation. The hole and the little ex- tension probably served the function of a cardinal attachment for the ends of the diductor muscles. Cleiothyridina ciriacksi, new species PLATE 650: FICURES 1-18 Small for genus, outline subcircular to slightly oval; sides and anterior margin strongly rounded; widest near midvalve. Beak and foramen small. Sur- face lamellose, spines numerous but length not known. Anterior commissure rectimarginate or with slight dorsad wave. Pedicle valve slightly deeper than brachial valve, moderately but unevenly convex, greatest convexity in posterior region. Anterior profile fairly strongly and somewhat narrowly domed with long moder- ately steep slopes. Umbonal and median regions swollen; anterior third somewhat flattened to very faintly sulcate. Brachial valve fairly evenly and moderately con- vex in lateral profile, broadly and moderately domed in anterior profile. Umbonal region slightly convex, median swollen, lateral slopes steep. Antero- median region in some specimens with faint fold. Pedicle valve interior with short but well-defined dental plates. Teeth small. Brachial valve with small concave hinge plate without apical foramen. MEASUREMENTS (in mm).— brachial length valve length width thickness USNM 763 154386a 5.2 4.8 5.1 3.2 154386b 7.2 6.7 6.8 4.6 154386c 8.8 8.0 9.5 5.2 154386d 9.0 8.0 8.7 5.2 154386e 9.7 8.6 9.4 5.4 154386f 9.8 9.0 9.9 5.8 154386g 9.8 10.0 10.8 6.1 154386h (holotype) 10.9 10.2 10.8 6.6 STRATIGRAPHIC OCCURRENCE.— Park City Forma- tion (Franson Member). LOCALITY.—USNM 763. TYPES.—Holotype: USNM 154386h. Figured par- atypes: USNM 154386g,i-k. Measured paratypes: USNM 154386a-g. DIAGNOSIS.—Small rectimarginate Cleiothyridina strongly and closely lamellose with low beaks and posteriorly swollen valves. NAME.—Named after Dr. Kenneth Ciriacks who collected the specimens. COMPARISON.—The only North American Permian species approaching this one in size are C. pilularis, new species, C. attenuata Cooper, and! C. gerardi (Diener). The first of these species is fairly strongly folded anteriorly and thus entirely unlike C. cir- iacksi, which has only the faintest trace of folding. Cleiothyridina attenuata is distinctly oval or trian- gular in outline, with the posterior attenuated and 2136 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY thus quite different. The last species is so much larger and more robust that no useful comparison can be made. This species suggests the common Pennsylvanian (Desmoines) species C. orbicularis (McChesney) but the Permian species has a more extended beak, somewhat fuller median regions, and less tendency to plication of the commissure in late stages. DISCUSSION.—From the accompanying descriptions of species of Cleiothyridina it seems evident that this hitherto rare genus is far more common than realized. The acidizing technique which is a more productive collecting procedure than most others is sure to reveal many more specimens and probably species. Cleiothyridina mulsa, new species PLATE 650: FIGURES 19-35 Small for genus, but medium size for Texas Per- mian species, flatly to moderately biconvex; outline subtrigonal to oval, greatest width normally some- what anterior to midlength; commissure rectimargi- nate to very weakly uniplicate; fold present on larger specimens, broad, low, expressed only at anterior, not standing above flanks; sulcus shallow, slightly depressing anterior midline of some speci- mens; concentric lamellae weak, closely spaced, few with spines, most with remnants of spine bases, spines preserved only near valve margins; growth laminae stronger, few, interrupting slope of shell. Pedicle valve moderately convex, greatest swell- ing in umbonal region; beak short, blunt, normally suberect; beak ridges indistinct; foramen incom- pletely subcircular, perforating apex of beak. Bra- chial valve flatter; beak rounded to obtusely pointed, apex within pedicle valve. Pedicle valve interior with proportionately large hinge teeth, elongate, parallel to sides of delthy- rium; dental plates fused to sides of valve almost entirely, free only at anterior edges in a few speci- mens, continuing along valve walls to form smooth area in umbonal part of valve; muscle marks located anterior to smooth area, weakly impressed; indi- vidual marks not differentiated; pallial grooves shallow, invisible on some specimens. Brachial valve interior with small elevated hinge plate, depressed medially, with small cardinal per- foration at apex; sockets deep, strongly tapered posteriorly; muscle area small, depressed in um- bonal region, individual muscle marks not differ- entiated; crura and spiralia not observed. MEASUREMENTS (in mm).— brachial length valve length width thickness USNM 705a 152459a 3.6 3.0 3.1 2.2 152459b 4.3 4.1 4.2 2.6 152459c 4.6 3.8 4.0 3.2 152459d 5.6 5.3 5.7 3.7 152459e 5.9 5.3 5.7 3.0 152459f 6.0 5.6 6.3 4.0 152459g 6.2 5.9 6.0 4.0 152459h 6.8 6.5 6.7 4.4 152459i (holotype) 7.1 6.7 7.0 4.2 152459J 8.6 7.9 7.8 5.0 STRATIGRAPHIC OCCURRENCE.—Skinner Ranch For- mation (base). LOCALITY.—USNM 705a. DIAGNOSIS.—Small, weakly uniplicate Cleiothyri- dina with vestigial dental plates. TYPES.—Holotype: USNM 152459i. Figured par- atypes: USNM 152459h,k,l. Measured paratypes: USNM 152459a-h,j. Unfigured paratypes: USNM 152459a-g. COMPARISON.—Cleiothyridina mulsa is character- ized by its small size, weak concentric lamellae with entire spines rarely preserved except at anterior, moderate biconvexity, nearly completely fused den- tal plates, and its weakly uniplicate anterior com- missure. It is similar in size to C. rectimarginata, new species, from lower in the Wolfcampian, differ- ing primarily in its lesser convexity and its unipli- cation. It is larger than C. nana, new species, from the Road Canyon Formation, and its fold is pro- portionately weaker. It is much smaller, less con- vex, and has a much lower fold than C. pilularis, new species, from the Lamar Member of the Bell Canyon Formation in the Guadalupe Mountains. It is smaller than species from other Permian areas, and differs from most described Carboniferous spe- cies in most of the same features that distinguish C. rectimarginata, (see below). Cleiothyridina nana, new species PLATE 650: FIGURES 36-49, 84-99 Very small for genus, flatly to moderately bicon- vex; outline ovate, normally slightly elongate, NUMBER 21 2137 greatest width near midlength; commissure weakly uniplicate; fold very low and broadly rounded; sul- cus shallow, present only at commissure: not pro- ducing trough along pedicle valve; concentric lam- ellae closely spaced, those near margins with short but closely spaced spines, those farther posterior with fewer and lower spines and numerous spine bases; growth laminae weak and few. Pedicle valve moderately convex; beak thick, nearly straight to suberect; foramen proportionately large for genus, incompletely subcircular, piercing apex of beak. Brachial valve slightly less convex, with obtusely pointed beak projecting into pedicle valve. Pedicle valve interior with small hinge teeth; dental plates fused to valve walls for most of length; area proportionately large, extending anterior to midlength, beginning anterior to smooth region on floor in umbonal area; individual muscle marks not distinguished. Brachial valve interior with triangular depression in middle, apical perforation small, round, at pos- terior of depressed portion, without evidence of cardinal tooth; crura extending forward from hinge plate, full extent of crura and spiralia not ob- served; muscle area smaller than in pedicle valve, oval, individual marks not observed. MEASUREMENTS (in mm).— brachial length valve length width thickness USNM 709c 152456a 3.4 3.2 3.2 2.0 152456b 4.0 3.7 3.9 2.5 152456c 5.0 4.5 4.3 3.3 USNM 7l0u 154387a (holotype) 4.2 3.8 3.8 2.7 154387b 4.6 4.3 4.2 2.8 STRATIGRAPHIC OCCURRENCE.—Road Canyon For- mation. LOCALITIES.—USNM 709c, 710u, 722f, 726d. DIAGNOSIS.—Very small Cleiothyridina with slightly folded anterior commissure. TYPES.—Holotype: USNM 154387a. Figured par- atypes: USNM 152456a,b; 154387b. Measured para- types: USNM 152456a-c, 154387b. COMPARISON.—Cleiothyridina nana is the smallest species of the genus known from the Texas Per- mian, and is smaller than any other species with which we are acquainted. It differs from the some- what larger, but nevertheless small, Wolfcampian species C. rectimarginata, new species, in its flatter convexity, narrower outline, and especially in its slightly folded anterior commissure. These features also distinguish it from the Wolfcampian species C. mulsa, new species. It is much smaller, narrower, and less convex than the Guadalupian species C. pilularis, new species, and its commissure is much less strongly folded. No foreign or Carboniferous species of Cleiothyridina is sufficiently similar to C. nana to warrant detailed comparison. Cleiothyridina pilularis, new species PLATE 650: FIGURES 50-83 Small for genus but large for Texas Permian, moderately to strongly biconvex; outline trans- versely subelliptical to subpentagonal, greatest width near midlength; commissure uniplicate; fold low, broadly rounded, beginning about 5 mm ante- rior to brachial beak; sulcus shallow, gently rounded, also beginning about 5 mm anterior to pedicle beak; concentric lamellae strong, regularly spaced, with intervals increasing slightly toward anterior; spine bases in single row along each lamella, but no spines observed; growth laminae strong, break- ing slopes of valves, widely and irregularly spaced. Pedicle valve moderately convex, greatest con- vexity located in umbonal region; beak short, thick, suberect to erect; beak ridges rounded; foramen incomplete, subcircular, perforating apex of beak. Brachial valve slightly less strongly convex longi- tudinally, slightly more transversely; beak obtusely pointed, apex within pedicle valve; umbonal region anterior to apex somewhat swollen. Pedicle valve interior with rather large hinge teeth elongate parallel to sides of delthyrium; dental plates free only immediately below teeth, elsewhere tightly fused to valve walls, continuing to floor to form smooth area behind muscle field; muscle marks distinct, in large muscle area; adductor marks large, lateral, diductor marks smaller, mesial, not dis- tinctly differentiated from one another except by midline of valve, located in posterior half of muscle area; pallial grooves deep, widely and regularly spaced, nearly parallel, radiating only slightly. Brachial valve interior with elevated semiellepti- cal hinge plate slightly depressed in middle, per- forated near apex, perforation with small, poste- riorly pointing cardinal tooth; hinge sockets wide, 2138 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY deep, posteriorly tapering; crura extending forward from anterior edges of hinge plate: complete extent of crura, and spiralia, not observed; muscle area fairly large oval, lying in umbonal region, posterior half bisected by low median ridge, individual muscle marks clearly distinct from one another only at posterior border of area, there forming 2 or 4 small indentations of border; pallial grooves deep, slightly radial as in pedicle valve. MEASUREMENTS (in mm).— brachial length valve length width thickness USNM 738b 152461a 6.8 6.5 6.2 4.5 152461b 7.2 6.7 7.4 4.3 152461c 7.4 6.8 7.0 5.1 152461d 8.1 7.7 9.0 5.0 152461e 8.6 8.4 9.0 5.7 152461 f 8.9 8.0 8.9 5.7 152461g 9.0? 8.1 8.4 6.0 152461h 9.2 8.3 8.8 6.0 15246H 9.2 8.7 9.9 6.8 152461J 9.3 8.7 9.6 6.4 152461k 9.4 9.0 9:3 7.3 152461-1 9.6 8.7 10.2 7.4 152461m 9.9 8.5 9.4 7.3 152461n 10.5 9.8 12.0 6.4 152461o 10.8 9.9 11.5 7.9 152461p 11.3 10.0 11.0 8.2 152461q (holotype) 10.4 9.0 10.7 8.1 STRATIGRAPHIC OCCURRENCE.—Bell Canyon For- mation (Lamar Member); Capitan Formation. LOCALITIES.—Lamar: AMNH 40; USNM 725e, 728p, 738b. Capitan: USNM 750. DIAGNOSIS.—Fairly large Cleiothyridina with strong anterior folding. TYPES.—Holotype: USNM 152461q. Figured par- atypes: USNM 152461d,s,u,v; I54388a,b; 154389a,b. Measured paratypes: USNM 152461a-p. Unfigured paratypes: USNM 152461a-c,e-p,r,t. COMPARISON.—Cleiothyridina pilularis is charac- terized by its small size and rather strong convexity, although it is the largest species of the genus in the Texas Permian. It has what appear to be spine bases along the concentric lamellae, but few spines are preserved so the length and shape of the spines could not be determined. This species differs from the abundant Wolfcampian species C. rectimargi- nata, new species, in its much larger size, well- developed fold and sulcus, more transverse outline, and lower maximum convexity. It is much larger than any of the other rare Texas species, and more strongly folded; therefore, detailed comparisons are unnecessary. Cleiothyridina pilularis resembles species of Cleiothyridina from other areas more closely than it resembles the stratigraphically remote species from nearby regions. It is larger, more convex, more strongly folded, and more transverse than either C. attenuata Cooper or C. gerardi (Diener) from the Permian of Oregon. It somewhat resembles Athyris globulina Waagen and A. capillata Waagen from the Salt Range Permian, but is not as convex as either of those species, and is more strongly folded than the former. It is much smaller than normal specimens of C. royssii (Leveille) from the Salt Range and is less transverse, more pentagonal and more strongly folded than A. acutomarginalis Waagen. It does not greatly resemble other species described by Waagen or Reed (1944) from that region. Cleiothyridina rara, new species PLATE 510: FIGURES 48-55 Small for genus, slightly wider than long, outline roundly elliptical; sides and anterior margin well rounded; beak low, rounded; foramen open, no trace of deltidial plates. Anterior commissure recti- marginate. Surface with concentric rows of fine spines not well preserved. Pedicle valve about same depth as brachial valve; evenly and moderately convex in lateral profile but anterior profile more strongly convex and forming moderately convex dome, somewhat narrowed me- dially, with long steeply sloping sides. Median region swollen. Brachial valve having approximately same con- vexity in both profiles, strongly swollen umbo and median region. Interior not known. MEASUREMENTS (in mm).—Holotype (USNM 154518): length 9.5, brachial valve length 8.8, width 9.6, thickness 5.5. STRATIGRAPHIC OCCURRENCE.—Word Formation (Willis Ranch Member). LOCALITY.—USNM 706e. DIAGNOSIS.—Cleiothyridina with valves nearly equal in depth, and length and width nearly equal. TYPES.—Holotype: USNM 154518. COMPARISON.—This species can be compared only with C. pilularis and ciriacksi, both new species, NUMBER 21 2139 which are of about the same size. The earlier species from the Wolfcampian formations are all much smaller and quite unlike. C. rara differs from C. pilularis in being rectimarginate whereas C. pilu- laris is strongly uniplicate. It differs from C. ciri- acksi in having a less deep pedicle valve, in having more distant concentric bands of spines, and a more swollen brachial valve. This unique specimen was taken from the resi- dues of USNM 706e from which thousands of speci- mens have been taken. It is thus an exceedingly rare species. Cleiothyridina rectimarginata, new species PLATE 651: FIGURES 1^4 Small for genus, moderately to very strongly bi- convex; outline subovate or roundly subtrigonal, length and width nearly equal, maximum width located slightly anterior to midlength; commissure normally rectimarginate, rarely flexed slightly dor- sally or ventrally; valves normally not folded or indented, some specimens with slight indentation of both valves barely perceptible near extreme ante- rior; concentric lamellae closely spaced, those near margins bearing numerous closely crowded spines up to 1 mm in length, lamellae farther posterior with spine bases or sporadically preserved spines; growth laminae stronger, widely and irregularly spaced. Pedicle valve moderately convex in medium size specimens, strongly convex in larger specimens; beak short but rather long for genus, normally erect or slightly incurved; foramen apical, subcircular, circle not complete; beak ridges rounded, indistinct. Brachial valve similarly convex, rarely more strongly convex; beak swollen but broadly rounded anterior to apex: apex obtusely pointed, curved into pedicle valve. Pedicle valve interior with small, knoblike hinge teeth, slightly elongate parallel to delthyrial sides; dental plates short, narrow, meeting valve walls only short distance below hinge teeth, fused to walls for most of width of plates; valve floor be- tween dental plates smooth; muscle area located anterior to smooth area, muscle marks weakly impressed; pallial grooves shallow, invisible in many specimens. Brachial valve interior with small trigonal or crescentic hinge plate, slightly concave, apex with small elongate ovate perforation with short poste- riorly pointing projection in some specimens; crura extending anteriorly from edges of hinge plate, full extent not observed; hinge sockets large, open, tapering posteriorly; muscle area elongate elliptical, bisected in posterior by low median ridge, anterior and posterior adductor marks only subtly differen- tiated in few specimens, area extending about a third length of valve; spiralia not observed. MEASUREMENTS (in mm).— brachial length valve length width thickness USNM 701c 152465a 6.0 5.5 6.1 3.4 152465b 6.6 5.7 6.2 5.0 152465c 7.3 6.6 7.3 4.5 152465d 8.7 8.9 7.8 7.7 USNM 701d 152467a 3.4 3.2 3.3 1.9 152467b 6.5 5.9 6.1 4.2 152467c 8.6 8.0 8.8 5.7 USNM 701h 152469a 4.4 3.8 3.9 2.4 152469b 4.6 4.2 3.9 2.8 152469c 4.7 4.2 4.3 2.9 152469d 5.0 4.6 4.5 3.1 152469e 5.8 5.0 5.0 3.3 152469f 5.9 5.4 5.4 3.8 152469g 6.6 5.6 5.5 5.0 152469h 6.7 6.1 6.4 4.7 152469i 6.8 6.0 6.5 4.0 152469J 6.9 6.6 6.7 4.5 152469k 7.2 6.8 7.6 5.2 152469-1 7.8 6.8 7.0 5.7 152469m 7.9 6.9 7.2 5.9 152469n 7.9 7.0 7.7 6.5 USNM 701k 152471a 2.3 2.1 2.0 1.2 152471b 2.6 2.4 2.3 1.5 152471c 2.8 2.7 2.7 1.5 152471d 3.0 2.9 2.7 1.9 152471e 3.2 2.8 2.9 2.0 15247If 3.3 3.0 3.2 1.8 152471g 3.6 3.3 3.1 2.1 15247lh 3.8 3.5 3.7 2.2 152471i 4.0 3.5 3.8 2.4 152471J 4.3 3.9 3.7 2.3 152471k 6.4 5.5 5.6 4.7 152471-1 6.4 6.0 6.3 3.9 152471m 6.5 5.8 6.1 5.1 15247ln 6.9 6.4 6.0 4.7 152471o (holo type) 7.3 6.4 7.7 5.0 STRATIGRAPHIC OCCURRENCE.—Moran Formation; 2140 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY Coleman Junction Formation; Neal Ranch Forma- tion; Cibolo Formation. LOCALITIES.—Moran: USNM 709b. Coleman Junc- tion: USNM 766. Neal Ranch: USNM 701, 701a, 701c, 701d, 701 h, 701k, 701-1, 721g, 727e, 742c. Cibolo: USNM 728-1. DIAGNOSIS.—Small, rectimarginate Cleiothyridina. TYPES.—Holotype: USNM 152471o. Figured par- atypes: USNM 152467a; 152469j,k,n; 152471-1; 154391a-d; 154392a,c,d. Measured paratypes: USNM 152465a-d, 152467a-c, I52469a-n, 152471a-n. Un- figured paratypes: USNM 152467b,c; I52469a-i,l,m; 152471a-k,m,n. COMPARISON.—Cleiothyridina rectimarginata is characterized by its small size, rectimarginate com- missure, strong to very strong convexity, subequal length and width, and its bluntly rounded beaks. It is more strongly convex and more consistently rectimarginate than C. mulsa, new species, which occurs somewhat higher in the section in the Glass Mountains. It is much smaller than C. pilularis, new species, which occurs in the Bell Canyon For- mation (Lamar Member) in the Guadalupe Moun- tains, and lacks the strongly folded commissure of that species. It differs from the minute Road Can- yon species C. nana, new species, in its larger size, stronger convexity, and unfolded margin. This species is smaller and more convex than C. attenuata Cooper from the Permian of Oregon, and its beaks are blunter and less attenuate. The only species of Cleiothyridina reported by Dunbar and Condra from the Pennsylvanian of Kansas and Oklahoma is C. orbicularis (McChesney). Cleiothy- ridina rectimarginata differs in its smaller maxi- mum size, greater convexity, less transverse outline, and rectimarginate commissure. Cleiothyridina rectimarginata is smaller and more convex than most species of the genus that have been described from the Permian of other conti- nents. These features distinguish it from C. gerardi (Diener) of India and Russia, and from C. pectini- fera (Sowerby) reported by Tschernyschew (1902) and others by Netschajew (1911). Its convexity is similar to that of C. capillala (Waagen) from the Salt Range, but it is much smaller and has no fold. Likewise it is smaller than species called C. royssii by various authors, and not folded. Species that more nearly approach the size of C. rectimarginata were reported by Weller (1914) from the Mississippian of the Midcontinent, but even among these, the maximum size is somewhat greater than that of the Permian species. Most of Weller's small species also are rectimarginate or nearly so, thus resembling C. rectimarginata. Among them, C. tenuilineata (Rowley) is broader and somewhat less convex, and has more attenuate beaks; C. hirsuta (Hall) is considerably flatter and proportionately wider, characters that are devel- oped even further in C. lenticularis Weller. Others of the numerous Mississippian species reported by Weller are much larger than C. rectimarginata, and also are easily distinguished by their folded com- missures. Cleiothyridina species undetermined PLATE 651: FIGURES 73-77 A small shell from the Hueco Canyon Formation is figured because it is well preserved, retaining the characteristic spines, and to document presence of the genus in this unit. STRATIGRAPHIC OCCURRENCE.—Hueco Canyon For- mation. LOCALITY.—USNM 499b = 725z. TYPES.—Figured specimen: USNM 154394. COMPARISON.—This small, nearly circular, recti- marginate shell is less strongly convex than C. rec- timarginata. It may represent a separate species, but its stratigraphic level is similar enough to sug- gest that it is a variant of that species. Genus Composita Brown, 1849 Composita Brown, 1849:131.—Hall and Clarke, 1894:93.— Buckman, 1906:324.—Weller, 1914:484.—Dunbar and Con- dra, 1932:362.—Williams et al., 1965:H662. Shell biconvex; outline subovate, subpentagonal or subtrigonal, commonly widest near midlength; commissure uniplicate, rarely rectimarginate; fold beginning far anterior, normally not standing high above flanks; sulcus shallow, beginning some- what earlier than fold; costae absent, but some species parasulcate at anterior margin; radial ornament absent; growth lines fine, closely and regularly spaced; growth laminae stronger, more widely and randomly spaced, strength and fre- quency varying with species and individuals. Pedicle valve moderately to strongly convex transversely and longitudinally, convexity rather NUMBER 21 2141 even, normally greatest in posterior third; beak typically thick, rounded, without well-defined beak ridges, suberect to slightly incurved, length and attenuation variable, foramen large, ovate, epithy- ridid to permesothyridid; delthyrium completely filled by brachial umbo, without deltidial plates. Brachial valve most strongly convex near umbo, longitudinally rather flat along fold, strongly con- vex transversely; beak short, slightly attenuate with apex within pedicle valve. Pedicle valve interior having two knoblike hinge teeth, one at anterior of each edge of del- thyrium; dental plates slightly divergent from teeth to floor, continuing anteriorly along floor in some species as pair of low ridges outlining posterior part of muscle area, space between dental plates and valve wall filled by secondary shell material in many specimens of some species; floor between dental plates smooth, probably filled in life by pedicle and pedicle adjustor mus- cles; major muscle area ovate, in posterior third of valve; diductor muscle marks large, fusiform, anteriorly and laterally surrounding elongate, heart- shaped median adductor marks, low crest in ante- rior part of muscle area where diductors meet along midline; pallial marks light, radiating from margins of muscle area, consisting of numerous narrow lines without central primary trunks; floor of valve lateral and slightly anterior to muscle area thickened and pitted in large adults, pits shallowing and disappearing anteriorly and laterally, arranged in radiating rows, some con- tinuing anteriorly as pallial lines; valve edges smooth, without traces of seats for setae, sharp in some species, slightly thickened, flattened or flanged in others; valves butting at margins ex- cept in extreme posterior, edge of brachial valve there slightly overlapping edge of pedicle valve. Brachial valve interior with flat, nearly square hinge plate and flat, nearly square cardinal proc- ess meeting one another near right angle in apex of beak; cardinal process projecting posteroven- trally along brachial beak into delthyrial area of pedicle valve, mesially concave, with light striae at seat of attachment of diductor muscles, bounded at each side by low ridge, ventral side of process cemented to apex of beak; hinge plate projecting anteroventrally, essentially constituting short web between and lateral to crura; sockets deep, one on each side of hinge plate, formed by pair of plates continuous with lateral bounding ridges of cardinal process; crura extending anteriorly slightly beyond hinge plate, slender, fragile, slightly convergent, anterior ends attached to mesial sides of broad ribbonlike descending lamellae; lamellae proceeding directly posterior parallel to crura for short distance, then curving toward floor of brachial valve, continuing anteriorly above floor, bowing distally then converging, nearly meeting where nearest to floor, there bifurcating, one branch of each continuing anteriorly to form spiralia, other branch very short, meeting and fusing with dorsally projecting braces of jugum; spiralia tightly coiled into about 9 loops in adults, diameter decreasing rapidly toward sides, axis of coiling nearly directly transverse to shell; arms of jugum joined to descending lamellae, meeting at midline, there expanding, developing, serrated and fringed anterior edges, continuing ventrally and slightly posteriorly as single process on midline, process bifurcating near beginnings of descending lamellae (where joined to crura) each branch broadening to form ribbonlike band, parallel, distal, and following curvature of pos- terior part of descending lamella; muscle area narrow, elongate, sides slightly constricted about midway in length, dividing area into two distinct halves, one occupied by posterior adductor muscle marks and having low median ridge, other occu- pied by anterior adductor marks, without median ridge; floor around muscle area thickened and pitted in adults; pallial marks radiating from pe- riphery of muscle area, each narrow trunk bifur- cating near valve margin. TYPE-SPECIES.—Spirifer ambiguus Sowerby, by original designation of Brown, T., (1849:131). COMPARISON.—Composita is characterized by its biconvex streamlined shape with narrow hinge, lack of interarea or beak ridges, uniplicate commis- sure, and proportionately large, oval epithyridid or permesothyridid pedicle foramen. Lack of beak ridges and deltidial plates, and the position and shape of the foramen distinguish it externally from Dielasma. The longer more erect beak, larger foramen, more elongate outline, and lack of external surface spines distinguish it from Cleio- thyridina. Poorly preserved specimens might be confused with Neophricadothyris or Martinia, but they can be distinguished if the oval foramen is visible; the latter two genera have trigonal 2142 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY delthyria, and the apex of the beak is unperfo- rated. DISCUSSION.—The hinge plate and cardinal pro- cess of Composita are somewhat more complex than heretofore recognized. Hall and Clarke (1894:94) described the anterior face of the hinge plate as the seat of the diductor muscle marks, but instead, the hinge plate and cardinal process are distinct structures. Each is nearly square in out- line, and they meet one another nearly at a right angle. The cardinal process extends postero- ventrally, with its posterior surface fused to the apex of the beak of the valve, and its interior face bearing the marks of the diductor muscles. The hinge plate extends anteriorly and slightly ventrally, and is merely a thin web supporting the posterior ends of the crura in juveniles, be- coming secondarily thickened in adults. The hinge sockets are continuations of the lateral bounding ridges of the cardinal process that fit precisely between the dental plates, and extend dorsally past the sides of the hinge plate. Species of Composita are highly variable, as most workers who have dealt with them have noted. Specific characters are details of shape, including form of plication, length and thickness of beak, size of foramen, strength of growth lami- nae, convexity, and to some extent size of shell. Internal features are consistent within the genus, with some ontogenetic variation such as that pro- duced by shell thickening. Composita affinis Girty PLATE 652, FIGURES 1-44 Composita emarginata var. affinis Girty, 1909:389, pi. 15: figs. 6-7b. Not Composita emarginata affinis Girty, R. E. King, 1931: 128, pi. 43: figs. 12-17.—Cloud, 1944:65, pi. 18: figs. 20-22. [= C. enormis, new species.] About average size for genus, flatly to modera- ately strongly biconvex; outline ovate, slightly elongate to nearly circular, widest near mid- length; commissure rectimarginate in small and middle size shells, weakly to strongly uniplicate in middle size to large shells; fold consistently low on brachial valve, may produce high sinu- osity in anterior margin, crest gently rounded to flattened, producing straight anterior outline in some shells; sulcus shallow, normally expressed only as tongue at anterior margin of valve, ex- tending to fill fold, not as definite trough in valve; growth laminae moderately strong, numer- ous; radial fibers weak; valve edges slightly flanged. Pedicle valve moderately and rather evenly convex; beak short, slightly attenuate, suberect; foramen small, periphery entire, or slightly open dorsally. Brachial valve moderately convex, with low rounded crest along fold; beak short, blunt, slightly curved. Pedicle valve interior with large, thick, blunt hinge teeth, slightly hooked; dental plates attached to walls at posterior, free but stout at anterior; pedicle area between plates and muscle area anterior to plates distinctly impressed; posterior of valve thickened floor with numerous shallow pits in posterior, becoming aligned and merging into radial pallial lines toward margins. Brachial valve interior with exceptionally strong, thick hinge plate, formed between strong, trough-shaped crural bases; cardinal process short, thick, unusually distinctly bilobed, each lobe with small circular, distinct muscle scar; crura and spiralia not observed; muscle marks moderately deeply impressed in apical part of valve; posterior of valve slightly thickened, shallowly pitted, with pits aligning to form radial pallial vascula. STRATIGRAPHIC OCCURRENCE.—Capitan Lime- stone; Bell Canyon Formation (Pinery, Rader, and Lamar members). LOCALITIES.—Pinery: AMNH 524. Rader: AMNH 388, 410; USNM 725f, 740a, 740i, 740j. Lamar: AMNH 25, 37, 38, 39, 40, 384, 430, 528, 347, 348, 351; USNM 725e, 728i, 728p, 728q, 738, 738b. Capitan: AMNH 817, 853; USNM 725k, 725-1, 725p, 732q, 737a, 739, 750b. DIAGNOSIS.—Outline elongate, convexity moder- ate, growth lines many and strong, beak short, foramen incomplete, cardinal internal structures thickened. TYPES.—-Lectotype (here designated): USNM 118609a (Girty, 1909, pi. 15: fig. 6). Figured para- types: USNM 118609b (Girty, 1909, pi. 15: fig. 7). Figured hypotypes: USNM 153002a-k,m. Meas- ured hypotypes: USNM 153002-l,n-z, a'-z', a"-d". COMPARISON.—Composita affinis is characterized by its moderate biconvexity, its subcircular to slightly elongate subovate outline, its numerous distinct growth laminae, its short pedicle beak NUMBER 21 2143 MEASUREMENTS (in mm).— USNM 738 153002-1 153002n 153002o 153002p 153002q 153002r 153002s 1530021 153002u 153002v 153002w 153002x 153002y 153002z 153002a' 153002b' 153002C 153002d' 153002C 153002P 153002^ 153002h' 153002i' 153022J' 153002k' 153002-1' 153002m' 153002n' 153002o' 153002p' 153002q' 153002^ 153002s' 153002t' 153002u' 153002V 153002W 153002x' 153002y' 153002z' 153002a" 153002b" 153002c" 153002d" brachial valve valve length width thickness 3.1 2.9 2.8 1.9 3.9 3.5 3.5 2.4 3.9 3.6 3.8 2.1 4.0 3.7 3.8 2.2 4.3 3.9 3.9 2.3 4.5 4.0 4.3 2.5 4.8 4.3 4.2 3.0 5.0 4.7 4.8 2.8 5.2 4.7 4.7 3.1 5.7 5.2 5.3 3.3 6.0 5.6 5.7 3.0 6.6 6.0 6.0 3.5 7.2 6.6 6.5 3.8 7.5 6.7 6.9 3.7 7.8 7.0 7.3 4.3 8.1 7.5 7.3 4.4 8.9 7.9 7.4 4.5 9.4 8.8 8.5 5.4 9.6 8.9 9.2 5.1 10.3 9.4 9.5 5.4 10.7 9.9 10.0 5.6 11.5 10.5 10.0 5.9 12.3 11.2 11.9 5.9 12.6 11.6 11.3 6.0 13.0 11.8 11.4 7.2 14.1 12.7 12.4 7.0 15.2 13.8 13.8 7.5 16.4 15.1 14.7 8.3 17.0 15.6 15.0 9.2 17.5 15.6 16.0 8.6 18.0 16.6 16.4 9.4 18.8 17.6 16.0 9.6 19.7 18.7 18.8 10.0 20.3 18.6 17.6 10.6 21.2 19.3 18.8 10.6 22.1 19.8 20.6 9.3 22.1 21.9 22.0 c.11.0 23.0 21.3 20.8 13.0 24.0 23.0 24.7 13.4 24.5 22.6 23.3 12.2 25.0 23.0 23.9 22.9 27.0 24.7 24.0 14.4 26.3 24.2 22.7 15.9 28.8 25.9 25.8 c.13.0 with periphery of the foramen complete or nar- rowly incomplete, its somewhat thickened posterior and pitted interior of the valves, and its ex- ceptionally strong, thickened hinge teeth, hinge plate, and cardinal process. Composita emarginata Girty is similar in outline, but emarginate, thicker, and more convex than C. affinis. Speci- mens that R. E. King (1931) identified as C. affinis now are termed C. enormis, new species, from which C. affinis differs in its smaller maximum size, more circular outline, lower convexity, shorter pedicle beak, and stronger, more thickened in- ternal structures. Composita strongyle, new species, from the Wolfcampian also is flat and somewhat circular, but C. affinis differs in its larger size, less con- sistently circular outline, more numerous and distinct growth laminae, smaller and less elon- gate pedicle foramen, and thickened posterior, interior floors, and more robust cardinalia. It differs from C. stalagmium, and C. crassa, both new, in its somewhat smaller maximum size, less transverse outline, stronger growth laminae, lower convexity, shorter beak, and lower fold. DISCUSSION.—Girty (1909) established C. affinis as a variety of C. emarginata. R. E. King (1931) and Cloud (1944) treated it as a trinomial, not specifying whether as a variety or as a subspe- cies. Clearly it is related to C. emarginata, but we believe that it is sufficiently distinct to war- rant status as a separate species. Girty's specimens from several levels in the Capitan Formation seemed to occur with C. emarginata. More de- tailed collecting shows the two forms to be strat- igraphically somewhat separated, with C. emargin- ata more prevalent in the Rader Member and its Capitan equivalents, and C. affinis abundant much higher, in the Lamar Member and equivalents. Composita apheles, new species PLATE 652: FIGURES 45-88 About average size for genus, somewhat small for Permian species, flatly to moderately strongly biconvex, outline subelliptical, widest near mid- length; commissure weakly to rather strongly uniplicate, weakly parasulcate in many specimens; fold evenly arched or slightly flattened at ante- rior crest, not standing prominently above flanks; sulcus shallow or not depressed, with weak me- dian groove in many specimens; growth laminae weak to distinct, most frequent near margins, some shells nearly smooth, others with weakly tegulated effect. Pedicle valve moderately inflated in umbonal region; beak thick, blunt, suberect to erect, rarely incurved; foramen proportionately somewhat small, 2144 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY typically oval, rarely circular. Brachial valve less strongly convex, with low crest from slightly in- flated umbo to anterior margin. Pedicle valve interior with short, thick, slightly curved teeth; short thin dental plates fused to walls for most of length, anterior edges free only for about half their height; muscle area shallowly to rather deeply impressed, bilobate at anterior; diductor marks large, elongate, surround- ing smaller median adductor marks; posterior part of valve moderately thickened, emphasizing muscle depressions and radial pallial lines, filling space around dental plates. Brachial valve interior with strong, slightly thickened hinge plate, deeply incised in juve- niles, fused along midline in adults, there pro- truding slightly as small median node; crural bases forming sides of hinge plate, continuing posteriorly to produce socket ridges; cardinal process short, rather thin, bilobed, each lobe with weak subcircular diductor muscle mark on anterior surface; descending lamellae, jugum and spiralia observed only as fragments, apparently normal for genus; muscle area spatulate, moder- ately to rather deeply impressed, somewhat short for genus, posteriorly bisected by short, low ridge; posterior part of many valves thickened second- arily, recessing muscle area and producing pitted inner surface; pits shallow, aligned radially. STRATIGRAPHIC OCCURRENCE.—Skinner Ranch For- mation (Decie Ranch, Poplar Tank, and Sullivan Peak members); Hess Formation. LOCALITIES.—Decie Ranch: USNM 707a, 707g, 714t, 715c, 720g, 727u. Poplar Tank: USNM 708e. Sullivan Peak: USNM 707, 707b, 707c, 707d, 715f, 715j, 722h, 722-1, 727a. Skinner Ranch: AMNH 520; USNM 705a, 705b, 707x, 710r, 716p, 719y, 720e, 723-1, 723s, 724q, 726h, 730r. Hess: USNM 726n. DIAGNOSIS.—Shell small, beak short and thick, fold low and evenly arched. TYPES.—Holotype: USNM 154537L Figured paratypes: USNM 153003a,b; 154536a; 154537a-e, g. Measured paratypes: USNM 153003a-z, a'-r'. Unfigured paratypes: USNM 154536 (many). COMPARISON.—Composita apheles is character- ized by its below average size for a Permian species of Composita, its short, thick ventral beak, low and evenly arched fold, somewhat transverse outline, moderate convexity with greatest swel- MEASUREMENTS (in mm).— brachial length valve length width thickness USNM 705a 153003a 2.8 2.5 2.3 1.5 153003b 4.1 3.7 3.2 2.3 153003c 4.4 4.1 3.6 2.8 153003d 4.9 4.3 3.8 2.9 153003e 5.0 4.5 4.0 3.0 153003f 5.4 5.0 5.3 3.4 153003g 5.8 5.4 5.1 3.5 153003h 6.2 5.4 5.4 3.8 1530031 6.9 6.2 6.6 4.1 153003J 7.3 6.7 6.9 4.6 153003k 7.7 7.3 6.9 4.6 153003-1 8.0 7.1 7.0 4.7 153003m 8.4 7.6 7.9 4.8 153003n 8.6 7.8 7.9 5.4 153003o 9.5 8.6 8.7 5.7 153003p 10.0 8.8 8.7 6.2 153003q 10.5 9.8 9.8 6.0 153003r 10.9 9.7 9.9 6.2 153003s 11.3 10.1 9.8 6.9 153003t 12.0 10.7 11.2 6.6 153003u 12.2 11.0 12.1 6.6 153003v 12.6 11.5 12.0 7.0 153003w 13.0 11.3 12.7 8.7 153003x 13.7 12.4 13.7 8.4 153003y 13.8 11.5 13.9 9.3 I53003z 14.4 12.6 14.7 8.8 153003a' 15.1 13.0 14.4 9.3 153003b' 15.3 13.0 15.7 9.3 153003c' 16.0 14.5 16.6 9.9 153003d' 17.1 15.5 17.8 11.2 153003e' 17.8 15.9 17.4 11.3 153003f 18.0 15.9 18.0 12.0 153003g' 19.0 16.7 20.0 12.0 I53003h' 19.0 17.2 16.9 12.0 153003i' 19.9 17.7 19.5 12.8 153003J' 20.1 18.2 19.9 12.0 153003k' 20.5 18.4 19.3 13.5 153003-1' 20.7 18.5 19.0 13.1 153003m' 21.0 19.0 21.4 12.3 153003n' 21.6 19.1 20.3 14.1 153003o' 21.6 19.3 22.7 13.7 153003p' 22.5 20.1 20.2 15.4 153003q' 23.5 20.7 22.6 c.14.0 153003r' 24.6 22.1 25.7 c.14.0 USNM 720e 154537f (holotype) 20.5 18.0 19.3 14.0 ling in the umbonal regions, and its slight sec- ondary thickening in the posterior part of each valve. It is similar to several of the middle-sized species, notably C. cracens, C. imbricata, and C. apsidata, and somewhat less so to C. stalag- mium and C. crassa, all new. It is wider and NUMBER 21 2145 has a shorter beak and somewhat stronger growth laminae than C. cracens; it is more convex, has a higher narrower fold, and weaker, less numerous growth laminae than C. imbricata, and is less convex, less strongly folded, and has weaker and fewer growth laminae than C. apsidata. It is smaller than C. crassa or C. stalagmium, and in addition is less convex and less strongly folded. The outline of some specimens is similar to that of C. stalagmium, but other features, especially the much smaller average and maximum size of C. apheles makes it easy to distinguish from that species. The fold of C. apheles is stronger, the convexity greater, and the outline less circular than in C. affinis Girty or C. strongyle, new species. Composita apsidata, new species PLATE 653: FIGURES 11-37 Composita mira R. E. King [not Girty, 1909], 1931:129, pi. 44: fig. 7 [not figs. 3-6, 8]. About average size for genus, moderately to strongly biconvex; outline subovate to roundly subpentagonal, widest near midlength; commissure strongly uniplicate, fold high and narrow at anterior, beginning early in growth of shell, standing above flanks only at anterior; sulcus moderately depressed, with narrow shallow me- dian groove in most specimens; growth laminae rather strong, giving shingled effect to many shells, widely and irregularly spaced, most num- erous near margins. Pedicle valve strongly and rather evenly con- vex; beak thick, blunt, suberect to erect; foramen proportionately normal in size. Brachial valve somewhat less strongly convex, greatest inflation in umbonal region; profile along fold nearly flat. Pedicle valve interior with dental plates thick- ened or fused to walls by secondary shell mater- ial; muscle area depressed, especially in second- arily thickened valves, extending about half length of valve; adductor marks small, median, sur- rounded by larger diductor marks. Brachial valve interior with thickened hinge plate, short median lobe extending forward be- tween crural bases; cardinal process projecting posteriorly, nearly perpendicular to hinge plate, each of two small lobes with distinct circular diductor muscle mark; crura extending forward' from crural bases at sides of hinge plate, short, tapered; descending lamellae attached weakly nearly perpendicular to crura; jugum long, with finely digitate median projection; spiralia coiled laterally with transverse axis, probably about 8 loops on each side; muscle area distinctly im- pressed, posterior part bisected by low rounded ridge, muscle marks shallower toward anterior of area. MEASUREMENTS (in mm).— brachial length valve lengtli width thickness USNM 702e 153004h 2.9 2.4 2.5 1.4 153004i 3.2 2.9 2.8 1.8 153004J 3.4 3.0 3.0 1.9 153004k 4.0 3.7 3.5 2.0 153004-1 4.3 4.0 3.8 2.7 153004m 4.8 4.4 4.4 2.6 153004n 5.2 4.7 4.6 2.5 153004o 5.7 5.2 5.1 3.4 153004p 5.9 5.3 5.7 3.2 153004q 6.8 6.2 5.7 3.7 153004r 7.0 6.3 7.0 4.3 153004s 7.6 6.7 7.0 4.3 153004t 7.7 6.9 7.4 4.5 153004u 8.4 7.6 7.8 4.8 153004v 8.7 8.0 7.8 4.8 153004w 10.4 9.2 9.7 5.8 153004x 11.8 10.6 11.4 6.8 153004y 13.2 11.7 12.0 7.8 153004z 13.9 12.4 12.3 8.0 153004a' 14.0 12.6 12.8 9.4 153004b' 14.3 12.7 13.7 8.4 153004c' 15.0 13.5 13.7 10.0 153004d' 15.8 14.4 15.0 9.1 153004e' 17.5 15.7 15.9 10.3 153004P 17.7 15.7 16.5 11.8 153004g' 18.0 15.7 15.1 11.2 153004h' 18.1 16.1 17.5 10.5 1530051' 18.2 16.0 16.9 12.4 153004J' 19.0 16.8 17.4 12.3 153004k' 19.4 17.5 18.4 14.6 153004-1' 19.8 17.5 18.3 13.2 153004m' 20.5 18.0 17.2 14.7 153004n' 21.0 18.5 18.9 14.7 153004o' 21.0 18.5 19.7 15.2 153004p' 22.1 20.3 21.8 15.5 153004q' 23.0 19.9 21.9 15.6 153004r' 23.5 21.3 23.0 16.4 153004s' 24.0 21.4 21.6 16.1 153004d (holotype) 22.3 20.4 21.8 15.5 12.0 Formation King 174 YPM 12203 21.3 19.3 18.0 STRATIGRAPHIC OCCURRENCE.—Hess (Taylor Ranch Member). 2146 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY LOCALITIES.—USNM 702d, 702e, 716n. DIAGNOSIS.—Shell thick and convex, fold high, growth lines few but strong. TYPES.—Holotype: USNM 153004d. Figured paratypes: USNM 153004a-c, e-g. Measured and unfigured paratypes: USNM 153004h-z, a'-s'. COMPARISON.—Composita apsidata is character- ized by its thick convex shell with the fold high at the anterior, and its rather widely spaced but strong growth laminae that produce the effect of overlapping shingles. In this respect it resembles C. imbricata, new species, differing in its smaller maximum size, more narrowly arched and less flat- tened fold, and especially in its narrower outline and proportionately greater thickness. It is smaller and narrower than most specimens of C. stalagmium or C. crassa, both new, and differs further from them in its stronger and more numerous growth laminae. It is proportionately a little wider than C. enormis, and also differs from that species in its smaller size, stronger growth laminae, and shorter pedicle beak. Composita affinis Girty has somewhat similar growth laminae, but is flatter and more circular than C. apsidata. Composita cracens, new species, is similar in shape, but C. apsidata is thicker, and has stronger growth laminae distributed over most of the shell. It also is thicker than C. apheles, new species, and has stronger growth laminae, a narrower and more strongly arched fold, and commonly a propor- tionately narrower outline. DISCUSSION.—This species was included by R. E. King (1931) in the group designated C. mira (Girty). The type of C. mira is a Cleiothyridina, as ex- plained below under discussion of Composita im- bricata. The fo-m illustrated by R. E. King (1931, pi. 44: fig. 7) . listinct from that in fig. 4 on the same plate, and oeiongs to C. apsidata as presently constituted. Composita bucculenta, new species PLATE 654: FIGURES 1-68 Small for genus, strongly biconvex; outline transversely subpentagonal; commissure strongly parasulcate; fold beginning about 3-5 mm ante- rior to brachial beak, crest slightly flattened at anterior, lateral troughs deep, producing triloba- tion of shell longer than about 5 mm; sulcus only at commissure, not forming depression in valve; growth laminae absent from some shells, normally two or three rather strong near valve edges. Pedicle valve strongly inflated in umbonal re- gion; beak short, thick, blunt, suberect to erect; foramen proportionately small, oval or elliptical, periphery incomplete at anterior; edge of valve flanged in most specimens. Brachial valve also most strongly convex near posterior; beak blunt, strongly incurved; valve edge normally flanged. Pedicle valve interior with short thin dental plates cemented to wall in posterior, with ante- rior edges free; teeth short, sharp, slightly hooked; muscle area shallowly impressed, individual marks not distinguishable. Brachial valve interior with short hinge plate anteriorly emarginate, sides formed by hinge sock- ets and crura; cardinal process low, broad, ce- mented to apex of valve; muscle area weakly impressed, apparently typical for genus; descend- ing lamellae and jugum as described for genus; full spiralium not observed, fragments appear normal. MEASUREMENTS (in mm).— brachial length valve length width thicknt USNM 702ent 153005e (holotype) 10.0 9.6 11.7 7.9 153005g 2.9 2.7 2.6 1.7 153005h 3.4 3.2 3.3 2.2 153005i 3.7 3.4 3.6 2.4 153005J 4.0 3.8 4.1 2.8 153005k 4.3 4.0 4.3 3.0 153005-1 4.5 4.2 4.8 3.1 153005m 4.9 4.7 5.0 3.9 153005n 5.1 4.7 5.6 3.9 153005o 5.6 5.1 5.6 4.0 153005p 6.2 5.6 6.1 4.7 153005q 6.3 5.7 6.5 5.1 153005r 6.4 6.0 6.6 5.7 153005s 6.9 6.4 7.3 6.0 153005t 7.0 6.5 7.2 5.2 153005u 7.4 6.9 7.8 6.2 153005v 7.8 7.3 8.3 6.5 153005w 7.9 7.3 8.9 6.1 153005x 8.0 7.5 9.0 6.6 153005y 8.8 7.9 8.9 7.3 153005z 9.0 8.6 9.2 7.3 153005a' 9.6 8.9 9.6 8.0 153005b' 9.8 8.8 10.5 7.8 153005c' 9.8 9.0 10.9 7.8 153005d' 10.3 9.6 11.8 7.9 STRATIGRAPHIC OCCURRENCE.—Skinner Ranch NUMBER 21 2147 Formation (Sullivan Peak Member); Hess Forma- tion (and Taylor Ranch Member); Cathedral Mountain Formation (Wedin Member); Road Canyon Formation. LOCALITIES.—Sullivan Peak: USNM 707d, 722h. Taylor Ranch: USNM 702f, 702m. Hess: USNM 726n. Wedin: USNM 714w, 717e, 723v. Cathedral Mountain: AMNH 500D; USNM 702, 702b, 702ent, 702-low, 702un, 703b, 708, 72lu. Road Canyon: AMNH 501; USNM 726f. DIAGNOSIS.—Shell small, outline transverse, um- bonal regions inflated, commissure parasulcate. TYPES.—Holotype: USNM 153005e. Figured paratypes: USNM 153005a-d,f; 154548a-g. Mea- sured paratypes: USNM 153005g-z,a'-d'. COMPARISON.—Composita bucculenta is charac- terized by its small size among Texas Permian species, its transverse outline, strongly inflated um- bonal regions of both valves, short pedicle beak and small foramen, and especially by its strong parasulcation, which actually produces an auxil- iary plication on each side near the fold of many individuals. It most resembles C. parasulcata, new species, from the Road Canyon and Word forma- tions, differing in its smaller size, wider outline, shorter thicker pedicle beak, and normally stronger parasulcation. It also resembles C. pilula, new species, but differs in its smaller size and wider outline, stronger parasulcation and shorter beak, and in its thinner shell and less strongly divided hinge plate. Other species are not closely similar to C. bucculenta. Composita costata, new species PLATE 653: FIGURES 1-10 Small for genus, strongly biconvex; outline transversely subelliptical to subpentagonal, widest near midlength or slightly posterior; commissure parasulcate, with 2 or 3 low costae on each side of some specimens; fold low, with flattened crest; sulcus not depressed below flanks; lateral para- sulcations distinctly outlining fold; sporadic auxil- liary costae expressed only near commissure, not plica ting major portion of shell; growth laminae very weak, apparent only near margins of some shells, leaving most of shell essentially smooth. Pedicle valve strongly inflated in umbonal re- gion; beak short, blunt, suberect; foramen sub- circular, proportionately somewhat small. Brachial valve strongly inflated in umbonal region, with nearly flat profile along crest of fold. Pedicle valve interior with very small teeth; dental plates short, thin, sloping posteriorly from teeth toward floor, fused to walls for about half length; muscle area weakly impressed in thin shell, size and pattern normal for genus. Brachial valve interior with hinge plate short, wide; cardinal process short, bilobed, somewhat concave mesially, each lobe with small diductor mark; sockets short, shallow, rather wide; muscle area shallow, details obscure; crura, lamellae, and spiralia not observed. MEASUREMENTS (in mm).— brachial length valve length width thickness USNM 725y 153006a (holotype) 5.3 4.8 5.4 3.8 153006d c.6.0 5.6 5.7 4.1 153006e 6.7 6.0 7.1 4.5 153006f 4.9 4.4 4.9 3.6 153006g 4.8 4.3 4.9 3.6 I53006h 4.4 3.9 4.4 3.2 153006i 4.4 4.0 4.1 3.3 153006J 4.0 3.8 4.1 3.6 153006k 4.0 3.7 4.0 2.9 153006-1 3.9 3.5 3.5 2.3 153006m 3.1 2.8 3.1 2.0 153006n 3.1 2.9 2.9 1.9 153006o 2.9 2.6 2.9 1.7 STRATIGRAPHIC OCCURRENCE.—Bone Spring For- mation. LOCALITY.—USNM 725y. DIAGNOSIS.—Shell small, outline transverse, com- missure parasulcate, many specimens weakly co- state. TYPES.—Holotype: USNM 153006a. Figured paratypes: USNM 153006b,c. Measured paratypes: USNM 153006d-o. COMPARISON.—Composita costata is characterized by its small size, transverse outline, parasulcate commissure, and weak costation of some shells. It clearly is related to C. bucculenta, new species, with many shells nearly identical in shape. It differs in its much smaller size (specimens of C. bucculenta the size of large C. costata are recti- marginate or have only the beginnings of plica- tion) somewhat weaker parasulcation, and in the costation of some shells. No other species closely resembles this distinctive little shell, so further detailed comparisons are unnecessary. 2148 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY thickness 1.3 1.5 1.3 1.6 1.9 2.0 2.1 2.4 Composita cracens, new species PLATE 653: FICURES 38-52 Composita emarginata affinis Stehli [not Girty, 1909], 1954: 532, pi. 27: fig. 15-18. About average size for genus, moderately bi- convex; outline subovate, commonly elongate, less commonly equidimensional, rarely transverse; com- missure uniplicate; fold standing only slightly above flanks, expressed as dull ridge along mid- line of valve, no sharp demarcation from flanks; sulcus shallow, some with weak narrow median trough; growth laminae commonly absent from most of shell, moderately strong and numerous near margins. Pedicle valve flatly to moderately convex, strong- est inflation in umbonal area; beak short, thick, suberect; foramen normal size, periphery very narrowly incomplete (rarely complete); valve edges sharp, or slightly flattened to meet oppo- site valve. Brachial valve somewhat less convex, beak and crest of fold slightly inflated or raised. Pedicle valve interior with strong, blunt hinge teeth; dental plates slightly bowed distally, ce- mented to valve walls by secondary shell for most of length, only anterior edges free; muscle area elongate, spatulate, moderately strongly impressed, pattern normal for genus; posterior of valve thickened somewhat, with shallow pitting aligning toward anterior to produce weak radial pallial lines. Brachial valve interior with strong hinge plate developed between stout crural bases; cardinal process bilobed, short to rather long, each lobe with distinct muscle scar; muscle area elongate, narrow, bisected in posterior by short, low ridge; posterior of valve thickened and pitted as in opposite valve; crura, descending lamellae, and spiralia not observed. MEASUREMENTS (in mm).— brachial length valve length width 1.9 2.0 2.0 2.3 2.9 3.0 3.6 3.4 2.0 2.1 2.1 2.4 2.9 2.9 2.4 3.7 2.1 2.3 2.4 2.7 3.2 3.3 3.7 4.0 USNM 7281 153007a 153007b 153007c 153O07d 153007c 153007£ 153007g 153007h 153007i 153007J 153007k 153007-1 153007m 153007n 153007o 153007p 153007q 153007r 153007s 1530O7t 153007u 153007v 153007w 153007x 153007y 153007z 153007a' 153007b' 153007c' 153007d' 153007e' 153007P USNM 728g 155122a 155122b 155122c 155122d 155122e 155122f 155122g 155122h 155122i 155122J 155122k 155122-1 155122m 155122n 155122o 155122p 155122q 155122r 155122s 155122t 155122u 155122v 155122w 155122x 155122y 155122z 155122a' 155122b' 155122C USNM 728e 153008a (holotype) brachial length valve length width 3.8 4.1 4.2 4.8 5.3 5.9 6.6 6.9 7.0 7.2 8.0 9.1 10.0 12.8 13.2 16.1 16.9 17.3 18.0 19.3 21.7 22.7 21.5 24.6 3.3 3.6 4.0 4.6 4.6 5.0 5.0 5.5 5.7 6.2 6.0 6.3 6.9 7.9 8.0 8.4 9.0 9.6 10.3 11.0 11.0 11.6 13.0 14.7 15.0 16.3 16.2 17.0 18.6 22.8 4.2 4.7 4.9 5.5 5.8 6.3 7.3 7.7 7.7 7.8 8.9 10.0 11.0 13.1 14.5 17.5 17.6 19.1 20.0 21.5 23.2 23.7 23.9 27.0 3.6 4.0 4.3 4.8 5.0 5.5 5.6 5.9 6.5 6.7 6.9 7.0 7.7 8.7 9.1 9.6 10.0 10.8 11.8 12.2 12.7 13.0 14.7 16.2 17.0 18.7 18.7 19.0 21.1 25.5 3.4 4.0 4.0 4.8 5.5 5.5 6.5 6.5 7.5 7.3 7.9 8.7 10.0 11.4 12.7 14.9 15.6 17.0 18.2 18.6 21.1 21.0 23.8 25.0 3.5 3.6 4.2 4.3 4.5 4.6 5.2 5.6 6.1 5.8 6.6 6.7 7.6 7.5 8.6 8.2 10.0 10.7 c.11.0 12.3 10.4 12.0 13.1 15.7 15.0 16.7 16.7 17.0 18.6 28.5 thickness 2.6 2.9 2.9 3.2 3.5 3.6 4.1 4.5 4.4 4.7 5.3 5.8 7.0 11.8 10.8 17.3 2.3 2.6 2.9 3.0 3.1 3.3 3.5 4.2 4.8 4.3 4.8 4.7 5.1 5.5 5.3 5.3 6.6 6.9 6.9 7.3 7.9 8.0 9.0 9.6 10.1 11.4 12.0 11.5 13.0 18.0 NUMBER 21 2149 STRATIGRAPHIC OCCURRENCE.—Bone Spring For- mation; Hueco Canyon Formation. LOCALITIES.—Bone Spring: AMNH 369, 492, 497, 591, 624, 625, 631, 632, 634, 697; USNM 728e, 728f, 728g, 728h. Hueco Canyon: USNM 712e, 719, 720a, 720b, 720c, 725b, 725z. DIAGNOSIS.—Outline elongate, fold strong at com- missure but not standing high above flanks, shell nearly smooth. TYPES.—Holotype: USNM 153008a. Figured paratypes: USNM 153007g'-k'. Measured and unfig- ured paratypes: USNM 153007a-z, a'-f; 155122a-z, a'-c'. COMPARISON.—Composita cracens is characterized by its average size for a Permian species of the genus, commonly elongate ovate outline, strong fold at the commissure, a low, rounded ridge along the shell, without being distinctly set off from the flanks, and its smooth exterior except for a few strong growth laminae at the margins. It is narrower and not as large as C. stalagmium, new species, and C. crassa, new species, which have similar appearing folding. Its maximum size is much smaller than that of C. enormis, new species, and its outline less distinctly elongate. It also is smaller than C. prospera, new species, somewhat less strongly folded, and its beak is shorter and blunter. Composita apheles, new species, is similar, but C. cracens is more strongly and narrowly folded, has weaker growth laminae, is not as trigonal in outline, and has a somewhat more attenuate pedicle beak. This species is much larger, and not likely to be mistaken for such new species as C. pilula, C. bucculenta, C. para- sulcata, and others that resemble this group. Stehli (1954) identified this species with C. affinis Girty. Aside from occurring at a very differ- ent level (Bone Spring, not Capitan) this species differs from Girty's in its stronger convexity, weaker growth laminae, more elongate and less circular outline, higher fold, and longer pedicle beak with proportionately larger foramen. It differs from the most abundant Wolfcampian species of the Glass Mountains, C. strongyle, new species, in its greater convexity, stronger fold, and especially in its less circular outline. DISCUSSION.—The locality where C. cracens is most abundant (USNM 728f = AMNH 629) is about a quarter mile south of the mouth of Victorio Canyon in the Sierra Diablo. In the collection of several hundred valves only one large shell is articulated, and that one is held to- gether by encrusting Bryozoa that cover the com- missure on the right side (there are numerous articulated small shells). This indicates that the collection probably represents a death assemblage, so there may have been considerable sorting before burial. This species also occurs at USNM 728e (AMNH 625) only a short distance away, at the entrance to Victorio Canyon. There and in nearby locali- ties in the Baylor Mountains the species is not as abundant, but a few more articulated adult shells are present. These are characteristically wider than those from USNM 728f, and more nearly resemble C. stalagmium, new species, from the Glass Mountains. However, they seem to be- long with the majority of C. cracens, on the basis of the shape of the fold, the typical appear- ance of the growth laminae at the margins, and by the presence in most shells of the shallow median groove in the sulcus that is completely absent from C. stalagmium or C. crassa, which otherwise are similar. Composita crassa, new species PLATE 655: FIGURES 1-39 Composita persinuata R. E. King [not Meek, 1877], 1931:130, pi. 43: figs. 18-19. About average size for genus, moderately to strongly biconvex; outline subtrigonal to subovate, normally widest anterior to midlength; commissure moderately to strongly uniplicate; fold standing only slightly above flanks at anterior, crest broadly or narrowly arched, or slightly flattened, beginning about 10 mm anterior to brachial beak; sulcus shallow, depressed below flanks only near anterior, many with shallow median groove; lateral broad plications shallow, producing weak parasulcation on some specimens; growth laminae moderately strong near margins of most specimens, weak on some, beginning farther posterior on others; weak radial lirae visible on some. Pedicle valve most strongly convex near mid- length or in umbonal region; beak thick, long, suberect to slightly incurved; foramen proportional to size of shell, ovate, periphery narrowly in- complete at anterior;" valve edges sharp or very 2150 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY slightly flanged. Brachial valve inflated in umbonal region; beak short, bluntly pointed, overlapped by pedicle beak; fold arising from flanks without sharp flexure. Pedicle valve interior with dental plates nearly parallel, anterior edges free, posterior halves ce- mented to valve walls; posterior not greatly thick- ened by secondary shell material; muscle marks shallowly impressed, pattern normal for genus; hinge teeth short, blunt, curved, supported by dental plates. Brachial valve interior with large hinge plate distinctly divided into three elements, two crural bases at sides and thin median part projecting forward slightly; sockets, deep, formed by socket plates lateral to crural bases; full spiralium not observed, fragments indicate pattern typical for genus; muscle marks moderately impressed, normal for genus; cardinal process broad, long, perpen- dicular to hinge plate, cemented to apex of valve, bilobed, with distinct muscle mark on anterior surface of each lobe. STRATIGRAPHIC OCCURRENCE.—Cathedral Moun- tain and Road Canyon formations; possibly Cibolo Formation. LOCALITIES.—Cathedral Mountain: AMNH 504; USNM 702a, 703a1, 71 lw. Road Canyon: AMNH 503, 509; USNM 703, 703a, 703c, 703d, 706f, 707e, 709c, 710u, 710z, 716x, 716xa, 716z, 719x, 720d, 721j, 721o, 721r, 721s, 721t, 721w, 721x, 721y, 721z, 722e, 722f, 722g, 723a, 724a. Cibolo (doubtful): AMNH 703. DIAGNOSIS.—Shell large, outline subtrigonal to subovate, umbonal regions inflated, beak long and thick, shell substance not thickened. TYPES.—Holotype: USNM 153009g. Figured paratypes: USNM 153009a-f,h,i. Measured para- types: USNM 153009j-z, a'-z', a"-e". COMPARISON.—Composita crassa is characterized by its relatively large size for the genus, which nevertheless is about average size for Permian representatives, its subtrigonal to subovate out- line, swollen umbonal regions, thick and pro- portionately long ventral beak, gently arched or slightly flattened fold, and its generally nonthick- ened valves, unusual in a species attaining this size. It most nearly resembles C. stalagmium, new species, differing in its more elongate outline, and thicker ventral beak, and a shallow median goove in the sulcus of many specimens. It differs MEASUREMENTS (in mm). brachial length valve length width •thickness USNM 719x 153009J 2.0 1.8 1.6 1.2 153009k 2.3 2.0 2.0 1.4 153009-1 2.8 2.5 2.6 1.6 153009m 2.9 2.6 2.4 1.7 153009n 3.0 2.7 2.2 1.8 153009o 3.7 3.3 3.1 2.3 153009p 4.0 3.6 3.0 2.3 153009q 4.3 3.9 3.6 2.6 153009r 4.5 3.9 3.8 2.7 153009s 5.3 4.7 4.0 3.3 1530091 5.5 5.0 4.6 3.3 153009u 5.9 5.1 4.0 3.8 153009v 6.1 5.5 4.9 3.8 153009w 7.0 6.0 5.0 4.7 153009x 7.5 6.6 6.0 4.4 153009y 7.9 7.0 6.4 5.4 153009z 8.0 7.1 7.3 4.5 153009a' 8.9 7.7 6.8 5.7 153009b' 9.2 8.3 8.8 5.4 153009c' 9.9 8.5 8.8 7.0 153009d' 10.1 9.0 7.4 7.0 153009e' 10.4 9.3 9.0 6.6 153009P 11.4 10.2 9.9 7.0 153009g' 12.0 10.8 10.0 7.5 153009h' 12.6 11.3 10.9 7.1 153009i' 13.0 11.7 10.3 8.3 153009J' 14.0 12.6 12.2 8.3 153009k' 14.4 13.3 13.6 8.5 153009-1' 14.7 13.2 12.9 9.3 153009m' 15.6 14.3 12.9 12.2 153009n' 15.6 14.9 15.4 10.3 153009o' 17.9 16.5 16.3 10.7 153009p' 18.4 16.3 17.3 10.5 153009q' 18.5 16.7 19.8 13.0 153009r' 19.7 18.0 19.6 14.7 153009s' 20.2 18.4 17.0 13.4 1530091' 21.5 19.2 19.6 16.0 153009u' 22.9 20.6 21.7 15.5 153009v' 23.0 21.5 22.7 17.7 153009w' 23.6 21.4 20.8 15.2 153009x' 24.9 23.0 27.9 16.9 153009y' 27.9 24.0 25.3 19.0 153009z' 28.0 25.0 26.0 18.1 153009a" 28.3 25.0 26.1 17.4 153009b" 28.4 26.4 24.0 20.8 153009c" 29.7 26.0 26.4 19.6 153009d" 31.9 28.0 30.0 20.6 153009e" 32.5 29.3 30.7 21.9 153009g (holotype) 33.0 29.3 30.5 22.2 from C. imbricata, new species, in the same features, and also in its less prominent growth laminae. This species is less elongate and more trigonal in outline than C. enormis, new species, NUMBER 21 2151 and does not reach as large a maximum size. It is larger than C. strongyle, new species, less cir- cular in outline, more convex in profile, and has a longer beak. This species is similar to C. cracens, new spe- cies, from the Bone Spring Formation, but differs in its larger maximum size, more trigonal out- line, greater thickness, and longer, thicker, more strongly curved beak. The greater thickness and absence of an indented anterior margin differen- tiates it from C. emarginata Girty, which attains a similar size. Composita prospera, new species, from the Getaway Member becomes much larger than C. crassa, whereas C. apheles, new species, from the Bone Spring Formation at Black John Canyon is smaller, more circular, thinner and has a shorter beak. Composita discina, new species PLATE 656: FIGURES 1-20 Composita mexicana [part] R. E. King [not Hall, 1857], 1931: 128, pi. 43: figs. 1-3,5,8,9 [not figs. 4,6,7,10,11]. About average size for genus, flatly to moder- ately strongly biconvex; outline subcircular, roundly subpentagonal, or ovate; commissure uni- plicate; fold low, crest evenly arched or bluntly ridged, standing distinctly above flanks only at anterior; sulcus shallow, normally with narrow median groove for most of length of shell; growth laminae weak, absent from some shells, most fre- quent near margins; radial fibrous ornament very weak. Pedicle valve evenly convex; beak short, blunt, normally suberect, less commonly erect; foramen ovate, about average proportionate size for genus. Brachial valve with low median crest, beginning with inflated and somewhat elongate beak. Pedicle valve interior with hinge teeth, dental plates and muscle area in normal arrangement; details not observed. Brachial valve interior with hinge plate formed between crural bases, inner hinge plates thinly fused at midline; cardinal process short, bilobed, cemented to valve apex; sockets deep, between hinge plate and valve walls; muscle area shallowly impressed; spiralia not observed. STRATIGRAPHIC OCCURRENCE.—Gaptank Forma- tion (Uddenites-bearing Shale Member); Lenox MEASUREMENTS (in mm).— brachial length valve length width thickness USNM 714p 153010d 3.8 3.4 3.2 2.5 153010e 4.7 4.3 4.4 2.8 153010E 6.8 6.0 5.9 4.0 153010g 8.4 7.7 7.9 5.0 153010h 12.3 11.0 11.6 7.3 153010i 13.6 12.1 12.0 7.4 153010J 14.2 12.8 12.8 8.0 153010k 14.6 12.8 13.9 9.0 153010-1 18.4 17.0 16.6 10.9 153010m c.19.0 17.7 18.7 12.0 USNM 711d 153011a 6.6 6.1 6.5 4.5 153011b 7.0 6.1 6.0 4.8 153011c 10.8 9.5 10.0 7.4 153011d 11.4 10.3 11.7 7.0 153011e 11.7 10.5 11.0 7.9 USNM 705 153012a 16.4 14.4 14.2 9.4 USNM 708q 153013a (holotype) 19.6 17.7 20.0 12.3 153013b c.10.0 c.8.5 9.3 5.5 153013c 15.5 13.7 15.2 8.4 153013d c.16.6 c.15.0 16.2 10.1 153013e 16.0 15.0 16.7 9.6 USNM 707w 153014a 9.0 8.0 8.4 5.4 153014b 10.5 8.9 9.8 6.3 153014c 11.8 10.7 11.0 7.0 153014d 12.6 11.2 12.6 7.5 153014e c.14.0 12.8 14.0 8.3 153014f 14.2 12.4 13.4 8.0 153014g 15.0 14.0 15.4 9.0 Hills Formation; Skinner Ranch Formation (Decie Ranch and Sullivan Peak members). LOCALITIES.—Gaptank: USNM 708p. Uddenites: USNM 713a. Lenox Hills: USNM 705, 705k, 713q, 713y, 716r. Decie Ranch: USNM 707a, 707v, 707w, 715a. Skinner Ranch: USNM 708q, 711d, 711p, 71 lz, 712p, 714p, 716q, 720e. DIAGNOSIS.—Outline equidimensional, beak short, dorsal umbo inflated, sulcus with shallow median groove. TYPES.—Holotype: USNM 153013a. Figured paratypes: USNM 153010a-c. Measured and un- figured paratypes: USNM 153010d-m, 15301 la-e, 153012a, 153013b-e, 153014a-g. COMPARISON.—Composita discina is character- ized by its moderate convexity, nearly equal length and width, short ventral beak, swollen dorsal beak, and shallow median groove in the sulcus 2152 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY of most specimens. It resembles C. strongyle, new species, but differs in the smaller size of most specimens, and in its less uniformly circular out- line, somewhat greater average convexity, and in its median groove in the sulcus. Lack of parasul- cation distinguishes C. discina from C. bucculenta, C. parasulcata, and C. pilula, all new, which are in about the same size range. C. discina is much smaller than and quite dissimilar from C. stalag- mium, C. enormis, C. prospera, or C. crassa, all new. Composita emarginata Girty PLATE 655: FIGURES 40-51 Composita emarginata Girty 1909:388, pi. 15: fig. l-5a. Large for genus, flatly to moderately strongly biconvex; outline subpentagonal with emarginate anterior; commissure rectimarginate in juveniles and some adults, uniplicate in most adults; fold low, broadly arched, not expressed as ridge or crest along shell, actually depressed in some shells, emphasizing emargination of anterior; sulcus shal- low, indenting shell only at emarginate anterior and for slight distance posterior in some, with narrow median groove in many; growth laminae moderately strong, widely and randomly spaced, more frequent near margins; radial fiberous orna- ment weak. Pedicle valve flatly to moderately convex; beak short, somewhat attenuate, suberect to slightly incurved; foramen normally rather small for size of shell, larger in some specimens, ovate, with periphery narrowly incomplete. Brachial valve somewhat more strongly convex; shallow median groove along flattened crest of fold of some specimens. Pedicle valve interior with large blunt hinge teeth; dental plates slightly convergent, outlining pedicle and adjustor muscle cavity; muscle area elongate, with larger distal diductors surrounding smaller median adductor marks; posterior of valve thickened, shallowly pitted; alligned pits radiating anteriorly, becoming shallow pallial lines. Brachial valve interior with large thickened hinge plate formed between crural bases; car- dinal process extending posteriorly, about perpen- dicular to hinge plate, bilobed, each lobe with small circular muscle marks on anteriorly facing surface; crura, descending lamellae, and spiralia not observed; muscle area elongate, moderately deeply impressed, pattern normal for genus, with low median ridge in posterior; shell thickened and shallowly pitted in posterior, as in pedicle valve. MEASUREMENTS (in mm).— thickness brachial length valve length width USNM 731 153015 3.0 2.6 2.4 1.6 USNM 733 153016a 4.9 4.4 3.9 2.7 153016b 7.9 7.4 7.9 4.4 153016c 8.8 8.0 8.3 4.5 153016d 37.3 33.9 31.9 ? USNM 740 153017a 8.9 8.0 7.7 4.8 153017b c.14.0 13.2 13.0 6.7 153017c 14.3 13.0 11.0 7.7 1530l7d 15.0 13.7 11.1 9.7 153017e 15.9 14.2 11.4 10.5 153017f 16.7 15.4 14.4 9.4 153017g 17.3 15.9 c.14.0 9.2 USNM 750a 153018a 17.1 15.3 c.17.5 9.0 153018b 20.6 18.3 17.8 12.3 153018c 21.5 19.0 19.6 13.0 153018d c.23.0 21.0 21.0 13.7 USNM 738a 153019a 9.2 8.1 7.9 4.8 153019b 11.4 10.0 10.6 6.0 153019c 12.7 11.3 11.6 6.4 153019d 17.3 15.7 14.9 10.5 153019e 19.2 17.0 16.1 11.0 153019f 19.5 17.8 19.3 10.0 153019g 23.5 21.8 c.21.0 16.4 153019h 23.9 21.5 21.7 15.0 153019i 24.0 21.9 21.0 16.7 153019J 28.8 26.0 27.6 15.0 153019k 33.7 31.0 c.35.0 20.3 USGS 2926 118608a (lectotype) 19.2 17.4 17.8 12.4 118608b 14.1 13.0 12.7 7.2 118608c 12.7 19.6 19.5 12.9 118608d 22.7 20.8 19.6 13.2 STRATIGRAPHIC OCCURRENCE.—Bell Canyon For- mation (Hegler, Pinery, and Rader members); Capitan Formation. LOCALITIES.—Capitan: AMNH 475, 803, 806; USGS 2926; USNM 725-1, 737a, 738a, 740, 740h, 740k, 740-1, 740m, 740n, 750a. Hegler: USNM 731. Pinery: AMNH 398, 401, 524, 537; USNM 733, 736, 736a. Rader: AMNH 388, 403, 410; NUMBER 21 2153 USNM 725g, 725n, 725o. Lamar: AMNH 37; USNM 738b. DIAGNOSIS.—Shell large, convexity low, fold and sulcus with shallow median grooves, anterior out- line emarginate. TYPES.—Lectotype (here designated): USNM 118608a (See Girty, 1909, pi. 15; fig. 2-2c). Figured paratypes: USNM 118608b-e (Girty, 1909, pi. 15: figs. 1-lc, 3-5a). Figured hypotypes: USNM 154545a, b; 154546a. Measured hypotypes: USNM 153015, 153016a-d, 153017a-g, 153018a-d, 153019a-k. COMPARISON.—Composita emarginata is char- acterized by its large maximum size, low bicon- vexity, shallow median grooves in the sulcus and along the crest of the fold in many specimens, and the shallow emargination of the anterior outline of most. Emargination may result from the meeting of the two shallow median grooves at the anterior, or in other shells it may be the result of strong indentation of the anterior tongue of the sulcus. Girty (1909) emphasized the two median grooves, but the anterior emargination seems to be present even in specimens where one or both grooves are absent, and is a more con- sistent specific character. This species most nearly resembles C. affinis Girty, which occurs mainly higher in the Guadalupian, but differs in its larger maximum size, stronger biconvexity, pres- ence of a shallow median longitudinal groove in one or both valves, and especially in its slightly or strongly emarginate anterior. It is not closely similar to other species from the region. Composita enormis, new species PLATE 656: FIGURES 21-51 Composita emarginata affinis R. E. King [not Girty, 1909], 1931:128, pi. 43: figs. 12-17.—Cloud, 1944:65, pi. 18: figs. 20-22. Large size for genus, profile moderately biconvex, cross section strongly biconvex; outline commonly narrow, elongate, subovate, rarely subcircular; commissure narrowly uniplicate, fold beginning about 10 mm or more anterior to pedicle beak, crest low, rounded, standing above flanks only slightly at anterior margin; sulcus shallow, de- pressed only at anterior where extending to fill fold; growth laminae weak, widely distributed, most frequent near margins. Pedicle valve evenly convex in posterior two- thirds, with greatest swelling just anterior to beak; umbonal region strongly convex transversely; beak short, normally not attenuate, suberect to slightly incurved; foramen proportionately some- what small, ovate, periphery narrowly open at anterior; edge of valve sharp or slightly flanged. Brachial valve slightly less strongly convex, great- est swelling just anterior to umbo; beak abruptly pointed, apex within pedicle valve. Pedicle valve interior with dental plates slightly divergent toward floor, closely approximating valve walls, space between plates and walls with varying amounts of secondary shelly material, completely filled in many specimens, partly filled in others, leaving anterior edges of plates free (proportionately slightly less secondary cementa- tion of dental plates in small shells); muscle area deeply impressed, especially in large shells with thickened posterior; adductor mark depressed slightly below surrounding diductor marks; pos- terior floor distinctly pitted in adults; radiating pallial marks relatively weak; valve edges slightly flattened mesially, flanged laterally. Brachial valve interior with short strong car- dinal process projecting nearly directly posteriorly, fused to apex of valve, edges slightly curled in- ward, areas of muscle attachment minutely cor- rugated; sockets deep, formed by edges of cardinal process extending lateral to hinge plate; crural bases stout, reinforced at posterior by secondary thickening of themselves and of socket plates; area between crural bases webbed over to form hinge plate; crura short, tapered anteriorly; de- scending lamellae and jugum, as described for genus; spiralia with 8 or 9 coils; muscle area elongate, narrow, slightly less strongly impressed than in opposite valve; posterior part of floor thickened and pitted; valve edges sharp at sides, to fit lateral flanging of opposite valve, flat on crest of fold, to fit flattened edge of pedicle valve there. STRATIGRAPHIC OCCURRENCE—Road Canyon For- mation; Word Formation (China Tank, Willis Ranch, and Appel Ranch members and lens be- tween the last two); Cherry Canyon Formation (Getaway Member). LOCALITIES.—Road Canyon: USNM 700v, 706f, 713, 721j, 732j, 736x. China Tank: USNM 706c, 726s. Willis Ranch: AMNH 505; USNM 706, 2154 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY MEASUREMENTS (in mm).— brachial length valve length width thickness USNM 706b 153020a 12.0 10.6 8.9 6.9 153020b 19.3 17.5 15.2 11-2 153020c 24.0 21.8 20.0 15.9 153020d (holotype) 28.8 25.5 24.5 16.6 153020e 28.0 25.8 25.0 14.6 153020f 2.6 ? 2.5 1.6 153020g 2.7 J 2.3 1.7 153020h 3.0 ? 2.4 1.8 153020i 3.4 ? 2.9 1.9 153020J 3.6 ? 3.0 2.2 153020k 4.2 } 3.5 2.6 153020-1 4.9 4.5 3.9 3.1 153020m 5.3 4.6 4.4 3.0 153020n 6.3 5.4 5.2 3.8 153020o 6.5 5.8 5.7 3.9 153020p 6.7 5.8 5.3 4.0 153020q 7.8 6.8 6.3 4.4 153020r 8.6 7.4 6.1 5.0 153020s 9.1 8.0 7.0 6.2 153020t 9.6 8.6 7.3 5.9 153020u 9.9 8.6 8.0 6.0 153020v 11.7 10.3 9.9 6.3 153020w 12.9 11.7 10.8 7.1 153020x 13.2 11.6 10.4 7.8 153020y 14.2 12.8 11.6 7.9 153020z 15.9 14.3 11.7 9.7 153020a' 16.8 14.4 12.0 9.0 153020b' 18.5 16.4 14.0 10.9 153020c' 18.7 16.7 14.4 10.6 153020d' 19.0 17.5 14.7 12.1 153020e' 20.0 17.3 15.4 12.7 153020P 20.0 17.8 16.3 13.0 153020g' 21.8 19.0 15.7 14.4 153020h' 23.5 21.2 17.0 13.4 153020i' 26.9 24.0 20.9 15.7 153020J' 27.0 23.9 21.7 16.1 153020k' 28.5 25.8 22.6 18.0 153020-1' 35.5 ? 34.6 ? USNM 706e 153021a 50.7 43.4 41.0 26.0 153021b 11.1 10.0 9.7 6.6 USNM 706c 153022a 17.4 15.0 13.7 9.7 153022b 25.1 23.2 20.2 15.6 153022c 25.6 13.3 20.5 15.9 153022d 26.7 23.9 18.8 15.8 706e, 724u, 735c. Lenses: USNM 706b, 732c, 737w. Appel Ranch: USNM 704, 706d, 714o, 715i, 716v, 719z, 722t, 726t, 727j. Getaway: USNM 728, 732. DIAGNOSIS.—Shell large, outline elongate, con- vexity low, beak short and blunt, fold low and narrow, posterior thickened, burying dental plates. TYPES.—Holotype: USNM 153020d. Figured paratypes: USNM 153020a-c,e,f; 153021a; 154538a. Measured paratypes: USNM 153020a-c, e-z, a'-l'; 153021a,b; I53022a-d. Unfigured paratypes: USNM 153020g-z. COMPARISON.—Composita enormis is characterized by its large maximum size, commonly elongate ovate outline, low longitudinal convexity, low and somewhat narrow fold, short blunt beak, and thickened posterior with short dental plates fused or nearly fused to sides of shell. This species was placed by R. E. King (1931:128) in C. emargin- ata affinis Girty, from which it differs in its narrower outline, weaker growth laminae, stronger convexity, and higher fold, with crest more rounded or pointed rather than somewhat flat- tened. It is more elongate, less convex, and has a shorter, less strongly curved beak, and its dental plates are more closely fused to the walls than in C. crassa, or C. stalagmium, both new. This species is smaller on average than C. prospera, new species, although the very largest specimens of each species reach about the same size. Composita enormis differs further in its nar- rower outline, somewhat lower convexity, propor- tionately smaller pedicle foramen, and its lower fold. It differs from C. parasulcata, new species, with which it occurs, in its much larger size, more elongate outline, less globular shape, and especially in its fold that begins much farther anterior, and lacks the strong lateral sulci of that species. Composita imbricata, new species PLATE 658: FIGURES 1-36 Composita mira R. E. King [not Girty], 1931:129, pi. 44: fig. 4, [not pi. 44: figs. 3,5-8]. Larger than average size for genus, moderately strongly biconvex; outline subovate to subtrigonal, widest anterior to midlength; commissure broadly uniplicate, fold low at commissure, standing out slightly above flanks; sulcus shallow, growth lam- inae numerous, strong, producing imbricated ef- fect, randomly spaced over most of shell, strongest and most frequent near margins. Pedicle valve slightly inflated in umbonal region; beak short, thick, suberect; foramen ovate, size proportionately normal, periphery narrowly in- complete. Brachial valve also convex in umbonal NUMBER 21 2155 thickness 1.0 1.1 1.4 1.5 1.4 1.7 1.8 1.8 1.8 2.0 2.3 2.3 2.5 3.0 3.3 3.3 3.6 3.9 4.7 4.4 4.7 5.4 5.5 5.8 24.7 6.0 6.8 6.5 6.3 STRATIGRAPHIC OCCURRENCE.—Cathedral Moun- tain Formation. LOCALITIES.—AMNH 500, 500B, 500D; USNM 702, 702b, 702un, 703b, 703bs, 708, 708c, 721u, 726o, 726u, 726y, 735b. DIAGNOSIS.—Shell large, outline trigonal, fold flat- tened, growth laminae producing shingled effect. TYPES.—Holotype: USNM 153023f. Figured paratypes: USNM 153023a-e, 154541a, 154541a, 154542a. Measured and unfigured paratypes: USNM 153023g-z, a'-z', a"-d"; 154541b,c; 155123a. COMPARISON.—Composita imbricata is character- ized by its large size (about average for Permian species), trigonal to ovate outline, flattened fold on many specimens, and by the rather strong growth laminae that produce a shingled effect over the anterior portion. Among the new Texas Permian species it most nearly resembles C. stalagmium and C. crassa, differing in its smaller maximum size, narrower outline, lower fold, and stronger growth laminae. It is larger, thicker, and more strongly folded than C. strongyle, and smal- ler and less elongate than C. enormis, both new. region, crest of fold flattened in many specimens to produce weak suggestion of divergent bounding ridges along sides. Pedicle valve interior with dental plates thick- ened or cemented to walls by secondary shelly matter; pedicle area smooth on floor between anterior edges of plates and extending anteriorly about half length of valve, moderately to strongly impressed, deepest in most thickened shells, small adductor marks surrounded by larger crescentic diductor marks. Brachial valve interior with short hinge plate formed between crural bases, secondarily thick- ened in some specimens; cardinal process short, distinctly bilobed, nearly perpendicular to hinge plate, each lobe with small circular diductor muscle mark; crura short, slender, projecting for- ward from crural bases at sides of hinge plate; descending lamellae and spiralia not observed; muscle area shallowly impressed, elongate spatu- late, extending about half length of valve. MEASUREMENTS (in mm).— brachial length valve length width 1.8 2.3 2.5 2.7 3.0 3.0 3.2 3.3 3.6 3.9 4.1 4.4 4.6 5.0 5.2 5.6 6.0 6.9 7.2 7.9 8.3 8.8 9.0 9.2 32.4 9.3 9.7 10.0 10.5 1.6 1.9 2.0 2.3 2.3 2.7 2.8 2.9 3.1 3.3 3.6 3.9 4.0 4.2 4.6 5.0 5.5 6.1 6.5 6.8 7.2 7.9 7.8 8.1 29.9 8.3 8.6 8.6 9.2 1.5 1.8 2.0 2.1 2.2 2.5 2.5 2.5 3.0 3.3 3.0 3.8 4.0 4.2 4.8 5.1 5.3 6.3 7.0 6.6 7.4 8.1 7.6 8.7 33.3 8.5 8.5 9.5 9.2 (holotype) USNM 702 153023g 153023h 153023i 153023J 153023k 153023-1 153023m 153023n 153023o 153023p 153023q 153023r 153023s 153023t 153023u 153023v 153023w 153023x 153023y 153023z 153023a' 153023b' 153023c' 153023d' 1530231 153023e' 153023P 153023g- 153023h' 1530231' 153023J' 153023k' 153023-1' 153023m' 153023n' 153023o' 153023p' 153023q' 153023r' 153023s' 1530231' 153923u' 153023v' 153023W 153023x' 153023y' 153023z' 153023a" 153023b" 153023c" 153023d" USNM 702b 155123a USNM 702un 154541b 154541c King 174 YPM 12203 brachial length valve length width thickness 11.3 10.0 10.6 7.6 11.4 10.0 9.3 6.8 11.5 10.4 9.7 7.7 12.1 11.0 12.0 8.3 12.5 11.3 11.0 7.9 13.0 11.8 12.5 7.9 13.2 11.6 12.9 9.8 14.2 12.5 13.9 9.4 15.9 14.6 14.0 10.5 16.5 14.8 15.9 9.3 16.9 15.0 15.8 9.0 17.1 15.8 16.3 9.5 18.0 16.5 17.1 10.3 19.7 17.9 18.8 12.2 20.1 18.1 19.0 12.8 20.9 19.3 19.8 11.8 21.8 20.4 19.5 14.0 22.0 20.0 20.5 13.6 23.5 21.8 23.0 14.6 25.0 23.8 26.4 16.5 25.1 22.6 24.7 14.0 26.6 24.4 27.4 18.8 33.0 c.30.0 37.6 c.23.0 25.7 23.9 25.2 13.7 40,5 46.2 c.44.0 25.7 14.7 21.7 23.7 c.23.0 2156 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY USNM 725a 154540a 154540b 154540e 154540i 154540J 154540k 154540-1 154540m 154540n 154540p 154540q 154540r Small to middle-sized specimens are similar to C. apheles in shape, but differ in their flat- crested folds and stronger growth laminae; C. imbricata attains a larger size than C. apheles. Composita cracens is similar in size and shape, but C. imbricata has stronger growth laminae, a more flattened fold, and attains a larger maximum size. It is larger than C. apsidata, new species, with which it was included by R. E. King (1931) under C. mira (Girty). In addition it is less con- vex, has a lower fold, lacks a median groove in the sulcus, and its growth laminae, while strong, are confined nearer the margins than in C. apsidata, new species. DISCUSSION.—Composita imbricata is typically silicified in such a manner that a rough outer surface is produced. This may reflect an original roughened or fibrous condition of the shell, or may be a peculiarity of preservation. R. E. King (1931) identified C. imbricata with C. mira (Girty), a name originally assigned to specimens that Meek (1877) identified as Athyris roissii Leveille. Examination of Meek's speci- mens in the U.S. National Museum shows them to belong to a large, broad species of Cleiothy- ridina, probably more nearly related to A. roissyi than to any species of Composita. The name applied to that species should be Cleiothyridina mira (Girty). Composita mexicana (Hall) PLATE 657: FIGURES 40-81 Terebratula mexicana Hall, 1857, pi. 20: fig. 2. Composita mexicana (Hall) Girty, 1909: p. 389 [including var. guadalupensis, p. 390, pi. 24: fig. ll-13b]; I909a:68, pi. 8: fig. 1.—R. E. King, 1931:128, pi. 43: fig. 1-11. Shell small, elongate to nearly equidimensional, moderately strongly biconvex; outline subpenta- gonal, widest anterior to midlength; commissure uniplicate to weakly parasulcate, fold low and flattened at commissure, crest barely raised above flanks; sulcus only a shallow and narrow trough; growth laminae very weak over most of shell, accentuated only near margins. Pedicle valve beak long, swollen, suberect; fora- men proportionately rather large, round to oval, incompletely formed. Brachial valve beak curved beneath foramen; greatest convexity farther for- ward than in opposite valve; valve edges flanged, brachial valve edge overlapping pedicle valve edge at flanks. Pedicle valve interior not thickened; teeth short and slight; dental plates short and thin; muscle area posteromesial, weakly impressed. Brachial valve interior with typically bilobed hinge plate; cardinal process consisting of thin flange project- ing ventrally from posterior part of hinge plate; sockets deep; muscle area dual, consisting of nar- row oval part median and somewhat anterior to two lateral lobes; spiralia and other brachial apparatus not observed. MEASUREMENTS (in mm).— brachial length valve length ividth thickness 9.6 8.5 8.3 6.7 10.9 9.3 10.3 6.7 11.7 10.2 10.7 7.8 3.4 2.9 2.3 2.1 4.2 3.5 3.5 2.4 5.0 4.3 4.0 3.5 5.4 4.8 5.0 3.4 7.2 6.2 6.7 4.8 8.0 6.9 7.4 4.9 10.4 8.9 9.0 6.7 10.9 9.4 9.6 7.7 11.9 10.5 9.8 8.0 STRATIGRAPHIC OCCURRENCE.—Hueco Formation. LOCALITIES.—AMNH 653, 700; USNM 725a, 725b. DIACNOSIS.—Shell small, strongly convex, sub- pentagonal; growth laminae and fold strong only near commissure. TYPES.—Holotype: figured by Hall in Emory, 1857, pi. 20: fig. 2. Figured hypotypes: USNM 154540a-i. Measured hypotypes: USNM 154540a, b,e,i-r. COMPARISON.—Composita mexicana resembles several of the small species in the West Texas area. It is typically more elongate, has a longer beak and is much less strongly convex than C. micella, new species, which occurs in the Cutoff Shale Member of the Bone Spring Formation. It is smaller, smoother, more elongate and more typically parasulcate than C. apheles from the Decie Ranch Member of the Skinner Ranch Formation. Another Bone Spring species, C. apsi- data, new species, is larger than C. mexicana, not as rotund, and has a lower and broader fold and a sulcus that appears as a narrow groove. NUMBER 21 2157 Composita mexicana is not likely to be confused with C. cracens, new species, also from the Bone Spring Formation, because it is much smaller and narrower, with a longer beak and broad, flat- tened fold. Composita bucculenta, new species, from the Road Canyon Formation, which is more strongly parasulcate than C. mexicana, and much wider, is very distinct from the latter despite its small size, being much more strongly convex, and having the fold stand well above the flanks, es- pecially toward the anterior margin. DISCUSSION.—As with so many of the species that were described very early in the exploration of the West, it is difficult to decide which of those in our collection should be Composita mexicana. The locality for the specimen figured by Hall is obscure; it is not even certain that it came from Texas. We chose to adopt R. E. King's concept of the species rather than Girty's, however, because King's and our specimens more nearly resemble Hall's figure. Following King, therefore, the spe- cies is an early Permian form; we settled the name upon a distinctive species from the Hueco Limestone of the Baylor Mountains. Girty's spe- cies from the "Black Limestone" (i.e., the Bone Spring Formation) is not quite the same, and we have included it only tentatively in the synonymy. Thus far we have been unable to establish the iden- tity of the Bone Spring species that Girty called C. mexicana. Composita nucella, new species PLATE 658: FICURES 37-70 Small, moderately strongly biconvex; outline sub- pentagonal or subovate, elongate or equidimen- sional, rarely transverse, widest near or anterior to midlength; commissure nearly rectimarginate to uniplicate, most commonly weakly or strongly para- sulcate; fold standing above flanks only at ante- rior, and only in about half of collection, crest gently arched or flattened; sulcus depressed slightly or not at all; growth laminae rather strong, espe- cially near margins. Pedicle valve slightly inflated in umbonal re- gion; beak relatively long, thick, suberect to erect; foramen average size, oval, periphery incomplete; valve edges slightly thickened and flanged. Brachial valve also most strongly convex in umbonal region, normally somewhat less strongly convex than op- posite valve. Pedicle valve interior with short hinge teeth slightly hooked inward; dental plates free for about half their length, fused to walls at posterior; muscle area elongate, spatulate, extending about half length of valve, pattern normal for genus. Brachial valve interior with bilobate hinge plate; cardinal process also bilobed, perpendicular to hinge plate, short, with small round muscle mark on each lobe; muscle area elongate, narrow, bisected in posterior by low median ridge; descending lam- ellae, jugum, and spiralia not observed. MEASUREMENTS (in mm).— brachial length valve length tuidth thickness AMNH 678 153024c (holotype) 12.4 10.9 10.7 8.7 153024g 2.7 2.6 2.1 1.6 153024h 3.0 2.8 2.7 1.8 153024i 3.1 3.0 2.6 1.8 153024J 3.3 3.1 3.0 2.0 153024k 3.6 3.2 3.0 2.0 153024-1 3.7 3.5 3.2 2.1 153024m 4.0 3.5 3.3 2.5 153024n 4.4 4.0 3.7 2.7 153024o 4.7 4.0 3.8 2.8 I53024p 4.9 4.5 4.3 3.2 153024q 5.2 4.8 4.3 3.1 153024r 5.8 5.3 5.0 3.7 153024s 6.2 5.6 5.7 4.0 153024t 6.5 5.7 5.3 3.9 153024u 7.0 6.3 6.0 4.4 153024v 7.9 7.0 6.0 4.8 153024w 8.7 7.9 7.4 5.4 153024x 8.9 8.0 7.9 5.8 153024y 9.0 8.0 7.6 5.8 153024z 9.7 8.7 7.5 6.6 153024a' 9.8 8.8 7.9 5.8 153024b' 10.0 8.9 8.9 7.0 153024c' 10.7 9.7 8.8 7.5 153024d' 11.0 10.0 9.0 7.7 153024e' 11.1 9.9 9.3 7.7 153024P 12.0 10.9 10.0 9.0 153024g' 12.0 10.6 10.3 8.1 153024h' 12.5 11.0 10.8 8.9 153024i' 12.7 11.3 10.9 8.7 153025J' 12.8 11.2 11.8 8.5 153024k' 13.0 11.9 11.6 9.1 153024-1' 13.6 12.5 13.3 9.3 STRATIGRAPHIC OCCURRENCE.—Bone Spring For- mation (and Cutoff Member). LOCALITIES—Bone Spring: AMNH 660. Cutoff: AMNH 678. USNM 747. 2158 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY DIAGNOSIS.—Shell small, elongate, commissure parasulcate, fold low, sulcus shallow, growth lam- inae rather strong. TYPES.—Holotype: USNM 153024c. Figured paratypes: USNM 153024a,b,d-f. Measured and un- figured paratypes: USNM 153024g-z,a'-l'. COMPARISON.—Composita nucella is character- ized by its relatively small size, commonly elongate, rarely transverse outline, typically parasulcate com- missure with low fold and shallow sulcus, and its moderately strong growth laminae. It is larger, narrower, and has a less distinctly defined fold than the parasulcate species C. bucculenta or C. parasulcata, both new. It most nearly resembles C. pilula, new species, from the Glass Mountains, differing in its less bulbous convexity, stronger and more consistent parasulcation, and longer pedicle beak. It is smaller and less strongly parasulcate than C. pyriformis, new species, from the Pinery Member. It is much smaller than the highly abundant and widespread species from the Glass Mountains such as C. crassa and C. enormis, both new, and the abundant Bone Spring species C. cracens, and C. apheles, both new. Composita parasulcata, new species PLATE 659: FIGURES 1-69 Small for genus, strongly biconvex, subglobular; outline commonly ovate, less commonly subpenta- gonal; commissure parasulcate, fold beginning about 5 mm anterior to pedicle valve beak, crest flatly rounded, rather prominent at anterior; sulcus de- pressed only at anterior of largest shells, normally expressed only as a slight flattening of valve form- ing a tongue extending into fold; growth laminae weak, widely spaced, absent from some specimens. Pedicle valve strongly and evenly convex; beak suberect to slightly incurved; foramen ovate, pro- portionately normal in size, narrowly incomplete at anterior; edges of valve normally slightly flanged, especially at anterior. Brachial valve slightly less strongly convex; beak bluntly rounded; anterior edges slightly produced on each side of fold, in- creasing apparent height of fold at commissure. Pedicle valve interior with short, subparallel dental plates, free or cemented to wall by second- ary shell material; teeth short, slightly hooked; muscle area shallowly impressed, linguiform, ex- panding slightly anteriorly from between dental plates; two shallow grooves extending anteriorly from muscle area, other pallial markings not apparent. Brachial valve interior with short strong hinge plate extending anteriorly in plane of commissure; cardinal process projecting ventrally nearly perpen- dicular to hinge plate, short, fused to apex of valve; hinge sockets formed at juncture of plate and process; muscle area moderately deeply im- pressed, bisected for short distance at posterior by low median ridge; crura short, forming sides of hinge plate; spiralia as described for genus, about 8 coils on each side, forming two conical chambers. MEASUREMENTS (in mm).— brachial length valve length width thickness USNM 706c 153026a 3.0 2.2 2.5 1.8 153026b 3.7 3.0 3.0 2.4 153026c 4.4 3.7 3.6 2.7 153026d 5.8 4.9 4.9 3.3 153026e 6.4 5.8 5.4 4.1 153026f 7.0 6.3 6.6 4.4 153026g 8.1 7.0 6.5 5.5 153026h 8.6 7.8 7.6 5.6 153026i 9.7 8.9 9.3 6.6 153026J 10.6 9.3 9.6 7.7 153026k 11.4 10.0 10.7 7.9 153026-1 11.9 10.6 11.1 8.3 153026m 12.9 11.2 12.4 9.2 153026n 13.9 11.7 11.7 9.5 153026o 14.1 12.7 13.9 10.1 153026p 14.9 13.3 13.3 11.7 USNM 706e 153025a 2.7 2.3 2.4 1.7 153025b 2.9 2.4 2.7 1.7 153025c 3.0 2.7 3.1 1.6 153025d 3.5 3.0 3.6 2.2 153025e 3.7 3.3 3.9 2.3 153025g 3.8 3.5 3.6 2.2 153025h 3.9 3.6 3.7 2.4 1530251 4.1 3.6 3.8 2.3 153025J 4.6 4.2 4.6 2.9 153025k 4.9 3.5 4.6 2.9 153025-1 5.4 4.9 5.1 3.5 153025m 5.7 4.9 4.5 3.6 153025n 5.7 5.0 5.7 3.8 153025o 6.3 5.5 6.0 3.9 153025p 6.6 5.8 6.0 3.9 153025q 7.1 6.7 7.1 4.4 153025r 7.9 7.1 7.1 4.9 153025s 8.3 7.8 8.2 6.5 153025t 8.9 7.9 8.0 6.0 153025u 9.3 8.7 9.1 6.3 153025v 9.5 ? 8.7 6.7 NUMBER 21 2159 1 ... brachial length valve length width thickn 153025w 10.0 8.9 8.7 6.9 153025x 10.5 9.3 9.4 7.0 153025y 10.1 9.0 8.8 7.5 153025z 10.8 9.2 10.0 7.8 153025a' 10.9 10.4 10.2 7.6 153025b' 11.4 10.5 10.7 7.4 153025C 11.9 10.7 11.1 8.5 153025d' 12.8 12.0 12.5 9.1 153025C 13.0 11.8 11.5 8.9 153025P 13.3 11.0 10.4 9.3 153025g- 13.5 12.0 13.0 9.8 153025h' 14.7 13.0 13.2 10.4 153025i' 15.0 14.0 12.8 11.0 153025J' 15.4 15.0 15.6 10.8 153025k' 15.7 14.5 14.8 11.0 153025-1' 16.0 14.8 14.1 10.7 153025m' 17.0 16.3 16.8 14.8 USNM 706b 154543e (holotype) 13.8 12.3 12.7 12.3 STRATIGRAPHIC OCCURRENCE.—Road Canyon For- mation; Word Formation (China Tank, Willis Ranch, and Appel Ranch members and lens be- tween the last two); Cherry Canyon Formation (Getaway Member). LOCALITIES.—Road Canyon: USNM 713. China Tank: USNM 706c, 726r, 733q. Willis Ranch: AMNH 506; USNM 706, 706e, 723t, 723w, 724u. Lens: USNM 706b. Word: USNM 737w. Appel Ranch: USNM 706d, 715i, 719z, 722t, 727j, 732c. Getaway: ANMH 512, 519, 496, 585, 600; USNM 728, 730, 732. DIAGNOSIS.—Small for a Permian species, out- line wide, profile convex, commissure consistently parasulcate. TYPES.—Holotype: USNM 154543e. Figured para- types: USNM 153025f,r,y,d', e',j'; 153026a,b; 154543 a-d,f,g. Measured paratypes: USNM 153025a-e, g-z, a'-m'; 153026a-p. Unfigured paratypes: USNM 153025a-e, g-p, s-v, a'-d', f'-i'; 153026a-i, k-n, p. COMPARISON.—Composita parasulcata is charac- terized by its relatively small size among Permian species of Composita, broad outline, convex profile, flanged valve edges on most specimens, and espe- cially by its parasulcate commissure. It most nearly resembles another parasulcate form C. bucculenta, new species, from lower in the section, differing in its larger size, proportionately somewhat narrower outline, weaker parasulcation, and longer, slightly more attenuate pedicle beak. It also resembles C. pilula, new species, to some extent, but differs in its normally stronger parasulcation, flatter crest of the fold, and longer pedicle beak. The small size and parasulcation distinguish it from other species in the Glass Mountains and West Texas Permian. Composita pilula, new species PLATE 657: FIGURES 1-39 Small, globular; outline ovate or subpentagonal, normally slightly elongate, widest anterior to mid- length; commissure weakly parasulcate to unipli- cate; standing only slightly above flanks at anterior; sulcus expressed only in commissure, not depressed along shell; growth laminae weak and widely spaced over most of shell, stronger and crowded near margins. Pedicle valve strongly and evenly convex; beak short, thick, suberect or erect; foramen small, pe- riphery narrowly incomplete; edge of valve flanged or shallowly grooved in most specimens. Brachial valve somewhat less strongly convex, greatest infla- tion in umbonal region; edge shaped to fit flange or groove of opposite valve. Pedicle valve interior with slender, sharp, hooked teeth; dental plates cemented to walls for all or most of length; muscle area shallowly impressed, pattern normal for genus. Brachial valve interior with small hinge plate, mesial parts not entirely fused in some specimens, leaving deep median notch; cardinal process bilobed, each lobe with small muscle scar on anterior-facing surface; muscle area elongate, narrow, low median ridge at poste- rior; crura, descending lamellae, and spiralia not observed. STRATIGRAPHIC OCCURRENCE.—Road Canyon For- mation. LOCALITIES.—USNM 706f, 720d, 721y, 724d, 724j, 732], 736x. DIAGNOSIS.—Shell small, outline elongate, beak short, growth laminae strong near margins, fold and sulcus very weak, commissure weakly para- sulcate. TYPE:.—Holotype: USNM 154539d. Figured para- types: USNM 153027t,u,z,c'; 154539a-c,e. Measured paratypes: USNM 153027a-z, a',b'. Unfigured para- types: USNM I53027a-s, v-y, a',b'. COMPARISON.—Composita pilula is characterized by its small size, elongate ovate outline, short pedicle beak, moderately strong growth laminae, 2160 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY MEASUREMENTS (in mm). brachial length valve length width thickness USNM 720d 153027a 3.0 2.8 2.9 1.9 153027b 3.4 3.1 3.0 2.0 153027c 4.5 3.9 3.9 2.7 153027d 4.9 4.7 4.9 2.9 153027e 5.0 4.5 4.5 3.5 153027f 5.3 4.9 4.9 3.0 153027g 5.7 5.2 5.7 3.6 153027h 6.9 6.3 5.9 4.2 1530271 7.2 6.0 6.3 4.1 153027J 9.0 7.3 6.9 4.8 153027k 8.0 7.0 7.8 5.3 153027-1 8.2 7.1 7.0 5.5 153027m 8.3 7.3 6.8 5.5 153027n 8.6 7.6 6.9 5.3 153027o 8.9 8.1 7.1 5.9 153027p 9.0 8.0 7.5 5.7 153027q 10.0 8.8 8.2 6.0 153027r 11.0 9.9 9.3 7.9 153027s 11.2 9.6 9.4 7.0 153027t 11.3 10.0 10.0 7.0 153027u 11.9 11.0 12.0 8.8 153027v 12.1 10.8 10.5 7.9 153027w 12.3 10.9 10.3 8.7 153027x 12.4 11.0 11.4 8.0 153027y 13.0 11.7 11.4 8.0 153027z 13.3 11.8 10.8 8.0 153027a' 13.3 11.4 11.7 9.8 153027b' 14.0 12.6 12.7 9.8 USNM 724j 154539d (holotype) 17.8 15.8 16.9 13.9 especially near the margins, and its weakly para- sulcate commissure, with low fold and