um ulletins ИШИ, VOLUME 84, NUMBER 317 OCTOBER 4, 1983 C ЗАО FOO! AUS. COMP, ZOOL LIBRARY Molluscan Paleontology, Paleoecology, and North Pacific Correlations of the Miocene Tachilni Formation, Alaska Peninsula, Alaska by Louie Marincovich, Jr. Paleontological Research Institution 1259 Trumansburg Road Ithaca, New York, 14850 U.S.A. PALEONTOLOGICAL RESEARCH INSTITUTION Officers ЕЗБЕ e rr ede о. Bruce M. BELL NJCROPEESEDENT О LA EI oan ct dalle EIE eee WILLIAM А. OLIVER, JR. ЕЕЕ UN LAT M LEE ои PHILIP C. WAKELEY И REASU ЛЕТ АНИНА син er ue UL NAH а. ROBERT E. TERWILLEGAR ТУБА SECRELARY 4 nk lee лут уру DE HENRY W. THEISEN ASSISTANT TREASURER 2 cya. ot ha жу ee Рам JOHN L. CISNE ПО звани кш с Le ICE кл M кы M КО aie PETER R. HOOVER ПН АРА ОР Moore ү пир ere MALE LU а er HENRY W. THEISEN Trustees BRucE М. BELL (to 6/30/84) WILLIAM A. OLIVER, JR. (to 6/30/86) RICHARD E. Вуко (to 6/30/86) JOHN РОЈЕТА, JR. (to 6/30/85) JOHN L. CISNE (to 6/30/85) JAMES E. SORAUF (to 6/30/85) ГЕЕ B. 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Hoover Director Paleontological Research Institution 1259 Trumansburg Road Ithaca, New York 14850 U.S.A. 607-273-6623 VOLUME 84, NUMBER 317 ОСТОВЕЕ 4, 1983 Molluscan Paleontology, Paleoecology, and North Pacific Correlations of the Miocene Tachilni Formation, Alaska Peninsula, Alaska by Louie Marincovich, Jr. Paleontological Research Institution 1259 Trumansburg Road -— Ithaca, New York, 14850 U.S.A. Library of Congress Card Number: 83-62774 Printed in the United States of America Allen Press, Inc. Lawrence, KS 66044 U.S.A. CONTENTS КУБО co MUI АОН. ке muc ME AUT MERGE MET MUTET MAREM Кс LU = MEE OCUETON T 8. МА Mer cuore У маис oA Ie e ДК КАН БИИР Е ТЕСИН еее Ри Acknowledgments углу. КОЛЛ... ТАРТ ЧЕ : Physical Süsügraphy vec e PEE E UU qi D а " Faunal Ороо И de ee te Са од E E ра Biostratigraphy uei ОО ТОГОС fea ok es scan ВИ Е A nN er еер ры РОСО RM NUM SEIN OUR INI S S UU E ~ Paleoecology куго alice alge сас oa a l a ИТ ИН an en ae К SUM кслс IE M ДЕ ELM ен, 5 Systematic Paleontology = ПИО ites seta eee не аз угул са В Rl Srey кыта аи то ЫК MM a са уа ee re MESO е пое м ИКИ ЛЛ Abbreviations а СО Л ТОТ ЕК О Т Е R сое сз сыт А ЕО ае ео оаа ри 8 Class Bivalvia а Family Nugülidae аалда виа и templet дови подобном ингени оон ор ааа : Family Nuedlamdae ehe e te eS ез гърне пн T MM I TM 3 Вани Gly cyaerididae: usce ccs RR ee а HUNC E Mo ыы а лкк a : Family Mytilidae EL Ол ERENT Оу uM. У ВН РРА AE AN ы = Family Pectinidae ыыы ын ont UN RM MM eee ВР ИЕ ae ee it кг Family Carditidae МА ит age у ул з АЕ + ча id Family Unguldide c sesso cecus tu Vc M EM MD кои se Family Chamidae. c celeris coron nio ores: vade ыр кы БРУНО ПАДА MOD NET 2 Bailly байар ра Ae e rue ар o e АНА Oe чы клы Du CE NL ICT m капу Veneridae r гара M MINES Situs qe eco D т АЕ y А Family Mactridae I LL TREE ide tt aC ет a ee LEN © Family Tellinidae ОПО tasse cos е ле ы ы E ee айы ы. oa аз Ае Деко So Ar ы ы niu qo ы инв наои ние HH ууу Ne or e TUNI a не пеш злу ол но т Family Pandoridae ber wi ta eaten ave po А ents орди er ee M эне Pany LYONA qu e с rar I DOCU Cl КО КЫК и т ш тасу ЕЕ bs Кашу, Petri plomidie: ars coe ук езше Sig преиспита нео Сш ЕАО свота. picti. DEAN Зена COGN МЕН уы C USER дании 0 ра i Family Trochidae SANA CHA RD EUNT о pores yi SIM Calyptraeidae eS Dl Nes ade NA RARUS GIQUECOE ешт ш ол у лан RUNS ais Family Naticidae мане Habis "Mn a" пера ок PRESENT C VES! vet ct tinte iR VIAE in ПР i bet ee ict и ул л О чи d eua hr c i LL LAE eH SODIUM TK x ORA cie Dies E di ME ntl in M MNT MR RIO si do M NODE DU Iria RC NERIS М л a КОШУ (Cristea eit ea oes te SL. Tanne Dobra enero ghee Уне v oil ТА а бана ух. није и га ен на ien Шз вену сен върне d. ccna p ncc quado He ту Appendix: (Clot [Setninteg) Borers ШЗ т: et бине. cosh OR ate, io E deep Oro. Ее dtc EN E zi БО А Ке Да BAM Мао т hene |. Pee ЕНИ МЕА C NIIS TIUS 29 Е еи MEC e ОНЕ ИЕ ВИ НБН ОВЕ Е C ORE Аи 131 LIST OF ILLUSTRATIONS Text-figure Page LE Map of the Worth Pace region, showing places mentioned Im texi о od tes 60 2. Map showing outcrop extent of Tachilni and Bear Lake Formations on the Alaska Peninsula ................................ 61 3. Maps showing location of Паст Formation fossil localities and measured Sections |... екс. mese ur eh актина нек e 63 4. Меавитей siraincrapiice sections апа fossil localities in the тасш Formation поканва кышы нын кишка шшк edere о. БА 66 5. Comelation.of Pactic Northwest. molltiscan stages with: foraminiferal Stages. 2. н ТЕ 69 0. Modem latitudinal ranges of northeastern Pacific mollusks m the Тас tanna ОЕ PO ees cue d ten ete ase сета 76 7. Modern bathymetric ranges in the northeastern Pacific of some Tachilni mollusks or their living analogues .................... К 9, 10. H LIST OF TABLES Page Molluscan species aud. ован m the Таш Formation ая foldout inside back cover ‚ТЕСШ I OC ERO be bivalves ТОША witk ORE UL ей and- closed VALVES) ан tete eec е UY 65 SEM Bo sana ciere amine ein cron casn an (8 лов а еј па тако his а сн ск cg tM UM ЕЕ ET 65 : Mollusks ТО only m the Cape: ПАС РАВНЕ МАКСА зе ФОО ан жк жик л S EIU SO rer pei Рао тета 67 WOM Ke found omiy im the Somi Walrus Fenk Stub докога) одит еко ее кор пони чел укку кучу чино дык оо rectum ORO DE. 67 . Mollusks found in the South Walrus Peak stratigraphic section, but only at the stratigraphically lowest localities, USGS POT о ara AE eU A EE Pe Сн а MERE UR ERU D СС cu A теге el uu caldi мн 67 . Tachilni mollusks also found in the unnamed upper member of the Bear Lake Formation, Alaska Peninsula ................... ff! . Tachilni mollusks also found in presumed Wishkahan faunas of the Yakataga Formation ............... олик Л ee ee eas qni Occurrences of Tachilm mollusks in some Miocene strata of the northeastern Расе пин uso eere de bore HM ЗЪРНА а 72 ОФОШТЕШ ев ot Taichin mollusks m вое Aran Miocene Шаа р а OE КОДДА, 73 ТЕСШ таба аи ко ока in Japanese Miocene ба она со tos LU ATEM EEE hate ilo e eei ИЕ 74 MOLLUSCAN PALEONTOLOGY, РАГЕОЕСОГ ОДУ, AND NORTH PACIFIC CORRELATIONS OF THE MIOCENE TACHILNI FORMATION, ALASKA PENINSULA, ALASKA By LouiE MARINCOVICH, ЈЕ. U.S. Geological Survey 345 Middlefield Road, MS 15 Menlo Park, California 94025 ABSTRACT The Tachilni Formation, composed mainly of fine- to medium-grained sandstone, crops out near the western end of the Alaska Peninsula, southwestern Alaska, and contains 53 molluscan taxa, including 36 bivalves and 17 gastropods. The high percentage of articulated, closed bivalve shells, including some found in life positions, suggests that Tachilni deposits were largely unaffected by post-mortem transport. The mollusks are inferred to have lived in a cool-temperate, inner shelf habitat. Many of the mollusks are known in Miocene faunas of Asia (Hokkaido, Sakhalin, Kamchatka) as well as western North America (California, Oregon, Washington). Several of the North American taxa suggest an age of early late Miocene (Wishkahan Stage) for the Tachilni fauna. Reliable correlations may be made with the Etolon Formation of western Kamchatka, the middle part of the Bear Lake Formation of the Alaska Peninsula, the lower to middle part of the Yakataga Formation of the eastern Gulf of Alaska, and the lower part of the Montesano Formation (type section of the Wishkahan Molluscan Stage) of southwestern Washington. Other possible correlatives of the Tachilni Formation are the Okkopezawa and Togeshita Formations of Hokkaido and the Nutovo Formation of Sakhalin. Newly described species are Cyclocardia sakamotoi and Lyonsia mooreae. Tachilni I 3E E AIRE Ze vo LAD DS 0, УА ЕО < 12 20, 36880 Н ОВИ #2 БЕНО ALG & RET 5. ЖЕФ ЕНЕ CE HIT 5 60 S Silo? СНУ S НО 185 & <, Tachilni ОКИ S ЛШ ОЮ ШЕ Б 00 COED, сп БОНИ uM s Ее СА Сол & её {з сиБонЖО #2 < жит (2 )7ар=7, жии, гуућу) ЕКТ 77 ОСЕ, ВЖ, DAF x32) ФАНИ И DMD NTO A. WS 2 О ДЕЖИ Tachilni А ҖИ НА ЯН (Wishkahan BE) рт Сад, EK, Tachilnil& АУ 7 0 Etolong, 7 7 477580 Bear Lake р, 7 2 A HIB RB 0) Уакајава ју « FRUT У У КУ МИЊО Montesanol (HARI 2 Wishkahan# O fX) (СЕМЕ СА ЈЕНИ >. Tachilni ЈЕ ножа y KEIM LIE ЕМ, 54 UBEKO Nutovoli & to ЈАЈНЕ СФ Фо С ОВУ С Cyclocardia sakamotoi & Lyonsia mooreae Н & L CALA Сод АВТОРЕФЕРАТ Тачилъная свита, состоящая главным образом из мелкозернистых и среднезернистых песчаников, выходит на поверхность около западного конца п-ова Аляска (юго-западная Аляска) и содержит 53 моллюсковых таксонов: 36 двустворчатых и 17 брюхоногих. Большое количество сочлененных замкнутых двустворчатых раковин (некоторые из которых даже находились в естественных при- жизненных положениях) предлагает, что на Тачильные отложения в значительной степени не влияло перемещение раковин после смерти. Предполагается, что эти моллюски обитали в прохладно- умеренной среде прибрежной части материкового шельфа (до 100 м глубиной). Многие из этих моллюсков известны в миоценовых фаунах Азии (Хоккайдо, Сахалин, Камчатка) и западной части Северной Америки (Калифорния, Орегон, Вашингтон). Некоторые из северо- американских таксонов указывают на то, что Тачильнан фауна находится в нижней части верхнего миоцена (в периоде Уйшкахан). Надежными аналогами Тачильной свиты являются Этолонская свита западная Қамчатка), средняя часть свиты Бэр Лэйк (по-в Аляска), нижние и средние слои свиты Якатага (восточная часть залива Аляска), и нижняя часть свиты Монтесано (типичное местона- хождение для моллюскового периода Уйшкахан; юго-западный Вашингтон). Другими возможными аналогами Тачильной свиты являются свиты Оккопезава и Тогешита (Хоккайдо) и Нутовская свита (Сахалин). Новые описанные в этом труде виды являются: Cyclocardia sakamotoi, Lyonsia mooreae. 60 BULLETIN 317 INTRODUCTION The Tachilni Formation is a marine sandstone unit that crops out at the western end of the Alaska Pen- insula in southwestern Alaska (Text-figs. 1, 2). The first published mention of fossils from beds now as- signed to the Tachilni Formation was by Grewingk (1850), who reported fossil mollusks from Morzhovoi Bay, immediately west of Cape Tachilni (Text-figs. 2, 3) and discussed and illustrated numerous Mesozoic and Cenozoic mollusks from the Alaska Peninsula and adjacent islands. Unfortunately, none of the Morzho- voi Bay fossils was illustrated. Girard (1843) had pre- viously described two Tertiary bivalves from Atka Is- land, Aleutian Islands, about 800 km (480 mi) southwest of Cape Tachilni, as well as other new mollusks from Kamchatka, U.S.S.R., but none from the Alaska Pen- insula. Eichwald (1871) mistakenly assigned to the Cretaceous Girard’s (1843) and Grewingk’s (1850) Ter- tiary mollusks from Atka, Unga, and Kodiak Islands (Text-figs. 1, 2), but noted no additional species from the Alaskan mainland. A summary of southern Alaskan Tertiary marine mollusks was presented by Dall and Harris (1892) and Dall (1896), who listed 46 molluscan taxa from the entire Gulf of Alaska region, including 24 taxa from the Alaska Peninsula, some from Unga and Kodiak Islands (Text-fig. 2). The authors in both works as- signed all mollusks to the ‘‘Astoria group” and cor- related them with Miocene strata at Astoria, Oregon. Most of the ‘‘Astoria group” mollusks listed from the Alaska Peninsula in Dall and Harris (1892) and Dall (1896) were collected by Dall and his associates during many summer field seasons. Collections made at Mor- zhovoi Bay came from the Tachilni Formation, and those made elsewhere on the Alaska Peninsula prob- ably came from the Bear Lake Formation. These early collections more than tripled the number of Alaska Peninsula Tertiary mollusks reported by Grewingk (1850) and allowed Dall to speculate on correlations with Tertiary faunas elsewhere in southern Alaska as well as in California, Oregon and British Columbia, Canada. Brief mention of Tertiary mollusks from the KAMCHATKA BERING SEA SAKHALIN - ATKA IS e^ Z KODIAK NA BRITISH === BITKINAR ТЄ амо (ў) coLumara ДЫ Joe EET ISLAND ALEUTIAN ISLANDS NORTH PACIFIC 0 1000 — ARCTIC OCEAN CHUKCHI SEA BEAUFORT SEA CANADA CAPE PENINSULA 24 УАКАТАСА GULF OF ALASKA N PUGET soon] 2000 3000 KILOMETERS SCALE Text-figure 1.—Мар of the North Pacific region, showing places mentioned in text. TACHILNI FORMATION MOLLUSKS: MARINCOVICH 61 western Alaska Peninsula was made by Dall (1904, 1908), though he did not cite species from the Cape Tachilni area. Very few geologic investigations were made on the Alaska Peninsula, especially at its remote western end, for more than half a century after Dall’s work (Wal- dron, 1961). The extraordinarily stormy climate, Mountainous terrain with rockbound coasts, and dif- ficulties of travel and logistics discouraged work in the area. Modern geologic reconnaissance studies of the Western Alaska Peninsula began with Kennedy, and Waldron (1955). Waldron (1961) named the Tachilni Formation and designated its type locality at Cape Tachilni (Text-fig. 3). Waldron’s field party collected fossil marine mollusks and echinoids at Cape Tachilni, but these were later “‘lost in transit," and the Tachilni F ormation was tentatively thought to be of ‘‘late Ter- Пагу” age in lieu of fossil evidence (Waldron, 1961, p. 687). MacNeil et al. (1961, p. 1802, 1804) considered the Tachilni Formation, which they referred to as "Beds west of Cold Bay (marine)," to be of early Pliocene age, “Базей on collections by Н. Н. Waldron (unpublished). "* In subsequent years fossils were collected from the Tachilni Formation at infrequent intervals, mostly by U.S. Geological Survey and petroleum company field parties. Tachilni strata unfortunately were not exam- ined by Burk (1965) during his monumental recon- naissance geologic study of the Alaska Peninsula. The first fossils named and illustrated from the type locality of the Tachilni Formation were two new mollusks de- scribed by MacNeil (1970). The use of helicopters in recent years has allowed extensive collecting of the Tachilni fauna, though no additional Tachilni mollusks have since been illustrated. The sand dollar echinoids from Cape Tachilni, including three new species, were 56° MORZHOVOI BAY LD BAY ~ со CAPE TACHILNI тї(?) DEER ISLAND Tbl ou 162° PACIFIC ss 160° BERING Ф Si Ma A х => OCEAN B 160° SEA 57° PORT HEIDEN BEAR LAKE Tbl бе is | - BLACK РЕАК тъ! ИЗ X m Y Тр! SCALE IN KILOMETERS Bear Lake Formation Tachilni Formation 55 S158" Text-figure 2.—Map showing outcrop extent of Tachilni and Bear Lake Formations on the Alaska Peninsula. 62 BULLETIN 317 described and illustrated by Wagner (1974). Allison (1978) recognized 19 mollusk taxa in the Tachilni strata, and Marincovich (in McLean, Englehardt, and How- ell, 1978) reported 31 mollusk taxa from the type-sec- tion and adjacent outcrops of the formation. Marin- covich (1981b) later increased the recognized molluscan fauna to 53 species. The present study is an expanded treatment of the fauna that I noted in my 1981b report. ACKNOWLEDGMENTS This study would not have been possible without the invaluable helicopter support provided to me in June 1977 by my colleague at the U.S. Geological Sur- vey in Menlo Park, CA, Hugh McLean. Most of the fossils reported on here were collected at that time. Some of McLean’s unpublished information on the physical stratigraphy of the Tachilni Formation, es- pecially regarding measured sections, is incorporated into this study. I would also like to thank Richard C. Allison, University of Alaska, College, AK, for the loan of fossils and discussions of taxonomic assign- ments during the early phase of this study. Barry Roth, California Academy of Sciences, San Francisco, CA, also provided thoughtful insight into the nomenclature of some taxa. Thanks are also due to Peter U. Rodda, California Academy of Sciences, for the loan of spec- imens, and to Kenji Sakamoto, U.S. Geological Sur- vey, Menlo Park, CA, for his fine photographic work that illustrates the Tachilni fauna. The following in- dividuals helpfully provided unpublished data and comments, which I have cited as oral or written com- munications in the text: John Barron, Kristin Mc- Dougall, and Hugh McLean, U.S. Geological Survey, Menlo Park, CA; Saburo Kanno, Joetsu University of Education, Niigata, Japan; Koichiro Masuda, Miyagi University of Education, Sendai, Japan; Hiroshi Noda, The University of Tsukuba, Ibaraki, Japan; Kenshiro Ogasawara, Tohoku University, Sendai, Japan, and, Judith Smith, Stanford University, Stanford, CA. I am also grateful for the perceptive reviews of this study by Barry Roth and by George L. Kennedy, U.S. Geo- logical Survey, Menlo Park, CA. Special thanks are due to Hiroshi Noda for translating my abstract into Japanese, and to Scott Samuel, Los Altos, CA, for translating it into Russian. PHYSICAL STRATIGRAPHY The Tachilni Formation crops out along the rugged southern coastline at the western end of the Alaska Peninsula, between False Pass and Thinpoint Cove (Text-figs. 2, 3). The formation was originally defined by Waldron (1961, p. 686) to include strata occurring along 8 km (5 mi) of coastline “гот the west end of Thinpoint Cove at least as far west as Cape Tachilni."' Waldron (1961) was unable to observe the detailed stratigraphy of these rocks or to map their inland ex- tent, due to the rugged terrain and hazardous landing conditions for the small boats he used. More recent mapping has shown that the formation crops out con- tinuously along the coast west of Cape Tachilni from Morzhovoi Bay to False Pass, and possibly on Deer Island east of Cape Tachilni (McLean, Englehardt, and Howell, 1978; McLean, 1979; Text-fig. 3). The Tachilni Formation consists mostly of dark brown to light greenish-gray, fine- to coarse-grained sandstone, and abundant similarly colored siltstone, with some pebble conglomerate and black shale (Wal- dron, 1961; McLean, 1979). The rocks are well bedded and range from semi-consolidated to well-indurated. The sediments are largely of marine origin, but pre- sumably nonmarine clastics containing carbonaceous fragments of plant megafossils occur at some outcrops (Waldron, 1961; McLean, 1979). The sandstone con- sists mainly of volcanic rock fragments, abrupt facies changes are common, many beds are lenticular, and channels are numerous (Waldron, 1961; McLean, 1979; H. McLean, written commun., 1982). Measurements of trough crossbeds at some Tachilni outcrops suggest bimodal current flow that resulted from tidally influ- enced environments (H. McLean, written commun., 1982). Tachilni sediments have been extensively in- truded by basaltic and silicic dikes, one of which has been radiometrically dated at about 2.1 m.y. (H. McLean, written commun., 1982). The thickness of the Tachilni Formation is not known, because its base is not exposed. Waldron (1961, p. 686—687) noted “ more than 200 feet" of strata near the type locality, and “а! least several hundred feet of material . . . exposed along the coast." McLean (1979) reported about 460 m (1,500 ft) of Tachilni strata, in composite section, exposed in coastal bluffs from False Pass to Thinpoint Cove, a straightline distance of about 45 km (28 mi) (Text-fig. 3). In a coastal bluff at the type locality of Cape Tachilni the formation is 75 m (250 ft) thick (Text-fig. 3; H. McLean, written com- mun., 1982). If strata on Deer Island are assigned to the Tachilni, as questionably mapped by McLean, En- glehardt, and Howell (1978) and McLean (1979), then the outcrop area of the formation extends an additional 19 km (12 mi) eastward. Tachilni strata have a low dip at most localities, usually less than 20°, and outcrops are discontinuous due to concealment beneath vege- Text-figure 3.—Maps showing location of Tachilni Formation fos- sil localities and measured sections. TACHILNI FORMATION MOLLUSKS: MARINCOVICH 63 A BERING SEA KA ; ALAS S MORZHOVOI BAY SOUTH WALRUS Tt PEAK N ES Ti у | Tt DEER ISLAND А ЛЕО САРЕ TACHILNI Tt(2)À ~M5 167 Tt —us 169 \ “м7256 4 M7204 Aat M7149 (Measured section) PACIFIC OCEAN 549 45'- N 0 10 к 1 SCALE IN KILOMETERS | Tachilni Formation M7150 Fossil Locality 162°30' NE А THINPOINT COVE South Walrus Pea measured section V 5, Uy Ed Ам o EA феи ЊЕ o9? às ws o o © © 54 57'4 M310 Cape Бре аА measured section N E a SEDES CAPE TACHILNI | M5166 CAS 60278 o 1 2 3 4 5 M5168 CAS 60279 INS БЕНО SCALE IN KILOMETERS " : 54°55'- М5163 Fossil Locality Contours in feet le 196855) 162/50 162945' 1 64 BULLETIN 317 tation and landslides, so no more than about 250 т (650 ft) of strata occur at a single outcrop. It is probable that Tachilni strata are disconformably underlain by tuffaceous volcaniclastic rocks of the Belkofski Formation, though a contact between the units has not been observed (H. McLean, written commun., 1982). Belkofski strata are at least 1,800 m (5,900 ft) thick and crop out over a wide area imme- diately to the northeast of Tachilni terrane (Waldron, 1961; Burk, 1965; McLean, Englehardt, and Howell, 1978; McLean, 1979). Abundant but poorly preserved plant megafossils have suggested a Paleogene age, in- cluding estimates as old as Paleocene, for most Bel- kofski rocks (Burk, 1965). However, a mixed assem- blage of deciduous and evergreen leaf fossils suggests an Oligocene age for one Belkofski outcrop on the northwestern shore of Belkofski Bay (McLean, 1979). In addition, an assemblage of four mollusk species, including Macoma (Macoma) optiva (Yokoyama, 1923), collected at a nearby outcrop suggests a Mio- cene age for part of the formation (Marincovich and McCoy, in press). 1 had previously inferred a probable Oligocene age for this assemblage (in McLean, 1979, p. 1522). It is probable that most of Miocene time passed between deposition of the youngest preserved Belkofski rocks and deposition of the Tachilni strata. The Tachilni Formation is unconformably overlain by Pliocene (?), Pleistocene and Holocene volcanic flows and breccias that cover extensive portions of the Alaska Peninsula in this area (Waldron, 1961; Burk, 1965; McLean, Englehardt, and Howell, 1978; Mc- Lean, 1979). In some places the Tachilni Formation forms the modern erosional surface. Waldron (1961, р. 687) noted that the formation ‘‘westward ... ap- pears to pass upward conformably into a basal se- quence of nonfossiliferous volcanic sedimentary rocks ..., but this gradational upper contact has not been observed by later workers. FAUNAL COMPOSITION There are 53 molluscan taxa in the Tachilni fauna: 36 bivalves (68%) and 17 gastropods (32%) [Table 1]. A similarly high ratio of bivalve to gastropod species is evident in many Tertiary mollusk faunas of the Gulf of Alaska region, based on unpublished data from U.S. Geological Survey collections. Kanno (1971, p. 13) documented the high percentages of bivalves in lower and middle Tertiary faunas of the Cape Yakataga area in the northeastern Gulf of Alaska (Text-fig. 1), in- cluding faunas of the Kulthieth (upper Paleocene and Eocene), Poul Creek (upper Eocene and Oligocene) and Yakataga (lower Miocene to Pleistocene) For- mations. Considered together, these three formations were found to have mollusk faunas of about two-thirds bivalves and one-third gastropods (Kanno, 1971), as does the Tachilni fauna. The only documented excep- tion to this general relationship is the late Oligocene or earliest Miocene fauna of the Narrow Cape For- mation on Sitkinak Island in the western Gulf of Alas- ka (Text-fig. 1). The mollusk fauna there is nearly equally divided among bivalves and gastropods, with 22 bivalves, 20 gastropods, one cephalopod, and one scaphopod (Allison and Marincovich, 1981). Surpris- ingly, for the modern northeastern Pacific mollusk fau- na, the proportion of bivalves to gastropods is the re- verse of that seen in most Alaskan Tertiary faunas. Schenck and Keen (1936, p. 937) studied the numbers and kinds of mollusks present within each five-degree increment of latitude from 25°N to 74°N in the eastern Pacific, and showed that for the interval of 55? to 59?N (the modern Gulf of Alaska) only 140 bivalve species were present compared to 343 gastropods and scaph- opods (scaphopods constitute a minor element and were not treated separately). Similarly high propor- tions of gastropods were observed in all other latitudes of this vast study area by Schenck and Keen (1936). Whatever the reason for the predominance of gastro- pod species in the modern northeastern Pacific, the apparent dominance of bivalves in Alaskan Tertiary faunas is equally enigmatic. A number of Alaskan Ter- tiary faunas with high percentages of bivalves have been intensively collected by trained paleontologists, so collecting bias probably is not a major factor. If there is a geologic, rather than biologic or environ- mental, reason for the different proportions of bivalves and gastropods in Tertiary and Holocene faunas of southern Alaska, it probably is related to fossil pres- ervation. Virtually all Tertiary strata in southern Alas- ka have been subjected to strong tectonic forces, and many also have been thermally altered by deep burial or by igneous or volcanic intrusion, or both. As a re- sult, many molluscan fossils seen in outcrop cannot be collected intact because they have been so exten- sively fractured or otherwise altered. Diagenetic pro- cesses may in some way be more destructive to gas- tropods than to bivalves. In any case, the relative proportion of bivalves to gastropods in the Tachilni fauna is similar to that among most other Alaskan Ter- tiary faunas. Twenty-eight of the 36 Tachilni bivalves (78%) are represented by at least one specimen with articulated, closed valves (Table 2). Lyonsia mooreae n. sp. and Mya (Mya) truncata Linnaeus, 1758 were also ob- served in life positions on the outcrop. These facts Тасни мі FORMATION MoLLusks: MARINCOVICH 65 Strongly imply that the Tachilni mollusk fauna lived at Its Site of deposition and contains few, if any, species introduced by post-mortem transport. The most common Tachilni species, those that oc- Cur in the greatest numbers and at several localities, are listed in Table 3. These species reflect the rela- tionship seen in the molluscan fauna as a whole (Table 1) in which the Cape Tachilni stratigraphic section Contains the greatest species diversity. Species that occur only in the Cape Tachilni section are listed in Table 4, and those that occur only in the South Walrus Peak section are listed in Table 5. These different as- semblages from the same formation reflect local en- vironmental differences that prevailed during deposi- tion, as well as a slight age difference between the two Stratigraphic sections. BIOSTRATIGRAPHY The measured stratigraphic sections with the most fossiliferous beds are those at Cape Tachilni and South Table 2.—Tachilni Formation bivalves found with articulated and closed valves. Asterisks (*) indicate taxa represented in collections by 50% or more articulated and closed specimens. Crosses (1) in- dicate species found in living positions (with long axis of articulated and closed shell oriented normal to bedding and posterior end di- rected upward). *Mya (Arenomya) elegans t*Mya (Mya) truncata *Mya new sp.? *Panomya izumo Panomya trapezoidis *Periploma (Periploma) cf. P. *Crenomytilus coalingensis (P.) aleutica *Cyclocardia cf. C. roundifor- *Peronidia aff. P. lutea alterni- mis dentata *Cyclocardia sakamotoi Protothaca (Protothaca) stal- Acila (Truncacila) empirensis Chlamys (Swiftopecten) cosi- bensis cosibensis Clinocardium hannibali Clinocardium meekianum new subsp.? *Cyclocardia sp. A *Felaniella parilis *Glycymeris grewingki t*Lyonsia mooreae *Macoma (Macoma) cf. M. (M.) astori eyi *Saxidomus sp. Siliqua cf. S. alta Spisula (Mactromeris) albaria Spisula (Mactromeris) brevi- rostrata *Macoma (Масота) орпуа Spisula (Mactromeris) polyny- Walrus Peak (Text-fig. 4). If the dips and strikes mea- Musculus (Musculus) niger ma Sured at Cape Tachilni by McLean, Englehardt, and *Yoldia (Cnesterium) scissura- ta Howell (1978) prevail throughout the intervening 4.5- km (2.7-mi) distance to South Walrus Peak, then the ase of the South Walrus Peak section would be about | km (3,280 ft) stratigraphically higher than the top of е measured section at Cape Tachilni. However, most 9f the terrain between these measured sections is cov- ‘red by vegetation, and the presence of faulting and folding within this covered interval is likely, consid- ering the tectonically active nature of this region. McLean (1979) reported only about 460 m (1,500 ft) of Tachilni Formation exposed throughout its outcrop area. Whatever the precise geometric relations be- tween the South Walrus Peak and Cape Tachilni strati- graphic sections, field relations suggest that the former section is stratigraphically higher than the latter one. Table 3.—The most common and abundant Tachilni mollusks. Occurrence in measured sections Only at Mostly at Equally in Only at South Cape Tachilni Cape Tachilni both sections Walrus Peak Bivalves Chlamys (Swiftopecten) cosibensis cosibensis sms E ease И коз: Clinocardium TEN А Ме ru er EN а Со CA cm BE MAI ИНИ с сс Boc. Clinocardium meekianum n. subsp. ы т ту о у ажене MEL ски Crenomytilus coalingensis ТО a hk Oe ei ee eae ce С у UOC M UR qp EEE UM Ut Glycymeris grewingki «sss Gus үкен ecu S E M AI LANE Масота (Масота) cf. M. (M.) astori sss tttm memet Sever v com RUE S ас диск ac sca o тј ж ат ae er ee тео жай аала Musculys (Musculus) niger sss МИ Е cun Ser ee ИНИ не rd B n Уа (Arenomya) elegans «ss: tte M M SE e IM EU DU p (Mya) ғипсаѓа "ssh IIIA Ihn uu acta ma ira АР DE аса ОСЕ и З.Р, lutea Ара пн аи (pee GO eerste t I namic ema Sane I ene TOP ове нА ат ERG еа аи Y a (Mactromeris) БО? ЙЛ: xu cues connessi пе euis EL с ан c hod Jue натовари e ваниле la (Cnesterium) SCISSUPGIQ ss tr eere rete eren rere re DTE cU c cu NP T EE EN ACE uS De ANTRO TUBE O p Gastropods Beringius IDI ек eae ra E MM UL cM C eae x ta ык! GS Sate се е ана айса (Cryptonatica) clausa sss: tttm — 9 | ahh D AE ES err ie E €Plunea (Neptunea) lyrata altispira tee eee e E LLL E M Le cuc LL E ертипеа (Neptunea) sp. D aff. №. (N.) modesta сс Se C Ms Na аи cM E осоне Polinj А Olinices (Euspira) pallidus 5s: mmm HO Pa E MEN E SM MEM TT А 66 BULLETIN 317 This relationship is also implied by the differences in faunal composition between the two stratigraphic sections. Table 5 lists the Tachilni species found only in the South Walrus Peak section, including Musculus (Musculus) niger (Gray, 1824), which has not previ- ously been recorded with certainty from Tertiary rocks, and Bulbus fragilis (Leach, 1819), known previously only in late Pliocene to Holocene faunas. Both species are absent from the Cape Tachilni section. Other South Walrus Peak species suggestive of a relatively young age include some whose oldest reliable occurrences are in late Miocene faunas, such as Clinocardium cf. C. ciliatum (Fabricius, 1780), C. hannibali (Keen, 1954), C. cf. C. pristinum (Keen, 1954), Panomya izu- mo Nomura and Hatai, 1939, Yoldia (Cnesterium) scissurata Dall, 1897, and Oenopota cf. O. candida (Yokoyama, 1926). The absence of all six of these rel- atively modern species at Cape Tachilni further sug- gests that the South Walrus Peak section is signifi- cantly higher stratigraphically than the Cape Tachilni section. Some of the mollusks found only at Cape Tachilni (Table 4) suggest that this section is older than that at South Walrus Peak. In contrast to several of the South Walrus Peak species whose oldest occurrences are in late Miocene faunas, Cape Tachilni species such as Macoma (Macoma) optiva (Yokoyama, 1923), Mol- opophorus bogachielii (Reagan, 1909), Neptunea (Go- likovia) plafkeri Kanno, 1971, and Polinices (Eu- spira) diabloensis (Clark, 1915) have their youngest reported occurrences in late Miocene faunas. So, al- though many of the mollusk species exclusive to the Cape Tachilini section do range into much younger strata, a significant group of species is best known from occurrences in middle Miocene or older faunas, and last appears in rocks of the Tachilni Formation and coeval strata elsewhere in the North Pacific. SOUTH WALRUS PEAK SECTION SECTION KENMORE HEAD SOUTH , Top of exposed Top of exposed rocks | Covered interval т wt gery ie Covered interval ne 20 — M7143 -M7140 M4044* M7139, M7202 M72 M7141 Covered intervals —М7 144 M7201* Volcanic dike ne umes interval Covered interval Fault with 3m displacement ,-M7149 М7200ж рита Two volcanic dikes lean Section continues overed by modern downward, was not beach deposits measured Covered by modern * Approximate fossil locality beach deposits —“^ CAPE TACHILNI SECTION rocks Text-figure 4.—Measured stratigraphic sections and fossil localities in the Tachilni Formation. See Appendix for descriptions of collecting localities. TACHILNI FORMATION MOLLUSKS: MARINCOVICH 67 The inferred chronostratigraphic separation be- tween the Cape Tachilni and South Walrus Peak sec- tions cannot yet be quantified. The discovery of open- ocean microfossils in these rocks, so far unsuccessful, ог a study of their paleomagnetic stratigraphy, not yet attempted, would be needed to learn the time differ- ss between deposition of the two stratigraphic sec- 1008. No well-defined biostratigraphic zonation has been established within any of the measured sections of the Tachilni Formation. In the lower part of the Cape Tachilni section (locs. M7142 and M7200; Text-fig. 4) there is only one species not found upsection, the late Miocene to Holocene bivalve Miodontiscus prolon- gatus (Carpenter, 1864b). In Ше middle part of the Section (locs. M4045, M7022, and M7141) only the late Miocene to Pliocene or Pleistocene bivalve Creno- mytilus coalingensis (Arnold, 1909) is found nowhere else at Cape Tachilni. Species found only in the upper Part of the section (locs. M7203 to M7140; see Table l) are: Acila (Truncacila) ermani (Girard, 1843) [stratigraphic range unknown], Pandora (Pandorella) Srandis Dall, 1877 [early Miocene (?) and Pliocene or Pleistocene to Holocene], Saxidomus sp., and Polini- Ces (Euspira) diabloensis (Clark, 1915) [middle (?) and late Miocene]. The known age-ranges of these taxa are SO broad that they are not useful for biostratigraphic ZOnation at Cape Tachilni. Taxa found only within a particular stratigraphic in- terval are more numerous in the South Walrus Peak Table 4.—Mollusks found only in the Cape Tachilni stratigraphic Section. Bivalves Acila (Truncacila) ermani Crenomytilus coalingensis Cyclocardia sakamotoi Cyclocardia sp. A Felaniella parilis yonsia mooreae Macoma (Масота) cf. М. (M.) astori Macoma (Macoma) optiva Miodontiscus prolongatus Mya new sp.? Pandora grandis Protothaca (Protothaca) staleyi Saxidomus Sp. Gastropods Calyptraea sp. Cancellaria? sp. Molopophorus cf. M. bogachielii Natica (Tectonatica) janthostoma Neptunea (Golikovia) plafkeri Oenopota sp. A Polinices (Euspira) diabloensis Table 5.—Mollusks found only in the South Walrus Peak strati- graphic section. Bivalves Clinocardium cf. C. ciliatum Clinocardium hannibali Clinocardium cf. C. pristinum Mizuhopecten mollerensis Musculus (Musculus) niger Panomya izumo Panomya trapezoidis Yoldia (Cnesterium) scissurata Gastropods Bulbus fragilis Fusitriton oregonensis Oenopota cf. O. candida section than at Cape Tachilni, though they still do not allow well-defined biostratigraphic zonation. Mollusks found only in the lowest part of the South Walrus Peak section (locs. M7145 and M7146; Text-fig. 4) are listed in Table 6. Taxa found only in the middle part of the South Walrus Peak section (loc. M7144) are Clinocardium sp. and Mizuhopecten mollerensis (MacNeil, 1967), and mollusks known only from the uppermost part of the section (loc. M7143) are Bulbus fragilis (Leach, 1819) and Polinices (Euspira) pallidus (Broderip and Sowerby, 1829). The large disparity in numbers of taxa known only from particular parts of this section is due Table 6.—Mollusks found in the South Walrus Peak stratigraphic section, but only at the stratigraphically lowest localities, USGS M7145 and M7146. Bivalves Chlamys (Swiftopecten) cosibensis cosibensis Clinocardium cf. C. ciliatum Clinocardium hannibali Clinocardium meekianum new subsp.? Clinocardium cf. C. pristinum Cyclocardia cf. C. roundiformis Glycymeris grewingki Macoma incongrua Musculus (Musculus) niger Mya (Arenomya) elegans Periploma (Periploma) cf. P. (P.) aleutica Peronidia aff. P. lutea alternidentata Siliqua cf. S. alta Spisula (Mactromeris) albaria Spisula (Mactromeris) brevirostrata Spisula (Mactromeris) polynyma Gastropods Beringius hertleini Buccinum cf. B. planeticum Fusitriton oregonensis Margarites (Pupillaria) new sp.? Natica (Cryptonatica) clausa Neptunea (Neptunea) sp. D aff. N. (N.) modesta 68 BULLETIN 317 partly to the richness of the lower fossiliferous beds and partly to the greater amount of time spent col- lecting from them. One species previously known only in late Pliocene to Holocene faunas, Bulbus fragilis, occurs only in the stratigraphically highest part of the South Walrus Peak section. However, species with no previous records as fossils, such as Buccinum cf. B. planeticum Dall, 1919, and Periploma cf. P. aleutica (Krause, 1885), occur at South Walrus Peak only in the stratigraph- ically lowest collecting localities (Table 6), rather than at the highest localities. With these two relatively youthful species are found taxa known only from Mio- cene faunas, such as Clinocardium cf. C. pristinum Keen, 1954, and Cyclocardia cf. C. roundiformis (П- yina, 1963). Thus, the stratigraphic occurrences of species in the South Walrus Peak section do not permit recognition of chronostratigraphic zones. The main hindrance to biostratigraphic zonation within individual Tachilni sections is the thinness of the exposed sections themselves. The section at Cape Tachilni is only 75 m (250 ft) thick, the South Walrus Peak measured section is about 120 m (394 ft) thick (Text-fig. 4), and most other Tachilni sections are thin- ner. In a region such as the Alaska Peninsula, char- acterized by high Tertiary sedimentation rates, these relatively thin rock sequences were probably depos- ited too quickly for the molluscan faunas to have undergone major evolutionary changes. The relative stratigraphic positions of less fossilif- erous Tachilni sections and outcrops, such as those southwest of Morzhovoi Bay (Text-fig. 3), are impos- sible to determine from available data. The most fos- siliferous of these localities is M7150, which yielded 20 molluscan taxa (Table 1) and is located 9.6 km (6.0 mi) southwest of the mouth of Morzhovoi Bay. Com- pared to the faunas of the two main sections, at Cape Tachilni and South Walrus Peak, the fauna at locality M7150 contains four species found only at Cape Ta- chilni [Macoma (Macoma) cf. M. (M.) astori Dall, 1909, M. (M.) optiva (Yokoyama, 1923), Molopopho- rus bogachielii (Reagan, 1909), and Natica (Tectona- tica) janthostoma Deshayes, 1839], four found at South Walrus Peak [Acila (Truncacila) cf. A. (T.) empirensis Howe, 1922, Clinocardium hannibali Keen, 1954, Mi- zuhopecten mollerensis (MacNeil, 1967), and Oeno- pota cf. O. candida (Yokoyama, 1926)], and 12 species found at both major sections. Thus, the fauna at lo- cality M7150 does not show a preferred correlation with either the section at Cape Tachilni or the some- what younger South Walrus Peak section. In addition, the fauna at locality M7150 contains both species whose youngest occurrences are in late Miocene faunas and species whose oldest occurrences are in late Miocene faunas, so there is no basis for inferring a relationship with older or younger parts of the Neogene. A similar situation prevails for other localities southwest of Morzhovoi Bay, including M7256 (with 11 taxa), M7149 (with eight taxa), and others contain- ing even fewer taxa (Table 1). Difficulties in correlat- ing these faunas with those at Cape Tachilni and South Walrus Peak are mainly due to diagenetic alteration of fossils southwest of Morzhovoi Bay. The common in- trusion of plutonic rocks in the latter area has not only destroyed much of the original fauna, but made the surviving specimens more difficult to identify. How- ever, all of the species found southwest of Morzhovoi Bay occur in the faunas at Cape Tachilni and South Walrus Peak, so they support the conclusion of McLean, Englehardt, and Howell (1978) and McLean (1979) that strata southwest of Morzhovoi Bay should be included in the Tachilni Formation. AGE AND CORRELATION The Tachilni molluscan fauna correlates well with late Miocene faunas of the North Pacific region, es- pecially with those assigned to the Wishkahan Stage of Oregon and Washington. Tachilni mollusks with re- liable records only in strata of late Miocene age are Clinocardium cf. C. pristinum (Keen, 1954) [from the San Pablo Group of northern California], Crenomyti- lus coalingensis (Arnold, 1909) [from central and southern California], and Polinices (Euspira) dia- bloensis (Clark, 1915) [from northern and central Cal- ifornia]. Other Tachilni mollusks have their first or last known occurrences in faunas of late Miocene age. Taxa known only in late Miocene or older rocks are Ma- coma (Macoma) optiva (Yokoyama, 1923) [from early to late Miocene faunas of Asia], and Cyclocardia cf. C. roundiformis (Ilyina, 1963) [from middle (?) to up- per Miocene strata of Asia]. In addition, the two large- shelled, few-ribbed Tachilni species of Cyclocardia, C. sakamotoi n. sp. and Cyclocardia sp. A, belong to a group of similar Asian species of Cyclocardia known only in upper Miocene strata. In contrast, the follow- ing taxa have their oldest known occurrences in late Miocene faunas: Miodontiscus prolongatus (Carpen- ter, 1864b) [from central California and Kamchatka], Musculus (Musculus) niger (Gray, 1824) [from eastern Kamchatka], and Oenopota cf. O. candida (Yokoya- ma, 1926) [from southern Sakhalin]. Taken together: the 11 taxa noted above comprise about 2196 of the Tachilni fauna. A possible early Pliocene age for all or part of the Tachilni Formation stratotype, as postulated by MacNeil et al. (1961), MacNeil (1970), and Wagner TACHILNI FORMATION MOLLuSks: MARINCOVICH 69 5 а Planktic Stages #1125 |югатипиег 3 dis zone Molluscan Benthic foraminiferal Pleistocene Нес” RRO 8 _ Pliocene и Moblipsifténmer OA. зид пай ы ----------< Delmontian > N17 Тау отапа asthe Глан eo 10} =] мв Wighkahen Mohnian Е N15 D 3 id Luisian = - Miocene |2| w Newportian Relizian wi an N8 S N7 Ма [^ 5 Saucesian 5 20 Е Pillarian e 4 = E = P22 А = E Juanian z 5 Zemorrian =. Sie ODOUR Euh. Logo se ЕС ы = Matlockian = m P18 5 up Galvinian Refugian 8 | -----------4 40} Zn >| ‘Tejon Narizian Eocene = Р10 8 “Transition” Ulatisian 50r 5 “Domengine’ Penutian = "Capay" Bulitian Text-figure 5.—Correlation of Pacific Northwest molluscan stages with foraminiferal stages [from Addicott (1981)]. (1974), is refuted by the presence of so many mollusks that suggest a late Miocene age, and by the lack of апу early Pliocene indicators. Tachilni strata are Somewhat older than thought by Allison (1977, 1978), Who referred the formation to the latest Miocene and Stated that the Miocene-Pliocene boundary might fall Somewhere within it. Marincovich (in McLean, En- Slehardt, and Howell, 1978) and McLean (1979) cited а late Miocene or Pliocene age for Tachilni mollusks, though after further study Marincovich (19815) in- erred an early late Miocene age for the fauna. Assignment of the Tachilni fauna to the Wishkahan olluscan Stage of Oregon and Washington (Text-fig. 15 suggested by several taxa. The Tachilni bivalves Clinocardium hannibali Keen, 1954 and Glycymeris 8rewingki Dall, 1909 are found in Oregon and Wash- 'Ngton only in Wishkahan faunas (Addicott, 1976a), and the bivalves Felaniella parilis (Conrad, 1848) and : acoma (Macoma) astori Dall, 1909 [the latter only entatively recognized in the Tachilni fauna] have their Stratigraphically highest occurrences іп Wishkahan Es of the same region (Addicott, 1976a). The latter О species are difficult to identify with certainty, so à ет use in making age inferences is limited. A large UMber of Tachilni mollusks have their earliest oc- currences in the Pacific Northwest in Wishkahan fau- nas, including: Acila (Truncacila) empirensis Howe, 1922, Protothaca (Protothaca) staleyi (Gabb, 1866), Yoldia (Cnesterium) scissurata Dall, 1897, and Mol- opophorus bogachielii (Reagan, 1909), and the genera Clinocardium Keen, 1936, Mizuhopecten Masuda, 1963 and Siliqua Megerle von Muehlfeld, 1811 (Addicott, 1976a). Based on their first, last, or exclusive appear- ance in Wishkahan faunas of the Pacific Northwest, the 11 Tachilni taxa cited above, making up about 2196 of the fauna, strongly suggest a Wishkahan age for Tachilni strata. Age assignments for the six Miocene and Pliocene molluscan stages proposed for Oregon and Washing- ton by Addicott (1976a) were based largely on the in- ferred chronostratigraphic ranges of numerous mol- lusks, with modest supporting evidence from benthic and planktonic foraminifers and radiometric dates. The Wishkahan Stage was considered to be of early late Miocene age. However, closely drawn ties between the molluscan faunas upon which the stages were based and radiometrically well-dated planktonic microfossils were not made. The Wishkahan Stage was interpreted differently by Allison (1977, 1978), who considered it to be of late middle Miocene to early late Miocene 70 BULLETIN 317 age. His conclusions were based on an attempted сог- relation between Pacific Northwest molluscan faunas, benthic foraminiferal stages of southern and central California, and the modern planktonic foraminiferal zones of Berggren and Van Couvering (1974). This interpretation was used for southern Alaskan faunas by McCoy and Marincovich (1980) and Marincovich (1980, 1981b). A recent restatement by Addicott (1981) of an exclusively early late Miocene age for the Wish- kahan is based on implied, but undocumented, ties with planktonic foraminifers (Text-fig. 5). To date, no systematic study of planktonic microfossil occur- rences in the Pacific Northwest molluscan stages has been attempted, and the relationship of the stages to sub-epoch boundaries is uncertain. Recent studies of diatom biostratigraphy in Pacific Northwest Miocene strata have created uncertainty about the age of the Wishkahan Stage and its relation- ship to the Graysian Stage. The type section of the Wishkahan Stage consists of the lowermost one-third, or 300 m (985 ft), of the Montesano Formation of Fow- ler (1965) exposed along the west fork of the Wishkah River, southwestern Washington (Addicott, 1976a, p. 105). The Graysian Stage stratotype is the conform- ably overlying two-thirds of the Montesano Formation exposed nearby along the middle fork of the Wishkah River, and was considered to be of late late Miocene age by Addicott (1976a). Armentrout (1981) has ten- tatively suggested that the Wishkahan and Graysian Stages are fully coeval and may include the latest mid- dle Miocene and earliest Pliocene as well as the late Miocene. His conclusions were based on diatom floras recovered from the type Graysian section in the upper Montesano Formation (Barron, 1981), and from strata of the Empire Formation at Coos Bay, Oregon (Barron and Armentrout, 1980), assigned to the Wishkahan by Addicott (1976a). These diatom studies suggest that the stratotype of the Graysian Stage is of early late Miocene age and that Empire Formation strata as- signed to the Wishkahan by Addicott (1976a) are of middle late Miocene age. Diatoms of the type Wish- kahan have not been studied, but the likelihood is that the Wishkahan and Graysian Stages may be at least in part coeval. The overlap, if any, of the two molluscan stages has not been determined. According to mega- and microfossil evidence sum- marized by Armentrout (1981), the base of the Wish- kahan Stage is questionably placed at about 12 m.y. old, or slightly older than the beginning of the late Miocene. The top of the Graysian Stage is placed by Armentrout (1981) at slightly less than 5 m.y. old, or virtually the same as the 5 m.y. age originally assigned to this boundary by Addicott (1976a). If the Wishka- han and Graysian are coeval, the top of the Wishkahan would also be at 5 m.y. or slightly younger. However, if Addicott’s (1976a) original estimate is correct, the top of the Wishkahan is about 7.5 m.y. old, as sug- gested more recently by Addicott (1981). In the pres- ent study of Tachilni mollusks, the Wishkahan is con- sidered to range from about 7.5 to 12 m.y. B.P. and to be of early late Miocene age. During the present study, Tachilni samples were barren of benthic fora- minifers (K. McDougall, oral commun., 1978), and lacked age-diagnostic diatoms (J. Barron, oral com- mun., 1982). The geographically closest strata correlative with the Tachilni Formation are those of the Bear Lake For- mation, which crops out on the distal half of the Alas- ka Peninsula, to the northeast of Cape Tachilni (Text- fig. 2). Based on unpublished studies of the Bear Lake Formation by U.S. Geological Survey and petroleum company paleontologists, its molluscan fauna is known to be at least as diverse as that of the Tachilni. Allison (1978, p. 175) noted that “А megainvertebrate fauna of about 40 species is known from the Bear Lake For- mation above the Unga Conglomerate and below the unconformably overlying strata." The fauna is now known to be much larger. As an example of the dis- parity between published and unpublished knowledge of the Bear Lake fauna, MacNeil (in Burk, 1965, р. 228) noted seven molluscan species from the Bear Lake stratotype, whereas I have collected about 25 species from the same beds. The biostratigraphy of the Bear Lake is poorly known because the inaccessibility of outcrops and extremely poor weather in the region have restricted collecting activities. Extensive faulting and coverage by tundra vegetation and late Cenozoic volcanic debris have also complicated study of the Bear Lake rocks. The Bear Lake molluscan fauna was de- scribed by Allison (1977, 1978) as ‘‘warm temperate,” but this may be untrue for the bulk of the fauna, which is similar in its inferred paleotemperature to the Ta- chilni fauna. Inferred warm temperate molluscan gen- era noted by Allison (1978, p. 175) possibly occur in one or more stratigraphically limited zones, and not generally throughout the Bear Lake sequence. The Ta- chilni Formation is correlative with the unnamed up- per member of the Bear Lake Formation, with which it shares at least the 23 taxa listed in Table 7. The faunal relationship between the Tachilni and the basal Unga Conglomerate Member of the Bear Lake Formation is much less certain, because fossils from the latter unit are very poorly known (MacNeil, 1973; Allison, 1978). Only two Tachilni mollusks, Chlamys (Swiftopecten) cosibensis cosibensis (Yokoyama, 191 1) and Mizuhopecten mollerensis (MacNeil, 1967), аге TACHILNI FORMATION MOLLUSKS: MARINCOVICH Т known to occur in collections from the Unga Con- glomerate. The latter unit was inferred to be of early Miocene age by MacNeil (1973) and of latest early Miocene to middle Miocene age by Allison (1977, 1978), 50 substantial faunal differences from the Tachilni molluscan fauna are expectable. In the vicinity of Black Peak, about 320 km (200 mi) Northeast of Cape Tachilni (Text-fig. 2), strata said to unconformably overlie the upper part of the Bear Lake Formation were correlated with the Tachilni Forma- Поп by Allison (1978, p. 175). Other workers had noted the presence of late Miocene mollusks in these beds (MacNeil et al ., 1961, annotation 3a) and had assigned them to the Bear Lake Formation (Burk, 1965; Det- terman, Yount, and Case, 1981) without recognizing a local unconformity. Allison (1978) gave no list of mol- lusks from the strata near Black Peak, and the 15 taxa reported from there by Marincovich (in Detterman, Yount, and Case, 1981) provide no firm basis for for- Mational assignment. Further study of the Bear Lake Molluscan fauna in the vicinity of Black Peak is under Way. Coarse volcaniclastic beds unconformably over- lying the Bear Lake Formation near its type locality, about 200 km (120 mi) northeast of Cape Tachilni, were thought to be of Pliocene age by Burk (1965, p. 94) and were referred to the Tachilni Formation by Allison (1978, p. 175). Meager field investigations in this area have so far produced no fossils that are unquestiona- ly from these volcaniclastic beds. These strata, which Table 7.—Tachilni mollusks also found in the unnamed upper Member of the Bear Lake Formation, Alaska Peninsula. Based on Specimens in U.S. Geological Survey collections. Bivalves Acila (Truncacila) empirensis Acila (Truncacila) ermani Chlamys (Swiftopecten) cosibensis cosibensis Clinocardium cf. C. ciliatum Clinocardium meekianum new subsp. Felaniella parilis Macoma (Macoma) cf. М. (M.) astori “coma incongrua Mizuhopecten mollerensis Mya (Arenomya) elegans Ya (Mya) truncata Peronidia aff. P. lutea alternidentata Siliqua Он, ана Spisula (Mactromeris) polynyma Yoldia (Cnesterium) scissurata Gastropods Buccinum cf. B. planeticum Margarites (Pupillaria) new sp.? Natica (Cryptonatica) clausa MRT На < : пса (Tectonatica) janthostoma N €ptune Q a (Neptunea) lyrata altispira ?) Neptunea (Golikovia) plafkeri Euspira) pallidus Polinices ( are about 1,525 m (5,000 ft) thick at their type locality and are largely of nonmarine origin, were named the Milky River Formation by Galloway (1974, p. 381, 384) and formally defined by Detterman, Yount, and Case (1981). A volcanic flow near the top of the Milky River Formation has been dated at 3 m.y. (Wilson in Det- terman, Yount, and Case, 1981). The Milky River For- mation may be younger than the Tachilni Formation, but learning its exact age and stratigraphic relationship to the latter unit will depend on future studies. A tenuous correlation between Tachilni strata and presumed upper Miocene beds on Atka Island, in the Aleutian Islands (Text-fig. 1), is based on the co-oc- currence of a single distinctive species, Acila (Trun- cacila) ermani (Girard, 1843). This species is reliably known only from its type locality in unnamed beds on Atka Island (Girard, 1843), from the Tachilni Forma- tion, and from the Bear Lake Formation near Bear Lake (Text-figs. 1, 2). The very limited occurrence of this species suggests a possible correlation between the beds on Atka Island and those on the Alaska Pen- insula. The Tertiary fauna on Atka Island has not been recollected since its original mention by Girard (1843). The Tachilni fauna is more confidently correlated with part of the Yakataga Formation near Cape Yaka- taga in the northeastern Gulf of Alaska (Text-fig. 1). The contact between the Yakataga Formation and un- derlying Poul Creek Formation is time-transgressive, ranging in age from about latest Oligocene or early Miocene to early middle Miocene (Ariey, 1978; Ad- dicott, Winkler, and Plafker, 1978; Allison, 1978), or from earliest early Miocene to late Miocene (McCoy and Marincovich, 1980). Wishkahan faunas have been recognized in numerous Yakataga Formation strati- Table 8.—Tachilni mollusks also found in presumed Wishkahan faunas of the Yakataga Formation. Asterisks (*) indicate taxa with first or last occurrences in Wishkahan faunas. Bivalves *Acila (Truncacila) empirensis Chlamys (Swiftopecten) cosibensis cosibensis Clinocardium ciliatum Felaniella parilis Macoma (Macoma) cf. M. (M.) astori Mya (Arenomya) elegans Mya (Mya) truncata *Saxidomus sp. *Siliqua cf. S. alta Spisula (Mactromeris) polynyma Gastropods Fusitriton oregonensis Natica (Cryptonatica) clausa *Neptunea (Neptunea) lyrata altispira *Neptunea (Golikovia) plafkeri Polinices (Euspira) pallidus аде first occurrence in this stage; 3 = taxon has last occurrence in this stage. BULLETIN 317 Occurrences of Tachilni mollusks in some Miocene strata of the northeastern Pacific. | = taxon is known only in this stage; 2 = taxon has |. PACIFIC NORTHWEST MOLLUSCAN STAGES > | < Е z се < CALIFORNIA о WISHKAHAN < UPPER MIOCENE = < STRATA m Са zZ. О — T ов ml 5 = | E = Е ac S 50 i © E ER = 23 & = = © 5 eo) 2 52 T Ill > = xs == Е Е ос 9 x^ ПРИ в er en а == = па д de к =, о E 5 2 = с во : mz ЕЕ = Бо е n UD реф Е „е Na laris Z. e г јео (үр rO fm Е Е xs * Ea Se wl Ones. S| Е- оча = B : nc um ссор 2 о а |ЕЕс c © Е ОБ e RI СЕ 54 os = | iE еее ае cuc mn ‚| = 521 а јез =) 53 Eos АКЕ њен Me = Cs S| 548 о ЕСЕ 9) о 22| Б |55855 | йо 585 à | SS] 2 Bivalves СИОН ЕРЕ ЕУ vewe време нек 2 2 2 X - ОСОО а Mee nts ЛУ ҮҮ А neo ~ 2 - — CORNOC OLOUN Пела ра Па Лә Е Е ОР — 1 - - Glirniocandium meekiamnumy sos | iim rev 9 - - — ChnocardliumspriStM unt. eg dete e Gore Pa ars 7 - — X Grenomp tilus CORMMBCTISIS., Fits sd v ice rats s tede - x -- РОО Л ДИЛ Пк бест оре жес жуу ус эы бу у” 2 5 ОРОТ ОТСТО, Л cone dep ere rr ner 1 | Macoma (Macoma) cf. M.(M.) astori .......... B - Macoma (Macoma) орпуа oudit ыйкы ы ылыш X - Miguiranautenm uet aos Vs educ Lr e an yen АЕ 2 5j - 17577 MERIT Oe RE Жү аыр жаш Ce АУ йы а 2 - КОКУ Полне А ote asm NLT и E ги скри раса Др А 2 2 - Provotnaca (РРОТОТНаСИ) SIQICW! оо. oerte er 3 - X ИО А TS. VOINEE APERIT ONSE са та 2 2 2 - SE ES НЕ VS ce PAEA MAC ИБН: X SymmiaeMacmromerisyulbulaw: 4e ea qat X — X Spisula (Mactronieris) brevirostrata ............ X X Уат (ОСУ ТЫ) SCTS SUT ILO осоо 2 Gastropods ЕСИНЕ а Кн анус ур ои Ива 2 ^ FIRNTHON УЫ, OE ce ree ima et x o aieo И 2 ПИО OF COONICIISTS. етике v dC Fran жок узж vele uum X Molopophorus cf. M. bogachielii .............. 2 2 2 5 Natica CLectonatica) JamtlostoTa: vues een vet ne P. 2 2 оа зе ава ка TN о аша аа 2 2 Polinices (EUspira) арене rc ew le уу... Х Х Polinices (Euspira) pallidus x graphic sections (Ariey, 1978; Addicott, Winkler, and Plafker, 1978), including the well-known section at Cape Yakataga (Text-fig. 1), where the first Wishka- han mollusks occur about 30 m (100 ft) above the base of the section (Ariey, 1978). The thickness of Wish- kahan-age strata in the Yakataga Formation is not known, due to the lack of detailed biostratigraphic studies, but thicknesses of 300 m (1,000 ft) or more are implied by some of the stratigraphic sections fig- ured by Addicott, Winkler, and Plafker (1978). Tachilni mollusks found in presumed Wishkahan faunas of the Yakataga Formation are listed in Table 8. Among these 15 taxa, five have their first or last known occurrences in Wishkahan faunas: Acila (Ттип- TACHILNI FORMATION MOLLUSKS: Table 10. MARINCOVICH Occurrences of Tachilni mollusks in some Asian Miocene strata. = WESTERN | КАМСНАТКА = Lm dee ре = d x ner s A ba: KURIL о № 2 ISLANDS 5 о © 0 A Ф < КАУКАК 2 GROUP is рак вер ова раван Е Е Salaun E ilt ee Е ш ш jg = Es ЕБ | * M NC ECOLE UC па MR RE nir MET E nmm “| шщ m x 2 > ~ < О | Bivalves Chlamys (Swiftopecten) cosibensis cosibensis ..... X X X X X — CUIU GIANT: США „улы хуа с На — - X X X GTOHO TUS ООСО = eee OL S MELOS UD X -- (Ој отне ено. КО дер кор ә et ТТА Е X — - — - етей ФИЙ Ws vecta o и X X - — СЕТЕ кин E NI ME X = : = — - -- Macom (Macoma (OLIN E ара M X X X X X X МОДОН GUS DOLIA CLES пада eU IEEE X - - MIE CMV PURO e ДИЛГЕ ЕС и ТЛ ЛУ Л ОГЛ x X X Јајој нео (о КУК OR РА ВАРА САБА - - X - — = Provothaca:(Protothaca) пева ot a E ee : X = Spisula (Mactromeris) brevirostrata ............. - x —- Spisula (Mactromeris) polynyma с. за күлүк б X X X Gastropods NüticaN с вуртотанса) слао ен аи EUREN x X + Natica (Tectonatica) janthostoma ............... X Neptunea (Меринеа) ната, sd ага стан и е ees - X es = X Oenopota cf. O. candida Саса) empirensis Howe, 1922, Saxidomus Conrad, 1837, Siliqua Megerle von Muehlfeld, 1811, Neptunea eptunea) lyrata altispira (Gabb, 1869), and Neptu- nea (Golikovia) plafkeri Kanno, 1971. With the ex- ception of М. (G.) plafkeri, these taxa help to tie the l'achilni fauna to the relatively poorly known Yakataga auna as well as to the much better known faunas of pegon and Washington. The number of species found | both the Tachilni and Yakataga Formations may Crease as the fauna of the latter unit becomes better Eu However, probably in number of taxa and cer- ашу as а percentage of their total fauna, Tachilni о ја will probably remain better represented in е Веаг Lake Formation than in the Yakataga For- mation, This is due not only to the greater geographic йү of the Bear Lake fauna to the Tachilni fau- L3 but also to the faunal provincialism that had de- Oped in southern Alaska by the late Miocene. Та- chilni and Bear Lake molluscan faunas during the Wishkahan existed in a warmer marine climate than did the coeval glaciomarine Yakataga fauna. Despite the great geographic distance between the Alaska Peninsula and the Pacific Northwest (Text-fig. 1), the two areas shared a similar marine climate dur- ing the late Miocene and had а number of molluscan taxa in common. The strongest Tachilni faunal ties are with the fauna of the type Wishkahan Stage in the lower part of the Montesano Formation of southwest- ern Washington, and with other Wishkahan faunas in Washington, Oregon, and British Columbia, Canada (Table 9). One of these listed Tachilni species, Cli- nocardium hannibali Keen, 1954, was known previ- ously only in Montesano Formation Wishkahan fau- nules. Most of the taxa listed in Table 9 have their earliest known occurrences in the Pacific Northwest in faunas of Wishkahan age, based on the observations 74 BULLETIN 317 of Addicott (1976a), which suggests that the Tachilni strata are not significantly older than the lower part of the Montesano Formation. The presence of several Tachilni species in Wish- kahan faunas of the Empire, Quillayute and Skonun Formations (Table 9) reinforces the inferred Wishka- han age of the Tachilni fauna and its correlation with the fauna in the lower part of the Montesano Forma- tion. The lesser number of Tachilni mollusks in the type Newportian fauna of the Astoria Formation, and in the type Graysian fauna of the middle and upper parts of the Montesano Formation, reinforces the Wishkahan age inferred for the Tachilni fauna. Among the few Tachilni species that occur as far south as California (Table 9), Clinocardium pristinum Keen, 1954 and Polinices (Euspira) diabloensis (Clark, 1915) are notable in that the former is known only in the Neroly Formation and the latter is an uncommon species previously known only in a few upper Miocene faunas of California, including those in the Neroly and Santa Margarita Formations. On the meager evidence provided by these two species, the Neroly Formation of northern California is tentatively considered to be correlative with the Tachilni Formation. More than one-third of the Tachilni molluscan taxa also occur in Asian Miocene faunas, as shown in Ta- bles 10 and 11. The closest faunal ties are with the Etolon Formation of the Kavran Group in western Kamchatka, which contains eleven Tachilni taxa. The Etolon molluscan fauna has been referred to the late middle Miocene in recent Russian works (Menner, Baranova, and Zhidkova, 1977; Gladenkov, 1977). However, Menner, Baranova, and Zhidkova (1977, ta- ble 1) show the Etolon to be about 7 to 12 m.y. old, which coincides closely with the age of the Wishkahan Stage, assigned to the early late Miocene by other workers (Addicott, 1977, 1981). The Etolon Formation is considered here to be of early late Miocene age, roughly coeval with the Tachilni Formation. Ilyina (1963, р. 15-16) recognized 109 species-level mollus- can taxa in the Etolon fauna. Her species lists indicate a more thermally diverse fauna than I have inferred for the smaller Tachilni fauna. The Etolon fauna con- tains taxa indicative of both cooler and warmer water than are present in the Tachilni fauna. As shown in Table 10, the Etolon Formation has more species in common with the Tachilni Formation than do the un- derlying Kakert Formation or the overlying Erman Formation of western Kamchatka. The Tachilni bivalve species Cyclocardia sakamotoi n. sp., though not known in Asia, suggests by its size and sculpture a tie with the Etolon fauna. Large, few- ribbed Tertiary species of Cyclocardia such as C. eta- lonnensis (Slodkewitsch, 1935) and C. kavranensis Table 11.—Tachilni mollusks found in Japanese Miocene faunas. Bivalves Chlamys (Swiftopecten) cosibensis cosibensis Clinocardium cf. C. ciliatum Macoma (Macoma) optiva Mizuhopecten sp. Mya (Mya) truncata Panomya izumo Spisula (Mactromeris) polynyma Gastropod Oenopota cf. O. candida (Slodkewitsch, 1935), have been reported previously only from the Etolon Formation (Slodkewitsch, 1935, 1938a, 1938b; Ilyina, 1963). One other bivalve, tenta- tively identified in the Tachilni fauna as Cyclocardia roundiformis (Ilyina, 1963), also has been reported previously only in the Etolon (Ilyina, 1963). Another species, Miodontiscus prolongatus (Carpenter, 1864b), has its oldest Asian record in the Etolon fauna. On the other hand, Protothaca (Protothaca) staleyi (Gabb, 1866) is reported from Russia only in the Erman For- mation (Gladenkov, 1977), which overlies the Etolon strata, consists largely of nonmarine deposits (Пуша, 1963), and is of about late late Miocene age. The Kakert Formation of western Kamchatka un- derlies the Etolon, is of about late middle Miocene age, and has seven species in common with the Tachil- ni strata (Table 10). The presence of so many Tachilni species in this middle Miocene Asian unit [compared to only three Tachilni taxa in the upper upper Miocene Erman Formation] suggests an affinity of the Tachilni fauna with older Miocene faunas, rather than with fau- nas of the latest Miocene. Correlation of the Tachilni fauna with other Asian Miocene faunas is difficult because few Tachilni species occur in Sakhalin, the Kuril Islands and Japan. AS seen in Table 10, three Tachilni species occur in the Maruyama Formation of southern Sakhalin, two are known in the Nutovo Formation of northern Sakhalin, and similarly small numbers of species occur in for- mations on the Kuril Islands. The only previous report of the common Tachilni bivalve species Musculus (Musculus) niger (Gray, 1824) in a Miocene fauna 15 that of Ilyina (1963) from the upper Miocene Konstan- tin Formation of eastern Kamchatka. These Asian fau- nas might be coeval with the Tachilni fauna, but fur- ther study of them would be required to determine this. Well-founded correlations with Japanese formations are prevented by the rarity of species in common with the Tachilni fauna. Tachilni mollusks known in Jap- TACHILNI FORMATION MoLLUSKS: MARINCOVICH TS anese Miocene faunas are listed in Table 11. Their Stratigraphic occurrences, cited under individual sys- tematic entries herein, are widely scattered and pro- vide no firm basis for correlating individual Japanese formations with the Tachilni strata. Many Miocene mollusks probably occur in both Hokkaido and Alaska, but direct comparative studies of species from these two areas have not yet been done. Species not listed in Tables 10 and 11, including Lyonsia mooreae n. sp., Mizuhopecten mollerensis (MacNeil, 1967), and Peronidia aff. P. lutea alterni- dentata (Broderip and Sowerby, 1829), are clearly of Asian affinities and suggest that detailed species com- Parisons between Asian and Alaskan faunas will yield refined faunal correlations. In general composition the Tachilni fauna is analo- 50и to the cold-water, sandy substrate fauna of the Upper Miocene Kurosawa Formation of northeastern Honshu (Hayasaka, 1957). As noted by Chinzei (1978, P. 162), the Kurosawa fauna contains a mixture of Nearshore (Shiobara-type) and offshore (Yama-type) Molluscan assemblages. The Shiobara-type and Yama- type faunas are named for characteristic Miocene mol- Uscan faunas that occur near Shiobara and Yama townsites in central and northern Honshu, respective- ly (Chinzei, 1978). The Tachilni fauna is somewhat Closer in inferred paleoenvironment to the Shiobara- type assemblage, because of its preponderance of Shallow water taxa. However, because of the high lat- Itudes at which they occur, the Tachilni deposits ex- Pectably lack some characteristic Shiobara-type gen- era such as Dosinia Scopoli, 1777 and Anadara Gray, 1847, which are replaced by cooler water taxa such as ya Linnaeus, 1758, Clinocardium Keen, 1936 and Others, The Tachilni fauna may correlate with the cold, Shallow-water faunas of the Togeshita Formation, Western Hokkaido (Marincovich, 1981b), and the Okkopezawa Formation, eastern Hokkaido. The To- 8eshita fauna is approximately of late Miocene age and Consists of nearshore species preserved in coarse sandy Matrix (Uozumi, 1962; Chinzei, 1978). The Okkope- zawa fauna is of latest middle or late Miocene age (К. Ogasawara, oral commun., 1981). According to H. 1 ода (oral commun., 1981) Ше Okkopezawa mollus- ә fauna has often been cited by authors as the “АЕ йе, fauna" in the mistaken belief that it comes from * stratigraphically higher Atsunai Formation. The achilni fauna is not known to have species in com- Thon with the Togeshita fauna or the better-known Okkopezawa fauna. However, according to the un- Published data of K. Ogasawara (Tohoku University, endai, Japan), the Okkopezawa fauna contains the Ollowing genera that also occur in the Tachilni fauna: Cyclocardia Conrad, 1867, Felaniella Dall, 1899, Gly- cymeris Da Costa, 1778, Macoma Leach in Ross, 1819, Mizuhopecten Masuda, 1963, Panomya Gray, 1857, Spisula Gray, 1837, Yoldia Moeller, 1842, and Natica (Tectonatica) Sacco, 1890. The similarity in paleoen- vironments implied by the shared genera of these for- mations, and their similar inferred ages, suggests fur- ther study to determine if they have any species in common. PALEOECOLOGY Tachilni mollusks are inferred to have lived in a cool- temperate inner shelf habitat (Allison, 1978; Marin- covich, 19815). My use of the term *'cool-temperate"' is in the sense of Hall (1964), who states that there are fewer than four months per year when shallow-water temperatures are warmer than 10°C (50°F) at the northern limit of this marine climatic zone. In the northeastern Pacific, the cool-temperate zone includes latitudes 48°N to 56°N (Puget Sound to the Gulf of Alaska), and in the northwestern Pacific it ranges from latitudes 41°N to 43°N (northernmost Honshu and eastern Hokkaido) (Hall, 1964). The modern represen- tatives of Tachilni species useful for paleoclimatic in- ferences are listed in Text-figure 6, where their geo- graphic ranges in the northeastern Pacific are depicted. The presence of these species clearly suggests a cool- temperate marine climate during Tachilni deposition. Species in Text-figure 6 with entirely cold-water mod- ern habitats, such as Periploma (Periploma) aleutica (Krause, 1885) and Siliqua alta (Broderip and Sow- erby, 1829), reinforce the inference of a cool-water habitat for the Tachilni fauna. This inference is sup- ported by the presence in the Tachilni of the extinct taxa Neptunea (Neptunea) lyrata altispira Gabb, 1869 and Neptunea (Golikovia) plafkeri Kanno, 1971, whose earliest appearance in Alaska is in mid-Miocene gla- ciomarine deposits of the Yakataga Formation in the northeastern Gulf of Alaska (Kanno, 1971; Nelson, 1974). Additional cool-water indicators are Natica (Tectonatica) janthostoma Deshayes, 1839, which now lives mainly in the cool-temperate to cold waters from Hokkaido to Kamchatka, and the northern genus Ber- ingius Dall, 1886, which in the northeastern Pacific ranges from British Columbia, Canada, to the Arctic Ocean (Dall, 1921, p. 90). Cool-water taxa occur throughout the formation and there is no evidence of marine climatic changes during Tachilni deposition. The only southern extralimital species in the Tachil- ni fauna are Polinices (Euspira) diabloensis (Clark, 1915), known previously only from upper Miocene strata of northern and central California, and Cren- omytilus coalingensis (Arnold, 1909), from upper Mio- 76 BULLETIN 317 | CALIFOR- MOLLUSCAN PROVINCES ARCTIC ALEUTIAN OREGONIAN ee AND MARINE CLIMATES (COLD) (COOL- M TEMPER – -T TEMPERATE) (MUD TEMPERATE? ATE) SPECIES 70°N 60° N 50°N 40° N 30°N | | | NET BIVALVES Clinocardium ciliatum Miodontiscus prolongatus Musculus (Musculus) niger Mya (Arenomya) elegans Mya (Mya) truncata Pandora (Pandorella) grandis Panomya trapezoidis Periploma (Periploma) aleutica Siliqua alta Spisula (Mactromeris) polynyma Yoldia (Cnesterium) scissurata GASTROPODS Buccinum planeticum Bulbus fragilis Fusitriton oregonensis Natica (Cryptonatica) clausa Polinices (Euspira) pallidus Text-figure 6.— Modern latitudinal ranges of northeastern Pacific mollusks in the Tachilni fauna. Provincial boundaries from Hall (1964). Dashed lines indicate uncertain or sporadic occurrences. cene to Pleistocene faunas of central and southern California. Considering the convincing evidence for a cool-temperate Tachilni fauna, the presence of so few southern extralimital species is not surprising. Twenty-one Tachilni genera and species, or their closely related modern analogues, are useful for pa- leobathymetric inferences (Text-fig. 7). Based on their modern depth records, the narrowest range of depths needed to account for the presence of these 21 taxa at a given site is the interval from 20 to 40 m depth. However, because not all taxa are present at each col- lecting locality, depths from Ше low tide line to 50 m are more realistic inferences for individual Tachilni localities. There is no evidence for change in water depth during deposition of the formation. Carbonized plant debris, assumed to be of terrestrial origin, occurs throughout the Tachilni section. It is present to some degree at every outcrop, and is locally abundant. The abundance of plant material implies that a shoreline, and possibly a coastal river or stream, was near the Tachilni depositional site. A shallow-water regime is also implied at some outcrops by measure- ments of trough crossbeds resulting from bimodal cur- rent flow on a tidally-influenced inner-shelf bottom (H. McLean, written commun., 1982). More than three-quarters of the Tachilni bivalve taxa (28 of 36 species-level taxa) were represented by а! least one intact individual [having closed, articulated valves (Table 2)]. Many taxa are represented mostly or entirely by articulated, closed individuals, such а5 Glycymeris grewingki Dall, 1909, Macoma (Macoma) орпуа (Yokoyama, 1923), Lyonsia mooreae n. Sp» Mya (Arenomya) elegans (Eichwald, 1871), Mya (Mya) truncata Linnaeus, 1758, Periploma (Periploma) СЕ. Р. (P.) aleutica (Krause, 1885), and Peronidia aff. Р. lutea alternidentata (Broderip and Sowerby, 1829). In addition, specimens of Lyonsia mooreae and Myd (Mya) truncata were observed in living positions at outcrops, and a group of four specimens of the former species in apparent living positions has been preserved intact. This evidence from the bivalves strongly sug- gests that the Tachilni mollusk fauna was preserved entirely or largely in situ, and that faunal composition was not significantly affected by post-mortem trans- port by currents or wave action. TACHILNI FORMATION MOLLUSKS: MARINCOVICH 77 SYSTEMATIC PALEONTOLOGY INTRODUCTION The taxonomy and systematics used in this study are purposely conservative. This has been done be- Cause knowledge of Alaskan Tertiary molluscan fau- nas, and attempts at correlation around the North Pa- cific margin, are in their infancy. Innovative taxonomy Would likely impair our developing understanding of broad scale biogeographic trends and obscure possible faunal correlations within this extensive region. Iden- tification of Alaskan Tertiary mollusks involves bring- ing together three disparate literatures: the American, the Japanese, and the Russian. Any attempt to unify these philosophically divergent literatures requires Caution, especially when dealing with species-level taxa. The lack of comparative collections in America from Japanese and Russian faunas is a major hin- drance to making the detailed morphologic compari- Sons that are essential for identifying synonyms and Understanding the true stratigraphic and geographic ranges of taxa. My greater familiarity with the Amer- ican literature may have biased me in favor of using American taxonomy for species for which the use of Japanese or Russian names will later prove to be more TAXA DEPTH, IN METERS 0 50 100 200 300 ћ L 1 1 1 BIVALVES Clinocardium ciliatum Mytilus, 5.1. re *Felaniella sericata 5 Lyonsia teramachii Miodontiscus prolongatus | ———— Musculus niger Mya, 5.1. Pandora, s.l. Panomya Periploma, s.l. Protothaca, 565; Saxidomus Siliqua alta Spisula polynyma Yoldia scissurata GASTROPODS Buccinum planeticum Bulbus fragilis Calyptraea Margarites, s.l. Natica clausa р, 9linices pallidus T | i Я B ous 7.—Modern bathymetric ranges in the northeastern E of some Tachilni mollusks or their living analogues. Aster- ^55 Indicate analogous species. useful. However, I think that the conservative philos- ophy employed here will make it easier in later studies to deal with, and possibly to modify, the species-level taxonomy for Tachilni mollusks. A basic assumption I make is that Alaskan Tertiary molluscan faunas con- tain greater numbers of species from Asia and from the mid-latitude northeastern Pacific (especially Ore- gon and Washington) than have been recognized pre- viously. Future descriptive studies such as the present one will demonstrate the degree to which this is true. Large collections of fossils inevitably contain many specimens too poorly preserved for confident identi- fication to the species- or genus-level. Several of these indeterminate taxa in the Tachilni fauna are listed in Table 1. However, they are not specifically mentioned in the text, because they appear only to be imperfect remains of Tachilni species already discussed, not the remains of species new to this fauna. The species synonymies given here are relatively short, and mostly contain only references providing original descriptions, significant discussions, or illus- trations of each species. In the species synonymies and in Table 1 my usage of "cf.," “ай.” and '"?" refers in all cases to species-level taxonomy, not to generic allocations. INSTITUTIONAL ABBREVIATIONS ANSP—Academy of Natural Sciences, Philadelphia, Pennsylvania BM(NH)—British Museum (Natural History), Lon- don, England CAS—California Academy of Sciences, San Francis- co, California GS—Institute of Geology and Paleontology, Faculty of Science, Tohoku University, Sendai, Japan GT—Geological Institute, Faculty of Science, Tokyo University, Tokyo, Japan LSL—Linnaean Society of London, London, England SMF—Senckenberg Museum, Frankfurt am Main, West Germany SU—Stanford University, Stanford, California SUPTC—Stanford University Paleontological Type Collection [now housed at CAS, see above] TUE—Tokyo University of Education, Institute of Geology and Mineralogy, Tokyo, Japan UA—University of Alaska, Fairbanks, Alaska UCMP—University of California at Berkeley, Mu- seum of Paleontology, Berkeley, California USFC—U.S. Fisheries Commission, Washington, D.C. USGS—U.S. Geological Survey, Menlo Park, Cali- fornia 78 BULLETIN 317 USNM—National Museum of Natural History, Smith- sonian Institution, Washington, D.C. UZM—University Zoological Museum, Copenhagen, Denmark ZIL—Zoological Institute, Leningrad, U.S.S.R. ZMH—Zoologisches Museum, Humboldt Universi- taet, Berlin, Germany FORMAT Taxonomic categories above the species level gen- erally are not discussed here, except in the few cases where subgeneric assignments require comment. Be- cause Alaskan Tertiary mollusks are so poorly known, the discussion for each Tachilni species notes the main morphologic characters and includes comparisons, some extensive, with similar species. Where measure- ments of mollusks are given they follow the standard usage of Cox (1960) for gastropods and Cox (1969) for bivalves. Extensive literature citations of the strati- graphic and geographic ranges of species are given in order to relate the Tachilni fauna as fully as possible to other North Pacific faunas. Phylum MOLLUSCA Class BIVALVIA Linnaeus, 1758 Family NUCULIDAE Gray, 1824 Genus ACILA H. and A. Adams, 1858 Subgenus TRUNCACILA Schenck in Grant and Gale, 1931 Acila (Truncacila) empirensis Howe, 1922 Plate 12, figures 1—4 Acila empirensis Howe, 1922, p. 96, pl. 9, figs. 4, 5, 8; Addicott, 19703» p 11T pl: 5; tie. б. - Acila (Truncacila) empirensis Howe. Schenck, 1936, р. 85-86, pl. 9, figs. 3, 4, 6-10, 12; Weaver, 1942, pt. 1, p. 30-31, pl. 6, figs. 6, 7, 16; Addicott, Winkler, and Plafker, 1978, map sheet 2 [as а Discussion.—This species is among the largest of the species of Truncacila, as shown by the two largest Tachilni specimens at 27.7 mm and 26.3 mm long, and 22.0 mm and 22.1 mm high, respectively. Schenck (1936, p. 86) listed his largest examined specimen at 25.9 mm long and 19.2 mm high. Acila (Truncacila) empirensis is also distinguished by its relatively high degree of inflation and its fine and weakly impressed radial sculpture. In common with closely related species of Truncacila, it has a band of obsolete radial ribbing along its ventral margin. The axis of bifurca- tion of the radial ribs is more inclined than in many other species of Truncacila, and secondary bifurcation of the ribs develops at an early stage. As noted by Schenck (1936, p. 86), this species is most similar to A. (T.) conradi (Meek, 1864), from which it was said to differ by having a ventral area of obsolete radial ribbing, larger size, and greater degree of inflation. The presence of obsolete radial ribbing along the ven- tral margin does not help to separate A. (T.) empiren- sis from A. (T.) conradi, however, because some of Schenck's (1936) illustrations of A. (T.) conradi (е.2., pl. 8, figs. 12 and 14) clearly show obsolete radial rib- bing along the ventral margins of some specimens. Acila (Truncacila) empirensis does seem to be larger than A. (T.) conradi, as Schenck (1936, p. 83) gives a maximum size of 21.7 mm long and 16.5 mm high for the latter species. The degree of inflation of the valves is similar for the two species, based on Schenck's (1936) illustrations and specimens on hand. The radial sculp- ture of A. (T.) conradi is relatively coarser than in A. (T.) empirensis and stands in bolder relief. The pos- terior termination of A. (T.) empirensis is distinctly angulate, whereas it is rounded in A. (T.) conradi; the escutcheon of the former species is clearly pouted or centrally raised, but is much reduced or lacking in А. (T.) conradi. The first report of A. (T.) empirensis in Alaska was by Schenck (1936, p. 85), who question- ably identified it in the Yakataga district of the north- eastern Gulf of Alaska, in rocks now assigned to the Yakataga Formation of Miocene to Pleistocene age. MacNeil in Miller (1957) noted that ‘‘some specimens resemble A. empirensis Howe” in collections presum- ably from the Yakataga Formation. Addicott, Winkler, and Plafker (1978) also listed Acila (Truncacila) cf. А. (T.) empirensis from presumed Wishkahan faunas of the Yakataga Formation in the northeastern Gulf of Alaska. Thus, specimens from the Tachilni Formation are only the fourth reported occurrence, and the first verified report, of this species in Alaska. In Oregon and Washington, A. (Т.) empirensis has its highest stratigraphic occurrence in the Moclipsian Stage (Ad- dicott, 1976a, p. 111). The species has not subsequent- ly been found in Newportian faunas, so its known stratigraphic range is Wishkahan through Moclipsian and helps to establish a lower age limit for the Tachilni fauna. Type information.—Holotype: UCMP 30032. Type locality: Coos Bay, southwestern Oregon; Coos Con- glomerate Member of the Empire Formation; upper Miocene. Tachilni Formation occurrence.—USGS localities M309 (1 valve, as ‘‘cf.’’), M7146 (1 valve, as “сЕ.”), M7150 (1 articulated, closed specimen, as ‘‘cf.’’); UA locality A-169 (abundant valves); CAS locality 60278 (3 articulated, closed specimens). Figured specimens.—UA 2467, 2468. Stratigraphic and geographic range.—Known only TACHILNI FORMATION MOLLUSKS: MARINCOVICH 79 ш Miocene and Pliocene faunas of Alaska and the Ра- cific Northwest. Lower upper Miocene (Wishkahan): Coos Conglomerate Member of Empire Formation, Southwestern Oregon (Howe, 1922); Quillayute For- mation, western Olympic Peninsula, northwestern Washington (Weaver, 1942). Upper Miocene: Monte- sano Formation at Taholah, Aberdeen, and 1.5 mi north of Cape Elizabeth, western Washington (Schenck, 1936). Upper (?) Miocene: Yakataga Formation, Yak- ataga district (Schenck, 1936, as ‘‘questionably iden- Шеф”; MacNeil in Miller, 1957, as a possible identi- fication), Malaspina district (MacNeil in Miller, 1957, a5 à possible identification), and Lituya district (Ad- dicott, Winkler, and Plafker, 1978, as ‘‘cf.”’). Acila (Truncacila) ermani (Girard, 1843) Plate 12, figures 5-7 Nucula ermani Girard, 1843, p. 545—546, figs. 8a, b; Grewingk, 1850, P. 154, 280—281, pl. 5, figs. la, b [not figs. 4a, b, as stated]. Nucula (Acila) ermani Girard. Dall, 1896, p. 844; Dall, 1898, p. 572-573; Dall, 1899, p. 546; Grant and Gale, 1931, p. 117 [as "ermanni"]. Acila (Truncacila) ermani (Girard). Schenck, 1935, p. 1, 2; Schenck, 1936, p. 95-96, text-fig. 7(11). Discussion.—This species is unique among Tertiary Species of Truncacila in having radial sculpture so fine and weakly impressed that it is nearly invisible. Other distinguishing characters are its large size (the largest Tachilni valve is 35.8 mm long and 28.0 mm high) and broadly rounded anterior and posterior extremities. The Tachilni specimens have a band of obsolete radial rib- bing that is 5 mm wide at the midpoint of the ventral Margin, though this feature is not shown in the drawing of the type specimen (Girard, 1843; Grewingk, 1850). Acila (Truncacila) ermani is among the rarest of Alas- kan Tertiary mollusks. The only previously published lllustration of it is the drawing of the type specimen її Girard (1843), which was reproduced by Grewingk (1850). Schenck (1936) provided only an outline draw- Ше of the shell, derived from the figures of Grewingk (1850), and apparently lacked specimens to examine. he Principal morphologic features noted above clear- Y distinguish this species from others of Truncacila. he best-preserved Tachilni specimen is a left valve that 15 missing its anterior dorsal margin and the ex- terior surface on its early portion. Except for a ventral band of obsolete sculpture, all of the preserved shell Surface is covered with extremely weak radial costel- lae. The radial sculpture is weakest across the central Portion of the valve and strongest along the posterior rsal margin. Very fine concentric growth lines and Somewhat coarser corrugations are well preserved and €monstrate that the weak radial sculpture is original and not produced by abrasion or weathering. The in- terior ventral margin is smooth except for very fine, short crenulations at its anterior end. Girard (1843) described A. (Т.) ermani from a single place, Atka Island in the Aleutian Islands (Text-fig. 1), but did not cite a precise locality. Grewingk (1850, p. 154) noted an occurrence of the species in sandstone at ‘‘Sand Bay" (‘‘Sandbucht’’), which he placed along the north side of Korovin Bay, an embayment on the north-west side of Atka Island. An unnamed, shallow, sandy-bot- tomed lagoon is present on the north side of Korovin Bay, and a USGS field party explored this area in 1979 to locate the strata bearing A. (T.) ermani. Despite Girard's (1843, p. 546) description of the fossil-bearing stratum as a “соагве volcanic tuff, and Grewingk's (1850, р. 154) directions to a ‘‘30-foot-high bed of loose sandstone and hard claystone with fossils" at Sand Bay," no fossils were found. There is a long-aban- doned Russian townsite of Korovinski at the mouth of "Бапа Вау,’ however, so nineteenth century fur seal- ers or explorers could have collected fossils from this area. Additional Alaskan occurrences of A. (T.) ermani were reported in the Pribilof Islands, on St. Paul Island (Dall, 1896) and St. George Island (Dall, 1899). Al- though Schenck (1936) mentioned these localities he was unable to locate the specimens upon which Dall based his reports, and further stated that the where- abouts of the holotype was unknown. Besides the Tachilni shells, other specimens from the Alaska Pen- insula are on hand from USGS localities M3588 and M5173. Both localities are in the Miocene Bear Lake Formation. The exact location of M3588 is unknown and M5173 is near Bear Lake (Text-fig. 2), but speci- mens from both collections are in identical matrix, so they may represent nearby sites. The larger collection, from M3588, contains about 25 specimens that show the weak radial sculpture that becomes obsolete ven- trally, the large size, and the broadly rounded extrem- ities of the Tachilni specimen. At USGS locality M3588 most specimens of A. (T.) ermani are articulated and closed and occur with the intertidal bivalve Septifer sp., which suggests that the nuculid lived in extremely shallow water there. Type information.—Holotype: location unknown (Schenck, 1936). Type locality: “in a hard volcanic tuff," Atka Island, Aleutian Islands, Alaska (Girard, 1843); formation and age unknown. Tachilni Formation occurrence.—USGS localities M309 (1 valve, as ‘‘cf.’’), M7140 (3 valves); CAS lo- calities 60279 (1articulated specimen), 60280 (1 valve). Figured specimen.—USNM 265854. Stratigraphic and geographic range.—Known only 80 BULLETIN 317 in presumed Miocene strata of Alaska. Probable mid- dle or upper Miocene: unnamed upper member of Bear Lake Formation, Alaska Peninsula (USGS coll.). Mio- cene (?): unnamed formation, Atka Island, Aleutian Islands (Girard, 1843; type loc.); unnamed formations on St. Paul and St. George Islands, Pribilof Islands (Dall, 1896, 1899). Family NUCULANIDAE H. and A. Adams, 1858 Genus YOLDIA Moeller, 1842 Subgenus CNESTERIUM Dall, 1898 Yoldia (Cnesterium) scissurata Dall, 1897 Plate 12, figures 8, 9 Yoldia scissurata Dall, 1897, p. 8 [new name for Yoldia arctica Broderip and Sowerby, 1829, not Gray, 1824]. Cnesterium scissurata (Dall). Addicott, 1976a, p. 108, 113, pl. 4, fig. 3, pl. 5; fig. 26. Discussion.—This species is characterized by a large shell with a broadly rounded but slightly produced an- terior end, and a strongly attenuated and upturned posterior end. The beaks are closer to the posterior end and the anterior dorsal margin is elevated and smoothly rounded. A low, bladelike projection along the posterior dorsal margin is partially preserved in one specimen (Pl. 12, fig. 9). The oblique concentric sculpture is developed best on the posterior portion of the shell and obsolete or absent on the anterior por- tion. Tachilni individuals are larger than those noted in modern populations. The three most complete Tachil- ni specimens have lengths of 52.4, 45.3 and 43.4 mm, whereas a ‘‘maximum length to 40 mm"' was noted for modern specimens from the western Beaufort Sea (Bernard, 1979a, p. 21). This species is similar in outline and sculpture to several other North Pacific species of Cnesterium, no- tably Y. (C.) ensifera Dall, 1897, Y. (C.) seminuda Dally 1871 Y. (Cx) smigata ай, 1909, and Y. (65 kuluntunensis Slodkewitsch, 1936. Some workers have considered Y. (C.) scissurata and Y. (C.) ensifera to be synonymous (Grant and Gale, 1931, p. 131; Kanno, 1971; p. 3»; Bernard, 1979a, p. 21), but MacGinitie (1959, p. 154—155) and Roth (1979, p. 214) cited con- chological characters for separating the two. Mac- Ginitie (1959) noted that Y. (C.) scissurata is higher anteriorly and has a relatively longer anterior end and shorter posterior end (measured from the umbo) than Y. (C.) ensifera. She also observed that the posterior dorsal blades are longer and higher and the posterior rostrum more upturned in Y. (C.) ensifera. Roth (1979) further noted that Y. (C.) ensifera is equilateral and strongly compressed, whereas Y. (C.) scissurata is more inflated and has its beaks posterior to the mid- line, and that the oblique, grooved sculpture of the latter species tends to be coarser. Based on Holocene collections at the California Academy of Sciences, Roth (1979) gave the range of Y. (C.) scissurata as Point Barrow to Kodiak Island, Alaska, and the range of Y. (C.) ensifera as British Columbia to southern Califor- nia, with an intervening gap of about 1,500 km (900 mi). Yoldia (Cnesterium) strigata Dall, 1909, described from the Wishkahan Empire Formation at Coos Bay. Oregon, has been considered a subspecies of Y. (C.) scissurata by some workers (Grant and Gale, 1931, p. 131; Weaver, 1942, p. 51) and a junior synonym of it by others (Bernard, 1979a, p. 21). The oblique con- centric sculpture that is obsolete or absent from the anterior portions of Tachilni individuals and USGS Bering Sea Holocene specimens here assigned to Y. (C.) scissurata, is evidently well developed on the an- terior of Y. (C.) strigata (Dall, 1909; Weaver, 1942; Roth, 1979). Anterior oblique concentric sculpture is well developed on Beaufort Sea specimens assigned to Y. (C.) scissurata by Bernard (19792), so criteria for recognizing species in this species-complex evi- dently are not well-defined. As a further complication, Y. (C.) seminuda, known in Pliocene(?) or Pleistocene to Holocene faunas of the northeastern Pacific (Dall, 1871; Roth, 1979), is characterized by an anterior end that commonly lacks concentric sculpture, and is oth- erwise very similar in outline to Y. (C.) scissurata. A taxonomic review of this species-complex may result in Y. (C.) seminuda being recognized as the earliest proposed name for a highly variable species. The most closely related Asian Tertiary species ap- pears to be Y. (C.) kuluntunensis Slodkewitsch, 1936. reported in middle to upper Miocene strata of the Ka- kert, Etolon, Erman(?) and coeval formations of West Kamchatka, Sakhalin, and Karaginsky Island (Slod- kewitsch, 1936, 1938a, 1938b; Gladenkov, 1972, 1977). Published illustrations of Y. (C.) kuluntunensis do not allow detailed comparisons with Y. (C.) scissurata, but the former species appears to differ from the latter mainly by having well-developed oblique concentric sculpture over its entire shell surface. Most related Asian Tertiary species of Cnesterium are treated in works by Khomenko (1931, 1937), Uozumi (1957), and Gladenkov (1972). Roth (1979, p. 213) gave a modern depth range of 13 to 92 m for Y. (C.) scissurata. Type information.—Holotype: presumably in BM(NH). Type locality: unknown. Tachilni Formation occurrence.—USQGS localities M7144 (1 valve), M7146 (abundant valves), M7150 (abundant articulated specimens), M7256 (2 valves): UA locality A-301 (1 articulated specimen, 1 valve). TACHILNI FORMATION MOLLUSKS: MARINCOVICH 81 Figured specimens.—USNM 265855; UA 2469. Stratigraphic and geographic range.—Because of widespread confusion between Y. (C.) scissurata and Similar species, published occurrences of this species are impossible to evaluate. A modern northern range limit at about Point Barrow, northwestern Alaska, is generally agreed upon, but cited southern limits vary from Kodiak Island, Alaska (Roth, 1979), to the Gulf of California, Mexico (Parker, 1964, p. 157). The ear- liest geologic occurrence is equally uncertain. Addi- Cott (1976a, p. 110) stated that Y. (C.) scissurata first appeared in the Pacific Northwest in Graysian faunas. Family GLYCYMERIDIDAE Newton, 1922 Genus GLYCYMERIS Da Costa, 1778 Glycymeris grewingki Dall, 1909 Plate 12, figures 10-17 Pectunculus kaschewarowi Grewingk, 1850, p. 51, 94, 98, 190, 279— 280, pl. 5, figs. 3a-3d [nomen dubium]. Glycymeris grewingki Dall, 1909, p. 107, pl. 2, fig. 13. Glycymeris gabbi Dall, 1909, p. 108, pl. 11, fig. 5. ?Glycymeris conradi Dall, 1909, p. 107—108, pl. 11, fig. 2 [not Axi- naea conradi Whitfield, 1885; renamed Glycymeris larvata Han- na, 1924]. ?Glycymeris coalingensis Arnold, 1909, p. 80-82, pl. 19, fig. 3. Discussion.—This is a characteristic Tachilni bi- Valve that occurs abundantly at some outcrops. The Valves are commonly about 40 mm long, may be equi- dimensional, but are usually slightly longer than high. The lower two-thirds of the valve margin forms a 8mooth, nearly circular curve. The umbo is prominent and placed very slightly to distinctly nearer to the pos- terior extremity. The principal radial sculpture con- Sists of 30 to 35 low, rounded costae separated by much narrower interspaces. The radial costae of most, but not all, specimens gradually become obsolete to- ward the posterior extremity, and some specimens also have obsolete radial ribbing along the ventral margin. adial costae are absent along the dorsal margins. Extremely fine, closely-spaced radial costellae are Present across the whole exterior of each valve and become obsolete only along the dorsal margins. Con- centric sculpture consists only of incremental growth lines which, when very fine, form a minute reticulate Pattern where they intersect the radial costellae. The earliest name for this species may be G. ka- SChewarowi (Grewingk, 1850), but the original descrip- Поп given by Grewingk does not closely match his four illustrations, so the identity of his species remains a question, Glycymeris kaschewarowi was described as ауе 50 radial costae, but Grewingk’s illustrations (1850, ы. 5, figs. 3a, d) show two valves with count- able radial ribs and these have 29 and 24 ribs, respec- tively. In addition, he states that each valve has 28 hinge teeth, but shows 29 teeth on one valve (fig. 3c) and 31 teeth on another (fig. 3b). Tachilni specimens of Glycymeris are not preserved well enough for com- plete tooth-counts. Grewingk’s stated measurements of length 47 mm, height 45 mm are similar to those of the largest Tachilni specimens. The circular outline and elevated umbo of G. kaschewarowi are similar to those of several North Pacific species of Glycymeris. Grewingk (1850) cited G. kaschewarowi occurring on the Alaska Peninsula at Pavlof Volcano and Pavlof Settlement (now abandoned), both on the west side of Pavlof Bay (Text-fig. 2) and about 80 km northeast of Cape Tachilni, as well as on St. Paul Island in the Pribilof Islands, Bering Sea, and on Unga and Kodiak Islands, western Gulf of Alaska (Text-figs. 1, 2). It is likely that Grewingk’s type specimens are lost, be- cause Kafanov (1980, p. 305) states that the holotype of an Alaskan Tertiary species of Cardium described by Grewingk (1850) and presumed to be in Leningrad is lost. In view of Grewingk’s (1850) confusing original citation of G. kaschewarowi, and the availability of other names for Tachilni specimens of Glycymeris, his species name is considered here to be a nomen du- bium. Glycymeris grewingki and G. gabbi Dall, 1909, were described in the same publication and first synony- mized by Arnold and Hannibal (1913) under the former name, though not all later workers have maintained that usage. A third species of Glycymeris named by Dall (1909) in the same publication, G. conradi, is also probably a synonym of G. grewingki. All three of Dall’s (1909) species have their type localities in the Empire Formation at Coos Bay, Oregon. Recent collections made from these beds suggest the presence of only one species of Glycymeris in the Empire Formation (Roth, oral commun., 1979). Glycymeris coalingensis Arnold, 1909, of central and southern California, has been considered a synonym of G. grewingki by several workers (Howe, 1922; Grant and Gale, 1931; Woodring, Stewart, and Richards, 1940; Hertlein and Grant, 1972). If this is accepted then G. grewingki is not restricted to faunas of Wish- kahan age as stated by Addicott (1976a, as “С. gab- bi^") for Pacific Northwest faunas, but ranges into both older and younger rocks, as noted by Roth (1979, p. 236). The Asiatic species most similar to G. grewingki is G. yessoensis (Sowerby, 1889), a taxon reported in Neogene strata from northern Honshu and Hokkaido to Sakhalin and western Kamchatka. The two species are similar in shape and sculpture, though G. yes- soensis may have a greater average size; 42 specimens 82 BULLETIN 317 of G. yessoensis from the Pliocene Omma Formation measured by Ogasawara (1977, p. 94) showed some individuals reaching about 50 mm in length and height, which is larger than any Tachilni specimen. Ogasa- wara’s (1977) study also demonstrated that his speci- mens had a consistently greater length than height throughout ontogeny; in contrast most specimens of G. grewingki are virtually equidimensional. Based on published illustrations of G. grewingki and G. yes- soensis, these species may be separable by the number of crenulations along the interior ventral shell margin. It appears that G. grewingki has about 20 to 22 cren- ulations and G. yessoensis about 26 to 29. Tachilni specimens of G. grewingki have 20 to 21 crenulations. Illustrations of “С. coalingensis" given by Slod- kewitsch (1938b, p. 104, pl. 9, figs. 4, 5, 5a) seem identical to the Tachilni species. Slodkewitsch (1938a, 1938b) cites this species as ‘‘uncommon’’ in the “‘low- er horizon of the Kavran" Group in western Kam- chatka, strata now referred to the Kakert Formation of the Kavran Group and assigned a middle Miocene age (Menner, Baranova, and Zhidkova, 1977; Gla- denkov, 1980). The same author reports G. yessoensis in strata now assigned to the overlying Etolon For- mation of the Kavran Group in western Kamchatka (Slodkewitsch, 1938b, p. 104), but not in older rocks. Glycymeris grewingki occurs throughout Tachilni strata and is locally abundant. About half of all spec- imens are articulated and have their valves closed or slightly agape. The genus is common in the North Pa- cific today and is reported from the intertidal zone to 365 m depth in the northeastern Pacific (Keen and Coan, 1974). Type information.—Holotype: USNM 107784. Type locality: Coos Bay, southwestern Oregon; Empire Formation; upper Miocene. Tachilni Formation occurrence.—USGS localities M309 (2 valves), M5163 (13 articulated, closed speci- mens, 6 valves), M7139 (1 articulated, closed speci- men, | valve), M7142 (2 articulated, closed specimens, | valve), M7146 (2 articulated, closed specimens, 5 valves), M7201 (2 articulated specimens, | valve); UA locality A-170 (2 articulated, closed specimens, 4 frag- ments); CAS locality 60280 (3 valves). Figured specimens.—USNM 339752, 339753; UA 2470, 2471, 2472. Stratigraphic and geographic range.—The occur- rence of this species is uncertain, due to questions of synonymy with other species. The species is consid- ered to be restricted in the Pacific Northwest to Wish- kahan strata (Addicott, 1976a), including the Empire Formation at Coos Bay (Dall, 1909; Howe, 1922), and at Cape Blanco (Roth, 1979, p. 236), Oregon, and the Skonun Formation, British Columbia, Canada (Addi- cott, 1978). If G. coalingensis is a synonym, then oc- currences include the middle Miocene Oursan For- mation near Pleasanton, Alameda County, northern California (Hall, 1958), the Jacalitos Formation (of for- mer usage) and the lower part of the Etchegoin For- mation of central California (Woodring, Stewart, and Richards, 1940; Adegoke, 1969; Stanton and Dodd, 1976), and the Pliocene San Diego Formation near San Diego, southern California (Hertlein and Grant, 1972). Family MYTILIDAE Rafinesque, 1815 Genus CRENOMYTILUS Soot-Ryen, 1955 Crenomytilus coalingensis (Arnold, 1909) Plate 13, figure 1 Mytilus (Mytiloconcha) coalingensis Arnold, 1909, p. 73—75, pl. 195 fig. 5, pl. 22, fig. 6; Arnold and Anderson, 1910, p. 108, 125, pl. 41, fig. 5, pl. 44, fig. 6; Grant and Gale, 1931, p. 246. Mytilus coalingensis Arnold. Woodring, Stewart, and Richards, 1940, p. 90, pl. 32, figs. 3, 4. Crenomytilus coalingensis (Arnold). Soot-Ryen, 1955, p. 23. Mytilus (Crenomytilus) coalingensis sternbergi Hertlein and Grant, 1972, p. 163-164, pl. 41, figs. 10, 14. Discussion.—This robust mytilid is characterized by its large size, straight to slightly concave ventral mar- gin, shell that is greatly thickened in the apical region, moderately coarse concentric sculpture, and fine, faint radial striae. It is the largest known Alaskan Tertiary mytilid. Apexes of the Tachilni specimens are not well pre- served, so it is not known if they are ''elongate falcate and longitudinally grooved and ridged as Arnold (1909, p. 73) noted for the type specimens from the Kettleman Hills of southern California. Proportions of the existing Tachilni shells do suggest, however, that the apexes were elongate. In all other details of mor- phology as well as size Tachilni specimens are iden- tical to Kettleman Hills specimens of C. coalingensis figured by Arnold (1909) and Woodring, Stewart, and Richards (1940). Variation in shell outline of C. coalingensis is well illustrated by two specimens described by Woodring, Stewart, and Richards (1940, pl. 32, figs. 3, 4) from one locality in the type area. The two adult shells differ strongly in length, as well as in sinuosity of the ventral margins, inflation of the dorsal margin, falcation of the apexes, inflation of the valves, and coarseness of the concentric growth lines. These differences are greater than among any of the Tachilni specimens. Creno- mytilus coalingensis sternbergi Hertlein and Grant, 1972, described from the Pliocene San Diego Forma- tion of southern California, was said to differ from typical C. coalingensis by having valves that are less TACHILNI FORMATION MOLLUSKS: MARINCOVICH 83 convex. This variant is present in populations of C. coalingensis from the Kettleman Hills, however, so the distinctive character of the San Diego subspecies 15 lost. The fine crenulations of the interior margin, espe- cially the anterior ventral margin, that characterize Crenomytilus (Soot-Ryen, 1955, p. 23) are not visible on Tachilni specimens, of which no interiors are well- preserved. The extremely fine and closely spaced ra- dial striae of C. coalingensis are clearly present on better-preserved portions of the worn Tachilni shells. At least ten Miocene mytilids have been described from California (Keen and Bentson, 1944, p. 71-72). Some of these are probably synonymous with C. coa- lingensis, especially considering the broad morpholog- 1с range of that species. Among the likely synonymous Species are Mytilus perrini Clark, 1915, and M. tram- Pasensis Clark, 1915, from upper Miocene strata of the San Pablo Group in northern California, and pos- sibly M. kewi Nomland, 1916, from the upper Miocene Etchegoin Formation of the Kettleman Hills, southern California. Crenomytilus coalingensis has not been re- Ported from the Pacific Northwest, where its closest relative is Mytilus ficus Dall, 1909, described from the Wishkahan Empire Formation at Coos Bay, south- Western Oregon. Krishtofovich (1964, p. 189, pl. 45, fig. 3, pl. 46, figs. 1, la) cites "Mytilus (Mytiloconcha) aff. coalingensis" from Miocene strata on Sakhalin, but her illustrated specimens are too worn for identi- fication. Gladenkov (1977) noted C. coalingensis re- stricted to the Erman “Нопгоп” of the easternmost U.S.S.R. The Russian mytilid most similar to C. coa- lingensis appears to be Mytilus kamtschaticus Slod- Kewitsch, 1938a (p. 114-115, pl. 46, figs. 4, 4a, pl. 47, fig. 1), reported from the Miocene Kavran Group along the Vayampol River of western Kamchatka and in the Vicinity of Popupianya Bay, eastern Kamchatka. The USsian species evidently differs most from С. coalin- Sensis by lacking radial sculpture, though the two Species resemble each other in gross morphology. Zhidkova (1972, p. 116, pl. 38, fig. 1, pl. 39, figs. 1—4) Ilustrated Crenomytilus cf. C. grayanus (Dunker, 1853) ин the “РПосепе” Рагизћауа Formation of Iturup Sland, Kuril Islands, and some of the poorly pre- Served illustrated specimens could represent C. coa- "gensis. There appear to be no Japanese records of - Coalingensis. In the modern northeastern Pacific, species of My- tilus Linnaeus, 1758 live attached to hard substrates from the intertidal zone to 40 m depth (Keen and Coan, 1974), Crenomytilus grayanus (Dunker, 1853), the type Species of Crenomytilus, is the only modern species assigned to Crenomytilus by Soot-Ryen (1955). It lives in northern Japanese waters, where it has been col- lected in depths from the intertidal zone to 168 m (No- mura and Hatai, 1936). Type information.—Holotype: USNM 165551. Paratype: USNM 165557. Type locality: “А north- west of Anticline Ridge, 6 mi north-northeast of Coa- linga, SW. 4 sec. 34, T. 19 S., R. 15 E. Lowest Etch- egoin bed or Glycymeris zone," Fresno County, southern California (Arnold, 1909, p. 33); Etchegoin Formation; upper Miocene. Tachilni Formation occurrence.—USGS localities M4045 (4 articulated, closed specimens, 3 valves), M7142 (fragments of 3 specimens), M7200 (1 articu- lated, closed specimen); UA locality A-169 (2 articu- lated, closed specimens). Figured specimen.—USNM 339754. Stratigraphic and geographic range.—There are ex- tensive records of this species in upper Miocene strata of central and southern California, with fewer reports in Pliocene or Pleistocene rocks. Upper Miocene: Etchegoin and San Joaquin Formations, Coalinga re- gion, central California (Arnold, 1909; Arnold and An- derson, 1910; Woodring, Stewart, and Richards, 1940; Adegoke, 1969); Castaic Formation, Los Angeles County, southern California (Stanton, 1966); Pancho Rico Formation, Salinas Valley, central California (Durham and Addicott, 1965). Presumed upper Mio- cene of San Pablo Group, Contra Costa County, northern California (Clark, 1915). Upper Miocene or (?)lower Pliocene: Towsley Formation, Los Angeles County, southern California (Kern, 1973). (?)Pliocene: Niguel Formation, Orange County, southern Califor- nia (Vedder, 1961). (?)Pliocene or Pleistocene: Fer- nando Formation, Orange County, southern California (Zinsmeister, 1970); Merced Formation, northern Cal- ifornia (Martin, 1916); San Diego Formation of San Diego County, southern California, and northwestern Baja California, Mexico (Hertlein and Grant, 1972). Genus MUSCULUS Roeding, 1798 Musculus (Musculus) niger (Gray, 1824) Plate 13, figures 2, 3 Modiola nigra Gray, 1824, p. 244. not Modiolaria nigra (Gray). Khomenko, 1931, р. 58—59, pl. 10, fig. 1 [=M. kryshtofovitschi Krishtofovich (ex Simonova MS), 1964]; Slodkewitsch, 1938b, pl. 54, figs. 10-12 [=M. kryshtofovitschi]. Modiolaria nigra (Gray). Slodkewitsch, 1938b, p. 119, pl. 54, fig. 9. Musculus niger (Gray). MacGinitie, 195, p. 157—158, pl. 18, fig. 6, pl. 21, fig. 6. Musculus nigra (Gray). Ilyina, 1963, p. 118, pl. 51, fig. 10. Musculus (Musculus) niger (Gray). Bernard, 1979a, p. 27—28, fig. 87: Discussion.—Ihis is the first report of this distinc- tive species of Musculus in Tertiary rocks of Alaska. Musculus niger is the largest member of the genus (Bernard, 1979a, p. 28) and is further characterized by its relatively elongate proportions, sculpture of nu- merous, fine radial threads on its posterior portion, a smooth central part of the valve, and fewer and more widely spaced anterior radial ribs. The strength of the anterior radial ribs evidently varies, because the an- terior ribs of Tachilni specimens are much weaker than on modern Beaufort Sea specimens discussed by Ber- nard (1979a, p. 28), but similar in strength to those of modern Beaufort, Chukchi and Bering Sea specimens in USGS collections. Bernard (1979a, p. 27) cites a maximum shell length of 45 mm for Beaufort Sea Ho- locene specimens, but several Tachilni specimens ex- ceed 60 mm in length, and one modern USGS speci- men from Peard Bay, northwest Alaska is 71 mm long. Dall (1921, р. 23—24) lists 11 species of Musculus that occur in Alaskan waters, but the true number of Alaskan species is smaller. Bernard (1979a, p. 27) lists three species and subspecies as synonyms of M. niger. The large size, elongate proportions, and fine, clearly expressed posterior radial sculpture of M. niger dis- tinguish it from other species of Musculus. No other species of Musculus is reported in Alaskan Tertiary faunas. Musculus niger has been reported in eastern Kam- chatka, in unnamed Miocene (?) beds along the Great Chazhma River (Slodkewitsch, 1938b, p. 119), and in the upper Miocene (?) Konstantinovsk beds of the Valaginsk Range (Ilyina, 1963, p. 118). Khomenko (1931, p. 108) has also reported this species in the Miocene and Pliocene ‘‘Supranutovo Group” [=upper part of Nutovo Formation, fide Krishtofovich (1964)] along the Great Garomai River of eastern Sakhalin. Krishtofovich (1964, p. 196-197) subsequently named Musculus kryshtofovitschi Krishtofovich (ex Simo- nova MS),* 1964, and allocated to it Khomenko's (1931) and Slodkewitsch's (1938b) records of M. niger from Sakhalin and Kamchatka. Illustrated specimens of M. kryshtofovitschi clearly differ from M. niger by having a relatively higher shell, an obliquely truncated ante- rior end, and posterior radial threads of varied width. However, Ilyina’s (1963) record of M. niger from the upper Miocene (?) Konstantinovsk beds of eastern Kamchatka appears to be valid, based on her illus- trated specimen. Пута (1963, p. 118) notes that she had earlier described *'Modiolaria osipovskiensis Il- yina," and implies that it is a junior synonym of M. * Krishtofovich (1964, p. 196) attributed authorship of Modiolaria kryshtofovitschi to A. Simonova, who wrote an unpublished manu- script in 1939. Because Simonova's manuscript evidently was never published, authorship of the species belongs to Krishtofovich (1964), who was the first to name and describe the species in print. BULLETIN 317 niger, but she gives no further reference to the name. Musculus niger is a circumboreal species that lives in the Pacific as far south as southern California and the Sea of Japan, and is found from the low intertidal zone to 60 m depth (Bernard, 1979a, p. 28). АП Ta- chilni specimens are disarticulated, which may have been caused by this species frequently having its an- terior end only buried in substrate, as seen in modern populations (Bernard, 1979a, p. 28). Type information.—Holotype: in BM(NH), number unknown. Type locality: Orsund Bay, Sweden (Old- royd, 1924). Tachilni Formation occurrence.—USGS localities M310 (1 valve), M7146 (abundant valves), M7258 (1 articulated specimen, 2 valves). Figured specimens.—USNM 339755, 339756. Stratigraphic and geographic range.—This species is reported in upper Miocene to Holocene faunas. Up- per Miocene (?) Konstantinovsk beds, Valaginsk Range, eastern Kamchatka (Ilyina, 1963). A report of this species in Miocene beds on Unga Island, western Gulf of Alaska (Dall, 1896, p. 844) is probably in error. There are numerous records from Pleistocene deposits of circumarctic regions, including the Gubik Forma- tion of northern Alaska (USGS collections). This species is cited as a modern panarctic and circumbo- real one by Bernard (19793), living in the Pacific as far south as the Sea of Japan and Santa Barbara, southern California. Bernard (1979a, p. 28) gives northeastern Pacific occurrences from the low intertidal zone to 60 m depth, cites Beaufort Sea records of 27—64 m and notes that other workers have reported finds as deep as 376 m. Family PECTINIDAE Rafinesque, 1815 Genus CHLAMYS Roeding, 1798 Subgenus SWIFTOPECTEN Hertlein, 1935 Chlamys (Swiftopecten) cosibensis cosibensis (Yokoyama, 1911) Plate 13, figures 4—9, Plate 14, figures 1,2 Pecten cosibensis Yokoyama, 1911, p. 4, pl. 1, figs. 3, 4. Pecten turpiculus Yokoyama, 1925, p. 18, pl. 2, fig. 4. Pecten heteroglyptus Yokoyama, 1926, p. 304, pl. 33, figs. 1—5, 8. Chlamys cosibensis (Yokoyama). Masuda, 1959, p. 122-125, pl. 13, figs. 1-9; Masuda, 1973, p. 110—113, pl. 8, figs. 1—15, pl. 9, figs: 1-14. Chlamys cosibensis cosibensis (Yokoyama). Masuda, 1962, p. 162- 163. Chlamys (Swiftopecten) donmilleri MacNeil, 1967, p. 12, pl. 3, figs: 1, 4, 6. Chlamys (Swiftopecten) leohertleini MacNeil, 1970, p. 70, figs. 1-3. Discussion.—Tachilni specimens of Chlamys (Swiftopecten) cosibensis cosibensis display a char- TAcHILNI FORMATION MOLLUSKS: MARINCOVICH 85 acteristically broad range of sculptural variation. All Specimens have well-developed radial and concentric Sculpture, although the expression of these differs greatly between left and right valves. The primary ra- dial costae of the left valve are much narrower than the interspaces, whereas the opposite is true of the right valve. Both valves have densely crowded sec- Ondary and tertiary radial costae of varying strength. Concentric sculpture of the left valve consists of broad folds sharply raised into nodes where they intersect Primary radial costae. On the right valve, concentric Sculpture is made up of broad steps or constrictions. The complexities of sculptural variation and the taxo- nomic history for this species have been detailed by Masuda (1959, 1962, 1972, 1973). Many Tachilni in- dividuals are larger than the largest Japanese specimen noted by Masuda (1959, p. 124) as 74.2 mm high and 70.4 mm long. The largest Tachilni specimen, from USGS locality M7139, has slightly broken margins but Still is 109 mm high and 93 mm long. The first report of C. (S.) cosibensis, s.l., in Alaska Was by MacNeil (1967, p. 17), who tentatively recog- nized it on Tugidak Island, western Gulf of Alaska, in beds now assigned to the Tugidak Formation (Moore, 1969, p. A34), of late Pliocene and Pleistocene age (Allison, 1978, p. 177). Masuda (1973, p. 113) later Stated that MacNeil's (1967) Tugidak specimens were definitely not C. (S.) cosibensis, s.l., with which I agree, but he did not assign another name to them. MacNeil also named two other species of Chlamys from Alaskan faunas: Chlamys (Swiftopecten) don- Milleri MacNeil, 1967, from presumed middle Miocene beds of the Yakataga Formation, Yakataga district, northeastern Gulf of Alaska, and C. (S.) leohertleini acNeil, 1970, from the type locality of the Tachilni Formation. Chlamys (Swiftopecten) donmilleri also has ĉen reported in the early and (or) middle Miocene (Allison, 1978, p. 174) Unga Conglomerate Member of the Bear Lake Formation at Cape Aliaksin, about 170 km northeast of Cape Tachilni (MacNeil, 1967, as СГ.” and 1973). Kanno (1971, p. 49) figured speci- mens of С. (S.) donmilleri from the “lower” Yakataga огтапоп of the Yakataga district, and Addicott, Inkler, and Plafker (1978) cited an occurrence in the àkataga Formation of the Lituya district, to which they questionably assigned a Wishkahan age. Speci- mens of C. (S.) donmilleri from the Unga Conglom- erate have been assigned to C. (S.) cosibensis cosi- bensis by Masuda (1972, p. 400; 1978, p. 199—200), Whereas those from the Yakataga Formation of the akataga district have been referred by Masuda (1972, P. 400) to Swiftopecten swiftii (Bernardi, 1858). Chla- Ty CS Wiftopecten) swiftii and C. (S.) cosibensis cos- ibensis are very similar in form and sculpture, and relationships between the two taxa have been dis- cussed by MacNeil (1967) and Masuda (1972, 1978). Swiftopecten swiftii has an extensive distribution in Neogene deposits of California (Grant and Gale, 1931, p. 171-175), Japan (Masuda, 1962, p. 196), and adja- cent regions of the North Pacific. There are numerous records of C. (S.) cosibensis cosibensis in Miocene and Pliocene faunas of Japan (Masuda, 1959, 1962), Miocene deposits of Saishu Is- land, Korea (Masuda, 1962), and Sakhalin (Krishto- fovich, 1964) and Kamchatka (Slodkewitsch, 1938a, 1938b; Ilyina, 1963), U.S.S.R. Masuda (1962, 1978) gives the North Pacific stratigraphic range of C. (S.) cosibensis cosibensis as middle Miocene to lower Plio- cene, and he reports Japanese occurrences as old as early Miocene or possibly late Oligocene (Masuda, 1959, 1972, 1978) for the presumed ancestral subspe- cies, C. (8.) cosibensis hanzawae Masuda, 1959. There аге no undoubted Pliocene occurrences of C. (5.) co- sibensis cosibensis in Alaska, and Masuda's (1978, p. 200) assignment of the Unga Conglomerate Member of the Bear Lake Formation to the Pliocene, based solely on the presence of sculptural variants of the nominate subspecies, is not accepted herein. Speci- mens of C. (S.) cosibensis cosibensis occur at several USGS localities on the Alaska Peninsula in outcrops of the unnamed upper member of the Bear Lake For- mation, which is of middle or late Miocene age. АП occurrences of C. (S.) cosibensis, s.l., in Sa- khalin and Kamchatka appear to be of Miocene age. In western Kamchatka, C. (5.) cosibensis, s.l., is re- ported by Slodkewitsch (1938b, p. 108, as *Ресѓел (Chlamys) turpiculus Yokoyama, 1925”) in the "lower horizon’’ of the Kavran Group, an interval now ap- proximately equated with the Kakert Formation and assigned a middle Miocene age (Menner, Baranova, and Zhidkova, 1977; Gladenkov, 1980). Also in west- ern Kamchatka Пута (1963, р. 94—95) reported ““Сша- mys turpiculus’’ in the Etolon Formation of the Kav- ran Group, strata assigned by Menner, Baranova, and Zhidkova (1977) to the early late Miocene. The complex of C. (8.) cosibensis subspecies and related species occurring in Neogene strata of Kam- chatka and adjacent regions of the northwestern Pa- cific was discussed extensively by Sinel’nikova (1975). For C. (S.) cosibensis cosibensis Sinel'nikova (1975, p. 66) cited occurrences in the Kakert and Etolon For- mations of western Kamchatka and Ше ‘‘promontory Uandi’’ Formation (of unknown age) of Sakhalin. The Kakert and Etolon occurrences also have been noted by Slodkewitsch (1938a, 1938b), Ilyina (1963) and Gladenkov (1977). Occurrences in four formations in 86 BULLETIN 317 the Kuril Islands are reportedly of ‘‘Miocene and Plio- cene age (Zhidkova, 1972, p. 107). Three Tachilni specimens of C. (S.) cosibensis co- sibensis have their valves articulated and closed, and other specimens consist only of disarticulated valves. Together with the numerous other intact shells of Tachilni bivalves, these two specimens of Chlamys help to demonstrate that Tachilni mollusks were pre- served in situ and have not been greatly displaced downslope or along shore. The evidence for this pro- vided by a mobile epifaunal bivalve such as C. (S.) cosibensis cosibensis is especially compelling, be- cause such an organism is one most likely to be dis- articulated and transported by waves, currents, and downslope movements. Type information.—Holotype: TUE, registration number unknown (Masuda, 1962). Type locality: sea cliff of Shiba, Kanazawa-machi, Yokohama City, Kanagawa Prefecture, central Honshu, Japan; latitude 35?20'05"N, longitude 139?38'06"W; Koshiba Forma- tion; Miocene (Yokoyama, 1911; Masuda, 1962). Tachilni Formation occurrence.—USGS localities M309 (1 valve), M4044 (4 valves), M5163 (abundant fragments), M7139 (1 articulated, closed specimen, 5 valves), M7140 (1 valve, as “?”), M7141 (1 valve), M7146 (3 valves); UA locality A-170 (1 articulated, closed specimen); CAS localities 60278 (1 fragment, as ‘‘cf.’’), 60279 (1 articulated, closed specimen). Figured specimens.—USNM 339757, 339758, 339759, 339760; UA 2473. Stratigraphic and geographic range.—This subspe- cies is widely reported in numerous Miocene and Plio- cene formations of the northwestern Pacific, with most occurrences summarized by Masuda (1962). Most oc- currences are on Honshu and Hokkaido, Japan (Ma- suda, 1962), but it is also reported in Neogene faunas of Sakhalin (Zhidkova, 1972; Masuda, 1973), the Kuril Islands (Zhidkova, 1972), and western Kamchatka (Slodkewitsch, 1938a, 1938b; Ilyina, 1963; Sinel’- nikova, 1975). Russian records include the Kakert (middle Miocene) and Etolon (lower upper Miocene) Formations of western Kamchatka (Ilyina, 1963), and the Nutovo and Maruyama Formations (lower upper Miocene) of Sakhalin (Zhidkova, 1972). Alaskan rec- ords include the Unga Conglomerate Member (MacNeil, 1967, 1973; USGS collections) and un- named upper member (Marincovich in Detterman, Yount, and Case, 1981; USGS collections) of the Bear Lake Formation, Alaska Peninsula, and the Yakataga Formation of the northeastern Gulf of Alaska (Addi- cott, Winkler, and Plafker, 1978; USGS collections). All Alaskan records appear to be of about middle to late Miocene age, with no certain Pliocene occur- rences. Genus MIZUHOPECTEN Masuda, 1963 Mizuhopecten mollerensis (MacNeil, 1967) Plate 14, figure 18 Fortipecten mollerensis MacNeil, 1967, p. 43, pl. 4, fig. 1, pl. 5, 0590120, Mizuhopecten mollerensis (MacNeil). Masuda, 1978, р. 199. Discussion.—This is the largest Tertiary pectinid from the Alaska Peninsula, and is represented in the Tachilni fauna by several incomplete specimens. As noted by MacNeil (1967), the left valve bears about 16 low, rounded ribs separated by interspaces nearly twice as wide as the ribs, and the interspaces lack riblets or microsculpture. Ribs on the right valve are relatively broader, sometimes flat-topped, and separated by in- terspaces of equal or lesser width. MacNeil (1967) had no well-preserved right valves to study, but right valves now in USGS collections bear about 18 ribs. The fourth or fifth rib from the anterior and posterior ends is only about half the width of the other ribs on the right valve. Mizuhopecten mollerensis is conspicuous in Alaska Peninsula Miocene faunas because of its large size, but it is known from few specimens, most of which are not well preserved. As a result, its range of morpho- logic variation is not well known. Mizuhopecten ranges from Oligocene to Holocene in Japan (Masuda, 1978, p. 198), but is reported only in upper Miocene faunas of western North America (Addicott, 1981, p. 24). MacNeil (1967) tentatively considered M. mollerensis to be of late Miocene age, based on a single occurrence in the Bear Lake For- mation near Port Moller (Text-fig. 2). The species has since been found at several Bear Lake Formation 10- calities of presumed middle or late Miocene age (Ma- rincovich in Detterman, Yount, and Case, 1981). Its earliest possible occurrence is in strata thought to be- long to the Unga Conglomerate Member of the Bear Lake Formation near Port Moller (K. Masuda, written commun., 1982; USGS coll.), of early or middle Mio- cene age. Type information.—Holotype: USNM 645047. Paratype: USNM 645048. Type locality: USGS M2131, “А small knob extending above the level of the Recent terrace on the south shore of Port Moller, approxi- mately 3 miles southeast of Point Divide’’ (MacNeil. 1967, p. 43), Alaska; Bear Lake Formation; middle ої upper Miocene. Tachilni Formation occurrence.—USGS localities M7144 (fragments), M7149 (12 valves), M7150 Q valves). Figured specimen.—USNM 339761. Stratigraphic and geographic range.—Known only in Miocene rocks of the Alaska Peninsula. Lower O! middle Miocene: Unga Conglomerate Member (?) of TACHILNI FORMATION MOLLUSKS: MARINCOVICH 87 Bear Lake Formation near Port Moller (K. Masuda, Written commun., 1982; USGS collections). Middle or Upper Miocene: unnamed upper member of Bear Lake Formation, at several localities between Port Heiden and Port Moller (Marincovich in Detterman, Yount, and Case, 1981). Family CARDITIDAE Fleming, 1828 Genus CYCLOCARDIA Conrad, 1867 Cyclocardia cf. C. roundiformis (Ilyina, 1963) Plate 14, figures 3-8 Cardita roundiformis Пуіпа, 1963, р. 98—99, pl. 34, fig. 3. _Discussion.—Tachilni specimens tentatively as- Signed to this species have relatively small, nearly *quidimensional shells bearing about 28 radial ribs of Very low relief. The radial ribs are separated by much Narrower interspaces and crossed by fine concentric Srowth lines that may produce weak nodes on the ribs. The umbo is distinctly elevated and adult shell height 5 qual to or slightly greater than its length. The an- terior dorsal margin is shallowly concave, and the pos- terior dorsal margin is slightly convex. Based on five well-preserved Tachilni adults, the average length is 19.7 mm and average height 20.1 mm. The largest Specimen has a length of 20.6 mm and height of 21.2 mm. A juvenile specimen from locality M7139 has 31 ribs and is only questionably included with the other Tachilni Specimens. It is impossible to assign Tachilni specimens confi- dently to C. roundiformis for two reasons: Ilyina's Species is known to me only from one illustration ac- Сотрапута the original description (which was based ОП three specimens), and there are dozens of described North Pacific Oligocene to Holocene species of Cy- Clocardia of roughly similar morphology. Cyclocardia "oundiformis was characterized as having a small shell with rounded outline, elevated umbo, and 28 to 30 low radial ribs separated by fine interspaces (Ilyina, 1963). mensions of the holotype were given as length 23.7 mm and height 23.3 mm. Thus, by their shell size and Proportions, and the number and low relief of their ribs, the Tachilni specimens closely resemble C. "Oundiformis. Cyclocardia roundiformis is evidently known only i its type locality in western Kamchatka. A cita- Топ by Ariey (1978, р. 78-79) of "Cyclocardia sp. С, roundiformis (Ilyina)’’ from upper Oli- Босепе or lower Miocene rocks of the Poul Creek For- а аї Yakataga Reef, northeastern Gulf of Alaska, f ers to a different species. The single specimen re- “Tred to by Ariey (1978), which I have examined, has 0 or 31 radial ribs with trigonal cross-sections. The bathymetric range of living species of Cyclo- cardia from western North America is reported as in- tertidal to 2,211 m (Keen and Coan, 1974; Coan, 1977). The genus is well known in the Arctic Ocean and ranges in the eastern Pacific at least as far south as Panama (Keen, 1971, p. 109). Reports of the genus as far south as northern Chile (Olsson, 1961; Keen, 1971) need confirmation. Type information.—Holotype (of C. roundiformis): “Хо. 93/6338" (Ilyina, 1963; repository uncertain). Type locality: between the Etolon River and Nepro- pusk," western Kamchatka, U.S.S.R. (Ilyina, 1963); Etolon Formation of the Kavran Group; upper Mio- cene age. Tachilni Formation occurrence.—USGS localities M7139 (2 articulated, closed specimens, 3 valves), M7146 (1 articulated, closed specimen); UA locality А-170 (1 articulated, closed specimen). Figured specimens.—USNM 339762, 339763; UA 2474, 2500. Stratigraphic and geographic range.—Cyclocardia roundiformis is known only from its type locality. Cyclocardia sakamotoi new species Plate 14, figures 12-14 Diagnosis.—Shell large for the genus, with a round- ed trigonal shape, nearly central umbones with straight dorsal margins, and 10 major radial ribs on each valve. Description.—This species is characterized by a rounded trigonal shell that is large for the genus and bears 10 major radial ribs on each valve. In addition, four or five obscure radial riblets occur to either side of the major radial ribs and lie approximately parallel to the adjacent dorsal margins. The major ribs are raised in high relief, are rounded to somewhat trigonal in cross-section, and are separated by interspaces about half their width. These ribs produce a sinuous com- missure along the ventral shell margin. Concentric sculpture consists of fine growth lines that have a mi- nutely wrinkled appearance. The nearly central umbo is moderately elevated and the major portions of both the anterior and posterior dorsal margins are virtually straight. Due to the long and straight posterior dorsal margin, the posterior end of the shell is narrowly rounded for the genus. The escutcheon is lanceolate and extends for half the length of the posterior dorsal margin. The lunule is elongate but narrow and indis- tinct. The holotype is 34.0 mm in length, 30.5 mm in height, and 14.7 mm in thickness (both valves). Discussion.—Cyclocardia sakamotoi is distin- guished from the many other North Pacific Cenozoic species of Cyclocardia by its large size, few strong radial ribs, straight dorsal margins and nearly central umbo, and its rounded trigonal shape. Among Pleis- 88 BULLETIN 317 tocene and Holocene species, only C. crassidens (Broderip and Sowerby, 1829) seems to grow as large as C. sakamotoi and also to have relatively few radial ribs. However, the nearly circular shape and more nu- merous (12 to 16) radial ribs (Coan, 1977) of C. cras- sidens clearly separate it from the Tachilni species. Surprisingly, among the large number of described North Pacific Tertiary species of Cyclocardia, there seems to be no species that could easily be confused with C. sakamotoi. However, there are some Miocene taxa, especially those described from Kamchatka (Slodkewitsch, 1935, 1938a, 1938b; Ilyina, 1963), that resemble C. sakamotoi in their large size and few ra- dial ribs. The most similar among these are C. kavra- nensis (Slodkewitsch, 1935), with seven to nine ribs, and C. etalonnensis (Slodkewitsch, 1935), with 11 to 12 ribs, both described from the upper Miocene Etolon Formation of western Kamchatka. Slodkewitsch’s two species are distinct from C. sakamotoi by having rounded outlines lacking any trigonal aspect, umbones that are on the anterior third of the shell rather than being subcentral, strongly convex posterior dorsal margins and moderately concave anterior dorsal mar- gins rather than virtually straight margins, curved rather than straight radial ribs, and strongly prosogyrate beaks. The two Kamchatkan species share similar shell outlines and large size with C. crassidens, and may lie in the ancestral lineage of that species. The fragmentary Tachilni specimen referred to herein as Cyclocardia sp. A is similar in size to C. sakamotoi, but differs by having strongly prosogyrate beaks and a moderately concave anterior dorsal margin. The to- tal rib-counts of the two taxa are similar, but the large ribs of C. sp. A become progressively narrower to- ward the shell ends, whereas the major ribs of C. sa- kamotoi end abruptly near the dorsal margins and are succeeded by poorly developed riblets. Etymology.—This species is named for Kenji Sa- kamoto, photographer for the Branch of Paleontology and Stratigraphy, U.S. Geological Survey, Menlo Park, California, whose fine photographs of fossils have en- hanced many publications. Type information.—Holotype: USNM 339764. Type locality: USGS M7139, at the type locality of the Tachilni Formation, Cape Tachilni, Alaska Peninsula, Alaska; collected by L. Marincovich, Jr., June 1977. Tachilni Formation occurrence.—USGS locality M7139 (1 articulated, closed specimen); CAS locality 60279 (1 articulated, closed specimen). Figured specimen.—USNM 339764 (holotype). Stratigraphic and geographic range. from the type locality. Known only Cyclocardia species A Plate 14, figures 9, 10 Discussion.—Two incomplete specimens, one artic- ulated, represent a large species of Cyclocardia dif- ferent from other Tachilni species of this genus. The articulated specimen is 30.8 mm long, but may have been about 35 mm long before its posterior portion was lost. Twenty rounded-trigonal radial ribs are pre- served on each valve. The middle 12 ribs are most strongly developed, with four progressively narrower ribs on each side of these. The interspaces are one- fourth or less the width of the ribs. Fine, irregularly spaced concentric growth lines are most strongly developed ventrally. The umbones are moderately ele- vated, the anterior dorsal margin is moderately con- cave, and the posterior dorsal margin is slightly con- уех. The fragmentary Tachilni specimen is closest in size and sculpture to two Miocene species described from western Kamchatka, C. kamtschatica (Slodkewitsch, 1935) and C. kamtschatica dvalii (Slodkewitsch, 1938a). The main differences between Slodkewitsch’s two taxa are that the former is larger (length 35 to 40 mm, versus 33 to 35 mm) and has more numerous radial ribs (24 to 25, versus 20 to 23) than the latter (Slodkewitsch, 1935, 1938a, 1938b). The Tachilni specimen is clearly more similar to C. kamtschatica dvalii, which is known from upper Miocene rocks of the Etolon Formation in western Kamchatka (Slodkewitsch, 1938a, 1938b; Jl- yina, 1963). Additional Tachilni specimens are needed for a more certain identification. As noted in the dis- cussion of C. sakamotoi, that species also resembles Cyclocardia species A. Tachilni Formation occurrence.—USGS locality M7149 (1 valve); UA locality A-169 (1 articulated adult). Figured specimen.—UA 2475. Genus MIODONTISCUS Dall, 1903 Miodontiscus prolongatus (Carpenter, 1864b) Plate 14, figure 11 Miodon prolongatus Carpenter, 1864b, p. 642. Venericardia yatesi Arnold, 1907, p. 21-22, pl. 58, figs. 2a, 2b. Venericardia (Miodontiscus) prolongatus (Carpenter). Oldroyd, 1924, Voll, ps 115, р 240588. 5, б, Cardita (Miodontiscus) prolongatus (Carpenter). Grant and Gale, 1931, p. 276 [contains extensive synonymy]. Cardita (Miodontiscus) prolongata (Carpenter). Slodkewitsch, 19382 p. 336-339; Slodkewitsch, 1938b, p. 146-147, pl. 66, figs. 5-9. Miodontiscus prolongatus (Carpenter). Palmer, 1958, р. 83—84, pl. 8, figs. 1-7; Hertlein and Grant, 1972, p. 233-234, pl. 56, figs: 1—5. Discussion.—The single valve of this species in the Tachilni fauna, with a height of 7.0 mm and length 9 TACHILNI FORMATION MOLLUSKS: MARINCOVICH 89 6.2 mm, has the typically small size and elevated pro- Portions of Miodontiscus. The few radial ribs (13), Which are flattened and separated by narrowly incised Interspaces, as well as widely spaced, incised concen- tric lines, are characteristic of M. prolongatus. Carpenter (1864b, p. 424) cited 10—12 radial ribs for Holocene specimens of M. prolongatus. Slodkewitsch (19382, p. 336) reported 8—12 ribs for Kamchatkan Miocene specimens [the **18-21" ribs cited in Slod- kewitsch, 1938b, p. 146, is a typographical error], and Arnold (1907, p. 21) noted 8—9 ribs for Californian Pleistocene specimens of M. yatesi, a synonym. Thus, the presence of 13 radial ribs on the Tachilni speci- mens increases by опе the rib-count of M. prolongatus as reported in the literature. | Miodontiscus has not been reported before as a fos- Silin Alaska, though fossils are known from California and Kamchatka. The oldest reported occurrence of M. Prolongatus is in the upper Miocene Cebada Fine- Grained Member of the Careaga Sandstone and the lower Pliocene Foxen Mudstone in the Santa Maria District of southern California (Woodring and Bram- lette, 1950, р. 65; as ‘‘cf.’’), although the species is best known as a fossil in Pleistocene deposits of south- егп California (Grant and Gale, 1931). Slodkewitsch (1938b, p. 147) was the first to syn- Onymize M. yatesi (Arnold, 1907), a species described from the lower Pleistocene Santa Barbara Formation of southern California, with M. prolongatus, and 9odring and Bramlette (1950, p. 86) concurred in this Opinion. Slodkewitsch (1938b, р. 147) further suggest- ed that M. nakamurai (Yokoyama, 1926), described from the Pliocene Sawane Formation of Honshu, may * a synonym of M. prolongatus. Coan (1977, p. 384) also noted the close similarity of M. prolongatus and - nakamurai. Another closely related taxon is M. nakamurai annakensis (Oinomikado, 1938), described from the Miocene Itahana Formation of Honshu. > Туре information.—Syntypes: USNM 15472 (5 Specimens); Redpath Museum, McGill Univ., No. 2377 (4 specimens) (Palmer, 1958, p. 83-84). Type locality: еаћ Bay, northwestern Washington; Holocene. Tachilni Formation occurrence. —USGS locality M7142 (1 valve). Figured specimen.—USNM 339765. Stratigraphic and geographic range.—This species r known in upper Miocene to Holocene faunas. Upper Miocene: Cebada Fine-Grained Member of the Ca- "aga Sandstone, Santa Maria District, southern Cal- fornia (Woodring and Bramlette, 1950, as “‘cf.’’); Eto- lon Formation (?) of Kavran Group, on coastline near Mouth of Etolon River, western Kamchatka (Slodke- witsch, 1938a, 1938b). Lower Pliocene: Foxen Mud- stone, Santa Maria District, southern California (Woodring and Bramlette, 1950). Lower Pleistocene: Santa Barbara Formation, Santa Barbara, southern California (Arnold, 1907, as M. yatesi); Lomita Marl Member, Timms Point Silt Member, and unnamed sand member of San Pedro Formation, San Pedro, southern California (Woodring, Bramlette, and Kew, 1946). Up- per Pleistocene: Palos Verdes Sand, Newport Bay, southern California (Kanakoff and Emerson, 1959). Holocene: Middleton Island, central Gulf of Alaska, to San Diego, California (Dall, 1921), in depths of 9– 55 m (Burch, 1944, no. 39, p. 17). Family UNGULINIDAE H. & A. Adams, 1857 Genus FELANIELLA Dall, 1899 Felaniella parilis (Conrad, 1848) Plate 14, figures 15-17 Loripes parilis Conrad, 1848, p. 432, fig. 7. Diplodonta parilis (Conrad). Dall, 1900, p. 1182; Arnold, 1909, p. 140, pl. 17, fig. 5; Hickman, 1969, p. 42-43, pl. 3, figs. 2, 3, 5-7. Diplodonta (Felaniella) parilis (Conrad). Dall, 1909, p. ll pl. bl, fig. 6. Taras parilis (Conrad). Grant and Gale, 1931, p. 294. Taras (Felaniella) parilis (Conrad). Slodkewitsch, 1938а, p. 367— 369; Slodkewitsch, 1938b, p. 151, pl. 73, figs. 8—10. Felaniella parilis (Conrad). Addicott, 1976a, p. 107, pl. 3, fig. 9. Discussion.—This species is characterized by its nearly circular outline with prominent umbones, thin shell, and somewhat compressed valves. It is a large species for the genus, and the largest Tachilni speci- men, at 22.8 mm long and 20.5 mm high, is not an uncommon size for F. parilis. This species is well known in northeastern Pacific Tertiary faunas, but its taxonomic relationsips and stratigraphic range are uncertain. As Hickman (1969, р. 42) noted, ‘‘Diplodonta parilis has traditionally been regarded as a Miocene and Pliocene species, although it seems to be part of a complex of similar forms which appears in the Oligocene and extends into the Re- cent." The stratigraphic range of this complex has lately been extended into probable upper Eocene strata of the Pittsburgh Bluff Formation in Oregon (Moore, 1976, p. 46-47). The presence of F. parilis in Holocene faunas is based on its synonymy with F. sericata (Reeve, 1850), which is reported to range from Mon- terey Bay, California, to northern Peru (Keen, 1971, p. 129). Addicott (1976a, p. 107) cited the stratigraph- ically highest Pacific Northwest occurrence of F. par- ilis in Wishkahan faunas, but the biostratigraphic util- ity of the species will be in doubt until eastern Pacific Cenozoic species of Felaniella, of which at least a dozen have been named, are better known. 90 BULLETIN 317 Keen (1971, p. 129) states that F. sericata, which is at the very least the modern homologue of F. parilis, "may be found intertidally, but more commonly . . . in depths to 75 m on sand ог mud bottoms." Type information.—Holotype: ANSP, No. 4546 (fig- ured by Moore, 1962, p. 111, pl. 23, fig. 9). Type lo- cality: Astoria, Oregon; Astoria Formation; middle Miocene. Tachilni Formation occurrence.—USGS localities M7139 (1 articulated, closed specimen), M7142 (1 valve); UA localities A-169 (1 valve), UA A-170 (1 articulated, closed specimen). Figured specimens.—USNM 339766; UA 2476. Stratigraphic and geographic range.—Felaniella parilis belongs to a species-complex that ranges from about late Eocene to Holocene and within which taxo- nomic relationships are unclear. There are numerous northeastern Pacific records in late Eocene and youn- ger strata (Grant and Gale, 1931; Keen and Bentson, 1944; Moore, 1963; Hickman, 1969), and Addicott (19762) gives its highest occurrence in Pacific North- west strata in Wishkahan faunas. This species is also reported in the “пррег Kavran" Group of western Kamchatka by Slodkewitsch (1938a, 1938b), in strata now referred to the Kakert and Etolon Formations (Ilyina, 1963) and assigned an age of late middle to early late Miocene (Menner, Baranova, and Zhidkova, 1977; Gladenkov, 1980). Also reported by Slodke- witsch (1938а, 19386) in the *' Machigar зеспоп ' of the Schmidt Peninsula, northern Sakhalin, strata now re- ferred to the Machigar Formation of Oligocene age (Gladenkov, 1980, p. 1090). Family CHAMIDAE Blainville, 1825 Genus CHAMA Linnaeus, 1758 Chama sp.? Discussion.—A single imperfectly preserved valve that may represent Chama was found at UA locality A-170. The valve is roughly circular in outline, about 30 mm in diameter, and is cemented into a depression in the attached matrix. The hinge area is missing, but sculpture of fine, closely-spaced, irregular radial cos- tellae and coarse concentric laminae is reminiscent of several eastern Pacific species of Chama and Pseu- dochama Odhner, 1917 illustrated by Bernard (1976). Chamids are most diverse and abundant in the trop- ics, but some species occur in cool-temperate habitats. In the modern eastern Pacific, Chama arcana Ber- nard, 1976, ranges to 44°N latitude in Oregon (Ber- nard, 1976, p. 15), and C. pellucida Broderip, 1835, occurs at 33°S latitude in the Juan Fernandez Islands, Chile (Marincovich, 1973, p. 11). As noted by Bernard (1976, p. 2), most chamids inhabit exposed shorelines and cannot tolerate lowered salinity or high sedimen- tation rates; maximum abundance is just subtidal, though a few species occur to 200 m depth. The Tachilni specimen is not suitable for illustra- tion. Living or fossil species of Chama have not pre- viously been reported from Alaska, and the confir- mation of the presence of the genus in the Tachilni fauna requires further collecting. Family CARDIIDAE Lamarck, 1809 Genus CLINOCARDIUM Keen, 1936 Clinocardium cf. C. ciliatum (Fabricius, 1780) Plate 15, figure 1 Cardium ciliatum Fabricius, 1780, p. 410; Dall, 1904, p. 113. Laevicardium (Cerastoderma) ciliatum (Fabricius). Grant and Gale, NSB bs Go) SHO geil CORTE Clinocardium ciliatum (Fabricius). Clench and Smith, 1944, p. 15- 16, pl. 10; Kennedy, 1978, p. 440-441. Ciliatocardium ciliatum (Fabricius). Kafanov, 1980, p. 310, 312. Discussion.—This living circumarctic species is rep- resented in the Tachilni fauna by two specimens. The best-preserved specimen is an external cast of a right valve, subcircular in outline, 21.5 mm long by 18.4 mm high, and with 28 trigonal ribs (probably with another two or three ribs not preserved). The specimen is smaller than average for adults of C. ciliatum, and its poor state of preservation does not permit more cer- tain identification. This species is among the most common living northern bivalves, ranging throughout the Arctic Ocean and the high-latitude North Pacific and North Atlantic (Bernard, 1979a, p. 45). The subcircular to ovate, thin. inflated shell with trigonal ribs is distinctive among living bivalves of this region. However, the species has been named several times (see synonymy in Dall, 1901) because the number of radial ribs varies greatly among individuals. Kafanov (1980, p. 310) claimed that the rib-count may vary from 20 to 50, although a more frequently stated range is 28 to 40 (Bernard, 1979a, р. 45). This was the only living species assigned to Cil- iatocardium when Kafanov (1974, p. 1469) proposed the genus, though he later added two living Atlantic subspecies and one Japanese Pliocene subspecies (Ka- fanov, 1980, p. 311-313). In addition, Kafanov (1980) recognized 16 extinct North Pacific species he placed in Ciliatocardium, nearly all of which are described from Japan, Sakhalin and Kamchatka, the oldest of which is Oligocene. Of these 16 Tertiary species two: C. brooksi (Clark, 1932) and C. yakatagense (Clark: 1932), were reported from Alaska, in the Poul Creek and Yakataga Formations in the northeastern Gulf of Alaska (Clark, 1932; Kanno, 1971). Clinocardium уб TACHILNI FORMATION MOLLUSKS: MARINCOVICH 91 katagense differs from C. ciliatum by having a strong- ly elevated shell and only about 24 distinct radial ribs that are not trigonal (Kanno, 1971, p. 67). Clinocar- dium brooksi, however, is similar in shape, size, rib- count and rib shape to C. ciliatum, and differences between the two taxa are not well defined. The former Species is known from the upper Poul Creek (Clark, 1932; Addicott et al., 1971) and lower Yakataga (Кап- по, 1971) Formations of the Yakataga district, north- eastern Gulf of Alaska, in beds of about early Miocene age. The oldest records of C. ciliatum are in presumed middle Miocene beds of the Maruyama Formation of Sakhalin (Kafanov, 1980, p. 312). The present tenta- tive report of C. ciliatum in the Tachilni Formation is the oldest one claimed for Alaska, unless C. brooksi 15 considered conspecific. Clinocardum ciliatum has been reported living most often in outer shelf depths. Clench and Smith (1944, P. 16) cite this species in 183 m off Labrador, although Most of their northwestern Atlantic records are in depths of about 35 to 100 m. Living specimens have been found at 33 m off Point Barrow, Alaska (MacGinitie, 1959, p. 176), and in depths of 26 to 159 I in the western Beaufort Sea (Bernard, 1979a, р. 45). In the Gulf of Alaska region records range from about 2 to 91 m (Burch, 1944), and the species is reported In the eastern Pacific as far south as Puget Sound (Dall, 1921). The latter record requires confirmation because Bernard (19792) gives no eastern Pacific records south 9f the northern Gulf of Alaska. Я Type information.—Lectotype: UZM, по registra- Поп number (designated by Kafanov, 1980, p. 312). Type locality: Greenland; Holocene. Tachilni Formation occurrence.—USGS localities M7146 (1 valve), M7256 (1 valve). Figured specimen.—USNM 339767. Stratigraphic and geographic range.—This species ranges from middle (?) or upper Miocene to Holocene. Middle (2) Miocene: lower part of Maruyama For- Mation, Sakhalin (Kafanov, 1980). Upper Miocene: Omeutiyama Formation of the Koryak Upland; Oko- bykayska Formation, northern Sakhalin (Kafanov, 1980); Alekhinska, Kamuyska, and Golovninsk For- Mations of Kuril Islands (Zhidkova, 1972; Kafanov, 1980); Utsutoge Formation, northern Honshu, Japan (Kafanov, 1980). Reported also in Pinakul and Crestov Ormations of Chukotka, U.S.S.R., from faunas of Unknown age (Zhidkova, 1972, as ‘‘cf.’’). Reported from unknown formation on Popof Island, western Gulf of Alaska (Dall, 1904, p. 113), where marine strata are of Oligocene and Miocene age (Burk, 1965). Pliocene and Pleistocene: numerous records throughout the North Pacific (Grant and Gale, 1931; Kennedy, 1978; Kafanov, 1980). Holocene: Circumarctic and circum- boreal. In the Pacific, modern records cite the species as far south as northern Japan and the northern portion of the Gulf of Alaska (Bernard, 1979a), though Dall (1921) cited it at Puget Sound, Washington. Burch (1944) gave one report from Ketchikan, southeastern Alaska. Clinocardium hannibali Keen, 1954 Plate 15, figures 2-4 Clinocardium hannibali Keen, 1954, р. 18—19, pl. 1, fig. 16, text-fig. 9; Addicott, 1976a, p. 105. Keenocardium hannibali (Keen). Kafanov, 1980, p. 309. Discussion.—This is the most abundant Clinocar- dium in the Tachilni Formation, although well-pre- served specimens are rare. Tachilni specimens are characterized by relatively small size (averaging about 23 mm long), nearly equidimensional valves of round- ed trigonal outline, and about 37 radial ribs with flat or slightly rounded tops. Keen (1954, p. 18) gave average dimensions for this species of length 24.5 mm, height 24.5 mm, and noted that the radial ribs range in number from 35 to 40, which agrees well with the Tachilni specimens. The largest specimen cited by Keen (1954) was 42 mm long and 42 mm high, which is slightly larger than the larg- est Tachilni individual. There is a distinct variation in outline among the Tachilni specimens, ranging from the more orbicular to the more trigonal, but the ma- jority match well with the figure of the holotype (Keen, 1954, pl. 1, fig. 16). Within Tachilni strata C. hannibali occurs at few localities but in great numbers. It is the most abundant species in beds where it is found, occurring in jumbled accumulations of disarticulated valves. Specimens oc- cur nearly always as molds or casts bearing scraps of shell material. Type information.—Holotype: SUPTC, No. 8302. Paratype: SUPTC No. 8303. Type locality: SU locality NP-235, at intersection of Chehalis and Summit Streets, Aberdeen, Washington; lower part of Montesano For- mation; upper Miocene. Tachilni Formation occurrence.—USGS localities M7146, M7149, M7150, M7256 (as ‘‘cf.’’); UA locali- ties A-169, A-170, A-301. Specimens are abundant at all localities. Figured specimens.—USNM 339768, 339769. Stratigraphic and geographic range.—The only verified records of this species are in upper Miocene faunas. Upper Miocene: Montesano Formation at Ab- erdeen and nearby localities, Grays Harbor County, southwestern Washington (Keen, 1954). Addicott (1976a, p. 105) regarded this species as restricted to 92 BULLETIN 317 the Wishkahan Stage in the Pacific Northwest. Ques- tionably reported by Allison and Marincovich (1981, as ‘‘cf.’’) in upper Oligocene or lowermost Miocene strata of the Narrow Cape Formation on Sitkinak Is- land, western Gulf of Alaska (Text-fig. 1). Clinocardium meekianum (Gabb, 1866) new subsp.? Plate 15, figures 5—8 Discussion.—A large species of Clinocardium well- represented in the Tachilni fauna does not match ex- actly with described taxa. The Tachilni species of Cli- nocardium is characterized by relatively large size, moderately to distinctly oblique outline, and 30 or 31 radial ribs. The radial ribs are noded and their shape grades from rounded at the anterior end of the shell to rounded-triangular at the posterior end. The Tachilni taxon is related in shape and sculpture to С. nuttallii (Conrad, 1837), С. meekianum теек- ianum (Gabb, 1866), and C. meekianum myrae Ade- goke, 1969, and contains morphological characters of all three taxa. Clinocardium nuttallii is the common Miocene (?) or Pliocene to Holocene northeastern Pa- cific (California to Washington) species, C. meekia- num meekianum is a Miocene and Pliocene taxon in the same region, and C. meekianum myrae occurs in upper Miocene strata in central California. Clinocardium nuttallii is relatively equilateral in valve outline, and С. meekianum meekianum and С. meekianum myrae are distinctly oblique, whereas the Tachilni taxon includes both morphotypes. The best- preserved Tachilni specimens have 30 or 31 noded ra- dial ribs, whereas C. nuttallii has, according to various workers, 34 ribs (Keen, 1954, p. 21), “абош 34-35 ribs on average" (Kafanov, 1980, p. 305), ог 32 to 41 ribs . (Kilmer, 1973); C. meekianum meekianum is said to have 28 ribs (Кееп, 1954, p. 21), or 22 to 25 ribs *'typ- ically” (Adegoke, 1969, p. 118). Roth (1979, р. 303) states that C. meekianum meekianum has 21—27 ribs "exclusive of obscure ribs on the posterior slope," although most specimens have 22 or 23 ribs—he also names a new subspecies of C. meekianum having 22 to 28 ribs. Adegoke (1969, p. 118) reports 28 to 30 ribs for C. meekianum myrae. From these published ac- counts of other taxa, the Tachilni specimens of C. meekianum, with 30 or 31 ribs, occupy a medial po- sition in rib-count between C. nuttallii and C. meek- ianum meekianum. The radial ribs of C. meekianum new subsp.? clearly grade from rounded at the anterior end of the shell to rounded-triangular at the posterior end. This varying rib shape is also present in C. nuttallii but not, with one exception, in C. meekianum meekianum. For a new subspecies of C. meekianum, Roth (1979, p. 304) noted that in young specimens under 20 mm long the ribs are rounded-triangular in section; adult speci- mens, as large as 104.7 mm long and 101.4 mm high, have rounded ribs. The presence of rounded-triangular posterior ribs in C. nuttallii and C. meekianum new subsp.? is a link between the two taxa. The largest Tachilni specimen is 77.1 mm long and 66.9 mm high, and several other adults are nearly as large. The presence of both rounded and rounded-trian- gular radial ribs on the Tachilni taxon brings into ques- tion Kafanov's (1974, 1980) subgeneric division of Cli- nocardium. Ciliatocardium was created by Kafanov (1974, 1980) for species with triangular ribs, whereas other species were placed either in Clinocardium, 5.5., (having transverse nodular tubercula atop the ribs) or Keenocardium (lacking transverse nodular tubercula of the former and the triangular shape (on posterior ribs) of the latter). The type-species of Clinocardium, s.s., C. nuttallii, also has rounded-triangular posterior ribs on many Holocene specimens I have examined. The value of Kafanov's subgenera is doubtful. Tachilni Formation occurrence.—USGS localities M5169 (1 valve, as ‘‘cf.’’), M7140 (1 valve), M7146 (1 articulated, closed specimen, 10 valves), M7149 (1 valve), M7150 (1 articulated, closed specimen, 1 valve), M7201 (1 articulated, closed specimen); UA localities A-169 (1 valve), A-170 (2 valves), A-301 (1 articulated, closed specimen); CAS locality 60279 (1 articulated, closed specimen, | valve). Figured specimens.—USNM 339770, 339771, 339772. Stratigraphic and geographic range.—The possibly new subspecies noted here is known only in the Ta- chilni Formation. Addicott (1976a, p. 105) stated that in the Pacific Northwest C. meekianum, s.l., has its earliest occurrence in Wishkahan faunas. Clinocardium cf. C. pristinum Keen, 1954 Plate 15, figures 9—12 Clinocardium pristinum Keen, 1954, p. 16-18, pl. 1, figs. 9, 15, text- 158.03 Ө Keenocardium pristinum (Keen). Kafanov, 1980, р. 308, 310. Discussion.—Clinocardium pristinum was charac- terized by Keen (1954) as having a trigonal shell with prominent umbones and 42 to 48 flattened radial ribs that tend to become obsolete on the posterior slope: The largest specimen she noted, the holotype, is 53 mm long and 50 mm high. Tachilni specimens tenta- tively assigned to this species are similar in shell shape: rib-count and rib shape to C. pristinum, but differ in size and exact configuration of the posterior dorsal margin. Five Tachilni specimens are assigned to this taxon, of which the largest is 64 mm long. The two TACHILNI FORMATION MOLLUSKS: MARINCOVICH 93 best-preserved specimens each have 45 radial ribs, another specimen has 42 ribs with three or four addi- Попа! ribs evidently worn off, and a fourth specimen s incomplete and shows only 29 ribs. Where the radial ribs are well-preserved they are flat-topped or very slightly rounded and are separated by much narrower Interspaces. The only obvious difference bewteen typical C. Pristinum and the Tachilni specimens is in the shape of the posterior dorsal margin. On Tachilni specimens this margin is nearly straight or slightly convex and rounds smoothly into the posterior margin, whereas Keen's (1954) photos of C. pristinum show the pos- terior dorsal and posterior margins meeting at an angle of 140°. A large sampling of specimens from Alaska and California might show this to be a gradational fea- ture, but for now caution seems justified in applying this species name to Tachilni specimens. The species most similar in form to C. pristinum is C. hopkinsi Kanno, 1971, described from upper Oli- Босепе or lower Miocene beds of the Poul Creek For- mation in the Cape Yakataga area, Gulf of Alaska (Text-fig. 1). Kanno’s (1971) species is characterized by having about 40 flattened or slightly rounded radial ribs with cross-threads that tend to crowd together toward the ventral margin, and he listed his largest Specimen as 50 mm long and 42 mm high. The holotype of C. hopkinsi has a gently convex posterior dorsal margin that merges smoothly with the posterior margin (Kanno, 1971, pl. 5, fig. 7a), whereas the paratype has an angulate juncture of the posterior dorsal and pos- terior margins (a possible artifact of preservation). Another taxon similar in size and form to the Ta- chilni species is C. lispum Roth and Talmadge, 1975, described from the Pliocene Rio Dell Formation of northern California. The holotype of C. lispum, how- ever, has 59 radial ribs that clearly distinguish it from the Tachilni species. Type information.—Holotype: UCMP, No. 14838. ype locality: southwest part of Shell Ridge, near alnut Creek, Contra Costa County, northern Cali- fornia; "San Pablo Group, probably Neroly forma- Чоп” (Keen, 1954, р. 17); upper Miocene. Tachilni Formation occurrence.—USGS localities M7140 (1 valve), M7146 (3 valves), M7256 (1 valve), M7258 (1 valve). Figured specimens.—USNM 339773, 339774, 339775, 339776. is | гатетарћес and geographic range.—This species ‘nown for sure only in upper Miocene strata. Upper 'осепе: San Pablo Group, Neroly Formation, Contra Costa County, northern California (Keen, 1954). It Westionably occurs in middle Miocene beds of the Astoria Formation, southwestern Washington (Keen, 1954). Family VENERIDAE Rafinesque, 1815 Genus SAXIDOMUS Conrad, 1837 Saxidomus sp. indet. Plate 15, figure 13 Discussion.—Saxidomus is represented by a single articulated, closed individual in the Tachilni fauna. The specimen is 68.9 mm long and 52.2 mm high, of av- erage size for an adult of this genus, and the thick shell and rounded quadrate shell outline further suggest Saxidomus. Remnants of the exterior shell surface have fine concentric growth lines as the only sculpture, so the intact shell may have had a fairly smooth surface texture. Its state of preservation does not allow a reliable species assignment, but the Tachilni specimen is most similar to $. giganteus (Deshayes, 1839), known from upper Miocene to Holocene faunas of the northeastern Pacific (Addicott, 1978; Fitch, 1953). Living species of Saxidomus in the northeastern Pa- cific are reported in depths from the intertidal zone to 35 m, in substrates of sand and mud (Keen and Coan, 1974). Tachilni Formation occurrence.—USGS locality M7139 (1 articulated, closed specimen). Figured specimen.—USNM 339777. Genus PROTOTHACA Dall, 1902 Subgenus PROTOTHACA Dall, 1902 Protothaca (Protothaca) staleyi (Gabb, 1866) Plate 16, figures 1—4 Dosinia staleyi Gabb, 1866, p. 24, pl. 7, fig. 42. Tapes staleyi (Gabb). Gabb, 1869, p. 57, pl. 16, figs. 17, 17a. Paphia staleyi (Gabb). Arnold, 1909, p. 25 [as *'2"], p. 27 [as 7], pe ol fas“ И p.335999: ple 26. nig s Jas 25 Arnold and Anderson, 1910, p. 109, 110, 112, 126 [all as ‘*?’’], 129, 132, pl. 48005. S asn a Venerupis (Protothaca) staleyi (Gabb). Stewart, 1930, p. 222-223, pl. 15, fig. 4. Protothaca staleyi (Gabb). Addicott, 1969, р. 73-74, pl. 2, figs. 5, 6, 8, pl. 4, fig. 1. Discussion.—The shell of this species is subquad- rate, thick-walled, and strongly inflated. Sculpture consists of fine, subdued radial costellae, and fine, closely but irregularly spaced concentric growth lines. The radial and concentric sculpture are of approxi- mately equal strength, although the concentric lines seem to be slightly stronger in places. The relatively great thickness of the shell is shown well on a broken left valve (Pl. 16, fig. 1), in which the shell near the posterior ventral margin is nearly 4 mm thick. This species is similar in appearance to several other late Cenozoic species of Protothaca of western North America. The most common living species in this re- gion, P. (P.) staminea (Conrad, 1837), is of about the same size as P. (P.) staleyi, but has a less quadrate outline, a much thinner and less inflated shell, and radial sculpture that is distinctly stronger than the con- centric lines. In addition, the radial costellae of P. (P.) staminea become broader anteriorly, which does not happen in P. (P.) staleyi. Another related living species is P. (P.) laciniata (Carpenter, 1864a), which at a length of 50 to 80 mm (McLean, 1978, p. 79) is larger than P. (P.) staleyi. The valves of P. (P.) laciniata are subquadrate, thick, inflated, and have evenly devel- oped sculpture across the entire shell surface, as in P. (P.) staleyi. However, the well-developed radial and concentric sculpture of P. (P.) laciniata intersect to form a rasp-like surface (McLean, 1978, p. 79), which does not happen in P. (P.) staleyi and is not present on Tachilni specimens. Protothaca (Protothaca) la- ciniata appears to be the modern species most closely related to the extinct P. (P.) staleyi. Among Tertiary species, P. (P.) staleyi hannibali (Howe, 1922), known from rocks of Miocene to Pleis- tocene age in northwestern California and southwest- ern Oregon, may be a junior synonym of P. (P.) sta- leyi. Purportedly separate from P. (P.) staleyi by being more quadrate in shape, less inflated, and having bi- furcate radial costellae, P. (P.) staleyi hannibali is difficult to identify consistently. As noted by Roth (1979, p. 381), differences between the two taxa “аге somewhat analogous to environmental differences be- tween modern populations and individuals of P. stam- inea." Another species related to P. (P) staleyi is P. (P.) montesanoensis (Weaver, 1912), described from : the upper Miocene Montesano Formation of Washing- ton. Based on the few published illustrations (Weaver, 1912, 1942; Addicott, 1969, 1976a), P. (P.) montesan- oensis evidently is characterized by a somewhat cir- cular outline, subdued radial sculpture and robust con- centric growth lamellae. An Alaskan Tertiary taxon possibly related to P. (P.) staleyi was first cited by Grewingk (1850, p. 278— 279, pl. 5, figs. 2a-e) as “Уепегирв реши Deshayes var." and was reported to occur on the Alaska Pen- insula, Unga Island, and possibly on St. Paul Island. Grewingk's localities include rocks now known to be of Oligocene or Miocene age. His description of a thick- shelled bivalve 38 to 42 mm long and having numerous radial ribs and concentric growth lines, as well as a venerid hinge, may place the taxon in Protothaca. However, he illustrated relatively broad radial ribs that are different from those of P. (P.) staleyi. No addi- BULLETIN 317 tional specimens matching Grewingk’s (1850) descrip- tion have been found in Alaska. Based solely on Gre- wingk’s mention of this taxon, Dall (1904, p. 116) proposed the new name Protothaca grewingkii. Protothaca (Protothaca) staleyi has been reported numerous times in upper Miocene and Pliocene strata from central California to southwestern Oregon. Its oldest verified occurrence is in the Wishkahan faunas of the Empire Formation, southwestern Oregon (Roth, 1979, p. 381), so this species aids in establishing a lower age limit for the Tachilni fauna. Gladenkov (1977) reported P. (P.) staleyi in western Kamchatka only in the Erman Formation, which he refers to the upper- most Miocene. Protothaca is a common dweller in modern near- shore environments. In the northeastern Pacific, the genus is known in depths from the intertidal zone to 45 m, in sand or gravel, or nestling in crevices (Keen and Coan, 1974). Type information.—Neotype: ANSP, No. 4490 (Stewart, 1930). Type locality: Mark West Creek, а branch of the Russian River, Sonoma County, north- ern California; Merced Formation; Pliocene. Tachilni Formation occurrence.—USGS localities M7140 (1 articulated, closed specimen as ‘‘cf.’’, and | valve), M7142 (1 articulated, closed specimen, 1 valve); UA locality A-169 (1 valve). Figured specimens.—USNM 339778, 339779. Stratigraphic and geographic range.—The follow- ing occurrences are taken from Roth (1979, p. 381- 382). Lower upper Miocene (Wishkahan): Empire Formation, Cape Blanco, southwestern Oregon (Roth, 1979). Upper Miocene: Tahana Member of Purisima Formation, northern California (Addicott, 1969); Ti- naquaic Sandstone Member of Sisquoc Formation, southern California (Woodring and Bramlette, 1950); Ohlson Ranch Formation, northern California (Peck; 1960); Etchegoin Formation, central California (Ade- goke, 1969); Graciosa Coarse-Grained Member and undifferentiated Careaga Sandstone (Woodring and Bramlette, 1950). Pliocene: ‘‘Merced (?)’’ Formation, Santa Clara County, northern Californa (Addicott, 1969). Family MACTRIDAE Lamarck, 1809 Genus SPISULA Gray, 1837 Three species of Spisula (Mactromeris) are recog- nized in the Tachilni fauna: S. (M.) albaria (Conrad. 1848), S. (M.) brevirostrata Packard, 1916, and S. (М.) polynyma (Stimpson, 1860). The last is by far the most common in Tachilni deposits, followed in order of abundance by 8. (M.) albaria and S. (M.) breviros- trata. TACHILNI FORMATION MOLLUSKS: MARINCOVICH 95 Several dozen names are available for North Pacific Cenozoic species of Spisula and it is likely that most have no value. The three used for Tachilni specimens are well known in the western American literature and are usually treated as distinct species. However, I at- tempted to discriminate Tachilni species on the basis of ratios of length to height, and posterior length to total length, and learned that the three shell forms in- tergrade. This agrees with findings of Moore (1963, р. 83), in reference to S. (M.) albaria of the Miocene Astoria Formation, that the same amount of variation shell outline may be found in single populations of Olocene species of Spisula. The three species in the Tachilni fauna seem to represent end members of an unbroken morphologic series. Determining the degree to which the three morphotypes intergrade, in the Tachilni Formation and elsewhere, would require an effort beyond the scope of this study. Until such a Study is done the value of North Pacific species of Spisula in making age inferences is extremely limited. Subgenus MACTROMERIS Conrad, 1868 Spisula (Mactromeris) albaria (Conrad, 1848) Plate 16, figures 5-7 Mactra albaria Conrad, 1848, p. 432, fig. 4; Arnold, 1910, p. 30, pl. . I9, fig. 4. Spisula albaria (Conrad). Dall, 1909, p. 130, pl. 10, fig. 1. Spisula (Mactromeris) albaria (Conrad). Moore, 1963, p. 82-83, pl. de 1-3, pl. 31, figs. 9, 11; Weaver, 1942, p. 239, pl. 57, figs. Discussion.—Tachilni specimens assigned to 5. (M.) albaria are characterized by their small size, relatively Inflated valves; and elevated trigonal outline. Com- Pared to the more numerous specimens of S. (M.) Polynyma (Stimpson, 1860), S. (M.) albaria has a more elevated umbo and more narrowly rounded posterior end. Tachilni specimens lack a prominent posterior Eire extending from the umbo to the ventral margin hat Moore (1963, p. 83) noted for well-preserved Specimens from the Miocene Astoria Formation in Or- egon. As Moore (1963) further noted, the variety of shell outlines present in Tertiary 5. (M.) albaria may * observed in single collections of Holocene species ОЁ Spisula. b At least seven subspecies of 5. (M.) albaria have пије described (Packard, 1916; Weaver, 1942), rang- ng in age from the middle (2) Oligocene subspecies S. m albaria scapoosensis Clark, 1925, in Oregon, to е Pliocene subspecies S. (M.) albaria coosensis Owe, 1922, in California. The stratigraphic or bio- ecographic utility of these subspecies is questionable, ?nsidering the difficulty in distinguishing the species itself from related forms such as 5. (M.) polynyma. Weaver (1942) cited S. albaria ranging from late Mio- cene to Holocene, an interval that is thought to contain S. (M.) polynyma and other species by most workers. There are no undisputed records of 8. (M.) albaria from Asia. Zhidkova (1972, p. 140) cited this species, as ''cf.", from Miocene and Pliocene strata of Sa- khalin and the Kuril Islands, but her figures are of the 5. (M.) polynyma morphotype. Type information.—Holotype: ANSP (missing and presumed lost; Moore, 1963, p. 83). Type locality: As- toria, Oregon; Astoria Formation; middle Miocene. Tachilni Formation occurrence.—USGS localities M7139 (1 articulated specimen), M7146 (1 valve, as ‘‘cf.’’); UA localities A-169 (1 valve), A-170 (1 valve). Figured specimen.—USNM 339780. Stratigraphic and geographic range.—This species is reported to range from the middle or upper Oligo- cene (Clark, 1925; Addicott, 1973) to Holocene (Weaver, 1942) in the northeastern Pacific, but many literature citations are questionable. The morphotype recognized in the Tachilni fauna is usually cited in Miocene strata of California, Oregon and Washington. Addicott (1976a, р. 105) reported 5. (М.) albaria ar- noldi (Dall, 1922) restricted to Wishkahan faunas in the Pacific Northwest, but that morphotype is not present in Tachilni collections. Spisula (Mactromeris) brevirostrata Packard, 1916 Plate 16, figures 8, 9 Spisula (Hemimactra) brevirostrata Packard, 1916, p. 296—297, pl. 28, figs. 1а, 16, 2; Faustman, 1964, p. 124, pl. 1, fig. 8. Discussion.—Tachilni specimens assigned to 5. (M.) brevirostrata are characterized by a relatively elevat- ed shell outline, distinctly concave anterior dorsal margin, and broadly convex posterior dorsal margin, with a broadly rounded posterior end and much more narrowly rounded anterior end. The valves of Tachilni specimens assigned to S. (M.) brevirostrata are not as inflated as those of Tachilni specimens of 5. (M.) al- baria (Conrad, 1848), or so elongate as those of Tachil- ni specimens of 5. (M.) polynyma (Stimpson, 1860). The 5. (M.) brevirostrata morphotype 18 apparently best developed in adults, because no juveniles with this form occur in the Tachilni fauna or in USGS or UA collections from other formations. Type information.—Holotype: UCMP 11489. Type locality: UCMP 1875, along east bank of Eel River, one mile north of Scotia, Humboldt County, north- western California; Wildcat Group; Pliocene or Pleis- tocene. 96 BULLETIN 317 Tachilni Formation occurrence.—USGS localities M7146 (1 valve), M7150 (1 valve); UA localities A-170 (1 articulated specimen), A-302 (1 valve). Figured specimens. —USNM 339781, 339782. Stratigraphic and geographic range.—The follow- ing occurrences are cited by Roth (1979). Middle Mio- cene (Newportian): Astoria Formation, northwestern Oregon. Lower upper Miocene (Wishkahan): Empire Formation, Coos Bay region, Oregon. Pliocene: “Merced” Formation, Sonoma County, northern Cal- ifornia. Pliocene or Pleistocene: Rio Dell Formation and undifferentiated Wildcat Group, northwestern California. Pleistocene: Scotia Bluffs Formation, northwestern California. Spisula (Mactromeris) polynyma (Stimpson, 1860) Plate 16, figures 10—12, Plate 17, figures 1, 2 Mactra polynyma Stimpson, 1860, p. 3 [new name for Mactra ovalis Gould, 1840, not Sowerby, 1817]. Callista voyi Gabb, 1866, p. 24, pl. 5, fig. 41. Spisula (Hemimactra) voyi (Gabb). Packard, 1916, p. 283—285, pl. 13. fip... pl. 14. боз 1.2. ph 15; figs: 1 2. Spisula (Mactromeris) voyi korolevae Zhidkova, 1972, p. 140, pl. 24, figs. 1, 6. Discussion.—Most Tachilni specimens of Spisula belong to this morphotype, which is characterized by large, relatively elongate shells that are only moder- ately inflated. As with Tachilni specimens of 5. (M.) albaria (Conrad, 1848) and S. (M.) brevirostrata Pack- ard, 1916, most shells of S. (M.) polynyma are disar- ticulated and preserved as molds and casts, and their dentition is not visible. This species occurs commonly in the North Pacific and northwestern Atlantic oceans (Chamberlin and Stearns, 1963). The name S. (M.) voyi (Gabb, 1866) has often been used for Pacific populations, though it has long been recognized that differences from S. (M.) polynyma were slight at best (Stewart, 1930; Grant and Gale, 1931). Extensive synonymies for 5. (М.) poly- nyma are in Packard (1916), Stewart (1930) and Grant and Gale (1931). The oldest Alaskan record of this species may be that of Ariey (1978, p. 94), who tentatively recognized itin the lower part of the Yakataga Formation at Ya- kataga Reef, northeastern Gulf of Alaska, in rocks she assigned a Newportian age. I reexamined her speci- men and, due to its poor preservation, can only ques- tionably assign it to S. (M.) polynyma. Her evidence for a Newportian age is also not firm, and the specimen may be of Wishkahan age. Shells assignable to S. (M.) polynyma are in USGS collections from the middle and upper parts of the Yakataga Formation, but the age of the stratigraphically lowest occurrence is not yet known. This species is also well-known in the Bear Lake Formation on the Alaska Peninsula (Text-fig. 2). which is in part coeval with the Tachilni Formation. The first report of this species in the Tachilni fauna was by Allison (1978, p. 176), based on some of the present specimens, and no verified older occurrences in Alaska are known. A possible ancestor of S. (M.) polynyma is S. (M.) equilateralis (Clark, 1932), a sim- ilar species that occurs in upper Oligocene or lower Miocene strata of the upper Poul Creek Formation in the Cape Yakataga area. The oldest reliable northwestern Pacific record of 5. (M.) polynyma is that of Slodkewitsch (1938a, p. 485- 490) from the “иррег horizon of the Kavran" Group of western Kamchatka. In modern terms (Menner, Baranova, and Zhidkova, 1977) this stratigraphic in- terval is equivalent to the Etolon Formation of late Miocene age. Slodkewitsch (1938a) also cited this species from the ‘‘upper horizon of the Tighil (?)”’ Group of western Kamchatka, but those rocks are of Eocene age, so this record is likely based on a mis- taken identification or stratigraphic assignment. Zhid- kova et al. (1968, p. 125) report this species in upper Miocene or Pliocene rocks of Sakhalin, and Zhidkova (1972, p. 139-140) cited it in the lower Pliocene Okrug- lovska Formation and the middle or upper Pliocene Okeanska Formation of Paramushir Island, Kuril Is- lands. From the former formation Zhidkova (1972, p. 140) named a new subspecies, 5. (M.) voyi korolevae, which is synonymized here with S. (M.) рогупута. Records in Japanese Tertiary faunas are in need of review. This species has been cited in strata as old as the Eocene or Oligocene Poronai Formation (Takeda, 1953) and is frequently named in Miocene and Pliocene faunas (Hatai and Nisiyama, 1952; Masuda and Noda, 1976). Type information.—Holotype: location and type 10- cality unknown. Tachilni Formation occurrence.—USGS localities M4044 (1 articulated specimen), M5169 (1 valve) M7146 (abundant valves), M7150 (abundant valves): M7256 (5 valves), M7258 (1 valve); UA localities A-169 (abundant valves), A-302 (abundant valves). Figured specimens.—USNM 339783, 339784, 339785, 339786, 339787. Stratigraphic and geographic range.—Because of the profound taxonomic complexities surrounding the S. (M.) polynyma morphotype it is not now possible to cite its first appearance or give its biogeographic history. The species evidently had a North Pacific or- igin (Durham and MacNeil, 1967) and is widely ге ported in Miocene through Pleistocene faunas from northeastern Honshu to northwestern California. The TACHILNI FORMATION MOLLUSKS: MARINCOVICH 97 modern southern end-point of its range in Asia is var- lously cited as northern Sakhalin (Chamberlin and Stearns, 1963) or Fukushima Prefecture, northeastern Honshu (Kamada, 1962, p. 125). As documented by Chamberlin and Stearns (1963), the range in the north- eastern Pacific and Arctic Oceans is from Point Bar- Tow, northwestern Alaska, to the Straits of Juan de Fuca, Washington. In the northwestern Atlantic the Tange is from northern Newfoundland south to off of Long Island, New York. The species is absent from the intervening Arctic Ocean coast. For northwestern Atlantic populations Chamberlin and Stearns (1963) Observed that limiting temperatures for survival and reproduction are 5.5°C and 13°C, and further noted A specimens in depths from the intertidal zone to m. Family TELLINIDAE Blainville, 1814 Genus PERONIDIA Dall, 1900 Peronidia aff. P. lutea alternidentata (Broderip and Sowerby, 1829) Plate 17, figures 3—9, Plate 18, figures 1—3 Discussion.—This taxon is characterized by a large, elongate, inflated, and relatively heavy shell that is rounded anteriorly and truncated posteriorly. The an- terior end is distinctly longer than the posterior, and the only sculpture is of low, irregularly spaced, con- centric growth lines. The Tachilni taxon belongs to a group of late Ce- Dozoic tellinids closely related to the well-known North Pacific Pleistocene and Holocene subspecies Peroni- dia lutea alternidentata (Broderip and Sowerby, 1829). However, the two taxa differ in shell proportions, size, and pallial line configuration. Shells of P. lutea alter- "dentata are equilateral to slightly longer posteriorly (Coan, 1971, p. 9), whereas all Tachilni specimens are Onger anteriorly, and the difference in gross appear- ance between the two taxa is distinctive. The largest Tachilni specimen is 79.1 mm long, compared to 110 mm for the largest specimen of P. lutea alternidentata б РУ Coan (1971, р. 9). Internal molds of some achilni specimens preserve pallial lines and adductor Muscle scars. Compared to the pallial sinus of Р. lutea alternidentata (figured in Coan, 1971, fig. 1), the left- uve sinus of the Tachilni taxon is more spacious and as а much blunter anterior termination (Pl. 17, figs. "i 9), and the right-valve sinus is more highly arched ersally (PI. 17, fig. 6). Ner» Japanese tellinids are very similar to the Tach- axon: the Miocene species P. protovenulosa (No- mura, 19353) and the Pliocene or Pleistocene to Ho- 9cene species P. zyonoensis (Hatai and Nisiyama, 1939). Peronidia protovenulosa differs from the Tach- ilni taxon by being more elongate and having a more sharply angular posterior end. Nomura (1935a, p. 87) cited an average length to height ratio of 1.83 for four specimens of P. protovenulosa. This same ratio for six Tachilni specimens is 1.61, and a juvenile seventh specimen has a ratio of 1.82. These few measurements suggest that Tachilni adults differ in shell proportions from adult P. protovenulosa. Peronidia zyonoensis oc- cupies a middle position between P. protovenulosa and the Tachilni taxon. Ogasawara (1977, p. 124) noted an average length to height ratio of 1.72 for 18 speci- mens of P. zyonoensis from the Pliocene or Pleisto- cene Omma Formation of central Honshu. Thus, P. zyonoensis evidently is more elongate than the Tach- ilni taxon, and also has a sharper posterior end and a distinctly more flattened posterior dorsal margin. The average length to height ratio of six specimens of P. lutea alternidentata from the Chukchi Sea (UA col- lection) is 1.65, about the same as that of the Tachilni taxon and close to that of P. zyonoensis. Coan (1971, p. 8) considered P. zyonoensis a junior synonym of P. lutea alternidentata. More than half of the Tachilni specimens have closed, articulated valves, a condition that suggests little or no post-mortem transport. Tachilni Formation occurrence.—USGS localities M310 (1 valve, as “?”), M7139 (2 articulated, closed adults), M7142 (1 articulated, closed adult, and | valve), M7146 (1 articulated, closed adult), M7149 (1 valve), M7150 (abundant valves); UA localities A-169 (1 valve), A-170 (3 articulated, closed adults); CAS locality 60278 (1 valve). Figured specimens.—USNM 339788, 339789; UA 2477, 2478. Stratigraphic and geographic occurrence.—The Tachilni taxon belongs to a complex of northwestern Pacific tellinids that occur in Miocene and younger strata in Japan, Sakhalin and Kamchatka, and has modern representatives from southern Japan to Arctic Alaska. Genus MACOMA Leach in Ross, 1819 Subgenus MACOMA Leach in Ross, 1819 Macoma (Macoma) cf. M. (M.) astori Dall, 1909 Plate 18, figures 4—18 Macoma astori Dall, 1909, p. 128, pl. 14, figs. 1, 11; Weaver, 1942, pt. 1, p. 213, pt. 3, pl. 49, fig. 14; Moore, 1963, p. 81, pl. 28, fig. 15 [as ‘‘cf.’’], pl. 29, fig. 12 [refigured holotype]; Addicott, 1976a, p. 107, pl. 2, fig. 14. Discussion.—This shell is slightly elongate and 98 BULLETIN 317 ranges in outline from ovate to somewhat trigonal. The umbones are prominent and located about three-fifths of the distance from the anterior to posterior extrem- ity. The anterior dorsal margin is slightly convex and merges smoothly with the evenly rounded anterior margin. The ventral margin is evenly rounded except for a very slight flattening or convexity along its mid- dle to posterior portion. The posterior dorsal margin is straight to slightly convex and joins, with varied degrees of abruptness, a subtruncate to narrowly rounded posterior extremity. The valves are moder- ately inflated and have a weak flexure to the right pos- teriorly. A shallow groove just below the dorsal mar- gin extends from the umbo to the posterior extremity of most specimens, but is obsolete on some individu- als. Sculpture consists only of fine concentric growth lines. Interior features are not visible. The largest Tachilni specimen is 45.8 mm long and several other adults are nearly that size. The difficulties inherent in identifying species of Macoma are especially apparent in these Tachilni specimens. As noted by Coan (1971, p. 24), М. (M.) astori seems closely related to M. (M.) brota Dall, 1916. The latter species, in turn, is difficult to distin- guish from M. (M.) lipara Dall, 1916, and the two have been considered synonymous (Bernard, 1967). In ad- dition, M. (M.) brota may be so similar to some spec- imens of M. (M.) calcarea (Gmelin, 1791), that hy- bridization between the two has been suspected (Dunnill and Coan, 1968, p. 17). Tachilni specimens are only tentatively assigned to M. (M.) astori because that species is known from relatively few specimens, and because its range of morphologic variation is imperfectly understood. Most Tachilni shells have outlines similar to those of the type specimens of M. (M.) astori figured by Dall (1909), but many are relatively higher and are identical in out- line to a specimen figured by Moore (1963, pl. 28, fig. 15) as M. cf. M. astori. The most variable features of the Tachilni shells are their relative height, the degree to which the groove below the posterior dorsal margin is developed, and the degree of bluntness of the pos- terior termination. This taxon seems to be absent from Asiatic faunas. A specimen cited as M. astori and reported from un- named Miocene beds in eastern Kamchatka by Slod- kewitsch (1938b, p. 172, pl. 93, fig. 7) appears too poorly preserved to identify below the generic level. Seven of 28 Tachilni specimens are articulated and all but one of the former have closed valves. Type information.—Holotype: USNM 153937. Type locality: Coos Bay, southwestern Oregon; Empire Formation; upper Miocene. Tachilni Formation occurrence.—USGS localities M7140 (7 articulated, closed specimens, 15 valves), M7142 (2 articulated, closed specimens, 4 valves), M7150 (1 articulated, closed specimen, 4 valves), M7203 (2 valves); UA locality A-170 (1 articulated, closed specimen, 3 valves). Figured specimens.—USNM 339790-339800. Stratigraphic and geographic range.—Macoma (Macoma) astori has been reported only in Newport- ian and Wishkahan faunas of Oregon. Upper lower to middle Miocene (Newportian): Astoria Formation, northwestern Oregon (Moore, 1963; Addicott, 1976a). Lower upper Miocene (Wishkahan): Empire Forma- tion, Coos Bay, southwestern Oregon (Dall, 1909; Weaver, 1942; Addicott, 19762). Macoma (Macoma) optiva (Yokoyama, 1923) Plate 19, figures 1—10 Tellina optiva Yokoyama, 1923, p. 6, pl. 2, figs. 3a, 3b, 4. Macoma optiva (Yokoyama). Nomura, 1935b, p. 36, pl. 4, figs. 4. 12; Slodkewitsch, 1938b, p. 172, pl. 94, figs. 4—9; Kanno, 1960, p. 299—300, pl. 43, figs. 10а-10с, pl. 44, figs. 1, 2; Kamada, 1962, p. 128-130, pl. 15, figs. 1-6; Ilyina, 1963, p. 81-82, pl. 27, figs. 6. PA Macoma n. sp.? Moore, 1963, p. 81, pl. 29, figs. 10—11; Addicott, 1976b, p. 33, pl. 8, fig. 4. Discussion.—This species is characterized by its relatively large size and height, semicircular anterior outline, and sharply sloping posterior dorsal and ven- tral margins that join a narrow, subtruncate posterior end. The umbo is nearly central, but slightly closer to the anterior end. The valves are moderately inflated, moderately to strongly flexed to the right posteriorly; and sculptured only with fine concentric growth lines. The pallial sinus of Tachilni specimens agrees well in shape with that of a syntype specimen figured by Yo- koyama (1923, pl. 2, fig. 3b). This extinct Tertiary species is most closely related in form to M. (M.) obliqua (Sowerby, 1817), a Pleis- tocene to Holocene species of the northeastern Pacific and Arctic Oceans (Coan, 1971). However, M. (M.) optiva differs by being much larger (to 76.4 mm length herein, versus to 50 mm length for M. (M.) obliqua): by being slightly elongate posteriorly rather than being equidimensional or slightly elongate anteriorly, БУ having more sharply sloping posterior dorsal and ven- tral margins, by having a subtruncate rather than rounded posterior termination, and by having a po$- terior end usually more strongly flexed to the right. Macoma (Macoma) optiva has been widely report- ed in middle and upper Tertiary faunas of northern Japan and the far-eastern U.S.S.R. (Slodkewitsch. 1938a; Hatai and Nisiyama, 1952; Ilyina, 1963; Ma- TACHILNI FORMATION MOLLUSKS: MARINCOVICH 99 Suda and Noda, 1976). The only previous citation of this species in North America was that of Allison and Marincovich (1981), who tentatively assigned to this Species a juvenile specimen from upper Oligocene or lowermost Miocene beds of the Narrow Cape For- Mation of Sitkinak Island in the western Gulf of Alas- ka. That specimen still cannot be confidently assigned to М. (М.) optiva, so Tachilni specimens are the first Verified occurrence of this species in the northeastern Pacific. However, Moore (1963) was the first to note an evidently undescribed species of Macoma in Mio- сепе beds of Oregon, and Addicott (1976a, р. 101) thought this species was restricted to his newly pro- Posed Pillarian Stage (lower Miocene) of Washington and Oregon. Macoma (Macoma) optiva was described from up- Per Miocene beds of the Fujina Formation, then thought to be of Pliocene age, in southwestern Honshu (Yokoyama, 1923; Nomura and Hatai, 1939). All Jap- anese reports since then have been of Miocene occur- rences (Hatai and Nisiyama, 1952; Masuda and Noda, 1976). The oldest record of this species in Japan or elsewhere is from the Chichibu Basin of central Hon- shu, where M. (M.) optiva is reported in lower Mio- сепе rocks of the Nenokami Sandstone and the Ushi- Kubitoge Formation (Yokoyama, 1925; Kanno, 1960). his species is no longer thought to occur in Pliocene faunas, and the youngest Japanese occurrences are in Eus a late Miocene age (Masuda and Noda, Macoma (Macoma) optiva has been widely report- *d in Miocene faunas of western and eastern Kam- chatka (Slodkewitsch, 1938a, p. 472; 19386, р. 172; Ilyina, 1963, p. 81-82), Sakhalin (Ilyina, 1954, p. 231; hos 1963, p. 82), and the Kuril Islands (Zhidkova, 2, p. 138). Some of these occurrences originally уеге thought to be of Pliocene age, but evidently all аге now considered to come from Miocene faunas oe Baranova, and Zhidkova, 1977; Gladenkov, is 7). Gladenkov (1977) noted this species present only | the Kakert and Etolon Formations of Kamchatka, ° which he assigned middle Miocene ages. Menner, no and Zhidkova (1977) considered the same | ata to span an age of about early middle to early ale Miocene. There seem to be no reports of M. (M.) орпуа in early Miocene faunas of the far-eastern S.S.R., which may be the result of incomplete col- ов in that region, because the species is known in rata of that age in Japan (Kanno, 1960), Oregon and aden (Addicott, 1976a, 1976b), and possibly aska (Allison and Marincovich, 1981). Eu on Kanno's (1960, p. 152-153, 155-156) ob- ^"lvations of lower Miocene faunas in the Chichibu le Basin [formerly thought to be of Oligocene age; S. Kanno, oral commun., 1981], this species had a rather broad bathymetric range. In those faunas, M. (M.) optiva occurs in inferred shallow-water assemblages (0—200 m) of the Nenokami Sandstone and the Shirasu Sandstone Member of the Ushikubitoge Formation, as well as in inferred deeper-water assemblages (more than 200 m) of the Tomita Siltstone Member of the Ushikubitoge Formation. The Nenokami and Shirasu faunas were inferred to represent warm to temperate marine hydroclimates, and the Tomita fauna to rep- resent a temperate to cold hydroclimate. Type information.—Type specimens [syntypes?]: GT, not numbered (Hatai and Nisiyama, 1952). Type locality: ‘Јаке cliff about 300 m NWW [2] of Jyakusan, N of Fujina,’’ Shimane Prefecture, southwestern Hon- shu, Japan (Hatai and Nisiyama, 1952); Fujina For- mation; upper Miocene. Tachilni Formation occurrence.—USGS localities M7150 (1 valve), M7256 (4 valves); UA localities A-169 (2 articulated, closed specimens), A-170 (5 articulated, closed specimens), A-302 (1 valve, as “?”); CAS lo- calities 60278 (1 articulated, closed specimen), 60279 (9 articulated, closed specimens, | valve), 60280 (1 valve). Figured specimens.—UA 2479-2483. Stratigraphic and geographic range.—Known mainly in Asian faunas, this species ranges from upper Oligocene or lowermost Miocene to upper Miocene. Upper Oligocene or lowermost Miocene: Narrow Cape Formation of Sitkinak Island, Trinity Islands, western Gulf of Alaska (Allison and Marincovich, 1981, as ср). Lower Miocene: Tomita Siltstone Member and Shirasu Sandstone Member of Ushikubitoge Forma- tion, and Nenokami Sandstone, Chichibu Basin, cen- tral Honshu, Japan (Kanno, 1960). Lower Miocene (РШагіап): Nye Mudstone, northwestern Oregon (Ad- dicott, 1976a); Clallam Formation, northwestern Washington (Addicott, 1976b). Upper lower or middle Miocene (Newportian): Astoria Formation, north- western Oregon and southwestern Washington (Moore, 1963: Addicott, 1976a, 1976b). Lower or middle Mio- cene: Honya Formation, Joban coal field, central Hon- shu, Japan (Kamada, 1962); Kuluven Formation of Vayampol Group and Ilyinsk Formation of Kavran Group, western Kamchatka (Slodkewitsch, 1938a, 1938b; Ilyina, 1963). Middle Miocene: Kakert For- mation of Kavran Group, western Kamchatka, and Kurasai Formation and lower part of Maruyama For- mation, south Sakhalin (Ilyina, 1963). Middle (?) Mio- cene: Numanouchi, Kokozura and Nakayama For- mations, Joban coal field, central Honshu (Kamada, 1962). Middle or upper Miocene: Okobykayska For- mation of north Sakhalin (Zhidkova, 1972). Upper Miocene: Fujina Formation, Shimane Prefecture, southwestern Honshu (Yokoyama, 1923; Nomura and Hatai, 1939). Miocene, exact age unknown: Sanku- betsu (Kanno, 1960), Kawabata and Tokomuro (Ma- suda and Noda, 1976), and Wakkanai (Hatai and Ni- зтуата, 1952) Formations of Hokkaido; Kadonosawa, Ainaigawa, Sunakose, and [?] Takahoko Formations of northern Honshu (Kanno, 1960; Masuda and Noda, 1976); Nagano, Itsukaichi, Okazaki, Ohno, and Ya- manouchi Formations of central Honshu (Masuda and Noda, 1976); Kaisekizan and Muro Formations of southern Honshu (Masuda and Noda, 1976); unnamed sandstone, Korf Gulf, eastern Kamchatka, and un- named beds along Kavran, Tnonkhlno, Lanych and Etolon Rivers, western Kamchatka (Slodkewitsch, 1938a, 1938b); Rykhlaya Group (Slodkewitsch, 1938a, 1938b) and Sertunai, Alexandrovska and Borska For- mations (Zhidkova, 1972) of Sakhalin; Alekhinska Formation, Kunashir Island, Kamuyska Formation, Iturup Island, and Shumnovska Formation, Paramu- shir Island, Kuril Islands, U.S.S.R. (Zhidkova, 1972). Macoma incongrua (von Martens, 1865) Plate 18, figure 19 Tellina incongrua von Martens, 1865, p. 430-431. Macoma incongrua (von Martens). Kanno, 1971, р. 77-78, pl. 6, fig. 6, pl. 9, figs. 9, 10, 12; Addicott et al., 1971, p. C20, figs. 5n, 5o [as ‘‘cf.’’]; Marincovich, 1980, p. C9, fig. 10; Allison and Ma- rincovich, 1981, table 6, pl. 1, fig. 26. Discussion.—This well-known Alaskan Tertiary species has valves that are inflated anteriorly and have a broadly rounded anterior end. The posterior dorsal and ventral margins slope steeply and join an acutely angled posterior termination. There is a distinct flex- ure to the right posteriorly. Macoma incongrua is represented in Tachilni col- lections by only three specimens, only one of which is well preserved. It differs from juveniles of M. (M.) optiva (Yokoyama, 1923) by its straight, not convex, anterior dorsal margin that joins the anterior margin at an angle rather than blending smoothly with it. In addition, M. incongrua has a narrowly rounded pos- terior extremity, compared to the subtruncate poste- rior end of M. (M.) optiva. Even though M. incongrua is the most common Tertiary species of Macoma Leach in Ross, 1819 in the eastern Gulf of Alaska (Kanno, 1971; Marincovich, 1980), it is rare in the western Gulf—the Alaska Pen- insula and adjacent islands. The only previous report of M. incongrua in the western Gulf of Alaska is in upper Oligocene or lowermost Miocene rocks of the Narrow Cape Formation of Sitkinak Island (Allison, 1978; Allison and Marincovich, 1981). In Japan, this BULLETIN 317 species is reported in Neogene faunas of central and northern Honshu and Hokkaido (Hatai and Nisiyama, 1952; Masuda and Noda, 1976). There seem to be no reported finds in the far-eastern U.S.S.R. Reports of M. incongrua in Pleistocene faunas of Oregon and Washington have been referred to M. (M.) obliqua (Sowerby, 1817) by Coan (1971) and Kennedy (1978). The modern occurrence of M. incongrua in the western Pacific is reported to be in muddy bottoms ranging in depth from the intertidal zone to 10 m (Kan- no, 1971). Type information.—Lectotype (designated by Coan, 1971, p. 26): ZMH, No. 7624. Type locality: Yoko- hama, Japan; Holocene. Tachilni Formation occurrence.—USGS localities M7142 (1 valve, as ‘‘cf.’’), M7146 (1 valve), M7150 (1 valve, as ‘‘cf.’’). Figured specimen.—USNM 339801. Stratigraphic and geographic range.—The known range of this species is from the upper Oligocene ог lowermost Miocene to Holocene. Upper Oligocene or lowermost Miocene (Juanian): Narrow Cape Forma- tion of Sitkinak Island, western Gulf of Alaska (АШ- son, 1978; Allison and Marincovich, 1981). Upper Oli- gocene or lower Miocene: upper part of Poul Creek Formation, Yakataga district, eastern Gulf of Alaska (Kanno, 1971). Upper lower to middle Miocene (New- portian): Topsy Formation, Lituya district, eastern Gulf of Alaska (Marincovich, 1980); Yakataga Formation, Yakataga district, eastern Gulf of Alaska (USGS coll.). Middle (?) Miocene: Chiganoura Formation, Miyagi Prefecture, northeastern Honshu, Japan (Nomura, 1935b). Middle or upper Miocene: Yakataga Forma- tion, Yakataga and Lituya districts, eastern Gulf of Alaska (Ariey, 1978; USGS coll.). Upper (?) Miocene: Takinoue Formation, Hokkaido, Japan (Kanno and Ogawa, 1964). Miocene, exact age unknown: Kami- yokoze Formation, Saitama Prefecture, central Hon- shu (Watanabe, Arai, and Hayashi, 1950), and Kubota Formation, Fukushima Prefecture, northern Honshu (Iwasaki, 1970), Japan. Pliocene: Chinkope Forma- tion, Hokkaido (Sawada, 1962). Holocene: Kyushu north to Hokkaido, Japan, the Kuril Islands, Korea, and China (Kuroda, Habe, and Oyama, 1971). Family SOLENIDAE Lamarck, 1809 Genus SILIQUA Megerle von Muehlfeld, 1811 Siliqua cf. S. alta (Broderip and Sowerby, 1829) Plate 19, figures 11—13, Plate 20, figure 1 Solen altus Broderip and Sowerby, 1829, p. 362. Siliqua patula alta (Broderip and Sowerby). Oldroyd, 1924, vol. 1, р. 190, pl. 47, figs. 1, 2. Siliqua alta (Broderip and Sowerby). Grant and Gale, 1931, p. 3887 389; ple 21, Dg: |, TACHILNI FORMATION MOLLUSKS: MARINCOVICH 101 _Discussion.—Compared to similar northeastern Pa- Cific species of Siliqua, this species is characterized bya relatively short shell, broadly rounded posterior end, and relatively elevated posterior dorsal margin or flange, with its greatest height posterior to the beaks (Roth, 1979, p. 335). Siliqua alta is characterized by а vertical internal rib (Roth, 1979), whereas Tachilni Specimens have ribs with a slight anterior slant. Com- bined with the preservation of Tachilni specimens only ЭВ Internal molds, the variation in rib inclination makes Identification as 5. alta somewhat tentative. The first appearance of Siliqua in the Pacific North- West was in Wishkahan faunas (Addicott, 1976a, p. 98). Approximately coeval occurrences are reported ш California (Roth, 1979, p. 330) in the upper Miocene Sisquoc Formation (Woodring and Bramlette, 1950) апа Santa Margarita Formation (Adegoke, 1969), as Well as in the upper Miocene San Pablo Group (Weav- er, 1949; Hall, 1958). The "Siliqua sp." reported by Kanno (1971) from the highest exposed bed of the Yakataga Formation at Yakataka Reef, northeastern Gulf of Alaska, is of Wishkahan or younger age. The earliest reported occurrence of S. alta is in Pliocene Strata of the Rio Dell Formation and undifferentiated Wildcat Group of northwestern California (Roth, 1979, P. 334). Siliqua lucida (Conrad, 1837) has been re- Ported in several upper Miocene formations in Cali- fornia (Roth, 1979, p. 339), as well as in the Wishkahan Skonun Formation of British Columbia (Addicott, 1978, P. 680). However, Tachilni specimens of Siliqua ap- Pear to differ from S. lucida by having an anteriorly Inclined rather than vertical internal rib, and by lack- Ing a groove to set off the posterior dorsal margin or ange, Modern species of Siliqua are reported to live in depths from the intertidal zone to 60 m, burrowed into Sandy or silty substrates (Kanno, 1971, p. 74). Type information.—Holotype: presumably in M(NH). Type locality: Arctic Ocean; Holocene. Tachilni Formation occurrence.—USGS localities 310 (2 valves), M5168 (1 articulated, open speci- Шеп), M7146 (2 articulated, closed specimens, 2 | es M7150 (4 articulated, closed specimens; 4 ar- Iculated, open specimens; 16 valves), M7256 (1 valve); A locality A-301 (1 valve). Figured specimens.—USNM 339802, 339803, 39804: UA 2484. Stratigraphic and geographic range.—The strati- е range of S. alta is difficult to assess from the à erature because of disagreement on the morphologic үе assigned by authors to Siliqua species. Although p^ (1979) reported the first S. alta in Pliocene strata Northwestern California, ће noted the presence of a form like S. alta in Neogene rocks of central and southern California, including the upper Miocene Sis- quoc Formation and Cebada and Graciosa Members of the Careaga Sandstone near Santa Maria (Woodring and Bramlette, 1950), the upper Miocene Etchegoin Formation of the San Joaquin Valley (Grant and Gale, 1931; Woodring, Stewart, and Richards, 1940), and the upper Miocene Pancho Rico Formation of the Salinas Valley (Durham and Addicott, 1965). Roth (1979) not- ed the following occurrences: Pliocene: Rio Dell For- mation and undifferentiated Wildcat Group, north- western California. Lower Pleistocene: type Merced Formation near San Francisco, California (Glen, 1959); unnamed beds at Moonstone Beach, northwestern California. Upper Pleistocene: Scotia Bluffs Forma- tion, northwestern California. Pleistocene: Gubik For- mation near Nome, Alaska (MacNeil, Mertie, and Pilsbry, 1943). Holocene: Chukchi and Bering Seas to Cook Inlet, Alaska, and northern Honshu, Japan (Habe, 1965), in depths of zero to 55 m (Roth, 1979). Family MYIDAE Lamarck, 1809 Genus MYA Linnaeus, 1758 Subgenus MYA Linnaeus, 1758 Mya (Mya) truncata Linnaeus, 1758 Plate 20, figures 2-7 Mya truncata Linnaeus, 1758, p. 670. Mya (Mya) truncata Linnaeus. Grant and Gale, 1931, p. 414—415 [contains extensive synonymy]; MacNeil, 1965, p. G38-G40, pl. 8, figs. 1-12, pl. 9, figs. 1-3, 5-20 [contains extensive synonymy]. Mya truncata Linnaeus. Nagao and Inoue, 1941, p. 155—156, pl. 33, figs. 5, 9, 10 [contains extensive synonymy]; Fujie, 1957a, p. 399— 400, pl. 3, figs. 1-4. Discussion.—Tachilni specimens are typical of this species and have ovate shells that terminate in sharply truncate and widely gaping posterior ends with flared margins. The umbo is moderately elevated, and an- terior end broadly rounded, and sculpture consists only of irregular, coarse growth lines. The pallial line and dentition are not observable on Tachilni specimens. The largest Tachilni specimen is 77.0 mm long and 59.1 mm high, and most other adults are close to this in size. Two juvenile specimens are questionably as- signed to this species because their posterior trunca- tions are poorly expressed (one is shown on Pl. 20, fige This is the most ubiquitous Alaskan Cenozoic species of Mya and occurs in several formations of Miocene and younger age. It has been reported previously in the Tachilni Formation (Marincovich in McLean, En- glehardt, and Howell, 1978), and occurs in USGS col- lections from the Bear Lake Formation. In the eastern Gulf of Alaska, М. (М.) truncata is known from nu- merous localities in the Yakataga Formation (Clark, 1932; MacNeil, 1965; Kanno, 1971) that range in age from Wishkahan (?) to Pleistocene, based on USGS collections. In the northwestern Pacific the species has been reported in Miocene and Pliocene strata of Hok- kaido (Nagao and Inoue, 1941; Fujie, 1957b), western Kamchatka, and northern Sakhalin (Slodkewitsch, 1938a, 1938b). As MacNeil (1965, p. G39) noted, M. (M.) truncata is known from many geographic local- ities and stratigraphic horizons in the North Pacific, Arctic and North Atlantic Oceans. The age of the first appearance of M. (M.) truncata is uncertain. MacNeil (1965, p. G39) considered the earliest occurrence to be in the lower part of the Ya- kataga Formation of the eastern Gulf of Alaska, and in the Chikubetsu Formation of Hokkaido, which he thought to be of early middle Miocene age. Strauch (1972) evidently thought the earliest representatives to be of late Miocene age from the northwestern Pacific. USGS collections show this species present in the ear- liest Wishkahan faunas of the Yakataga Formation at Cape Yakataga, but absent from the underlying New- portian fauna. The first appearance of Mya in the Pa- cific Northwest is also in Wishkahan faunas (Addicott, 1976a). The possibility that M. (M.) truncata occurs only in Wishkahan and younger faunas needs to be tested by further collecting. Nearly all Tachilni specimens of M. (M.) truncata are articulated and closed, and I collected some in life positions. This suggests that Tachilni sediments have lain undisturbed since deposition. The commonly ac- cepted bathymetric range for modern species of Mya is 0—50 m (Keen and Coan, 1974), though Bernard (1979b) claims depths to “100 m or more.”’ Type information.—Holotype: in collections of the LSL (Dodge, 1952, р. 28). Type locality: ‘‘in European seas"; Holocene. Tachilni Formation occurrence. —USGS localities M310 (1 valve, as ‘“‘cf.’’), M4044 (1 articulated, closed adult), M5166 (2 articulated, closed adults), M5169 (1 articulated, closed adult, 2 valves), M7142 (2 articu- lated, closed adults), M7143 (3 articulated, closed adults, and 1 valve), M7146 (2 articulated, closed adults, and 2 valves), M7149 (1 articulated, closed adult), M7150 (1 articulated, closed adult, 4 valves), M7256 (8 valves); UA localities A-170 (1 articulated, closed adult), A-301 (5 juvenile valves, as ‘‘?’’). Figured specimens.—USNM 339805, 339806; UA 2485, 2486. Stratigraphic and geographic range.—This ubiqui- tous species ranges from the middle or upper Miocene to Holocene. Many stratigraphic occurrences are cited BULLETIN 317 in the American, Japanese and Russian literature, and those given below are only the more relevant ones. Middle or upper Miocene: Honbetsu and Chikubetsu Formations, Hokkaido, Japan (Fujie, 1957a); Bear Lake Formation, Alaska Peninsula, Alaska (USGS coll.); Vayampol and Kavran Groups, western Kam- chatka (Slodkewitsch, 1938a, 1938b). Upper middle (?) Miocene (Newportian): lower part of Yakataga For- mation, Cape Yakataga, eastern Gulf of Alaska (MacNeil, 1965; USGS coll.). Lower upper Miocene (Wishkahan): Tachilni Formation, Cape Tachilni, Alaska Peninsula (Marincovich in McLean, Engle- hardt, and Howell, 1978); Empire Formation, Coos Bay, Oregon (Dall, 1909). Lower Pliocene: southern- most occurrence in Towsley Formation, Ventura County, southern California (MacNeil, 1965; Kern, 1973). Upper Pliocene: southernmost occurrence in Pico Formation, Ventura County, southern California (MacNeil, 1965). Undifferentiated Pliocene: Pomyr Group, Schmidt Peninsula, northern Sakhalin (Slod- kewitsch, 1938a, 1938b). Lower Pleistocene: south- ernmost eastern Pacific report in Timms Point Silt Member of San Pedro Formation, San Pedro, southern California (Clark, 1931). Upper Pleistocene: numerous literature citations in circumarctic and circumboreal regions, but the southernmost occurrence is unknown to me. Holocene: circumarctic and circumboreal; in the Atlantic, south to the Bay of Biscay and the Med- iterranean, and Cape Cod; in the eastern Pacific, south to at least Puget Sound, Washington, possibly to northern California; in the western Pacific, south to Rikuchu, Iwate Prefecture, northeastern Honshu (Bernard, 1979b). Subgenus ARENOMYA Winckworth, 1930 Mya (Arenomya) elegans (Eichwald, 1871) Plate 20, figures 8, 9, Plate 21, figures 1—3 Mya crassa Grewingk, 1850, p. 282-283 [not p. 355, as stated bY previous workers], pl. 6, figs. 2a-2d; Eichwald, 1871, p. 124. not Mya crassa Vallot, 1801, p. 7. not Mya crassa Wood, 1815, p. 106, pls. 20—21. Anatina elegans Eichwald, 1871, p. 119-121 [new name for ‘“‘My4 arenaria Linnaeus" of Grewingk, 1850, p. 283—284, pl. 6, figs: 3a-3c [= Муа crassa Grewingk, 1850]. Mya intermedia Dall, 1898, p. 857; Dall, 1921, p. 52, pl. 4 [not Муа intermedia Sowerby, 1814, p. 173]. Mya (Mya) arenaria profundior Grant and Gale, 1931, p. 414 [new name for Mya crassa Grewingk, 1850]. Mya (?Arenomya) elegans (Eichwald). MacNeil, 1965, р. 629-630: pl. 2, figs. 3—4, 6-8, pl. 3, figs. 1, 4 [contains extensive synonymy! Mya (Arenomya) elegans (Eichwald). Bernard, 1979b, p. 199-200. figs. 19-21. Discussion.—Tachilni specimens of M. (A.) elegans have an elongate trigonal shell with a broadly rounde TACHILNI FORMATION MOLLUSKS: MARINCOVICH 103 anterior end and narrowly rounded posterior end. The umbo is moderately to strongly elevated, so that some Specimens have their height nearly equal to their length. The posterior gape is small. Sculpture consists only of relatively coarse concentric growth lines. As seen on Some internal molds of articulated specimens, the Chondrophore is large, alate, and has a relatively shal- low ligamental pit and a large anterior buttress that forms a triangular platform. The pallial sinus opens broadly and extends about two-thirds of the distance from the posterior to anterior adductor muscle. Tachil- n Specimens are about 80 mm long and 60 mm high, with the largest specimen 101.0 mm long and 77.5 mm high (PI. 21, figs. 1-3). Specimens of M. (A.) elegans similar in form to Tachilni shells occur in Miocene faunas of the type Narrow Cape Formation on Kodiak Island, and the Bear Lake Formation at several localities on the Alas- ka Peninsula. The largest known collection of Tertiary Specimens of M. (A.) elegans comes from the Yellow Bluff Creek section of the Bear Lake Formation (USGS Coll.), near Black Peak on the Alaska Peninsula (Text- fig. 2). Most specimens from the Yellow Bluff Creek beds, of probable middle or late Miocene age, are Identical to Tachilni shells, but several are relatively More elongate and have less elevated umbones, as in the Yellow Bluff Creek specimen designated as the Пеогуре of M. crassa by MacNeil (1965, pl. 2, fig. 3). Ost specimens of M. (A.) elegans from the type Nar- row Cape Formation on Kodiak Island are similar to the пеогуре of M. crassa, although some have a more Steeply sloping posterior dorsal margin and conse- dently more sharply pointed posterior termination. Modern specimens assigned to M. (A.) elegans dif- fer from Tertiary specimens by being larger (to 180 mm long: Bernard, 1979b) and by having a relatively More elongate shell with a less elevated umbo, a rel- atively more elongate posterior end, a posterior ter- mum that is expanded and broadly rounded, a серег pallial sinus, and a much wider posterior gape. Us Possible that Holocene specimens are at least sub- %РесійсаПу distinct from Tertiary specimens. Ап ex- ade study of large populations, beyond the scope Of the present study, is needed to test this idea. Alas- ч Pleistocene specimens of M. (A.) elegans, not a merous in collections, seem to have the morphology a modern individuals. Dall (1921, pl. 5) figured the Perimposed life-size outlines of 28 modern speci- mens of M. (A.) elegans from Chignik Bay, Alaska E ш to usefully illustrate the variation in shell E. те found in a single population. However, there e to be no modern individuals of M. (A.) elegans have the elevated trigonal shell and small poste- rior gape of the Alaskan Tertiary fossil forms. The nomenclatural history of this species is some- what confused. The type specimens of M. crassa Gre- wingk, 1850, were Tertiary fossils reported to come from Pavlof, a now-abandoned Aleut Indian village or camp on the east side of Pavlof Bay (Orth, 1967, p. 743), along the Pacific coast of the Alaska Peninsula about 120 km northeast of Cape Tachilni (Text-figs. 2, 3). The only Tertiary strata in the environs of Pavlof are Paleocene or Eocene rocks of the Tolstoi Forma- tion (Burk, 1965), which are not a possible source for M. crassa. As suggested by MacNeil (1965, p. G30), Pavlof was probably only a base of operations for Eu- ropeans, and specimens of M. crassa probably were carried there from elsewhere on the Alaska Peninsula. After learning that the type specimens of M. crassa had been lost from the Zoological Institute in Lenin- grad, MacNeil (1965, p. G30, pl. 2, fig. 3) designated a neotype from beds of presumed Pliocene age along Yellow Bluff Creek, near Black Peak, Alaska Penin- sula, about 330 km northeast of Cape Tachilni (Text- fig. 2). Tertiary beds at Yellow Bluff Creek are now assigned to the Bear Lake Formation and thought to be of middle or late Miocene age. MacNeil (1965, p. G30, pl. 2, fig. 7) also designated a neotype from the same lot for M. (A.) elegans. In effect, MacNeil (1965) fixed the morphologic concepts of M. crassa Gre- wingk (a homonym) and M. (A.) elegans, based on neotype specimens from the same locality in the Bear Lake Formation at Yellow Bluff Creek. It is not known whether one or two species of Mya occur in the Yel- low Bluff Creek beds, due to sparse collecting and the wide variation in shell form of specimens of Mya col- lected there. Further study may show the two named species from Yellow Bluff Creek to be synonymous. Until then, it seems best to retain M. (A.) elegans for Tachilni specimens, because this name is well-estab- lished in the modern literature, in contrast to Gre- wingk's (1850) obscure homonym, M. crassa. Mya (Arenomya) elegans has been reported as a fossil only on the Alaska Peninsula, the Aleutian Is- lands, and Kodiak Island. Grewingk (1850) gave rec- ords from Kodiak and Unga Islands, from the Aleutian Islands of Atka [as ‘‘?’’] and Unalaska, and from Ше Alaska Peninsula at Pavlof, Morzhovoi Bay, and Port Moller. He also obscurely referred to a specimen from near Cape Romanzof in the northeastern Bering Sea, but it is unclear if this is a modern or fossil shell. Eichwald (1871) also cited its presence on Kodiak and Unalaska Islands. MacNeil (1965, p. G30) cautioned that some of these older records may be based on species other than M. (A.) elegans, and added several Alaskan Miocene to Holocene localities to the known occurrences. This species has been reported twice be- fore from the Tachilni Formation (Marincovich in McLean, Englehardt, and Howell, 1978; Allison, 1978). No precise bathymetric data have been published for M. (A.) elegans, though the species apparently lives only in relatively shallow water, as do other species of Mya. Bernard (1979b, p. 199) noted that the species is “‘rarely collected because of its deep in- faunal habitat and its absence from the intertidal and extreme shallow water zones." Bernard (1979b, p. 185) stated that individuals of the genus may be present at depths of “100 m or more," though he provided по documentation, and a more widely accepted figure for maximum living depth of species of Mya is 50 m (Keen and Coan, 1974). АП Tachilni specimens are articulat- ed, closed individuals that suggest little or no post- mortem transport. Type information.—Type specimen(s): [of M. (A.) elegans] lost from ZIL (MacNeil, 1965). Neotype: USNM 644272 (designated by MacNeil, 1965). Type locality: (of neotype): USGS locality M807a, beds on east side of Yellow Bluff Creek, near the headwaters, about 45 km south of Port Heiden, Alaska Peninsula; Bear Lake Formation; middle or upper Miocene. Tachilni Formation occurrence.—USGS locality M5163 (1 specimen), M5166 (3 specimens), M7139 (1 specimen), M7141 (1 specimen), M7146 (1 specimen), M7149 (11 specimens, 2 valves), M7202 (1 specimen); UA locality А-170 (2 specimens). Figured specimens.—USNM 339807, 339808. Stratigraphic and geographic range.—This species is cited in middle or upper Miocene to Holocene fau- nas, but there are no verified reports from Pliocene strata. Middle or upper Miocene: Bear Lake Forma- tion at Yellow Bluff Creek (MacNeil, 1965; USGS coll.) and at Bear Lake (formational type section; USGS coll.), Alaska Peninsula; Narrow Cape Formation type section, Narrow Cape, Kodiak Island (USGS and UA coll.). Lower upper Miocene: Tachilni Formation, Cape Tachilni, Alaska Peninsula (Marincovich in McLean, Englehardt, and Howell, 1978; Allison, 1978). Reputed Miocene occurrences in the Aleutians on Atka Island (Grewingk, 1850, as ‘‘?’’) and Unalaska Island (Gre- wingk, 1850; Eichwald, 1871), as well as on the Alaska Peninsula at Pavlof, Port Moller and Morzhovoi Bay (Grewingk, 1850), require confirmation; the Port Mol- ler report probably is from the Bear Lake Formation and the Morzhovoi Bay report probably is from the Tachilni Formation. Middle (?) Pleistocene: unnamed strata on St. Paul Island, Pribilof Islands (MacNeil, 1965) and on St. Lawrence Island, Bering Sea (Hop- kins, Rowland, and Patton, 1972). Holocene: Reported northern record is in the eastern Bering Sea, in Kus- BULLETIN 317 kokwim Bay north of Cape Newenham (MacNeil, 1965), but newer USGS collections contain beach-drift shells from as far north as Nokolek in the eastern Chukchi Sea at latitude 70?19'57"N; also reported from the Pribilof Islands and on the Pacific side of the Alas- ka Peninsula at Chignik and Kukak Bays (MacNeil, 1965) and northward as far as Cook Inlet (Bernard, 1979b). Mya new species? Plate 21, figures 4—9 Discussion.—This Tachilni taxon is characterized by a relatively elongate shell having a produced posterior end that has a moderate gape and flared margins. The posterior margin is bluntly rounded to subtruncate, compared to the broadly rounded anterior margin. The anterior dorsal margin is convex and slightly raised, the umbo is slightly elevated, and the posterior dorsal margin is depressed and straight to slightly concave. The ventral margin is straight to weakly convex and roughly parallel to the dorsal margin. The valves are only moderately inflated and their sculpture consists only of fine to coarse, irregularly spaced concentric growth lines. Of the two Tachilni specimens, one (Pl. 21, figs. 7-9) has its beaks nearly central but set very slightly to the anterior, and the other (РІ. 21, figs. 4- 6) has its beaks set a greater distance to the posterior of the shell center line. One specimen has a length of 55.4 mm and height of 29.0 mm and the other has à length of 50.2 mm and height of 27.0 mm. Among the large number of described species of Муа in the North Pacific (Clark, 1932; Nagao and Inoue; 1941; Krishtofovich and Ilyina, 1954; Fujie, 1957а, 1957b; Ilyina, 1963; MacNeil, 1965; Strauch, 1972). this species seems most closely related to M. (M.) truncata Linnaeus, 1758, M. (M.) salmonensis Clark. 1932, and M. (M.) majanatschensis Пуіпа, 1963. The moderately large gape and flared posterior margins ally the Tachilni taxon with M. (M.) truncata, although Mya n. sp.? is distinctly less inflated, smaller in size» relatively more elongate, and lacks the truncated pos- terior end of M. (M.) truncata. Mya (Mya) salmonen- sis, described from Oligocene rocks of the Poul Creek Formation in the northeastern Gulf of Alaska, is of similar size and elongate proportions to the Tachiln! taxon (Clark, 1932; MacNeil, 1965), but is known from few specimens, making comparisons with other species difficult. The holotype and paratype of M. (M.) sal- Monensis (Clark 1932 р listless OS ИЕ refigured by Addicott et al., 1971, figs. 5i, p, q, t, w) differ from the Tachilni specimens by having posterior ends with only a slight gape and unflared margins, a more inflate shell with a more elevated umbo, and a much more TACHILNI FORMATION MOLLUSKS: MARINCOVICH 105 Steeply sloping posterior dorsal margin. The types of М. (M.) salmonensis also have umbones relatively much closer to their anterior ends than do the Tachilni Specimens. A specimen of M. (M.) salmonensis fig- ured by MacNeil (1965, pl. 7, figs. 1, 4) is very similar to Clark’s (1932) figured types, but differs by having a lower umbo and less steeply sloping and relatively More elongate posterior end. Thus, the posterior end of MacNeil’s (1965) figured specimen is more similar to that of the Tachilni taxon than to Clark’s (1932) types. However, MacNeil’s (1965) specimen clearly lacks the flared posterior margin that is such a prom- nent feature of the Tachilni taxon. The specimens here assigned to Mya n. sp.? are also Similar in form to one figure (a paratype?) of M. (M.) Majanatschensis Пута, 1963 (pl. 31, fig. 5), a species hown from middle or upper Miocene strata of the Kakert Formation of western Kamchatka. Ilyina (1963, Ве 85) reported М. (М.) majanatschensis occurring in large numbers" with Macoma optiva (Yokoyama, 1923), which is a common Tachilni bivalve. The ho- lotype and most other illustrated specimens of M. (M.) majanatschensis Пуіпа (1963, p. 84-85, pl. 31, figs. 1, 3, 4, 6, 7) clearly differ from the Tachilni specimens of Mya by having strongly elevated umbones set very Close to the anterior end of the shell, a relatively ele- Vated shell outline with strongly concave posterior dorsa] margins and moderately convex ventral margin, and more strongly inflated valves. Both species have Similar posterior ends, with moderate gape and flared Margins. However, one of Ilyina's specimens (1963, pl. 31, fig. 5) resembles Mya n. sp.? by having elongate Proportions, a relatively low (and apparently some- What worn) umbo set slightly anterior of the shell Center line, and a nearly straight ventral margin. It is Possible that the Tachilni taxon falls within the mor- Phologic range of M. (M.) majanatschensis, and *qually likely that Ilyina's (1963, pl. 31, fig. 5) speci- men and the Tachilni specimens belong to another, Possibly undescribed species. Both specimens of Mya n. sp.? have articulated, Closed valves as evidence for little or no post-mortem transport. Tachilni Formation occurrence. (2 articulated, closed specimens). Figured specimens.—UA 2487, 2488. UA locality A-301 Family HIATELLIDAE Gray, 1824 Genus PANOMYA Gray, 1857 Panomya izumo Nomura and Hatai, 1939 Plate 21, figure 11 ф ; “nomya izumo Nomura and Hatai, 1939, p. 6, figs. 2a, b; Strauch, 1972, р. 65, pl. 4, fig. 2. Discussion.—This bivalve is one of the rarest in North Pacific Tertiary faunas. It was previously known from one formation in southwestern Honshu, and the Tachilni occurrence is its first outside Japan. The shell of P. izumo is relatively short and less quadrate than other species of Panomya (Strauch, 1972), and has a broadly and evenly rounded anterior end, slight an- terior placement of the umbo, and obliquely truncated posterior end. The posterior end is distinctive because of the broadly rounded and somewhat produced pos- terior ventral margin, narrow posterior dorsal angu- lation, and the ‘‘backward’’ slope of the posterior truncation (Г.е., the dorsal shell margin is shorter than the ventral margin). Illustrations of the holotype of P. izumo show a moderately elevated umbo, which is not clearly seen, but is suggested, on the slightly crushed Tachilni specimens. Sculpture of both Japanese and Alaskan specimens consists only of coarse, irregularly spaced concentric growth lines that crowd together at the posterior dorsal angle. The holotype, and only pre- viously illustrated specimen, of P. izumo is 54.5 mm long and 41.0 mm high (Nomura and Hatai, 1939). The most complete Tachilni specimen is 73.3 mm long and 52.4 mm high. A second and far less complete Tachilni specimen is about 45 mm high. Panomya izumo is not close in form to any other species. Panomya chrysis Dall, 1909, a coeval North American species, described from a single mold in the Wishkahan fauna of the Empire Formation at Coos Bay, Oregon (Dall, 1909, p. 133—134, pl. 11, fig. 7), differs from P. izumo by having a truncate posterior end that slopes in the opposite direction, a straight rather than broadly curved ventral margin, and a con- vex rather than concave posterior dorsal margin. Ac- cording to Strauch (1972, p. 78, fig. 12), P. izumo is descended from P. chrysis. The original citation of P. izumo, repeated by Strauch (1972), is the only record of the species known to me. Subsequent study of the molluscan fauna of the Fujina Formation (Ogasawara and Nomura, 1980) produced no new specimens. Modern catalogs of Japanese Ter- tiary mollusks (Hatai and Nisiyama, 1952; Masuda and Noda, 1976) also include no further mention of P. izu- то. Рапотуа is a northern cool-water genus, known from depths of five to 300 min western North America (Keen and Coan, 1974). Both Tachilni specimens have articulated and closed valves, suggesting little or no post-mortem transport. Type information.—Holotype: GS, No. 51884. Type locality: Izumo, Shimane Prefecture, southwestern Honshu, Japan; Fujina Formation; upper Miocene. USGS localities Tachilni Formation occurrence. 106 BULLETIN 317 M7143 (1 articulated, closed specimen), M7146 (1 ar- ticulated, closed specimen). Figured specimen.—USNM 339809. Stratigraphic and geographic range.—This species was previously reported only from upper Miocene strata of the Fujina Formation, Izumo, Shimane Pre- fecture, southwestern Honshu, Japan (Nomura and Hatai, 1939). Panomya trapezoidis Strauch, 1972 Plate 21, figure 12 Panomya trapezoidis Strauch, 1972, p. 61-62, 70-74, pl. 4, figs. 1, 3-12, text-figs. 10а-10п, 10s—10v. Panomya (Panomya) cf. P. (P.) trapezoides [sic] Strauch. Gla- denkov, Norton, and Spaink, 1980, p. 60, pl. 10, figs. 11-14. Discussion.—The single well-preserved specimen of Panomya trapezoidis in the Tachilni fauna closely re- sembles several specimens figured by Strauch (1972), although it is not identical in form to his figure of the holotype. The shell outline of P. trapezoidis is ex- tremely variable, however, and Tachilni specimens fall within the morphologic limits noted by Strauch (1972). The best-preserved Tachilni specimen is 48.7 mm long and 27.6 mm high, slightly smaller and more elongate than average for specimens measured by Strauch (1972, p. 67). The posterior margin of Tachilni specimens is shallowly concave, and the posterior dorsal margin is produced, as is common in P. trapezoidis. The ante- rior margin of the best-preserved Tachilni specimen is somewhat narrowly rounded, a feature that occurs in about half of the individuals figured by Strauch (1972). The central part of the best-preserved Tachilni speci- men is slightly concave and separated from the ante- rior and posterior portions of the shell by two radial ridges. This central concavity seems to occur in all specimens illustrated by Strauch (1972), but the de- velopment of radial ridges appears to vary widely, with many individuals lacking them. Panomya trapezoidis is among the most variable species in a genus noted for infraspecific variability. Roth (1979, p. 395) suggested possible synonymy of P. trapezoidis with P. chrysis Dall, 1909, described from the upper Miocene Empire Formation at Coos Bay, Oregon. Panomya cf. P. chrysis, so identified by Roth (1979, p. 392) occurs in lower and upper Pleis- tocene strata of northwest California and southwest Oregon, and resembles P. trapezoidis except for hav- ing a generally stronger flexure or re-entrant along the posterior margin (Roth, 1979, p. 393). Strauch (1972, p. 64) cited the oldest occurrence of P. trapezoidis in presumed upper Oligocene rocks of the Poul Creek Formation in the Cape Yakataga area, south-central Alaska, based on Clark’s (1932, p. 832, pl. 17, figs. 6, 7, 9) report of ‘‘Panomya (Arctica) tur- gida Dall’ and “Рапотуа n. sp.” there. Clark’s (1932) two taxa were reported from a total of five localities near Cape Yakataga, but none of these was assigned with certainty to the Poul Creek Formation by Addi- cott et al. (1971, p. C19) and one was placed in the lower Yakataga Formation. Kanno (1971, p. 95) re- ported “Рапотуа arctica” from the Yakataga but not the Poul Creek Formation near Cape Yakataga, and Ariey (1978, р. 114) collected “Рапотуа arctica” from two localities in the upper Poul Creek Formation, as well as in the Yakataga Formation, near Cape Yakata- ga. In USGS collections from the Yakataga area, P. trapezoidis is present only in the Yakataga Formation fauna. Because the boundary between the Poul Creek Formation and overlying Yakataga Formation appears to be time-transgressive (McCoy and Маппсомтећ, 1980), the uppermost Poul Creek strata may be of late Oligocene age at one locality and perhaps as young as early middle Miocene age at another. Thus, the age of the first occurrence of P. trapezoidis is not known with certainty, and the species may not occur in strata as old as Oligocene. Strauch (1972) reported many Miocene through low- er Pleistocene occurrences in California, the Pacific Northwest, and Europe, and cited a modern range from Kodiak Island, western Gulf of Alaska, to the Puget Sound region, Washington (Text-fig. 1). Many addi- tional literature records of species of Panomya in the eastern North Pacific need to be reevaluated for pos- sible assignment to P. trapezoidis. Living species of Panomya in the eastern North Pa- cific are reported from depths of five to 300 m by Keen and Coan (1974). Type information.—Holotype: SMF, No. SMF 2200996. Type locality: horizon 15/1 of the upper Westtjornes Beds, Hallbharnarstadakambur, Tjörnes, north Iceland; Pleistocene. Tachilni Formation occurrence.—USGS locality M7150 (1 valve); UA locality A-169 (1 articulated, closed specimen, as ‘‘cf.’’). Figured specimen.—USNM 339810. Stratigraphic and geographic range.—This species ranges from upper Oligocene or lower Miocene to Но" locene. Upper Oligocene (?): Poul Creek Formation, near Cape Yakataga, south-central Alaska (Ariey> 1978). Lower Miocene: Poul Creek and Yakataga For- mations, near Cape Yakataga, south-central Alaska (Clark, 1932; Kanno, 1971; Ariey, 1978). Reported by Strauch (1972, text-fig. 13) in Miocene to lower Pleis- tocene deposits of California, Oregon, Washington: Iceland, England, and the Netherlands. Holocene: Kodiak Island, western Gulf of Alaska, to Puget Sound region, Washington (Strauch, 1972). TACHILNI FORMATION MOLLUSKS: MARINCOVICH 107 Family PANDORIDAE Rafinesque, 1815 Genus PANDORA Bruguiere, 1797 Subgenus PANDORELLA Conrad, 1863 Pandora (Pandorella) grandis Dall, 1877 Plate 21, figure 10 Pandora (Kennerlia) grandis Dall, 1877, p. 5; Oldroyd, 1924, vol. l, р. 87-88, pl. 15, fig. 10; Grant and Gale, 1931, p. 261—262, pl. 13, figs. 5a, 5b. Pandora wajampolkensis Slodkewitsch, 1935, p. 304-306, pl. 29, figs. 3a, 3b; Slodkewitsch, 1938а, p. 272-273; Slodkewitsch, 19386, P. 126-127, pl. БУНЕ аре ри Discussion.—The relatively large size and very broadly rounded and expanded posterior end distin- 8uish this species from other North Pacific species of E UNS The single Tachilni specimen, at 37.5 mm Ong and 26.2 mm high, is of typical size for P. (P.) grandis. The species is further characterized by a ми radial flexure that extends from the umbo i the anterior ventral margin, lack of sculpture other àn concentric growth lines, and a straight to slightly convex posterior dorsal margin. Most other species of andora have a more strongly concave posterior dor- за! margin. E There are numerous living North Pacific species of andora (Dall, 1921; Oldroyd, 1924), but P. (P.) gran- 15 18 not easily confused with the others. Boss and Merrill (1965, p. 181) note that Pandora is a cosmo- ны genus with a preference for cooler waters of шее northern hemisphere, and that it is most highly E. erentiated along the coasts of eastern Asia, and oo and eastern North America. Roth (1979, p. ) cites the living Alaskan species P. forresterensis | Пет, 1918) as a junior synonym of P. (P.) grandis, and evidently is also the first to place the latter species In Pandorella. E Tachilni specimen of P. (P.) grandis is the only ез еа Miocene occurrence of this species in North <. erica. Dall (1896, p. 845) reported this species in locene" rocks of St. Paul Island, Pribilof Islands, E Sea, but this occurrence is of Pliocene or Pleis- M age. Based on its synonymy with P. wajam- oo Slodkewitsch, 1935, noted here for the first of 36 Р. (P.) grandis occurs in the “иррег horizon" ЊЕ Xe Vayampol Group in western Kamchatka (Slod- Witsch, 1938a, p. 272; 1938b, p. 127). In modern Usage, this stratigraphic interval is equivalent to the i Ventek and Kuvulen Formations, and is assigned an Е. of about early Miocene (Menner, Baranova, and НЕ Ра. 1977; Gladenkov, 1980). Slodkewitsch’s | 938b) illustrations show typical examples of P. (P.) erandis, but the occurrence of this species in western amchatka needs verification, because it has not been cited from there in later Russian works (Ilyina, 1963; Gladenkov, 1972). There are no certain Pliocene re- ports of this species, although Grant and Gale (1931, p. 262) refer to possible Pliocene occurrences in north- ern California. Data on the habitat of modern P. (P.) grandis are scant. Kennedy (1978, p. 501) cites a depth range of 18 to 372 m, in mud or sand, and P. (P.) grandis has been collected at Wrangell, southeastern Alaska, from a mud bottom at 91 m depth (Burch, 1944, No. 37, p. 16). The genus is reported in depths of five to 400 m in the eastern Pacific (Keen and Coan, 1974). Type information.—Holotype: USNM 171069. Type locality: Unalaska Island, Aleutian Islands, Alaska; Holocene. Tachilni Formation occurrence.—USGS locality M7139 (1 valve). Figured specimen.—USNM 339811. Stratigraphic and geographic occurrence.—This species ranges from the lower Miocene (?), Pliocene or Pleistocene to Holocene. Lower Miocene (?): upper Vayampol Group, Belogolovaya River, western Kam- chatka (Slodkewitsch, 1935, 1938a, 1938b). Pliocene or Pleistocene: St. Paul Island, Pribilof Islands, Alaska (Dall, 1896). Lower Pleistocene: Rio Dell Formation (Roth, 1979) and type Merced Formation (Martin, 1916), northern California; Anchor Silt (Rodda, 1957) and San Pedro Formation (Clark, 1931; Woodring, Bramlette, and Kew, 1946; Valentine, 1961), southern California. Upper Pleistocene: deposits in lower Fra- ser Valley and Vancouver Island, British Columbia, Canada (Wagner, 1959); EIk River Formation, south- western Oregon (Roth, 1979). Holocene: Pribilof Is- lands, Bering Sea, Alaska, to Siletz Bay, Oregon (Dall, 1921). Family LYONSIIDAE Fischer, 1887 Genus LYONSIA Turton, 1822 Lyonsia mooreae new species Plate 22, figures 1—4 Diagnosis.—Shell small for the genus, with a short and sharply truncated posterior end, straight to slight- ly convex dorsal margins, and fine radial costellae made up of microscopic beads. Description.—Shell ovate in outline, with a broadly and evenly rounded anterior end and a very slightly produced posterior end that is abruptly truncated; ventral margin evenly rounded, anterior and posterior dorsal margins straight to slightly convex, umbo mod- erately elevated; posterior dorsal portion of shell somewhat flattened and set off by a low angulation that extends from the umbo to the posterior ventral margin. Left valve slightly smaller than right with its umbo set below that of the right valve. Sculpture on each valve consists of fine, irregular concentric growth lines and very fine radial costellae; radial costellae are best developed on central portion of each valve and are missing from anterior one-third of valve and from flattened posterior dorsal area; costellae are separated by interspaces most commonly of greater, but rarely of equal width; radial costellae consist of closely spaced microscopic beads that are most distinct toward the ventral margin; on the proximal portion of each valve, these microscopic beads coalesce into a virtually con- tinuous, intermittently beaded thread; costellae are absent from umbones, evidently due to erosion during life. Posterior gape narrow but distinct. Largest spec- imen too poorly preserved for accurate measurement, but is close in size to the holotype, which is 14.9 mm long and 10.0 mm high; smallest specimen is 10.0 mm long and 7.3 mm high. Discussion.—Four specimens of Lyonsia mooreae n. sp. are present in a single hand sample of Tachilni sandstone and comprise the first occurrence of Lyon- sia as a fossil in Alaska. Each of the four individuals has articulated and closed valves, and the long axes of the shells are nearly in parallel alignment. Lyonsia тоогеае n. sp. is most similar in form to the living Japanese species L. teramachii (Habe, 1952). The latter species was proposed as the type-species of Bentholyonsia Habe, 1952, which was later considered to be a junior synonym of Lyonsia by Prezant (1981, p. 68). Lyonsia teramachii is similar in adult shell out- line to L. mooreae, but differs by being larger (up to 22.5 mm long and 15.8 mm high: Habe, 1952, 1958), having a concave rather than straight or convex pos- terior dorsal margin, and having its beaded radial cos- tellae more strongly expressed as well as covering the whole valve exterior. Judging from the young speci- men of L. teramachii figured by Kuroda, Habe, and Oyama (1971, p. 478, pl. 121, fig. 18), juveniles equal in size to L. mooreae are more elongate, with higher umbones and less sharply truncated posterior ends. The geographic range of L. teramachii is from Shi- koku, southern Japan, to the Boso Peninsula, central Honshu, and it occurs on fine-sand bottoms at 20 to 200 m depth (Kuroda, Habe, and Oyama, 1971, p. 478). ‘Etymology.—This species is named in honor of El- len J. Moore, my colleague at the U.S. Geological Survey, Menlo Park, California. Type information.—Holotype: USNM 339812. Paratypes: USNM 339813, 353151, 353152. Type lo- cality: USGS M7142, one m above base of measured stratigraphic section at Cape Tachilni (Text-figs. 3, 4); approximately 91 m (300 ft) east of southwest corner BULLETIN 317 section 31, T. 60 S, R. 89 W, on south boundary of section, False Pass (D-3) quadrangle, Alaska Penin- sula, Alaska; collected by L. Marincovich, Jr., June 1977. Tachilni Formation occurrence.—USGS locality M7142 (4 articulated, closed specimens). Figured specimens.—USNM 339812 (holotype); 339813 (paratype). Stratigraphic and geographic range.—Known only from its type locality. Family PERIPLOMIDAE Dall, 1895 Genus PERIPLOMA Schumacher, 1817 Subgenus PERIPLOMA Schumacher, 1817 Periploma (Periploma) cf. P. (P.) aleutica (Krause, 1885) Plate 22, figures 5—9 Anatina? aleutica Krause, 1885, р. 38—39, pl. 3, fig. 7. Periploma (Periploma) aleutica (Krause). Bernard, 1979a, p. 59, fig. 104. Periploma alaskana Williams, 1940, p. 37, fig. 1. Discussion.—Tachilni specimens of Periploma cf. P. aleutica have a broadly rounded anterior end, and an evenly curved ventral margin, with the posterior end produced, truncated and set off by a broad and shallow radial sulcus. The posterior dorsal margin is slightly concave, the umbo moderately elevated, and the anterior dorsal margin slightly convex. The main difference in shape between these and typical speci- mens of P. aleutica is that the latter has a more evenly rounded and broadly expanded posterior ventral mar- gin. The posterior ventral margin of Tachilni speci- mens is more narrowly produced (though not to a uni- form degree among individuals) than in typical specimens of P. aleutica. Tachilni specimens evident- ly are larger than modern individuals of P. aleutica from the western Beaufort Sea, where the largest was cited by Bernard (1979a, p. 60) as being 36.8 mm long: Dimensions of the best-preserved Tachilni specimens are: Two unnumbered specimens from USNM UA 2489 USGS locality M7140 339815 52.8 mm 41.4mm 38.4mm 38.1 mm 39.0mm 32.1 mm 27.8 mm 28.2 mm Length: Height: This Tachilni taxon is virtually identical in shell form to several North Pacific species of Thracia Leach іп Blainville, 1824, that occur in middle Tertiary to Ho- locene faunas (illustrated in Oldroyd, 1924, and Ka- TACHILNI FORMATION MOLLUSKS: MARINCOVICH 109 Mada, 1955). However, most well-preserved Tachilni Specimens have slightly eroded umbonal areas, where the trace of an internal buttress is clearly visible, ra- diating a short distance from the beak to the posterior ventral margin (Pl. 22, figs. 7, 9). Periploma has such а buttress supporting a chondrophore, whereas Thra- Cla lacks both. All Tachilni specimens also show the unmistakable presence of a nacreous interior shell lay- er where the valve exteriors are worn, which is another feature of Periploma not present in Thracia. At least 32 Cenozoic species of Periploma have been described from the North Pacific. Even though Tach- ni specimens seem to be closest to P. aleutica, the Morphologic variability of some species of Periploma Makes species-level taxonomy uncertain. For exam- ple, the only previously reported Tertiary species of Periploma from Alaska, Periploma (Aelga) bes- Shoense (Yokoyama, 1924), has a posterior margin that Varies from broadly rounded to rostrate (Kamada, 1962, IN 76; Kanno, 1971, p. 97). Tachilni specimens tenta- tively assigned to P. aleutica may eventually turn out to be one of several middle Tertiary Asiatic species. Periploma aleutica is known to live in Alaskan Waters, from the northern Gulf of Alaska to the west- ет Beaufort Sea (Bernard, 1979a, p. 59). Dead spec- Imens from the western Beaufort Sea were found in 709m depth (Bernard, 1979a). Periploma is a distinct- „У cold-water element in the Tachilni fauna. The genus 15 reported to range from 20 to 90 m depth in the north- astern Pacific (Keen and Coan, 1974). The present record is the first report of P. aleutica as a possible fossil. The fact that the thin, edentulous shells of all аспі specimens are articulated and closed is strong evidence for lack of post-mortem transport. Type information.—Holotype: location unknown. Уре locality: southern Bering Sea, north of Akutan ass, Aleutian Islands, Alaska [between Akutan and Nalaska Islands], at depth of 70 fms (Krause, 1885). Tachilni Formation occurrence.—USGS localities P (2 articulated, closed specimens), M7146 (1 ar- t ulated, closed specimen); UA locality A-170 (3 ar- culated, closed specimens). poured specimens.—USNM 339814, 339815; UA Stratigraphic and geographic occurrence.—Tachil- n Formation specimens are the first reported fossils Of this Species. Modern occurrences are reported from 9ntague Island, northern Gulf of Alaska, and the hukchi Sea (Williams, 1940), as well as the southern ering Sea (Krause, 1885) and western Beaufort Sea ernard, 19793), Class GASTROPODA Duméril, 1806 Family TROCHIDAE Rafinesque, 1815 Genus MARGARITES Gray, 1847 Subgenus PUPILLARIA Dall, 1909 Margarites (Pupillaria) new species? Plate 22, figures 10—15 Discussion.—Two Tachilni specimens match the definition of Margarites (Pupillaria) given in Кееп and Coan (1974): they are turbinate and umbilicate, have a nacreous interior and sculpture only of spiral riblets, апа are ‘‘medium-sized’’ (6 to 20 mm in diameter). The largest and best-preserved Tachilni specimen is 9.1 mm high and 11.2 mm in diameter and has five- and-one-half whorls, of which four show spiral sculp- ture. The spiral costellae are slender, slightly flat- tened, only slightly raised, and are separated by smooth interspaces of somewhat greater width. Ten costellae are visible on the penultimate whorl and about 18 on the body whorl above the broadly rounded periphery. On all earlier whorls the costellae are тоге widely spaced immediately below the suture and more closely bunched on the anterior part of the whorl. However, costellae on the body whorl, especially its anterior half, are more or less evenly spaced and separated by in- terspaces of equal or lesser width. Below the periph- ery, costellae also number about 18 and become rel- atively wider toward the umbilicus. The umbilicus is broadly open and circular in basal view. Nacreous shell material is visible where the exterior surface is decor- ticated. More than a dozen species of Margarites, s.l., are known from high-latitude North Pacific middle Ter- tiary faunas (Weaver, 1942; Hatai and Nisiyama, 1952; Masuda and Noda, 1976), and a similar number of Ho- locene species of Margarites (Pupillaria) occur in the same region (Dall, 1921). The Tachilni species is dif- ficult to compare to described taxa, because of inad- equate illustrations and descriptions accompanying some of the latter. It does not seem to be identical to any known Holocene species. The one species of Margarites previously reported from Alaska Peninsula Tertiary rocks is M. peninsu- laris Dall, 1904 (p. 110-111, pl. 9, fig. 6), described from Oligocene strata of the Stepovak Formation (MacNeil in Burk, 1965, p. 224). Relatively large at a height of 12 mm, M. peninsularis has spiral sculpture consisting only of a peripheral keel and one or two much weaker costellae (Dall, 1904, and USGS coll.), so is clearly distinct from the Tachilni species. The only other known Alaskan Tertiary species of Mar- garites, '*Margarites sp. nov. cf. M. chappelli Dur- ham, 1944," reported in Miocene rocks of the Yaka- taga Formation in the northeastern Gulf of Alaska by Ariey (1978, p. 121—122, pl. 1, fig. 6), differs from the Tachilni species by having a smooth exterior. Mar- garites chappelli, a late Eocene species from Wash- ington, also has a smooth exterior (Durham, 1944, p. 154). Among northwestern Pacific Tertiary species of Margarites, the Tachilni taxon is most similar to M. (P.) sinzi Nomura and Hatai, 1939, which is found only in upper Miocene strata of the Fujina Formation in Shimane Prefecture, southwestern Honshu (Oga- sawara and Nomura, 1980, p. 85, pl. 12, figs. 4a-c). The two species have similar sizes, proportions, whorl profiles, and broadly open umbilici, but the Tachilni species is characterized by more numerous spiral cos- tellae. The Fujina species is reported to have six cos- tellae on the penultimate whorl and five above the pe- riphery of the body whorl, whereas the Tachilni taxon has 10 and 18 costellae, respectively. Fine secondary costellae are evidently present in the interspaces of the body whorl above the periphery of M. (P.) sinzi, whereas secondary costellae are absent from the Tachilni species. A bathymetric range of 0-230 m for modern Mar- garites, s.l., of the eastern Pacific is given by Keen and Coan (1974). Tachilni Formation occurrence.—USGS locality M7146 (1 adult); UA locality A-170 (1 adult). Figured specimens.—USNM 339816; UA 2490. Stratigraphic and geographic range.—So far as known, this species 15 unique to the Tachilni fauna. Family CALYPTRAEIDAE Schumacher, 1817 Genus CALYPTRAEA Lamarck, 1799 Calyptraea species indeterminate Plate 22, ПеПГев 16, 17 Discussion.—The single Tachilni specimen of Са- lyptraea consists mostly of an incomplete internal mold. A small matching fragment of external mold bearing some shell material shows that the exterior surface is smooth except for obscure growth lines. The only previous report of a Tertiary species of Calyptraea from the Alaska Peninsula is by MacNeil (in Burk, 1965, p. 226, 227). He noted an indeterminate species in rocks of the Stepovak Formation southeast of Stepovak Bay, Alaska Peninsula, to which he as- signed an age of ‘‘Oligocene, probably middle or late.”’ This specimen, in the USGS collections at Menlo Park, is an external mold that approximates the shape, size and smooth exterior of the Tachilni species. MacNeil (in Burk, 1965, p. 227) further noted *'Calyptraea cf. C. alaskana (Dall) and C. tokunagai Hatai and Nisi- BULLETIN 317 уата” from the Stepovak Formation on Unga Island. MacNeil's “С. alaskana” probably refers to Trochita alaskana Dall, 1904 (p. 118—119, pl. 10, figs. 2, 6), described from the Oligocene Stepovak Formation on Unga and Popof Islands. Dall's (1904) original descrip- tion and figures indicate a high-spired gastropod very unlike the Tachilni specimen of Calyptraea and prob- ably assignable to a different genus. Calyptraea to- kunagai Hatai and Nisiyama, 1952 (p. 118) [non Hi- riyama, 1955, p. 116, as stated by Masuda and Noda, 1976, p. 13; ICZN, 1961, Art. 13(a)iii] is reported in Oligocene beds of the Asagai Formation in Fukushima Prefecture, northeastern Honshu. It has a flat conical shell bearing fine spiral striae and a nearly central apex (Yokoyama, 1924; Masuda and Noda, 1976). The fine spiral striae of C. tokunagai seem to distinguish it from the Tachilni species. In the northeastern Gulf of Alaska, Kanno (1971, p. 108) cited a specimen of Calyptraea in the upper part of the Poul Creek Formation in the Yakataga district, presumably in strata of Oligocene or early Miocene age. Kanno (1971, pl. 12, figs. 5, 6) illustrated coarse. obscure radiating ribs on the specimen from Poul Creek. These ribs separate it from the smooth-sur- faced Tachilni and Stepovak specimens. The specimens of Calyptraea from the Tachilni and Stepovak Formations that I have examined are similar to the better-preserved specimen of ‘‘Calyptraea sp.” figured by Addicott (1978, p. 680, fig. 5k) from the Skonun Formation of British Columbia, Canada. The Skonun fauna was correlated with the Wishkahan Stage by Addicott (1978) and assigned an early late Miocene age. Species of Calyptraea are said to live in warm [0 temperate regions (Kanno, 1971), but one modern eastern Pacific species has been reported as far north as Port Etches, Hinchinbrook Island, northern Gulf of Alaska, at 60*20'N latitude (Dall, 1921, p. 163). A depth range for eastern Pacific Calyptraea of intertidal to 140 m was given by Keen and Coan (1974). Tachilni Formation occurrence.—U A locality A-170 (1 young adult). Figured specimen.—U A 2491. Stratigraphic and. geographic range.—The present specimen of Calyptraea is the first of that genus ге“ ported from the Tachilni Formation, and the first сег- tain report of the genus in Alaskan rocks younger than Oligocene. Family NATICIDAE Forbes, 1838 Genus POLINICES Montfort, 1810 Subgenus EUSPIRA Agassiz in J. Sowerby, 1838 TACHILNI FORMATION MOLLUSKS: MARINCOVICH 111 Polinices (Euspira) diabloensis (Clark, 1915) Plate 22, figure 19 Natica (Euspira) diabloensis Clark, 1915, p. 486—487, pl. 68, fig. 7. Polinices (Euspira) diabloensis (Clark). Marincovich, 1977, p. 267— 269, pl. 23, fig. 10. Discussion. —This uncommon species is more elon- Sate than average for a naticid, and has a relatively elevated spire. The umbilicus is narrowly open and bounded by a broad cordlike angulation on the base 9f the shell. The umbilical callus is narrow and not clearly set off from the inner lip. The parietal callus is thick, solidly fills the posterior apertural angle, and has à weak anterior lobe that projects slightly above the umbilicus. An average specimen of P. (E.) diabloensis 15 45 mm high and 37 mm in diameter, based оп mea- Surements of 13 specimens (Marincovich, 1977). A single Tachilni specimen bears the distinctively elongate shape, elevated spire, umbilical morphology, and thick, parietal callus of P. (E.) diabloensis. This Specimen represents the first occurrence of this species Outside of California, where Р. (E.) diabloensis is re- Ported in rocks of middle (?) and late Miocene age. As Doted by Marincovich (1977, p. 269), the species is best considered an exclusively upper Miocene one, because its middle Miocene record is based on a single Occurrence and requires verification by further col- lecting, This species is similar in morphology to three other Species of Euspira known in Alaskan Tertiary faunas: Р. (E.) lincolnensis (Weaver, 1916), P. (E.) ramonen- sts (Clark, 1918), and P. (E.) pallidus (Broderip and Owerby, 1829). Polinices lincolnensis occurs in upper Ocene to middle Miocene strata of the Pacific North- West, and in lower to middle Miocene strata of central California. In Alaska the species has been tentatively recognized in the Narrow Cape Formation of Sitkinak Island (Text-fig. 1) in the western Gulf of Alaska (Al- lison and Marincovich, 1981), which contains a Juan- lan (late Oligocene or earliest Miocene) molluscan fau- па, and in the Oligocene Stepovak Formation on the Maska Peninsula (UA specimens). Polinices diabloen- sts differs from P. lincolnensis by its larger size, more elevated spire, more strongly impressed suture, thin- ner parietal callus, and thinner inner lip-umbilical cal- "5 (Marincovich, 1977, p. 268). The umbilicus of P. 2. пета is usually more broadly open than in P. T оепзіз, and some specimens of the former species i M a distinct swelling at the midpoint of the umbil- fal callus. Polinices ramonensis differs from P. dia- депз by being much smaller (14 mm is an average eight for the former species), by having a slitlike um- Шсиз, and by having a relatively thinner parietal cal- Us. Polinices ramonensis is known in upper Oligocene and lower Miocene strata of the Poul Creek Formation in the Yakataga district (Clark, 1932) and in the Juan- ian fauna of the Narrow Cape Formation of Sitkinak Island (Allison and Marincovich, 1981), as well as in upper Oligocene and lower Miocene beds of California and Washington (Marincovich, 1977, p. 269). It has been common in North Pacific faunas since the Plio- cene. Polinices pallidus, discussed below, differs from P. diabloensis by its distinctly lower spire, relatively smaller umbilical opening, its usually more slender in- ner lip and, in larger adults, by its much thinner pa- rietal callus (Marincovich, 1977, p. 269). Polinices diabloensis is a distinctly North American faunal element that aids in correlating the Tachilni Formation with strata in California. Type information.—Holotype: UCMP, No. 11595. Type locality: Walnut Creek, Contra Costa County, northern California; San Pablo Formation; upper Mio- сепе. Тасћит Formation occurrence.—USGS locality M7140 (1 adult) Figured specimen.—USNM 339817. Stratigraphic and geographic range.—The follow- ing information is from Marincovich (1977). This species is known only in middle (?) and upper Miocene strata. Middle (?) Miocene: Temblor (?) Formation, Calaveras Valley, Santa Clara County, northern Cal- ifornia. Upper Miocene: Santa Margarita Formation, north Coalinga area, and Domengine Ranch quadran- gle, central California; upper part of the San Pablo Formation, Contra Costa County, northern California; Neroly Formation, Contra Costa County, northern California. Polinices (Euspira) pallidus (Broderip and Sowerby, 1829) Plate 22, figures 18, 23 Natica pallida Broderip and Sowerby, 1829, p. 372. Polinices (Euspira) pallida (Broderip and Sowerby). Dall, 1921, p. 164, pl. 14, fig. 5; Oldroyd, 1927, vol. 2, pt. 3, p. 126, pl. 97, fig. 9. Polinices pallidus (Broderip and Sowerby). MacGinitie, 1959, p. 91, plene. Polinices (Euspira) pallidus (Broderip and Sowerby). Marincovich, 1977, p. 278-281, pl. 25, figs. 1-6, 8 [contains extensive synony- my]. Discussion.—This naticid is recognized by its rela- tively elongate proportions, small umbilical opening, and a narrow umbilical callus that has a gentle central swelling. The parietal callus is characteristically thin, has a distinct anterior lobe, and moderately fills the posterior apertural angle (Marincovich, 1977). One Tachilni specimen (Pl. 22, fig. 18) is considered to be typical of P. (E.) pallidus, while two are only tenta- tively assigned to this species due to imperfect pres- ervation. A fourth specimen (РІ. 22, fig. 23) placed in this species is remarkable for its large size and other atypical morphologic features. The one unusually large Tachilni specimen is 55.8 mm high and 46.5 mm in diameter, compared to an average size for P. (E.) pallidus of 25 mm high and 20 mm in diameter. The largest specimen previously known is a Holocene individual from Bristol Bay, Alaska, 46.7 mm high and 41.8 mm in diameter (Ma- rincovich, 1977, p. 279). The large Tachilni specimen is further atypical in having a parietal callus that is relatively thicker than usual for the species and more heavily fills the posterior apertural angle. However, in the most important morphologic features, those of the umbilical area, this specimen is typical of P. (E.) pal- lidus. The occurrence of this large specimen in the Tachilni fauna is anomalous in that it contradicts the observation of Marincovich (1977, p. 281) that fossils of P. (E.) pallidus are much smaller than living spec- imens. The very large size and parietal callus thickness of this specimen are not considered to have taxonomic importance. A comparison between P. (Е.) pallidus and the oth- er Tachilni species of Euspira, P. (E.) diabloensis (Clark, 1915), is made in the discussion of the latter species. Polinices (Euspira) pallidus first appeared in middle Miocene faunas of southern California and the Yaka- taga Formation, Yakataga district, Alaska, became common across the North Pacific margin during the Pliocene, and has remained abundant in high-latitude North Pacific, Arctic, and North Atlantic faunas to modern times (Marincovich, 1977). There are no un- doubted Tertiary occurrences of P. (E.) pallidus in Asia. Reports from the Pliocene of east-central Hon- shu (Yokoyama, 1920, р. 77) and the Miocene of Oki- nawa (MacNeil, 1960, p. 57) appear to be based on other naticid species. In modern seas, P. (E.) pallidus clearly prefers cold- water habitats, but its possible presence in Miocene warm-water faunas of central and southern California (Marincovich, 1977) suggests that the species may have had a broader thermal tolerance in the Tertiary than it does today. Type information.—Holotype: unknown and pre- sumably in BM(NH). Type locality: Icy Cape, Chuk- chi Sea coast, northwestern Alaska; Holocene. Tachilni Formation occurrence.—USGS localities M7139 (1 adult), M7143 (2 adults, as “с .”), M5163 (1 adult); UA locality A-169 (1 adult). Figured specimens.—USNM 339818; UA 2492. Stratigraphic and geographic range.—The follow- ing information is from Marincovich (1977), except as BULLETIN 317 noted. The species ranges from the middle Miocene to Holocene. Middle Miocene: Kern River area, southern California. Middle Miocene to Pliocene: Yakataga Formation, Yakataga district, Alaska. Up- per Miocene: Etchegoin Formation, Coalinga area, central California. Upper Pliocene or lower Pleisto- cene: Tugidak Formation, Tugidak Island, Trinity Is- lands, western Gulf of Alaska; Rio Dell Formation, Humboldt County, northwestern California (Roth, 1979). Pliocene or Pleistocene: Tjórnes sequence, Ser- ripes and Mactra groups, Iceland. Lower Pleistocene: unnamed beds at Moonstone Beach, Humboldt County. northwestern California (Roth, 1979); Santa Barbara Formation of Smith (1912), Santa Barbara, southern California. Lower and upper Pleistocene: Gubik For- mation, Arctic coastal plain, northern Alaska (USGS coll.). Upper Pleistocene: EIk River and Port Orford Formations, Cape Blanco area, southwestern Oregon (Kennedy, 1978; Roth, 1979); terrace deposits at Point Ano Nuevo, northern California (Kennedy, 1978). Ho- locene: Circumarctic, south to the U.S.—Mexican bor- der in the eastern Pacific; to Japan in the western Pa- cific; to North Carolina in the western Atlantic; to the North Sea and Portugal in the eastern Atlantic (new southern range end-point, herein, based on one spec- imen from *'coast of Portugal, 1430 m" depth, loaned to me by Rosina Fechter, Zoologische Staatssa- mmlung Muenchen, West Germany). Reported in depths from 15 to 4,794 m, this species may occur intertidally too. Genus BULBUS Brown in Smith, 1839 Bulbus fragilis (Leach, 1819) Plate 22, figure 20 Natica fragilis Leach, 1819, p. 62. Bulbus fragilis (Leach). Marincovich, 1977, p. 335-338, pl. 31, figs: 4—7 [contains extensive synonymy]. Discussion.—The shell of this species is very thin and the distinctive umbilical callus is a thin, narrowly semicircular wash that nearly conceals a slitlike um- bilicus at its base. Because the one Tachilni specimen is somewhat crushed, the spire appears to be lowe! and the suture more deeply impressed than usual for this species. The parietal callus of the Tachilni spect men is nearly imperceptible, a common feature in В. fragilis. The minute spiral costellae typical of this species are not well-preserved, though their presence is suggested on some parts of the shell. Bulbus fragilis 18 known in the Tachilni fauna by 4 single specimen that is the first Miocene occurrence of this species. An extensive synonymy and discussion of this species is given in Marincovich (1977). TACHILNI FORMATION MOLLUSKS: MARINCOVICH 113 Bulbus fragilis is a distinctly cool-water element in the Tachilni fauna, because its modern range includes Only the Arctic, North Pacific, and North Atlantic Oceans. It has been reported on sand and mud bot- toms in depths of 37 to 317 m in the northeastern Pa- cific and in depths to 600 m in the northern Atlantic (Marincovich, 1977). Type information.—Holotype: location unknown (Marincovich, 1977). Type locality: Baffin Bay, be- tween Greenland and Canada; Holocene. Tachilni Formation occurrence.—USGS locality M7143 (1 young adult). Figured specimen.—USNM 339819. Stratigraphic and geographic range.—The Tachilni Specimen is the oldest one known. The following range Information is taken from Marincovich (1977): Upper Pliocene: Beringian marine transgression, Kivalina, Western Alaska. Middle Pleistocene: Kotzebuan ma- "Ine transgression, type section, Baldwin Peninsula, Kotzebue Sound, Alaska. Undifferentiated Pleisto- сепе: Scotland, Iceland, and possibly England and Northern U.S.S.R. This species is present in several 0565 collections from the Pleistocene Gubik For- Mation, northern Alaska. Holocene: circumarctic. In the eastern Pacific, south to Atka and Unalaska Is- lands, Aleutian Islands, and the Shumagin Islands; in the western Pacific, south to Iwate Prefecture, north- west Honshu, Japan; in the western Atlantic, south to assachusetts Bay; in the eastern Atlantic, south to the Lofoten Islands, Norway. Genus NATICA Scopoli, 1777 Subgenus CRYPTONATICA Dall, 1892 Natica (Cryptonatica) clausa Broderip and Sowerby, 1829 Plate 22, figure 21 Natica clausa Broderip and Sowerby, 1829, p. 372. «пса (Cryptonatica) clausa Broderip and Sowerby. Arnold, 1903, Р. 313-314, pl. 10, fig. 13; Dall, 1921, p. 163, pl. 14, fig. 11; MacNeil, io р. C109, pl. 13, figs. 12, 13, pl. 15, fig. 19; Marincovich, » р. 410-418, pl. 41, figs. 7-10, pl. 42, figs. 1-6 [contains extensive synonymy]. Discussion.—This well-known species is among the E common Tachilni gastropods and is the most | ndant naticid in Alaskan marine Tertiary strata. It j easily recognized by its globose shell with low to меу elevated spire, completely closed umbili- ты and smooth, semicircular umbilical callus. Its cal- eous operculum is rarely fossilized. ks high-latitude North Pacific faunas of late Ceno- © age N. (C.) clausa is most similar to N. (C.) oregonensis (Conrad, 1865), a middle Miocene to early Pliocene species of Oregon and Washington, and to Natica (Tectonatica) janthostoma Deshayes, 1839, a Miocene to Holocene species. The former species dif- fers from N. (C.) clausa by having a more elevated spire and from the latter species differs by having an open umbilicus. A discussion of N. (C.) clausa and its many synonyms is given in Marincovich (1977). The oldest published occurrence of this species is in the late Oligocene or earliest Miocene (i.e., Juanian) fauna of the Narrow Cape Formation on Sitkinak Is- land, western Gulf of Alaska (Allison and Marinco- vich, 1981). The species also occurs in probable lower Miocene strata in the upper part of the Poul Creek Formation in the Yakataga district, Alaska (Clark, 1932; Marincovich, 1977). It is common in middle Mio- cene to Holocene faunas from Japan to California. This circumarctic species is a cool-water indicator. Even though N. (C.) clausa lives as far south as Japan and southern California, it does so by dwelling in cool water at progressively greater depths southward. Modern specimens are found in depths as shallow as nine m in northern Alaska, but no shallower than about 150 m off of southern California (Marincovich, 1977, p. 418). Type information.—Holotype: unknown. Type lo- cality: unknown. Tachilni Formation occurrence.—USGS localities M7139 (1 adult, 2 juveniles), M7146 (3 adults, as “сЕ.”), M7201 (1 adult), M7203 (1 adult); UA localities A-169 (1 adult), A-170 (1 adult), A-301 (abundant at outcrop); CAS locality 60279 (1 adult). Г Figured specimen.—USNM 339820. Stratigraphic and geographic range.—Numerous Miocene to Holocene occurrences for the northeastern Pacific are cited in Marincovich (1977). The oldest known specimens occur in the late Oligocene or ear- liest Miocene fauna of the Narrow Cape Formation, Sitkinak Island, western Gulf of Alaska (Allison and Marincovich, 1981). Northwestern Pacific fossil oc- currences are not well documented, though the species is commonly cited in Neogene and Pleistocene faunas of northern Japan, Sakhalin and Kamchatka. The species is circumboreal in modern seas, living in the eastern Pacific south to San Diego, California (32°43' М); in the western Pacific, south to Japan and Korea; in the western Atlantic, south to Cape Hatter- as, North Carolina; and, in the eastern Atlantic, south to Spain and perhaps the Mediterranean. Living spec- imens have been collected in depths from nine to 970 m on soft bottoms, in progressively greater depths from north to south (Marincovich, 1977). 114 BULLETIN 317 Subgenus TECTONATICA Sacco, 1890 Natica (Tectonatica) janthostoma Deshayes, 1839 Plate 22, Ngure 22 Мапса janthostoma Deshayes, 1839, р. 361. Natica (Cryptonatica) janthostoma Deshayes. Dall, 1921, р. 164, pl. 14, пр. 12; Oldroyd, 1927; vol. 2, pt: 3; p. 123; pl. 97, fig: 5. Natica (Tectonatica) janthostoma Deshayes. Marincovich, 1977, p. 405—408, pl. 40, figs. 10-13, pl. 41, figs. 2—5 [contains extensive synonymy]. Discussion.—This species is characterized by its well-developed semicircular umbilical callus, strong funicle, and relatively small umbilical opening poste- rior to the umbilical callus. The umbilicus is always open, in contrast to the otherwise similar Natica (Cryptonatica) clausa Broderip and Sowerby, 1829, in which the umbilicus is always closed by a semicircular callus. The illustrated Tachilni specimen, at 35 mm high, is slightly larger than previously known fossil specimens but much smaller than the largest Holocene individuals, which attain 61 mm in height (Marinco- vich, 1977). Tachilni specimens of N. (T.) janthostoma consti- tute the first occurrence of this species in Alaska Ter- tiary strata. This species was previously known in Alaska only in Pleistocene faunas of the Gubik For- mation in northern Alaska (USGS coll.). Outside of Alaska, this species has been reliably reported as a fossil only in Neogene and Pleistocene faunas of the western U.S. and Canada. Addicott (1976a, p. 105) noted its lowest occurrence in Washington and Oregon in Wishkahan faunas. As noted by Marincovich (1977, p. 407), earlier reports of N. (T.) janthostoma as a late Tertiary and Quaternary fossil in Japan are based on the related species N. (T.) janthostomoides (Kuroda and Habe, 1949). Тће main differences between these two species are that N. (7.) janthostomoides has a narrower umbilical callus, so that the umbilicus is open along most of the callus margin instead of only at its posterior end, and has an umbilical sulcus relatively much smaller than in N. (T.) janthostoma. In addition, the operculum of N. (7.) janthostomoides has two shallow grooves near its outer margin, whereas the operculum of N. (7.) janthostoma is virtually smooth. Natica (Tectonatica) janthostoma is an extralimital element in the Tachilni fauna, because it currently lives only in the northwestern Pacific, as noted below. Its modern bathymetric range is unknown. Type information.—Holotype: unknown. Type lo- cality: Kamchatka, U.S.S.R.; Holocene. Tachilni Formation occurrence.—USGS locality M7150 (1 adult); UA locality A-301 (2 adults). Figured specimen.—U A 2493. Stratigraphic and geographic range.—The follow- ing information is largely from Marincovich (1977), ex- cept as noted. The species ranges from lower upper Miocene to Holocene. Lower upper Miocene (Wish- kahan): Skonun Formation, Queen Charlotte Islands, British Columbia, Canada (Addicott, 1978); Empire Formation, Coos Bay, Oregon. Upper upper Miocene (Graysian): upper part of Montesano Formation, southwestern Washington. Upper (?) Pliocene: Mon- tesano Formation of Weaver (1912), southwestern Washington. Middle Pliocene or Pleistocene: Merced Formation, Sonoma County, northwestern California. Middle Pleistocene: EIk River Formation, southwest- ern Oregon. Holocene: Kamchatka to Hokkaido, and Vladivostok, U.S.S.R. Reported from Korea by Habe (1950). Family CYMATIIDAE Iredale, 1913 Genus FUSITRITON Cossmann, 1903 Fusitriton oregonensis (Redfield, 1846) Plate 23, figure 1 Triton oregonense Redfield, 1846, p. 163—168, pl. 11, figs. 2a, b. Argobuccinum (Fusitriton) oregonensis (Redfield). Oldroyd, 1927, VOL, 2, pt. 2; р.:242-243, р. 37, figs... 1-3. Fusitriton oregonensis (Redfield). Smith, 1970, p. 485—497, pl. 45, figs. 1–11, pl. 46, figs. 1, 2, 5, 6, 8, 13, 14, pl. 47, figs. 2, 3 [contains extensive synonymy]. Discussion.—This well-known North Pacific species is represented in the Tachilni fauna by a single incom- plete specimen that has well-preserved sculpture but lacks an aperture and anterior canal. Axial sculpture consists of coarse, unevenly spaced ribs and one weakly developed varix per whorl. Inconspicuous in- cremental growth lines also are present. The main spi- ral sculpture is of low, flat-topped costae that bear minute, weakly developed and closely spaced costel- lae. The spiral interspaces are less than one-third the width of the costae, except for Ше anteriormost рге- served interspace, which is about three-fourths the width of adjacent costae. Two or three thread-like cos- tellae of varied width are present in each interspace- The spiral sculpture of F. oregonensis is variable within broad limits, as thoroughly documented by Smith (1970). In general, however, typical specimens of F. oregonensis have relatively fine spiral costae that are bifurcate, and lack the faint spiral grooves of the Tachilni specimen that give the latter a more coarsely sculptured appearance. Specimens similar in sculptur- al coarseness to the Tachilni one were reported by Smith (1970, p. 503—504, pl. 46, figs. 3, 4) from pre- sumed Miocene deposits at Cape Yakataga and Mid- dleton Island, Alaska, and were referred to ‘‘Fusitri- ton sp.? aff. Е. oregonensis.” Smith (1970, p. 504) TACHILNI FORMATION MOLLUSKS: MARINCOVICH 115 noted an absence of varices оп the Cape Yakataga and Middleton Island specimens she examined, whereas weakly developed varices are present on the Tachilni Specimen. Апеу (1978, р. 133—134) also referred to Specimens of Fusitriton from the Cape Yakataga area Using Smith’s (1970) identification. Specimens illus- trated by Smith (1970) and Ariey (1978) differ from the Tachilni individual by having bifurcate spiral costae. Smith’s (1970) citation of a Miocene age for Mid- dleton Island specimens of ‘‘Fusitriton sp.? aff. Е. or- *Sonensis'" from the Yakataga Formation is erro- neous. More recent paleomagnetic and molluscan faunal studies (Plafker and Addicott, 1976, p. 1, 23; Allison, 1978, p. 182) indicate an early Pleistocene age for the Yakataga Formation on Middleton Island, and ПО older rocks crop out there. Smith (1970) was also Uncertain whether her specimens from Cape Yakataga (Text-fig. 1) came from the Yakataga or underlying Poul Creek Formation, due to inadequate locality in- formation on museum specimen labels. Ariey (1978, P. 133-134) made extensive collections of mollusks from both formations at Cape Yakataga and found Fusitriton sp.? aff. F. oregonensis" only in the Ya- kataga Formation. Her citation of this taxon in the Poul Creek F ormation at Cape Yakataga, based on the reported occurrence there of ‘‘Fusitriton aff. F. mat- thewsonij (Gabb) and F. vancouverense (Clark and Arnold)" by MacNeil (in Miller, 1971, p. 4), is in error because Mediargo matthewsonii (Gabb, 1866) [includ- 1ng Bursa vancouverensis Clark and Arnold, 1923, as а Junior synonym] is not considered to be synonymous with F. oregonensis by Smith (1970) or later workers. Further, extensive USGS collections of Poul Creek mollusks contain no specimens that may be identified IF. oregonensis. Thus, the oldest known Alaskan Occurrence of F. oregonensis is in the stratigraphically ighest Newportian fauna and a Wishkahan fauna in the lower part of the Yakataga Formation at Cape akataga (Ariey, 1978), in beds of middle and late 'осепе age. Outside of the Yakataga district, Е. or- “80nensis has been found in Alaska only in the Topsy ?rmation of the Lituya district in the eastern Gulf of е Ska (Marincovich, 1980, p. C12-C13). The Topsy Una is of Newportian age and roughly coeval with akataga Formation faunas from which the oldest Specimens of Р. oregonensis at Cape Yakataga are nown, Smith’s (1970, p. 492) report of F. oregonensis in арапеѕе Miocene faunas requires verification, be- “ause Masuda and Мода (1976) cited only Pliocene or иптепсез in Japan. There seems to be no mention this Species in the Russian literature on Tertiary Mollusks of Sakhalin, Kamchatka and adjacent areas. “Еизитиоп sp.? aff. Е. oregonensis” of Smith (1970, p. 503—504, pl. 46, figs. 3, 4) is considered here to be a variant of F. oregonensis. The presence of coarse axial ribs, bifurcate spiral costae separated by narrow interspaces bearing one to three costellae, and overall shell form and size clearly ally the variant noted by Smith (1970) with F. oregonensis. The absence of vari- ces on the one individual of *'Fusitriton sp.? aff. F. oregonensis” illustrated by her, from Pleistocene beds on Middleton Island, may be peculiar to that individual because all Middleton Island Pleistocene specimens I examined in USGS collections have distinct varices, though they vary in strength among individuals. The Tachilni specimen differs from Smith's (1970) variant of F. oregonensis only by having spiral costae that are not bifurcate but that do bear minute, weakly devel- oped spiral costellae. However, as Smith (1970, p. 489) noted for Е. oregonensis, *'Spiral microsculpture is variable between and within whorls of different indi- viduals and is not a reliable specific character.’’ This view is reinforced by USGS specimens from the Cape Yakataga area, in which some spiral costae are bifur- cate but most are not. Smith (oral commun., 1981) does not object to considering *'Fusitriton sp.? aff. Е. oregonensis” as a coarsely costate variety of Е. ore- gonensis. In the modern North Pacific, F. oregonensis occurs in temperate to cold waters from central Honshu, Ja- pan, to southern California (Smith, 1970). The species is known in depths as great as 2,370 m, but has been observed in the intertidal zone from Puget Sound, Washington, to southeastern Alaska (Smith, 1970, p. 491). Southwest from the Bering Sea and south of Pu- get Sound, it lives in progressively greater depths, ev- idently showing its preference for cooler waters (Smith, 1970) and also occurs on seamounts in the Gulf of Alaska (Somerton, 1981). The species has been col- lected in temperatures of 7-11?C in Puget Sound and in waters less than 8°C off southern California (Val- entine and Emerson, 1961). Type information.—Holotype: lost (Smith, 1970, p. 489). Type locality: Straits of Juan de Fuca, Washing- ton; Holocene. Tachilni Formation occurrence.—USGS locality M7139 (1 adult). Figured specimen.—USNM 339821. Stratigraphic and geographic range.—This species is reported in upper lower (?) or middle Miocene to Holocene faunas. Upper lower (?) or middle Miocene (Newportian Stage): Topsy Formation, Lituya district, eastern Gulf of Alaska (Marincovich, 1980). Lower middle Miocene (Newportian Stage): Yakataga For- mation, Cape Yakataga and adjacent area, Yakataga 116 BULLETIN 317 district, northeastern Gulf of Alaska (Smith, 1970; MacNeil in Miller, 1971; Ariey, 1978). Lower upper Miocene (Wishkahan Stage): Empire Formation, Coos Bay, Oregon (Dall, 1909). Smith (1970, p. 492-493) listed questionable Miocene occurrences in Japan, and gave numerous Pliocene and Pleistocene occurrences in North Pacific faunas extending from central Hon- shu, Japan, to southern California. Masuda and Noda (1976) cited only Pliocene records in Japan. Holocene: from central Honshu (south to Niigata in the Japan Sea and south to Cape Inubo on the Pacific Coast) and Hokkaido, Japan, to southern Kamchatka, the Aleu- tian and Pribilof Islands (south of the line of floating winter ice), the Gulf of Alaska, and south along the Pacific Coast of North America to San Nicolas Island, southern California (Smith, 1970). Family BUCCINIDAE Rafinesque, 1815 Genus BUCCINUM Linnaeus, 1758 Buccinum cf. B. planeticum Dall, 1919 Plate 23, figures 2—4 Buccinum planeticum Dall, 1919, p. 326; Dall, 1925, p. 8, pl. 5, fig. 1; Oldroyd, 1927, vol. 2, pt. 1, p. 246-247, pl. 24, fig. 1; Kosuge, 19705001322. Шо. ө. Discussion.—Specimens assigned to this taxon con- sist of about six evenly rounded whorls that bear fine, closely spaced spiral costellae and coarse, irregularly spaced axial folds. Spiral costellae are separated by slightly narrower interspaces that each bear a medial thread. Axial folds are most strongly developed on early whorls and become progressively obsolete on adult whorls. In some instances, the axial folds do not extend onto the anteriormost portion of a whorl. All Tachilni specimens consist of incomplete molds and casts. Several individuals are 50 mm or more in height and probably exceeded 60 mm high when intact. Tachilni specimens match well the original descrip- „поп of this species, except that they lack the spiral costellae occurring as ‘‘fasciculate bands of five or six threads" (Dall 1919, p. 326). Tachilni specimens do not show this grouping of spiral costellae, and it also is not shown in illustrations of the holotype of B. pla- neticum (Dall, 1925, pl. 5, fig. 1; Kosuge, 1972, pl. Do fig. 8). The holotype of B. planeticum is 65 mm high and 35 mm in diameter (Dall, 1919), which is similar in size to Tachilni specimens. Illustrations of the ho- lotype show a distinct flexure of the outer lip at the shoulder that is not evident on earlier whorls. Evi- dence of a similar flexure is shown on two of the best- preserved Tachilni specimens (Pl. 23, fig. 3). Off western North America Buccinum is said to live in depths of 10 to 2,930 m (Keen and Coan, 1974). Type information.—Holotype: USNM 223098. Type locality: USFC station 3305, in 42 m depth southwest of Hagemeister Island, Bristol Bay, southeastern Ber- ing Sea; bottom temperature 5.5°С (Dall, 1919). Tachilni Formation occurrence.—USGS localities M7146 (4 adults), M7150 (9 adults), M7256 (4 adults), M7258 (1 adult); UA locality A-301 (4 adults, 2 juve- niles; abundant at outcrop). Figured specimens. —USNM 339822; UA 2494. Stratigraphic and geographic range.—This species has not been reported previously as a fossil. It was reported to be common in the eastern Bering Sea from Nunivak Island to Bristol Bay by Dall (1919, p. 326), who later gave a range from the Pribilof Islands, Ber- ing Sea, Alaska to the Queen Charlotte Islands, British Columbia, Canada (Dall, 1921, p. 99). Genus MOLOPOPHORUS Gabb, 1869 Molopophorus cf. M. bogachielii (Reagan, 1909) Plate 23, figures 5—7 Buccinum bogachielii Reagan, 1909, р. 218, pl. 5, figs. 51а, DI Molopophorus bogachieli [sic] (Reagan). Addicott, 1976a, p. 105, 110, pl. 3, fig. 13; Addicott, 1978, p. 680, 682, figs. 5c-e. Discussion.—Although M. bogachielii has not been cited often in literature it is an important index species in Oregon and Washington, where it occurs only in Wishkahan and Graysian faunas (Addicott, 1976a). The shell is elongate, with an elevated spire and short an- terior canal. There are fine, closely spaced axial folds on early whorls (Ада сок, 1976a, 1978), but these ap- pear to decline progressively in relief during ontogeny: so that none occurs on the adult body whorl. Two obscure, widely spaced spiral costellae occur on each whorl (Reagan, 1909), but are missing from the rela- tively poorly preserved Tachilni specimens. Two such spiral costellae are present on the penultimate whorl of a specimen figured by Addicott (1976a, pl. 3, fig. 13), but are not clearly shown on three other individ- uals figured later by him (Addicott, 1978, figs. 5с-5е): Four columellar folds are present on Tachilni speci- mens. The two anterior folds are very slender and set closely together, and the two posterior folds are wide! and set farther apart. Because this species is know” from few specimens, its range of morphologic varia- tion has not been defined. One variable aspect of she form appears to be the apical angle. A Pacific North- west Wishkahan specimen illustrated by Addicott (1976a) has an apical angle of 47°, whereas specimens from the Wishkahan Skonun Formation in British C lumbia have apical angles of 45°, 53°, and 56° (Addi- cott, 1978). The two Tachilni specimens have apical angles of 33? and 37“, and the more complete of these Тасни мі FORMATION MOLLUSKS: MARINCOVICH 117 һаз а clearly more elongate appearance than previ- ously illustrated specimens of M. bogachielii. For this reason my identification of the Tachilni specimens is tentative, The two line drawings accompanying the original description of M. bogachielii show only the body whorl ànd incomplete penultimate whorl of the type speci- men. Two obscure spiral costellae are visible on the body whorl, but not on the penultimate whorl, and no ахта] sculpture ог columellar folds were figured ог de- Scribed by Reagan (1909). My present concept of this Species therefore is based on illustrations published by Addicott (1976a, 1978), which show specimens more complete and better preserved than the holotype. Even though several Tertiary species of Molopophorus are known from California, Oregon and Washington (Weaver, 1942; Keen and Bentson, 1944), none is eas- Пу confused with M. bogachielii as used by Addicott (19762, 1978). Five Tertiary species of Molopophorus have been described from Japan (Masuda and Noda, 1976, p. 229), but they are not extremely close in form ?r Sculpture to M. bogachielii. The single Russian ref- °гепсе to a Tertiary species of Molopophorus (Zhid- kova, 1972, p. 66, pl. 15, fig. 3) cites ‘‘Molopophorus cf. anglonana (Anderson),’’ a Miocene species of Cal- Ifornia and Washington (Weaver, 1942, p. 470-471), in dá Miocene Okruglovska Formation of the Kuril Is- ands, Unfortunately, Zhidkova’s (1972) illustration Shows a very poorly preserved specimen whose ge- Пейс assignment is doubtful. The only previous report of Molopophorus in Alas- ka is a reference to M. matthewi Etherington, 1931, a *Wportian index species (Addicott, 1976a), at an un- Specified locality in the lower part of the Yakataga абод іп the Cape Yakataga area (Plafker апа Ad- ctl, 1976, p. 21). This species was not later noted эж Yakataga Formation by Апеу (1978) ог Addi- t, Winkler, and Plafker (1978), so its presence in aska needs verification. he presence of tentatively identified M. bogachielii he Tachilni fauna is an important faunal tie to the nae Northwest, where the species is known only in Wishkahan and Graysian Stages (Addicott, 1976a, P. 105, 110), у E. ype information.—Holotype: USNM 328362. Type d USGS 10127, Olympic Peninsula, northwest- : Washington; Quillayute Formation; lower upper l0cene, Tachilni Formation occurrence.—USGS locality 7150 (2 adults, as ‘‘?’’); UA localities A-170 (1 adult), 301 (1 adult). Figured specimens.—UA 2495, 2496. Stratigraphic and geographic range.—This species in t is reportedly restricted in the Pacific Northwest to the Wishkahan Stage (lower upper Miocene) and the Graysian Stage (upper upper Miocene). Wishkahan: Skonun Formation, Queen Charlotte Islands, British Columbia, Canada (Addicott, 1978); Empire Forma- tion, southwestern Oregon (Roth, 1979). Probable Wishkahan (Addicott, 1976a): Quillayute Formation, northwestern Washington (Reagan, 1909). Graysian: upper part of the Montesano Formation, southwestern Washington (Addicott, 1976а). Family NEPTUNEIDAE Roeding, 1798 Genus BERINGIUS Dall, 1886 Beringius hertleini MacNeil, 1970 Plate 23, figure 13 Beringius hertleini MacNeil, 1970, p. 72—74, figs. 4, 5; Marincovich in Detterman, Yount, and Case, 1981, sheet 2 [as ““?” |. Discussion.—Beringius hertleini is characterized by its large size, large siphonal fasciole, subsutural tab- ulation, and well-developed spiral costae on all whorls. Spiral costae are well-developed but subdued and sep- arated by interspaces of about equal or greater width. Interspaces of the earlier whorls rarely bear costellae, but spiral costellae are numerous on the final one-half of the body whorl of some large individuals. Axial growth lines are visible on all whorls and are fine ex- cept on the final one-fourth body whorl on large in- dividuals, where growth lines are more conspicuous and may be greatly thickened and raised. On some shells, including the holotype (MacNeil, 1970, fig. 5), axial growth lines behind the aperture largely conceal the spiral costae. This species is one of several large, Neogene nep- tuneids known from the Alaska Peninsula. The only such species equal in size to B. hertleini, however, is Tyrannoberingius rex Marincovich, 1981а, which was described from the Unga Conglomerate Member of the Bear Lake Formation at Cape Aliaksin (Text-fig. 2). Although Т. rex also has a prominent siphonal fas- ciole, the shell differs from B. hertleini by lacking spi- ral costae and having axial growth lines that become progressively coarser during ontogeny and have a very coarse, ropelike texture on the final one-fourth of the body whorl. The tabulate subsutural area of B. hert- leini is missing from T. rex, and the suture of B. hert- leini is appressed rather than narrowly channeled as in the latter species. The largest known specimen of B. hertleini 15 160 mm long and the largest known specimen of T. rex is 170 mm long (Marincovich, 1981a, p. 178). Other species of Beringius reported from the Unga Conglomerate at Cape Aliaksin are B. hataii MacNeil, 1973, апа В. aff. В. crebricostatus (Dall, 1877). Ber- ingius hataii is known only from fragmentary material and attains perhaps half the maximum length of B. hertleini, but the two species share predominately spi- ral sculpture. The spiral costae of B. hataii are more strongly raised than those of B. hertleini, however, and are separated by interspaces that are half or less the width of the costae. The spiral interspaces of B. hertleini are of diverse widths, but generally are as wide as or wider than the costae. Beringius crebricos- tatus is characterized by having coarse spiral costae that stand out in strong relief and are T-shaped in sec- tion. Except for fine incremental growth lines, axial sculpture is lacking. The largest Alaskan Tertiary ex- amples of this species in USGS collections are about 75 mm in length. The Unga Conglomerate specimen referred to Beringius cf. B. crebricostatus by MacNeil (1973) appears to be more elongate and to have more subdued spiral costae than typical individuals of B. crebricostatus, but it does seem to have the T-shaped costae that are unique among North Pacific gastro- pods. Beringius hertleini is known to occur only in the Tachilni Formation at Cape Tachilni and in the nearby South Walrus Peak stratigraphic section. However, unidentifiable fragments of a large gastropod that may be this species occur in several USGS collections from the Bear Lake Formation. Modern species of Beringius of western North America are cited in depths of 35 to 600 m by Keen and Coan (1974). Type information.—Holotype: USNM 646463. Type locality: USGS M4044, ‘‘upper ledge of the beach cliff at Cape Tachilni’’ (MacNeil, 1970, р. 69), Alaska Pen- insula, Alaska; Tachilni Formation; upper Miocene. Tachilni Formation occurrence.—USGS localities M4044 (4 adults, 2 juveniles), M5163 (1 juvenile), M7140 (1 adult), M7146 (1 adult), M7150 (1 fragment, as ‘*?’’); UA localities A-169 (2 adults), A-170 (1 adult), :A-301 (fragments, as ‘‘?’’); CAS localities 60278 (2 adults), 60279 (5 adults). Figured specimen.—U A 2498. Stratigraphic and geographic range.—This species is reliably reported only in the Tachilni Formation at Cape Tachilni and adjacent areas. It has been ques- tionably cited in middle or upper Miocene strata of the unnamed upper member of the Bear Lake Formation (Marincovich in Detterman, Yount, and Case, 1981) that crop out near Black Peak, Alaska Peninsula (Text- прага), Genus NEPTUNEA Roeding, 1798 Subgenus NEPTUNEA Roeding, 1798 BULLETIN 317 Neptunea (Neptunea) lyrata altispira Gabb, 1869 Plate 23, figure 8 Neptunea altispira Gabb, 1869, р. 44-45, pl. 14, fig. 2; Stewart, 192 o SES a oll esi ЦЕ 6; Neptunea (Neptunea) lyrata арта Gabb. Nelson, 1974, p. 111- Иви ови 3. 5, pls 3, ngs 1575 РА figs, 126. pS figs: 06 7, pl. 6, figs. 1-5 [contains extensive synonymy]; Nelson, 1978, p. 209, figs. 6-8. Discussion.—This subspecies of Neptunea is char- acterized by relatively coarse primary spiral costae separated by slightly narrower interspaces. The better preserved of the two confidently identified Tachilni specimens, a juvenile, bears a single thin costella in each interspace. More fully developed adults contain third-order spiral elements in interspaces on the pen- ultimate and body whorls (Nelson, 1974, p. 113). There is a broad, sloping, slightly concave subsutural area that contains obscure spiral lines. Axial sculpture con- sists only of growth lines that produce a rugose shell surface as they intersect the spiral costellae. This sub- species has a wide range of sculptural variation, which has been extensively described and illustrated by Nel- son (1974). This extinct taxon occurs widely in North Pacific late Cenozoic cold-water faunas. Its southernmost oc- currence in the eastern Pacific is in Pliocene or Pleis- tocene strata of northwestern California, and in the western Pacific it occurs as far south as Chiba Prefec- ture, east-central Honshu, Japan, in Pliocene deposits (Nelson, 1974, p. 116—118). However, N. (М.) lyrata altispira is most common in Neogene and Pleistocen? rocks rimming the Gulf of Alaska, although the ages of its occurrences there are not precisely known. The oldest known specimens occur in the Yakataga For- mation of the northeastern Gulf of Alaska (Nelson: 1974, p. 118), in rocks thought to be of latest middle or earliest late Miocene age (Nelson, 1978, p. 209). This subspecies, along with the rest of the N. (№.) lyrata (Gmelin, 1791) stock, remained in Alaskan waters during the Miocene and early Pliocene before expanding southward and northward (Nelson, 1974, 1978). The only previous identification of N. (N.) lyra- ta altispira in the Tachilni fauna was by Marincovich (in McLean, Englehardt, and Howell, 1978), and was based on the present specimens. This taxon is nof known to occur elsewhere on the Alaska Peninsula. although it does occur in the upper Pliocene or Plets- tocene Tugidak Formation of Tugidak Island, Trinity Islands, western Gulf of Alaska (Nelson, 1974, p. 117): Based on its biogeographic history, N. (N.) lyrat@ altispira had a strong preference for cold-water habi- tats (Nelson, 1974, 1978). Its initial appearance, in the lower part of the Yakataga Formation, coincided with TACHILNI FORMATION MOLLUSKS: MARINCOVICH 119 the onset of glacial marine conditions in the north- fastern Gulf of Alaska, and its later southward and Northward migrations occurred during the relatively Cold Pliocene and Pleistocene epochs (Nelson, 1974, 1978). Thus, this taxon is strong evidence for a cold- water element in the Tachilni fauna. Type information.—Holotype: ANSP 4322. Type lo- Cality: Scotia section of the Wildcat Group, probably In the Rio Dell Formation, Humboldt County, north- western California (Nelson, 1974, p. 116); upper Plio- cene or lower Pleistocene (Roth, 1979). Tachilni Formation occurrence.—USGS localities M4044 (1 adult), M7139 (3 adults, 1 juvenile), M7143 (? adults, 1 juvenile). Figured specimen.—USNM 339823. Stratigraphic and geographic range.—This subspe- “les is known to range from the upper middle Miocene Ог lower upper Miocene to lower or middle Pleisto- Сепе. Occurrences cited are those given by Nelson (1974), with exceptions noted. Upper middle or lower Upper Miocene to lower Pleistocene: Yakataga For- mation of Yakataga, Malaspina, and Lituya districts, and Middleton Island, northeastern Gulf of Alaska. liocene: Пока Formation of Chiba Prefecture, Kubo „огтаноп of Iwate Prefecture, and Hamada Forma- Поп of Aomori Prefecture, northeastern Honshu, Ja- Рап. Upper Pliocene or lower Pleistocene: Tugidak ?rmation, Tugidak Island, Trinity Islands, western Gulf of Alaska; Rio Dell Formation, Scotia, Humboldt County, northwestern California (Nelson, 1974; Roth, 1979), Lower Pleistocene: Yakataga Formation, Mid- dleton Island, northeastern Gulf of Alaska. Lower or Middle Pleistocene: Port Orford Formation of Baldwin (1964), Curry County, southern Oregon (Nelson, 1974; Roth, 1979). Neptunea (Neptunea) sp. D aff. N. (N.) modesta (Kuroda in Homma, 1931), of Nelson, 1974 Plate 23, figures 9, 10 Ne “Plunea (Neptunea) sp. D aff. N. (N.) modesta (Kuroda in Hom- Ma, 1931), Nelson, 1974, p. 201, pl. 32, figs. 3, 4. Discussion.—This Tachilni taxon is characterized by t. Spiral costae that are separated by much wider шу races occupied by well-developed primary and B costellae. The interspaces are three to four a E. the width of the spiral costae, and each contains Box primary costella that has two to six second- E o on each side of it. The subtabulate, slightly E subsutural area is wider than the interspaces um also contains primary and secondary costellae. (NN sculpture consists only of incremental growth Compared to the other Tachilni species of Neptu- nea, М. (N.) lyrata altispira Gabb, 1869, the present species has relatively much finer spiral costae, much wider interspaces, and finer primary costellae. Many individuals of N. (N.) lyrata altispira illustrated by Nelson (1974, 1978) have several costellae per inter- space, unlike the illustrated single-costellate Tachilni specimens, but their costellae appear to be coarser and less numerous than in N. (N.) sp. D aff. N. (N.) mo- desta. This species has been reported previously only on the Alaska Peninsula, in the Tachilni Formation at Cape Tachilni, and at an unidentified "upper Miocene or lower Pliocene" locality (Nelson, 1974). Мергипеа (Neptunea) modesta has been recognized in the Bear Lake Formation near Port Moller, Alaska Peninsula (Nelson, 1974, p. 201), in rocks of presumed middle or late Miocene age. Type information. —No name has been proposed for this taxon since first recognized by Nelson (1974). Tachilni Formation occurrence.—USGS localities M3591 (1 adult), M5163 (1 juvenile), M7139 (2 adults, 1 juvenile), M7140 (2 adults), M7146 (1 adult), M7150 (2 adults); UA localities A-169 (3 adults), A-170 (1 adult, 1 juvenile). Figured specimen.—USNM 339824. Stratigraphic and geographic range. in the Tachilni fauna. Subgenus GOLIKOVIA Habe and Sato, 1972 Neptunea (Golikovia) plafkeri Kanno, 1971 Plate 23, figures 16, 17 Known only Neptunea (Neptunea) plafkeri Kanno, 1971, p. 115-116, pl. 14, figs. EN Neptunea (Golikovia) plafkeri Kanno. Nelson, 1974, p. 387—390, pl. 63, fig. 7, pl. 64, figs. 3, 6, 7; Nelson, 1978, p. 208. Discussion.—One nearly intact adult of this species represents the first verified presence of N. (G.) plaf- keri in the western Gulf of Alaska. The Tachilni spec- imen is 68.9 mm high and 42.4 mm in diameter, with five whorls (protoconch missing) and a nearly com- plete apertural margin. All whorls have a narrow con- cavity just below the suture, and the body whorl has a subtabulate shoulder. Spiral sculpture is lacking and axial sculpture is of growth lines, some of which are weakly raised. The body whorl is proportionately more inflated than earlier whorls. As noted by Nelson (1974, p. 388), this species is most closely related, and perhaps ancestral, to N. (G.) smirnia (Dall, 1919), a Pliocene to Holocene species of the northeastern Pacific. Individuals in some fossil populations are difficult to assign to one species or the 120 BULLETIN 317 other, though М. (С.) smirnia commonly has а тоге elevated and slender spire, a more weakly developed subtabulate shoulder on the body whorl, and less con- cave subsutural whorl profiles on the early adult whorls (Nelson, 1974). This species has been confidently identified by Nel- son (1974) only in the lower part of the Yakataga For- mation in the northeastern Gulf of Alaska, although he tentatively assigned a body whorl from the Miocene Bear Lake Formation near Port Heiden, Alaska Pen- insula (Text-fig. 2), to N. (G.) plafkeri (Nelson, 1974, p. 390). This species also has been questionably iden- tified in the Newportian fauna of the Topsy Formation of the Lituya district, eastern Gulf of Alaska, in strata coeval with the lower part of the Yakataga Formation (Marincovich, 1980, p. C12). Ariey (1978, p. 142) re- ported N. (G.) plafkeri was present in the lower half of the type Yakataga Formation, including the low- ermost beds, at Cape Yakataga, but was absent from the underlying Poul Creek Formation. However, she did report this species from five localities in the Poul Creek Formation, but not in the Yakataga Formation, in her Lare Glacier stratigraphic section about 35 km east of Cape Yakataga (Text-fig. 1). If her species identification and formational assignment are correct, Ariey’s (1978) Lare Glacier specimens are the first in- dividuals of N. (G.) plafkeri from a pre-Newportian fauna. However, because Ariey (1978, p. 39-40) ob- served that the Poul Creek-Yakataga formational boundary is ‘‘subtle’’ in the Lare Glacier section, her report of N. (G.) plafkeri in the Poul Creek fauna must be viewed with caution. Ariey's (1978) Poul Creek fau- na at Lare Glacier is presumably of Pillarian (early Miocene) age. Finds of this species in other Poul Creek stratigraphic sections are needed to verify its presence so early in the Miocene. Based on past studies (Kanno, 1971; Nelson, 1974; Ariey, 1978) and Yakataga Formation specimens in _USGS collections, the probable highest occurrence of N. (G.) plafkeri is in Wishkahan faunas. More refined biostratigraphic studies may show that this species’ range extends into the Graysian Stage (upper upper Miocene), but there is currently no evidence for this. „Туре information.—Holotype: TUE, No. 10045. Type locality: TUE locality number 81104, dark gray, massive mudstone in lower part of Yakataga Forma- tion along Poul Creek, Yakataga district, Alaska; low- er or middle Miocene. Тасћит Formation occurrence.—U A locality A-301 (1 adult). Figured specimen.—U A 2499. Stratigaphic and geographic range.—This uncom- mon species is reported to range from the lower (?) Miocene to lower upper (?) Miocene. Lower (?) Mio- cene (Pillarian?): Poul Creek Formation (?), Yakataga district, Alaska (Ariey, 1978). Upper lower or lower middle Miocene (Newportian): Topsy Formation, Li- tuya district, Alaska (Marincovich, 1980; questionable identification). Middle and(or) upper Miocene (New- portian and(or) Wishkahan): Yakataga Formation, Yakataga district (Kanno, 1971; Nelson, 1974; Апеу, 1978), and Lituya district (Nelson, 1974), Alaska; Bear Lake Formation near Port Heiden, Alaska Peninsula, Alaska (Nelson, 1974; tentative identification). Family CANCELLARIIDAE Gray, 1853 Genus CANCELLARIA Lamarck, 1799 Cancellaria? species Plate 23, figures 11, 12 Discussion.—A single imperfectly preserved speci- men from UA locality A-301 consists of four whorls bearing axial and spiral sculpture. The body whorl has 15 curved axial costae that are best developed on the shoulder and become obsolete anteriorly. Eleven sim- ilar axial costae occur on the penultimate whorl, and remnants of axial costae are visible on all four рге- served whorls. Spiral sculpture above the periphery on the body whorl consists of about seven costae sep- arated by interspaces of about equal width that may each bear a costella. Sculpture below the periphery is less well preserved, but apparently consists only of spiral elements. Vestiges of spiral sculpture are see? on all preserved whorls. The aperture and inner lip are not well preserved. The specimen is 20.3 mm high an 17.6 mm in diameter. The absence of visible columellar folds on the poor- ly preserved inner lip precludes certain assignment to Cancellaria. Assignment to Buccinum Linnaeus, 1758, is another possibility that would depend оп collecting better-preserved specimens. However, species with similar whorl profiles and sculptural patterns from Tertiary faunas of Alaska (Kanno, 1971) and the Pa- cific Northwest (Weaver, 1942; Moore, 1963) have been assigned to Cancellaria. In the northeastern Pacific, modern species of Can- cellaria are found in depths of 25 to 550 m (Keen an Coan, 1974). Tachilni Formation occurrence.—UA locality A-301 (1 specimen). Figured specimen.—U A 2497. Family TURRIDAE Swainson, 1840 Genus OENOPOTA Moerch, 1852 Oenopota cf. O. candida (Yokoyama, 1926) Plate 23, figures 18—20 TACHILNI FORMATION MOLLUSKS: MARINCOVICH 121 Bela candida Yokoyama, 1926, р. 261—262, pl. 34, figs. 1, 2. Discussion.—Oenopota candida is a small species With about two nuclear and five adult whorls, a short anterior canal, and sculpture of coarse axial folds and Very fine, closely spaced spiral costellae. Yokoyama (1926) reported a height of 13.6 mm and diameter of 6.0 mm for one specimen, observed 21 axial folds on the body whorl and 17 on the penultimate whorl, and Noted that the shoulder normally has a rounded profile. He illustrated one specimen (Yokoyama, 1926, pl. 34, fig. 2) with a narrowly tabulate shoulder and referred to it as “var. angulata.” Hatai and Nisiyama (1952, P. 173) recognized the tabulate morphotype as a full Species, Tachilni specimens assigned to O. cf. O. candida ave rounded shoulder profiles, and the best preserved Specimen (PI. 23, figs. 18, 19) has 18 axial folds on its оду whorl and 17 on its penultimate whorl. Remnants of fine, closely spaced spiral costellae occur on all Tachilni specimens, but this spiral sculpture is largely worn away. Four adult whorls only are preserved on the most complete specimen. The largest Tachilni Specimen is 19.0 mm high by 11.1 mm in diameter, and the next smaller is 17.0 mm high and 10.6 mm in di- ameter, so both are larger than the single specimen “ited by Yokoyama (1926). Differences in size and ax- lal fold number, plus the relatively poor preservation of the Tachilni specimens makes their assignment to h Candida tentative. In addition, the large number of Similar turrids described from North Pacific late Ce- nozoic faunas is reason enough to exercise caution in assigning names to species in this family. As noted above, Yokoyama’s (1926) type material Contains two morphotypes, including specimens with bulate or rounded shoulder. This has led to varied «v erpretations of O. candida by subsequent workers, 9 that it is difficult to assess from the literature the ?rmational occurrence of the species. Previous re- к of О. candida are all from the northwestern Pa- ©, especially Japan, where the species is present in several formations usually assigned a Pliocene age (Hatai and Nisiyama, 1952; Masuda and Noda, 1976). Assignment of a lesser age to Tertiary epochal bound- aries in recent years suggests a probable Miocene age for some formations in which O. candida occurs. Kho- menko (1931, р. 100, pl. 12, figs. 20, 21) reported О. candida from inexactly described localities in the ‘‘up- per Pliocene" Supranutovo Group (=Nutovo Forma- tion of modern usage) of eastern Sakhalin, in strata that were later subdivided, renamed and assigned late Miocene and Pliocene ages (Menner, Baranova, and Zhidkova, 1977). Type information.—Holotype: GT, number un- known (Hatai and Nisiyama, 1952). Type locality: “беа cliff facing Mano bay, about 250 m [southeast] of the contact point of the two main roads near the primary school, Sawane-machi, Sado-gun (Sado Island), Ni- igata Prefecture, west-central Honshu, Japan (Hatai and Nisiyama, 1952); Sawane Formation; Pliocene. Tachilni Formation occurrence.—USGS localities M7143 (1 adult), M7146 (1 adult), M7150 (5 adults), M7256 (1 fragment, as **?’’). Figured specimens.—USNM 339825, 339826. Stratigraphic and geographic range.—This species has been reported only in Neogene strata of Honshu and Sakhalin. See discussion above. Oenopota species A Plate 23, figures 14, 15 Discussion.—4A single individual of Oenopota dif- fers from Tachilni specimens assigned to O. cf. O. candida (Yokoyama, 1926) by being distinctly more slender, smaller, and having a narrowly subtabulate shoulder. Remnants of relatively fine axial costae are present, but no spiral sculpture is preserved. Five whorls are present, with at least one nuclear whorl missing, and the specimen is 9.6 mm high and 4.7 mm in diameter. Preservation is not adequate for assigning even a tentative species name to this specimen. Tachilni Formation occurrence.—USGS locality M7139 (1 adult). Figured specimen.—USNM 339827. APPENDIX COLLECTING LOCALITIES United States Geological Survey (USGS), Menlo Park, California „309. False Pass (D-3) quadrangle, USGS 1:63,360, 1963 ed. се INE along Pacific shore between Thinpoint Cove and R 89 у ae 8.2 miles S 18° E of Frosty Peak, section 22, T 60 S, - Coll. by H. H. Waldron, August 22, 1947. i a False Pass (D-3) quadrangle, USGS 1:63,360, 1963 ed. m ae on Pacific shore between Thinpoint Cove and Sandy Кар v miles S 38? E of Frosty Peak, sections 25 and 26, T 60 S, - Coll. by H. H. Waldron, August 8, 1947. M3588.—Alaska Peninsula, Alaska. Coll. by Standard Oil Com- pany of California, 1965. M4044.—False Pass (D-3) quadrangle, USGS 1:63,360, 1963 ed. Upper ledge of beach cliff at Cape Tachilni, about 1,100 feet east and 300 feet north of southwest corner of section 36, T 60 S, R 90 W. Coll. by Standard Oil Company of California, 1968. M4045.—False Pass (D-3) quadrangle, USGS 1:63,360, 1963 ed. Base of beach cliff at Cape Tachilni, about 800 feet east and 100 feet south of the northwest corner of section 6, T 61 S, R 90 W. Coll. by Standard Oil Company of California, 1968. M5163.—False Pass quadrangle, USGS 1:250,000, 1949 ed. Near 122 BULLETIN 317 South Walrus Peak, 10,000 feet south and 36,100 feet east of latitude 55°N, longitude 163°W. Coll. by Union Oil Company, date un- known. M5166.—fFalse Pass quadrangle, USGS 1:250,000, 1949 ed. Near Cape Tachilni, 23,600 feet south and 26,800 feet east of latitude SS°N, longitude 163°W. Coll. by Union Oil Company, 1968. M5167.—False Pass quadrangle, USGS 1:250,000, 1949 ed. 40,000 feet south and 31,600 feet west of latitude 55°N, longitude 163°W. Coll. by Union Oil Company, date unknown. M5168.—Same location as M5166. Coll. by Union Oil Company, 1968. M5169.—False Pass quadrangle, USGS 1:250,000, 1949 ed. 44,000 feet south and 34,800 feet west of latitude 55?N, longitude 163°W. Coll. by Union Oil Company, date unknown. M5173.—Port Moller (D-1) quadrangle, USGS 1:63,360, 1963 ed. Within stratigraphic section extending from the northwest corner of section 34 to 1,000 ft east and 500 ft north of the southwest corner of section 27, T 48 S, R 69 W. Coll. by Union Oil Company, 1968. M7139.—False Pass (D-3) quadrangle, USGS 1:63,360, 1963 ed. Type locality of Tachilni Formation at Cape Tachilni, 49 meters above base of measured section, section 36, T 60 S, R 90 W; latitude 54*55'N, longitude 162?52'W. Coll. by Louie Marincovich, Jr., July 1977. M7140.—Same location as M7139, but 2.4 meters higher in mea- sured section. Coll. by Louie Marincovich, Jr., July 1977. M7141.—Same location as M7139, but about 9 meters lower in measured section. Coll. by Louie Marincovich, Jr., July 1977. M7142.—Same location as M7139, but 2 meters above base of measured section. Coll. by Louie Marincovich, Jr., July 1977. M7143.—False Pass (D-3) quadrangle, USGS 1:63,360, 1963 ed. South Walrus Peak stratigraphic section, 130 meters above base of measured section, section 19, T 60 S, R 89 W; latitude 54?57'N, longitude 162°50’W. Coll. by Louie Marincovich, Jr., July 1977. M7144.—Same location as M7143, but 94 meters above base of measured section. Coll. by Louie Marincovich, Jr., July 1977. M7145.—Same location as M7143, but 12 meters above base of measured section. Coll. by Louie Marincovich, Jr., July 1977. M7146.—Same location as M7143, but 6 meters above base of measured section. Coll. by Louie Marincovich, Jr., July 1977. M7149.—False Pass quadrangle, USGS 1:250,000, 1949 ed. Sea cliff exposure between False Pass and Morzhovoi Bay, 36 meters above base of Kenmore Head South stratigraphic section, latitude 54°51'41"N, longitude 164?38'42"W. Coll. by Louie Marincovich, Jr., July 1977. M7150.—False Pass quadrangle, USGS 1:250,000, 1949 ed. Sea cliff exposure on north side of Ikatan Bay, about 3.3 kilometers west of Kenmore Head, latitude 54?53'47"N, longitude 164?40'43"W. 'Coll. by Louie Marincovich, Jr., July 1977. M7200.—False Pass (0-3) quadrangle, USGS 1:63,360, 1963 ed. Type locality of Tachilni Formation at Cape Tachilni, about 7 meters above base of measured section, section 35, T 60 S, R 90 W; latitude 54°55'N, longitude 162*52'W. Coll. by Irven Palmer, USGS, 1977. M7201.—Same location as M7200, but about 42 meters above base of measured section. Coll. by Irven Palmer, USGS, 1977. M7202.—Same location and stratigraphic position as M7139. Coll. by Irven Palmer, USGS, 1977. M7203.—Same location as M7202, but 2.4 meters lower in mea- sured section. Coll. by Irven Palmer, USGS, 1977. M7204.—False Pass (D-3) quadrangle, USGS 1:63,360, 1963 ed. Float specimens from type locality of Tachilni Formation at Cape Tachilni, section 35, T 60 S, К 90 W; latitude 54955'М, longitude 162°52’W. Coll. by Irven Palmer, USGS, 1977. M7256.—False Pass quadrangle, USGS 1:250,000, 1949 ed. Sea cliff exposure about 15 kilometers southwest of Kenmore Head, at an elevation of about 400 feet, section 30, T 61 S, R 92 W. Coll. by Hugh McLean, USGS, June 1977. M7258.—False Pass (D-3) quadrangle, USGS 1:63,360, 1963 ed. Float specimens from base of South Walrus Peak stratigraphic sec- tion, section 19, T 60 S, К 89 W; latitude 54°58’16"N, longitude 163*10'00"W. Coll. by Hugh McLean, USGS, June 1977. California Academy of Sciences (CAS), San Francisco, California 60278.—False Pass (D-3) quadrangle, USGS 1:63,360, 1963 ed. Promontory on shore just east of line between section 5 and section 6, T 61 S, R 90 W. Coll. by Mobil Oil Corporation, 1975. 60279.—Same locality data as CAS 60278. 60280.—Same locality data as CAS 60278. University of Alaska (UA), Fairbanks, Alaska A-169.—False Pass (D-3) quadrangle, USGS 1:63,360, 1963 ed. About 100 yards upstream from beach, along a creek, slightly east of line between sections 5 and 6, T 61 5, R 90 W. Coll. by R. C. Allison, 1969. A-170.—False Pass (D-3) quadrangle, USGS 1:63,360, 1963 ed. In bluffs about 200—300 feet above beach level, along small creek. about 850 feet east of boundary line between sections 35 and 36, Ц 60 S, R 90 W. Coll. by К. C. Allison, 1969. A-301.—False Pass (D-3) quadrangle, USGS 1:63,360, 1963 ed. At base of low shoreline bluff, just north of second asterisk showing offshore rocks, section 24, T 60 S, R 89 W. Coll. by R. C. Allison: 1969. A-302.— False Pass (0-3) quadrangle, USGS 1:63,360, 1963 ed. In shoreline bluff about 460 feet north and 1600 feet east of south- west corner of section 26, T 60 S, R 89 W. Coll. by R. C. Allison: 1969. REFERENCES CITED Adams, H. and A. 1853—58. The genera of Recent Mollusca, arranged according to their organization. London, vols. 1—3. Addicott, W. O. 1969. Late Pliocene mollusks from San Francisco Peninsula, California, and their paleogeographic significance. Calif. Acad. Sci., Proc., ser. 4, vol. 37, No. 3, pp. 57-93, pls. 1-4. 1973. Oligocene marine biostratigraphy and paleontology of the lower part of the type Temblor Formation, California. U.S. Geol. Surv., Prof. Paper 791, pp. 1-48, pls. 1—9. 1976a. 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London, vol. 17, рр: 1-279. Uozumi, S. 1957. Studies on the molluscan fossils from Hokkaido. Part Il. Genera Yoldia and Portlandia. Hokkaido Univ., J. Бас. Sci:, ser. 4, vol. 9, No. 4, pp. 539-595, pls: 1-7. 1962. Neogene molluscan faunas in Hokkaido (Part 1. Se- quence and distribution of Neogene molluscan faunas). Hokkaido Univ., J. Fac. Sci., ser. 4, vol. 11, pp. 507—544. Valentine, J. W., and Emerson, W. K. 1961. Environmental interpretation of Pleistocene marine species—a discussion. J. Geol., vol. 69, Мо. 5, pp. 616- 618. Vallot, J. N. 1801. Exercise de histoire naturelle. Ecole Central Dept. Cote d'Or. Dijon. Pagination unknown. Vedder, J. G. 1961. Previously unreported Pliocene Mollusca from the south- eastern Los Angeles Basin. U.S. Geol. Surv., Prof. Paper 400-B, pp. В326-В328. Wagner, C. D. 1974. Fossil and Recent sand dollar echinoids of Alaska. J. Pa- leontol., vol. 48, No. І, pp. 105-123, pls. 1-3. Wagner, F. J. 1959. Palaeoecology of the marine Pleistocene faunas of south- western British Columbia. Geol. Surv. Canada, Bull. 52, pp. 1–67, pl. 1. Waldron, H. H. 1961. Geologic reconnaissance of Frosty Peak Volcano and vi- cinity, Alaska. U.S. Geol. Surv., Bull. 1028-T, рр. 677- Дио р 79: Watanabe, K., Arai, J., and Hayashi, Т. 1950. Tertiary geology of the Chichibu Basin. Chichibu Mus: Nat. Hist., Bull., No. 1, pp. 29292, pls. 1-6. Weaver, C. E. 1912. A preliminary report on the Tertiary paleontology of west ern Washington. Washington Geol. Surv., Bull. 15, РР: 1-80, pls. 1—15. 1916. Tertiary faunal horizons of western Washington. Univ: Washington Publ., Geol., vol. 1, No. 1, pp. 1—67, pls. is Sh, 1942 [1943]. Paleontology of the marine Tertiary formations of Oregon and Washington. Univ. Washington Publ., Geol.» vol. 5, pts. 1-3, pp. 1-789, pls. 1-104. 1949. Geology of the Coast Ranges immediately north of the San Francisco Bay region, California. Geol. Soc. AM Мат: 527 рр. 1=242, pls, 1=14, Whitfield, R. P. 1885. Brachiopoda and Lamellibranchiata of the Raritan clays TACHILNI FORMATION MOLLUSKS: MARINCOVICH 181 and greensand marls ој New Jersey. U.S. Geol. Surv. Monogr. 9, pp. 1-338, pls. 1-35. Willett, С. 1918. Description of a new Pandora of the subgenus Kennerlyia from Forrester Island, Alaska. Nautilus, vol. 31, No. 4, bp. 134—135. Williams, М. W. 1940. A new Periploma from Alaska. J. Entomol. Zool., Pomona College, Calif., vol. 32, No. 2, pp. 37-40, fig. 1. Winckworth, R. 1930. Notes on nomenclature, 5; some new names for British marine bivalves. Malacol. Soc. London, Proc., vol. 19, . 14-15. Wood, уу." 1815. General conchology; or a description of shells. London, pp. 1—246, pls. 1—60. Woodring, W. P., and Bramlette, M. N. 1950 [1951]. Geology and paleontology of the Santa Maria Dis- trict, California. U.S. Geol. Surv., Prof. Paper 222. pp. 1-185, pls. 1-23, text-figs. 1—9. Woodring, W. P., Bramlette, M. N., and Kew, W. S. W. 1946. Geology and paleontology of Palos Verdes Hills, Califor- та. U.S. Geol. Surv., Prof. Paper 207, pp. 1-145, pls. 1– 36. Woodring, W. P., Stewart, R., and Richards, R. W. 1940 [1941]. Geology of the Kettleman Hills oil field, California. Y. U.S. Geol. Surv., Prof. Paper 195, pp. 1-170, pls. 1-57. 9koyama, M, 1911. Pectens from the Koshiba Neogene. Geol. Soc. Tokyo, J., vol. 18, No. 208, pp. 1—5, pl. 1. 1920. Fossils from the Miura Peninsula and its immediate north. Imp. Univ. Tokyo, J. Coll. Sci., vol. 39, art. 6, pp. 1-193, pls. 1—20. 1923. On some fossil Mollusca from the Neogene of Izumo. Ja- pan. J. Geol. Geog.. vol. 2, No. 1, pp. 1-9, pls. 1-2. 1924. Molluscan remains from the lowest part of the Jo-ban coal-field. Tokyo Imp. Univ., J. Coll. Sci., vol. 45, art. 3, pp. 1-22, pls. 1-5. 1925. Tertiary Mollusca from Shinano and Echigo. Imp. Univ. Tokyo, J. Fac. Sci., sec. 2 (Geol., Mineral., Geog., Seism.), vol. 1, No. 1, pp. 1-22, pls. 1-7. 1926. Fossil shells from Sado. Imp. Univ. Tokyo, J. Fac. Sci., sec. 2 (Geol., Mineral., Geog., Seism.), vol. 1, No. 8, pp. 249-312, pls. 32-37. Zhidkova, L. S. 1972. Atlas of Neogene mollusks of the Kuril Islands. Acad. Sci. U.S.S.R., Siberian Dept., Sakhalin Complex Sci. Res. Inst., pp. 1-162, pls. 1-48, text-figs. 1—8. [In Russian]. Zhidkova, L. S., Kuzina, I. N., Lautenschlager, F. G., and Popova, Г. А. 1968. Atlas of the mollusks of the upper Miocene and Pliocene of Sakhalin. Acad. Sci. U.S.S.R., Siberian Dept., Sa- khalin Complex Sci. Res. Inst., рр. 1-179, pls. 1-50. [In Russian]. Zinsmeister, W. J. 1970 [1971]. A Late Pliocene macrofossil fauna of Newport Beach, Orange County, California. South. Calif. Acad. Sci., Bull., vol. 69, Nos. 3-4, pp. 121-125. PLATES Figure 1-4. 5-7. 8-9. 10-17. BULLETIN 317 EXPLANATION OF PLATE 12 AGH CERN а ПР АНТА А У Lio eq Me Hope RIS ш. у, на йы >. eR ppl aet ИЙ И 78 1. Left valve of articulated valves, UA 2467; note obsolete radial sculpture near ventral margin; length 27.7 mm, height 22.0 mm, x1.5; UA locality A-169. 2-4. Articulated valves, UA 2468; length 26.3 mm, height 22.1 mm, x1.5; UA locality A-169. 2. Left valve. 3. Escutcheon, with slightly raised area in center. 4. Right valve. verto (Exuncavtho Crna (GIANG) Fs: ара AN „Мик. Led к» ы, rre REET И cde cem loot а SER 79 5. Left valve, USNM 265854; showing extremely weak radial sculpture; length 35.8 mm, height 28.0 mm, x1; USGS locality M7140. 6. Central portion of left valve, USNM 265854 (see fig. 5); showing extremely weak radial sculpture and fine concentric growth lines; x3. 7. Posterior portion of left valve, USNM 265854 (see fig. 5); showing coarser posterior sculpture; x3. ПОР (ОСТЕО ИОТ аа sos c Sess ea cats ook feu er EE etos ua S RR BRL uar CUR па I A dS О нон а 80 8. Right valve, UA 2469; showing oblique concentric sculpture; length 43.4 mm, height 22.3 mm, x1; UA locality A-301. 9. Right valve, USNM 265855; with intact posterior end; length 52.4 mm, height 25.1 mm, x1; USGS locality M7146. In VO ET СТОНА ВР НЕ are МНОМ ы =з ene рае weir COE ые Aner. aa СЕ. 10-11. Left valve, UA 2470; length 45.9 mm, height 45.9 mm, x1; UA locality A-170. 10. Exterior, showing fine radial ribs. 11. Interior. 12. Hinge of left valve, UA 2471; length 32.9 mm, x1; UA locality A-170. 13. Right valve, USNM 339752; length 39.0 mm, height 37.5 mm, x1; USGS locality M7139. 14—15. Articulated valves, USNM 339753; length 43.8 mm, height 40.2 mm, thickness 19.3 mm, x1; USGS locality M7139. 14. Dorsal view. 15. Left valve, showing fine radial sculpture. 16-17. Right valve, UA 2472; length 42.4 mm, height 37.1 mm, x1; UA locality A-170. 16. Interior. 17. Exterior, showing fine radial sculpture. BULLETINS OF AMERICAN PALEONTOLOGY, VOLUME 84 PLATE 12 PLATE 13 oo m = 2 = © > = Q о = o = 2. o щ У S а. 2 = > z m > < щ © o 2 E ш 4 - =] em TACHILNI FORMATION MOLLUSKS: MARINCOVICH 133 EXPLANATION OF PLATE 13 Figure Page |. Crenomytilus.coalingensis (AMO) aa за тунеле кои е aM Db elus dE NU ЖЕЗ. tenets teenie aes ка си 82 Right valve, USNM 339754; length 106.9 mm, height 48.5 mm, х 1; USGS locality M4045. 2-3. Musculus А ЕЕ НК E ESO IU ОО uet ер ет экс» 83 2. Left valve, USNM 339755; showing radial sculpture best-developed on posterior portion; length 60.5 mm, height 28.3 mm, х1; USGS locality M7146. 3. Right valve, USNM 339756; showing well-developed posterior radial sculpture and weakly developed anterior radial sculpture; length 41.9 mm, height 23.1 mm, x1; USGS locality M7146. 84 4-9. Chlamys (Swiftopecten) cosibensis cosibensis (Yokoyama) ....... sehen heels 4. Left valve, USNM 339757; length 70.5 mm, height 80.0 mm, x1; USGS locality M7146. 5. Right valve, USNM 339758; showing well-developed step-like concentric sculpture; length 53.0 mm, height 60.9 mm, x1; USGS locality M4044. . Left valve, USNM 339759; length 60.0 mm, height 65.0 mm, х1; USGS locality M7146. 7-9. Articulated valves, UA 2473; length 71.5 mm, height 76.2 mm, thickness 39.7 mm, х1; UA locality A-170. 7 ей valve. 8. Anterior view, showing high relief of concentric sculpture. 9. Right valve. с Figure 1-2. 3-8. 9-10. 15-17. BULLETIN 317 EXPLANATION OF PLATE 14 ChiamysioSwirtopecten)- cosibensis cosibensis (Yokoyama) a en cee oy ук кыяны»... ааа нос Os RE a лк тулт 84 Left valve, USNM 339760; length 80.6 mm, height 93.5 mm, thickness 26.4 mm, х1; USGS locality M7146. 1. Lateral view, showing well-developed radial and concentric sculpture. 2. Posterior view, showing high relief of sculpture. Сусіюсалша A Cx ПОШТИ forms ULIS DI... em р а rs ean 87 3-4. Articulated valves, UA 2474; length 17.2 mm, height 18.2 mm, x1.5; UA locality A-170. 3. Left valve. 4. Right valve. 5. Right valve, USNM 339762; length 20.6 mm, height 21.1 mm, x1; USGS locality M7146. 6. Right valve, UA 2500; length 19.6 mm, height 20.3 mm, x1.5; UA locality A-170. 7-8. Articulated valves, USNM 339763; length 11.8 mm, height 10.5 mm, x2; USGS locality M7139. 7. Left valve. 8. Right valve. GYDIUCUPOIgESUCCIOS AME c cy ad boc a oc Ee rer wks aerei РР HT RI COMEDOR ADOS oo НИ 88 9. Right valve, UA 2475; showing coarse radial costae; length 30.8 mm, height 20.8 mm, x1; UA locality A-169. 10. Dorsal view, UA 2475 (see fig. 9); showing articulation of valves; x1. BEVITOOTCHSCOSCDEOIOHOUIHSWUITUDE DEED E OR tests CK es cee CITUR RD D ык лы л ИН 88 Right valve, USNM 339765; length 6.2 mm, height 7.0 mm, x2; USGS locality M7142. PROV СОНГ АИ СКОРО ОН 5 улса t eer et E E TED IBN DENDUM 87 Articulated valves, USNM 339764 (holotype); length 34.0 mm, height 30.5 mm, thickness, 14.7 mm, x1; USGS locality M7139. 12. Dorsal view. 13. Left valve. 14. Right valve. UG HANG: par SE ОО Е dr 2-4 у>. US ЖОЕЛ Е ELA 89 15-16. Articulated valves, UA 2476; length 16.4 mm, height 14.5 mm, thickness 6.1 mm, x2; UA locality A-170. 15. Right valve. 16. Dorsal view. 17. Right valve, USNM 339766; length 22.8 mm, height 20.5 mm, x1; USGS locality M7142. - MISHHODECIOITIROICTODSISSUNDUSNeI e EADEM Te а пи REO EE L.C LE 86 Fragment of right valve, USNM 339761; height 67.9 mm, x1; USGS locality M7150. PLATE 14 BULLETINS OF AMERICAN PALEONTOLOGY, VOLUME 84 PLATE 15 BULLETINS OF AMERICAN PALEONTOLOGY, VOLUME 84 Figure 2-4. . Clinocardium cf. C. pristinum Keen . Saxidomus sp. indet. TACHILNI FORMATION MOLLUSKS: MARINCOVICH 135 EXPLANATION OF PLATE 15 Page ‚ Clinocardium cf. C. ciliatum (Fabricius) cs LED бо оно E ооо оо лиман EE B FL LL 90 External cast of right valve, USNM 339767; length 21.5 mm, height 18.4 mm, x1; USGS locality M7146. Clinocardium hannibali Keen о... се ес ен n t ОРОХ эт ни 91 2-3. Articulated valves, USNM 339768; length 23.3 mm, height 18.7 mm, х2; USGS locality M7149. 2. Left valve. 3. Right valve. с ; 4. External mold of right valve, USNM 339769; length 26.0 mm, height 23.4 mm, x1.5; USGS locality M7150. . Clinocardium meekianum (Gabb) п. subsp.? .............. e t t ttn ИНО LLL 92 5. Left valve, USNM 339770; length 55.7 mm, height 45.7 mm, x1; USGS locality M7146. \ 6—7. Articulated valves, USNM 339771; length 71.0 mm, height 77.9 mm, х0.75; USGS locality M7201. 6. Right valve. 7. Left valve. | : 8. External mold of left valve, USNM 339772; length 70.0 mm, height 65.4 mm, х1; USGS locality M7146. ler ИН к принт 92 9. External mold of right valve, USNM 339773; length 38.7 mm, height 36.0 mm, x1; USGS locality M7146. | 10. Right valve, USNM 339774; showing nodose radial costae; length 25.3 mm, height 26.0 mm, х 1.5; USGS locality M7140. 11. External mold of left valve, USNM 339775; length 42.5 mm, height 38.6 mm, х1; USGS locality M7146. 12. External mold of left valve, USNM 339776; length 39.4 mm, height 38.0 mm, x1; USGS locality M7146. Left valve of articulated valves, USNM 339777; showing largely decorticated shell; length 68.9 mm, height 52.2 mm, х1; USGS locality M7139. 136 BULLETIN 317 EXPLANATION OF PLATE 16 Figure Page E РУОР US VOLO TOC) ES TALE TA (алоје на PCI ПР Aas трења каца но BODL od kat к re a ООУ EM ON NE A Dp 1-3. Articulated valves, USNM 339778; length 48.5 mm, height 43.8 mm, thickness 31.3 mm, x1; USGS locality M7142. 1. Left valve. 2. Dorsal view. 3. Right valve. 4. Right valve, USNM 339779; length 40.0 mm, height 34.5 mm, x1; USGS locality M7140. Ура (VACINOMICTIS) alburia e Olrád)., иу а leas ар EIN SIRE АНЕ аа ек Кулик ETE RIT ел и ae oem S 95 Articulated valves, USNM 339780; length 53.1 mm, height 40.3 mm, thickness 23.0 mm, х1; USGS locality M7139. 5. Left valve. 6. Dorsal view. 7. Right valve. 5-9. SPISHIDCMICITOHIErIS) SDECUDPOSUTAO БАСКАН а o teet bbl кл ку жук Cah UTE TOE ка жулуу А суол де ge 95 8. Left valve, USNM 339781; length 79.5 mm, height 60.2 mm, x1; USGS locality M7146. 9. Right valve, USNM 339782; length 68.1 mm, height 52.2 mm, x1; USGS locality M7150. 10:12 БРИНЕ (Мас Олег) РОУ YUM OPIO) orse a прста у, у. у кичуу sey lesley ао адейи кык «es alah Sr De wis ccr e gets нае анти 96 10. Right valve, USNM 339783; length 48.1 mm, height 25.5 mm, х1; USGS locality M7146. 11. Left valve, USNM 339784; length 76.4 mm, height 52.6 mm, x1; USGS locality M7146. 12. Left valve, USNM 339785; length 36.0 mm, height 22.8 mm, x1; USGS locality M7146. PLATE 16 BULLETINS OF AMERICAN PALEONTOLOGY, VOLUME 84 BULLETINS OF AMERICAN PALEONTOLOGY, VOLUME 84 PLATE 17 TACHILNI FORMATION MOLLUSKS: MARINCOVICH 137 EXPLANATION OF PLATE 17 Figure Page 1—2. Spisula (Mactromeris) polynyma (Stimpson) о... себе не hehehe 1. Right valve, USNM 339786; length 81.8 mm, height 53.7 mm, х1; USGS locality M7258. 2. Left valve, USNM 339787; length 65.0 mm, height 36.1 mm, х1; USGS locality M7146. 3-9. Peronidia aff. P. lutea alternidentata (Broderip and Sowerby) 1 +1... essere nn 97 3-4. Articulated valves, USNM 339788; length 79.1 mm, height 50.0 mm, thickness, 19.9 mm, x1; USGS locality M7139. 3. Dorsal view. 4. Right valve. 5—6. Internal mold of articulated valves, UA 2477; showing pallial sinus and adductor muscle scars [inked in by author]; length 77.0 mm, height, 48.3 mm, x1; UA locality А-170. 5. Left valve. 6. Right valve. 7-9, Articulated valves, UA 2478; length 70.3 mm, height 45.6 mm, thickness 19.2 mm, х1; UA locality A-170. 7. Dorsal view. 8. Right valve. " | 9. Internal mold of left valve, showing pallial sinus and adductor muscle scars [inked in by author]. BULLETIN 317 EXPLANATION OF PLATE 18 Figure Page |-3, Peronda: аш. лев aliernidentata: (Broderip апа Sowerby) зк. килик минери toss вина AM ЕЛЕН ta NE и 97 Articulated valves, USNM 339789; length 52.9 mm, height 29.0 mm, thickness 8.4 mm, х1; USGS locality M7139. 1. Left valve. 2. Dorsal view. 3. Right valve. А 15 Магота Тисо CU MEUM ка ОПАО А оа occa wove vob wa жак. INERENTI е тылу а леу гу 97 4. Left valve, USNM 339790; length 35.8 mm, height 27.6 mm, х1; USGS locality M7140. 5. Right valve, USNM 339791; length 42.4 mm, height 30.0 mm, x1; USGS locality M7140. 6. Right valve, USNM 339792; length 41.0 mm, height 30.0 mm, x1; USGS locality M7140. 7. Left valve, USNM 339793; length 37.0 mm, height 26.4 mm, x1; USGS locality M7140. 8. Left valve, USNM 339794; length 37.5 mm, height 28.5 mm; x1; USGS locality M7142. 9. Left valve, USNM 339795; length 40.3 mm, height 31.7 mm, x1; USGS locality M7140. 10–12. Articulated valves, USNM 339796; length 42.4 mm, height 39.0 mm, thickness 9.4 mm, x1; USGS locality M7140. 10. Dorsal view. 11. Right valve. 12. Left valve. 13-14. Articulated valves, USNM 339797; length 36.8 mm, height 31.4 mm, x1; USGS locality M7140. 13. Left valve. г 14. Right valve. ; 15-16. Articulated valves, USNM 339798; length 39.1 mm, height 26.7 mm, thickness 10.9 mm, x1; USGS locality M7140. 15. Dorsal view. 16. Left valve. 17. Internal mold of left valve, USNM 339799; showing pallial sinus and adductor muscle scars [inked in by author]; length 44.4 mm, height 36.4 mm, x1; USGS locality M7142. 18. Right valve, USNM 339800; length 42.1 mm, height 33.0 mm, x1; USGS locality M7142. 19; Macoma imeona rin (Von Майен у па ууа, кз иста «хэ oreet ens АИ ЫШ Rene ILLOD К EBENE URL S 100 Right valve, USNM 339801; length 37.8 mm, height 31.0 mm, x1; USGS locality M7146. BULLETINS OF AMERICAN PALEONTOLOGY, VOLUME 84 PLATE 18 BULLETINS OF AMERICAN PALEONTOLOGY, VOLUME 84 PLATE 19 TACHILNI FORMATION MOLLUSKS: MARINCOVICH 139 EXPLANATION OF PLATE 19 Figure Page 1710. Масота (Macoma) optiva (Yokoyama) ose eres eee ot шк ш Оо а et о 98 1. Left valve hinge, UA 2479; x2; UA locality A-169. 2-4. Articulated valves, UA 2480; length 65.4 mm, height 52.5 mm, thickness 15.6 mm, х1; UA locality A-170. 2. Left valve. 3. Dorsal view, showing posterior flexure to the right. 4. Internal mold of right valve, showing part of pallial sinus and adductor muscle scars [inked in by author]. 5-6. Articulated valves, UA 2481; length 60.0 mm, height 54.5 mm, thickness 23.1 mm, х1; UA locality A-170. 5. Dorsal view. 6. Left valve. 7. Left valve of juvenile specimen, UA 2482; length 35.5 mm, height 29.6 mm, х1; UA locality A-170. 8-10. Internal mold of articulated valves, UA 2483; length 55.7 mm, height 47.3 mm, thickness 15.6 mm, х1; UA locality A-170. 8. Dorsal view. 9. Right valve, showing part of pallial sinus [inked in by author]. 10. Left valve, showing pallial sinus [inked in by author]. 100 11-13. Siliqua cf. 5. alte (Broderip and Зону) (ics oxen сока какао Ft UE a ANS ORES AURI TP iae sa бик 11. Internal mold of articulated, open valves, USNM 339802; length 42.0 mm, height 18.5 mm (of left valve, bottom), х1; USGS locality M7146. 12. Latex cast of left valve, USNM 339803; length 32.0 mm, height 16.4 mm, x 1; USGS locality M7146. 13. Internal mold of left valve, UA 2484; length 42.9 mm, height 24.5 mm, х1; UA locality A-301. BULLETIN 317 EXPLANATION OF PLATE 20 Figure Page |- SImmguasckesdalmauoderip'andasowerby)s ayo а ен и OPIDO н OO Pera ame EM Ve 100 Internal mold of articulated valves, USNM 339804; length 59.3 mm, height 28.1 mm (of right valve, below), x1; USGS locality M7150. 226 Му ИУ APU COT Linnaeus 269 osos Ree te ICO Pre ree ОИ ols noue M My ip asters ee лат fade AE E a rob vu 101 2-3. Articulated valves, USNM 339805; length 77.0 mm, height 59.1 mm, thickness 43.2 mm, x1; USGS locality M7142. 2. Dorsal view. 3. Left valve. 4—5. Articulated valves, USNM 339806; length 76.1 mm, height 52.7 mm, thickness 34.5 mm, х1; USGS locality M7146. 4. Dorsal view. 5. Right valve. 6. Right valve of juvenile, UA 2485; showing truncated posterior end; length 32.3 mm, height 22.5 mm, х1; UA locality A-301. 7. Left valve of juvenile questionably assigned to the species, UA 2486; with imperfectly truncate posterior end; length 39.7 mm, height 24.2 mm, x1; UA locality A-301. SOS Mae AWEHOHIYOEIEgans (БИЕШ ALG bara d. quip Js Dac at tee iOS ИИ o анаја en о 102 Articulated valves, USNM 339807; length 80.9 mm, height 58.2 mm, thickness 40.7 mm, x1; USGS locality M7146. 8. Dorsal view. . 9. Right valve, showing narrowly rounded posterior end. PLATE 20 BULLETINS OF AMERICAN PALEONTOLOGY, VOLUME 84 PLATE 21 Figure 1-3. 10. © | Рапотуа trapezovdis: Stauch съ Жн уле ee ны уе ин Right valve, USNM 339810; length 48.7 mm, height 27.6 mm, х1; USGS locality M7150. TACHILNI FORMATION MoLLUSKS: MARINCOVICH 141 EXPLANATION OF PLATE 21 Mya (Arenomya) elegans, Eichwald ка. се и сыр она оста te ч зч а gue e ee eene 102 Internal mold of articulated valves, showing outline of pallial sinus, USNM 339808; length 101.0 mm, height 77.5 mm, thickness 42.7 mm, x0.67; USGS locality M7139. 1. Left valve. 2. Right valve. 3. Dorsal view. te Mya тереен е DE E pee M e ЕЕ 104 4—6. Articulated valves, UA 2487; length 55.4 mm, height 29.0 mm, thickness 15.8 mm, х1; UA locality A-301. 4. Left valve. 5. Dorsal view, showing flared posterior gape. 6. Right valve. ; 7-9. Articulated valves, UA 2488; length 50.2 mm, height 27.0 mm, thickness 13.0 mm, x1; UA locality A-301. 7. Left valve. 8. Dorsal view, showing flared posterior gape. 9. Right valve. Pandora (Pandorella) grandis Пай .......... 600 t ctt 6n ШЕЕ 107 Right valve, USNM 339811; length 37.5 mm, height 26.2 mm, х 1; USGS locality M7139. . Panomya izumo Nomura and Hatal ..... урт tv t зэ. у. ees ИИО 35355 105 Left valve, USNM 339809; length 73.3 mm, height 52.4 mm, x 1: USGS locality M7143. + BULLETIN 317 EXPLANATION OF PLATE 22 SUITE а АЕ WA) SSS. oie во СНА een eee те с И ce ee REEL DLL LE кше 107 1-3. Articulated valves, USNM 339812 (holotype); length 15.2 mm, height 10.0 mm, thickness 6.0 mm; USGS locality M7142. 1. Right valve, showing extremely fine beaded radial sculpture and posterior truncation, х2. 2. Dorsal view, х2. 3. Enlargement of right valve to show radial sculpture, x3. 4. Left valve, USNM 339813 (paratype); length 9.9 mm, height 6.8 mm, x2; USGS locality M7142. . Periploma (Periploma) cf. P. (P.) aleutica (Krause) «1.1.6... eevee hehehe 108 5. Right valve, UA 2489; length 52.8 mm, height 39.0 mm, x1; UA locality A-170. 6—7. Articulated valves, USNM 339814; length 50.7 mm, height 40.0 mm, thickness 17.5 mm, x1; USGS locality M7140. 6. Dorsal view. 7. Left valve. 8—9. Articulated valves, USNM 339815; length 38.1 mm, height 28.2 mm, x1; USGS locality M7146. 8. Right valve. 9. Left valve. . Margarites (Pupillaria) new species? |... cco ete rete ree rine rue e ees eee nene eerte reel eee ee eiie en 109 10-12. USNM 339816; height 9.1 mm, diameter 11.2 mm, x2; USGS locality M7146. 10. Apertural view. 11. Right-oblique view to show spiral sculpture on whorls. 12. Basal view, showing broadly open umbilicus and spiral sculpture. 13-15. UA 2490; height 8.0 mm, diameter 10.1 mm, x2. UA locality A-170. 13. Apertural view. 14. Apical view. 15. Basal view. "Calyptraenspeciesudetenminate 1... eene аот 110 Internal mold, mostly decorticated, UA 2491; height 8.3 mm, greatest diameter 22.6 mm, х1; UA locality A-170. 16. Apical view. 17. Side view. . Polinices (Euspira) pallidus (Broderip and Sowerby) .......... 2000 cece eet hehehe 111 18. Apertural view, UA 2492; height 35.0 mm, diameter 32.9 mm, x 1; UA locality A-169. 23. Apertural view, USNM 339818; height 55.8 mm, diameter 46.5 mm, х1; USGS locality M7139. . Polinices (Euspira): diabloensis (Clark): rise сек бан oe vn elem noice CODO ие Е и! Apertural view, USNM 339817; height 31.4 mm, diameter 26.6 mm, х1; USGS locality M7140. 20. Bulbus fragilis (Leach) ........................... 23.3 E uu LE ME tee weer ye е кк ккк бр да кка 112 Apertural view of juvenile, USNM 339819; showing umbilicus nearly concealed beneath thin callus; height 10.7 mm, diameter 9.6 mm, х3; USGS locality M7143. . Natica (Cryptonatica) clausa Broderip and Sowerby .................. Hehe hehehe 113 Apertural view, USNM 339820; showing umbilicus closed by thick callus; height 23.5 mm, diameter 22.0 mm, х1.5; USGS locality M7139. Майса (Tectonatica) janthostoma Deshayes нео ея 114 Apertural view, UA 2493; showing open umbilicus and sulcus above umbilical callus; height 35.0 mm, diameter 32.9 mm, х1; UA locality A-301. РГАТЕ 22 BULLETINS OF AMERICAN PALEONTOLOGY, VOLUME 84 PLATE 23 Figure 11—12. 16—17. 18—20. . Fusitriton oregonensis (Redfield) TACHILNI FORMATION MOLLUSKS: MARINCOVICH 143 EXPLANATION OF PLATE 23 Backside view, USNM 339821; showing axial and spiral sculpture; height 33.0 mm, diameter 21.0 mm, x1.5; USGS locality M7139. Buccinum ot: B. planeticum DUE у. улуш А о о с от ва ава aa долоо на 2. Apertural view, UA 2494; showing spiral sculpture; height 50.0 mm, diameter 34.1 mm, х1; UA locality A-301. 3-4. Mostly decorticated specimen, USNM 339822; showing axial and spiral sculpture; height 50.3 mm, diameter 36.9 mm, x1; USGS locality M7146. . Molopophorus cf. M. bogachielii (Reagan) а e t t t ttt TEE LLL LL LC 116 5. Apertural view, UA 2495; height 30.8 mm, diameter 18.2 mm, x1; UA locality A-301. 6-7. UA 2496; height 35.1 mm, diameter 16.7 mm, X1; UA locality A-170. 6. Apertural view, note columellar folds and sculpture on early whorls. 7. Backside view. . Neptunea (Neptunea) lyrata аїйѕріга Сабы... НЕНИ 118 Backside view of small specimen, USNM 339823; height 30.4 mm, diameter 19.8 mm, x1.34; USGS locality M7139. . Neptunea (Neptunea) species D aff. N. (N.) modesta (Kuroda in Homma) of Nelson ......... pene ek] e eee ene 119 USNM 339824; note fine spiral sculpture; height 56.1 mm, diameter 33.1 mm, x1; USGS locality M7146. 9. Apertural view. 10. Backside view. D MM EM rre О ы ме ши куо хок Л ux pU d 120 UA 2497; height 20.3 mm, diameter 17.6 mm, x 1.5; UA locality A-301. 11. Apertural view. 12. Backside view. ‚ Beringius herten Mac Nal o. иа стерео оо uas I I MM eo МЕЧ 117 Partly decorticated specimen, UA 2498; height 109.4 mm, diameter 68.6 mm, х1; UA locality A-169. Oenopota species A пособие пасион а EQ Mb c суы у А с pee e eene nennen 121 Mostly decorticated specimen, USNM 339827; height 9.6 mm, diameter 4.7 mm, x3; USGS locality M7139. 14. Apertural view, showing remnants of axial and spiral sculpture. 15. Backside view, showing remnants of axial sculpture. Neptunea (Golikovia plafkeri Kamno vss. nce шли НИН OO РА УМИ 119 UA 2499; height 68.3 mm, diameter 42.1 mm, х1; UA locality А-301. 16. Apertural view. з : 17. Backside view, showing subtabulate shoulder and barnacle encrustations at apex and on outer lip. E qu E MM cu ел б ху a 120 Oenopota cf. О. candida (Yokoyama) нет 18-19. Worn specimen, USNM 339825; showing axial sculp 18. Apertural view. 19. Backside view. 20. USNM 339826; showing axial and spiral sculpture; height 19.0 m ture; height 17.0 mm, diameter 10.6 mm, x2; USGS locality M7143. m, diameter 11.1 mm, x2, USGS locality M7146. 144 BULLETIN 317 INDEX Note: Page numbers are in light face, plate numbers are in bold face type; numbers in italics indicate principal discussions. Acila H. & A. Adams, 1858 78 EEEN I ONE ОДИНА Е aera meee nee rds 78 Acila (Truncacila) Schenck in Grant and Gale, 1931 ......... 78,79 OMANI CCG MESO)! а аа И tee. 78 empr enas OWE, 1922 eedem 12:5 69:78:76. 132 СУДАРА КОЛО Howe, 1922 oe 68,78 errari (Gand, 849) eres ree I 67,71,79,132 Ка сива па ЖАШ ои А esee а pé e Ehe tore herb mere rere дуо» 89 2 M ST NOTAE 656) SIRE E 78,80 JA Or eM RU VATER UR REOR MODERNE UMEN IEEE 93,94 АСО ЫЕ) жайнак е ннн MN. MU ps Addicott (19768) essri 69,70,74,78,80-82,89-92,94,95,97-99, 101,102,114,116,117 Doo Cen) scx sts а а Se А а а ет 98,99 P adoro) MESSEN е Ва с с MM cc ес CERE 74 АКШ КО Шу. ыы. e cr NEM 82,93,101,110,114,116,117 P ideo ст | vcs ur MM о СШ 70,74,86 Addicott, Winkler, and Plafker (1978) ......... 71,72,78,79,85,86,117 АСОИ ОО SIDA) Mur. me MEME... e 91,100,104,106 ОЕЕО (LOO) И ПНЕ и cs cole EE кырр 82,83,92,94,101 АТЕНЕ АЕ ОЕША А еи еннен ЕР Ио 100 Alaska ла ы чт ж неси И 109 Таоа со sep den а О ИН КАГЫ э И о 109 АМД Ар г. я ине КИ ы КЫ Н ny 60,71,79,80,103,104,113 па ода р ЗНА МОРА РАИ rime E sonics 19 SANCS Den а E E E E E a рн 79 КОШЕ ГУ КУ ы... E EE E К EE иа А UO BOO аена Т ND ярни 64 lelciv admin m on и Н MN Ar E А та 71,103,118 Ја ако ВА Же. ЖУДИ: Тае 1122 Сар АША Н ане 85,117 Саро ОШОО нее E iun 103 Саре асое Ba... 60-62 ,65 ,66,68,70,71,81,88, 102—104, 108,118,119,121,122 Cape ааба... 64,71,72,93,96,102,106,114,115,117,120 КЕШЕ ly A M UIN MEME EDEN лыо CES Do НИВИ 103,104 ОЩЕ СНУ НИ р tuae de MR KD TENE Ie 61 (an ШИРК РОНЕ Иран ест eb Р, 101,104 [JOE TOTIS dore Ра лын а Дрина ach T Ка «e ETE UR 62 Ране Pill сеника oua а ионов кровно 62,108,121,122 Froo ya lo meer e DD И ууш 121 СООТ Е е пи на ЕИ я 110 СУ ОИЕ M E а HT [ШУ FR ааа оо 122 ЈЕ Еее ооо B Ie MAD SEC ENDS ОРКА S LL ee 113 КО АОИ TEES 60,80,81, 103,106 PAE OS Cy et te tees к у rien Пн а ата 104 ICOLOS DIS ЕО ул наан Тик Tee TRIBU RT UR 79 Kotzebue Sound РАТА ТИЈ CH сени а „анале петина укыу АГЫ Т. 113 КА А RC OY ote B CER Rte и 104 Lare СЛЕПЕ БА кор соон АКЫ и та ай 120 пуа ФО aap TUE 79,85,100,115,119,120 Wiles pine нин eL ИЕ ИНА РОН Ила се 79,119 ата а ОШ а ОСОНИИ TENE 89,114,115,119 МО ШИЕ ЕН cae EE A ааа 109 Моби одат Ва A МО УКИ ин 60,62,68,103,104,122 Noe КОКО о аана ESO RE 101 РӘХО Bayr E е 81,103 РАЙО СООО з пена па ин 81,103,104 Pity Ot yile UON S э vc ay cvs ун ee RR OS Y 81 Pear ЧАБУ МР Nene et et LL Loc аде E но iae 84 РОТ Ба ОУ КЕЕ ОУ: esee revo ere rie ce EDT D 80,81,91,97 Рој ОДО КЕ авина ЕА 86 ОРО а. tex парира ее 91,110 Тоор ВИ Хе Saxe ара REED NET OUT TOT OR costes 110 Роса ее е ttes an CORON е а 87,120 РОТОР аниони ра CHE ACA TA: 86,87,103,104,119,122 Топи (GT are др NUMEN. rcc pu poro i AME Ed 110 SIV MOON е шло дн. CL egre а ET EE EE DOES 121 SIMMONS LAGS: «cx ин лас ои Ба Lied aee 113 ОАК Таша амел ан а НИ 64,92,99,100,111,113 Sour Ма У Реа р бе 65,66,68,118,122 WLC DOVAK В ауто cinta sure rn rete асаа а 110 Орошон Mes bess. 627021 “ТУ Тапа ар та Лу аи пне аи unary 99,112,118,119 TLugidak Islanden те вратни ин лети О ОМА Ко 12, 18.119 јаја о Каа n кән ин л аныл СЕ 103,104,107,109,113 Unga Tand ere E 60,81,84,94,103,110 Wrangel occu лон ы a A ОК ur КО EA 107 Yakataga шо me we 78,79,85,91,100,106,110—113,115,119 Nakataga Reef уа ТА 87,96,101 YXellow Бш Слесар А 103,104 alaskana, ОЛЛО КОК ОЛ SUD КУ ТАТ А regen 108 КОШО аре dates GMMR RC ERC Ria ia rena eet cise рана ки 110 GIGS KONOM (Cle) «OLD ILC o is пленени E a E 110 albaria, NAIDU Clee зч а cae Ра АНА ЛА c А 95 SHOES ELC л Асе uy аланина РА 95 Spisula CVIGCTOMETIS)\. И. ПО ие 94 ,95,96,136 арала ато Spisula (Иса ОДА aniser ee OSEE ES 95 арапа COosensis, Spisula ШИШ Оё 1$). sege errara 95 albaria scapoosensis, Spisula (Мастотетз). не 95 ALG ИШЕ. ВО ШАО лу ти TOTO DOSE 91,100 aleutica, P. ПОО е TOO CURT T DOT ИЕ 108 ОШОО кк re ec E C CAM 108,109 РО ЛОЙ (UP eue oi en eee OE E ecco cc QU COR сената 75,108 aleutica (cf.), Periploma (Periploma) ...... TAAIE 68,76,108, 142 АЇ@ SEU MEOS Ка роуа Која tini t eE o ес 100 сусты Е о аы 62,122 АШЗО О К уру МИ кз он T с се осе 69-71 АШ ӨШ CMOS) = ын иек зс 62,69—71,75,85,96,100,104,115 Alison and Marmcovich 99 64,92,99,100,111,113 CUE CEES NIECE MIA о. TE te РАКА nodes 75,100,101 alta СОО I DRE UIN S er S C Oe ке 1920 а 100, 139,140 alispada NEPUNE y ce coe EUROS ENEE E 118 E SOA A E T E ОЛЛО о 100 Алаага УЕ BAT. cesse ETT E a a etre ЫМ 75,100 Anoma Cieta EAGLE ЖОГЫ О eet UR 102 АЛОНСО Ferse ES E ew eek ii E EN на 108 Айе О SE Е аен 107 anglonana K), Molo popho rus re eriin ieren ME: 117 TACHILNI FORMATION MOLLUSKS: MARINCOVICH 145 ANSP [Academy of Natural Sciences, Philadelphia, Pennsylvania] .......................- СОО ОНА E ӨН SIRE eae че EI ы накы ы ES 90 arctica, LEONG TBR УЛ СКЕ К ИКЕ ОАА pelt AC a A Јаја a rasa er ae a О mm ШЕЙ ШК кој јод ОТОО ТУО) И E “arenaria, ПИО E P E T rl Е Argobuccinum (Fusitriton) oregonensis (Redfield) Ariey (MILES) ra адаа шырыс ерт 71,72,87,96,100,106,110,115-117,120 EAUIMICTUTOUUCLOS eee ИУ Е ATO [CES O0 S) SCIRE P eat га CLOW Se ЕК HOUSE ВЛ E ANin et CIE (19 рими рет и а ie ОТ d Em Arnold (1909) ПОН СОЛО АН Н АН copre d Е ИИ Arnold and Anderson (1910) ... Arnold and Hannibal (1913) ... Asagai Богтапоп.................. CUSTOS УЛЫМ Жс д уы му А кыры ете 68 ,74,75,77,95,97,99, 107,112 ТОИР ОООО НЕ, 74,90,93 ,95 ,96,98,99 Ao ранно К eran МИНТЕ 60 astori, Macoma Macoma (Macoma) astori (cf.), ЛИР оре на пау ата ни tenen see pe ne 98 MOE OMANA COIE A E тИ 18 aN 68,97, 138 E О A ee Ct A EA TT MI 15 ГООО А OUR а лата ОКА: 5 УТО CONTACGI УМА BN TTE 81 Baffin Bay Baldwin (1964) ... Baron A Coe Е Shot АТТОО А ео ТОЗОТ 70 BD AVACIMBIS CAV Е E NE E TAS 102 Вар Ает Н er ye c eo Р иШ PANTS BSSSSKCSBORDIMUOUN ара с 59,60,70,71,73,79,80,85-87, 96,101—104,118—120 Unga Conglomerate Member 70,71,85,86,117,118 Миу ананас LEM DEM 80,84,91,108,109 IBS GU HL а а ОВО RES 121 БОКЕ ОСЕ OD ВИ tee Mt. ЕОМ Ded TRE 64 ВешИО диетата bee о5о AL TC M 108 «bengsrentandsvanveonverineselo7dyeee e eM ME 70 Bein a Лале аео ево UU 113 СОТ AD EE Olen А reor costatus КАВАЛА о о aff. B. crebricostatus (Dall, 1877) hataii MacNeil, 1973 ........ АТАР АМО СОО Е а 117,118,143 Bering сати т 80,81,84, 101,103,107, 109,115 Bristol Bay, Hagemeister Island (Об дойка етае би рта renee УЛЫ ТЕ Жеко КУЛА BAY mera ата о АЕН INGENUUS Е DATING A wie cpr МЕ НМР ICE T. Pribilof Islands .......... St. George Island .... St RAE MSIE YG oo e e Stein Геос АО S cerro epum ради ин И на 104 BOr IIO) ER E О idu К 98 Benard’ (197 G) ЫИ нл па ет des ЛК КЕТТ а 90 БОША ПОЛДУ КК аЙ 80,83,84,90,91,108,109 ohean Ообо EE 102—104 Вела ТОЕ ОИЕ етее 85 УО а ТОТСА ОТО) З ИВЕ ТОЛ Я 109 Тано ке ЕПА р sea gece e IE RS 97 ioina t RA ае оао аа а па eb eb ага 108 Теа Пе О Бе арени tate жүк PEE ийи быр кык 90 BM(NH) [British Museum (Natural History), Поупа Oneal |e е Босавшаш VIOLOPODHIOTUS л ОАА bogachielii, дека И RR 116 ОДО ONS ence eat me CD КЫНКЫ 66,68 69,117 bogachielii (cf.), Molopophorus ..................... gir 116,143 PORES ЕХО А рока КО че ote rer nat eters. MEE ETE Пра 100 ОБТ MEIN ОБ И ни ОТО И 107 brevirostrata, СЕСЕ ТОО) cete EM tele ieee ne ee 95 ри шай остготи авина ара 165 94 ,95,96,136 ПО ток к МЫ) Е eet e сыы ыкы алани аа а елен Ад жора Е 90 Broderip and Sowerby (1829) ............... 67,75 ,76,80 ,88 ,97, 100, 1117113] 14 brooksi, ТОСОО esie teet у к м л О CULO GU т an brota, Масота (Масота)... {ру кекш etc t ВИСОРАВНИ EUNT ш робите пиете па T IOI али M E ПО tr Bye COS Least te sup ыу ыты ree л cf. B. planeticum Dall, 1919 Bulbus Brown in Smith, 1839 ragus CEN rs ЈЕЗИКУ ce eee MON на 66—68,112,113,142 Br (US В чов у массаны ыы E sun асове дн: 89,91,107 BURR CLOGS) e eee ES 61,64,70,71,91,103,109,110 Bursa vancouverensis (Clark and Arnold, 1923) .................. PIS calcu eu MacomaxMacoma) ETC WERE E 98 СаО 59,60,68,70,74—76,80—85,89,92—96,101, 106,107;111—113, 1155118 Almeda eos Pleasanton- me E S ен ти ee ee 82 (OSA НОРТОН Re eR ини ыны из И ТАШ ЕА ee 83, 111112 (БОШКЕ ӨС Б ORO. песак ы GP ROI SY FUE аЬ 83,93, 111 МО Gre OKO ether иа иаа ылан cies teet e FE aes 111 Domehginedauchguadranglessse e еы НОА Е БРЕЗНО ОО csset ына анаа Humboldt Со. ... IS з I E SC Olga К е peret bats E RR LE e CET CETERO] СЕУ ANCA eem estes eve et eva ИТО ЫЛАЙ СЕТ Str EDS seco ceret ie ta ATLAS Е ЈОНА ПО Се Go oss Monterey Bay пса Moonstone Beach ....... Newport Bay 8... OLE CO rae. ee eyes eins Point Ano Nuevo Salinas Valley SUDBDIGS OF а ааа 82,83,89,113 ап еро оо аала алан ia НЕО tee eee 83 Sanh Lan GIS СО inns ЗАЛИВИ Ua о 101 Seed OC iin Vell SW срна а аи а Ла ВИ И еи 101 нат ке о esas) incl а а Е Ва СИ ОА ае Pa 116 Sa PEU КО НА йаза зунда 89,102 О ааа e Ба an ke Nea виа 84,89,112 Оа СОАТА СО RUM re mA 94 ВАЗЕ СА А У АИК ИВА esc О МИНИ И Sa cep aller Mae e Im 111 сие АБВ асс То еее са ит. 89,101 QUOI COL rarest Sul cc НИ uie ad oye cae ennai. 96,114 VEAL МАКО MD Cee cd eM НЕ ОО DNE АКЫ 94 КИЛИ а До ва а SRM CE 94 МА ата ONG) А СЕЕ TL VN 102 УО АБО ЕОС . evens t Pe бре i aio Be 96 Сидра WARD ЕО on ces арени отела гас е еу oi. ИВЕ. 110 Е ИОА О НННП MS qu Tait RE TM 110 [107 Ro Dr s не m P UR АО IR 110 Sp. indet. 228-5055 110,142 гобиласар Hata and Nisiyama, 1052. „а. eere veemet entered es 110 ОКО TATA AM Ne LOIN noe te ene vee кердин» PR bee Trees 110 Qum ше о тыи een и ы оу сил к 113,114 БҮТӨ СОИ ононе 60,73,75,80,82, 101,110,116 Газ Are ven n дрена conn ua тле реси arcane ae ntc E nate 107 (сети tem othe У па Sy sve cas erered 114,116,117 Ме а И ота Susan tine ЕТСЕ Е 107 Па а а ci) Oras Givi sc диле и лаз Кы И DI issued Е о p ПЕРА MN S SUE M E o UN 97 CCCI Ta Eris ТОО act e SNR Eo NONO aie ee 120 USE ons В. Сезар тениска cuc St 2/5 а 120,143 candida, о qw t Чара Mer Dy inte ee 121 "Dietro you situm да окова Иб у HON) Ad ten. 121 candida. (E), Оёпорота..............,.... Мес 66,68,120,121,143 candida мас angulata, РОТОР irate, sss OPI E salen co 15] (Corre no Mea qu Pv A ане 102 Cae, ДЕШИ вее шоу, eese orco OnE otro bes uid 65—67 Саа roundyormis: Uyma, 19695. c куруне decor quc tied 87 Cardita (Miodontiscus) prolongata (Carpenter) .................. 88 (Morality IDA NUI Эбы... ә... зууну ауы коо жузу ne E RR. 81 onom ЈЕ уы УВО moar нем oc ы sa ce дава патената 90 Careaga Sandstone Cebada Fine-Grained Мешеу. юли... 89,101 Graciosa Coarse-Grained Member ........................... 94,101 GIN QUSE AIL cR ECL tales сите ove us eran verre келку ИСТЕ 94 КИН АТИНИ оо ОСЕ ее 67 ,68 ,74,88 ,89 CAS [California Academy of Sciences, Sam Francisco, Californra] .................. 77-80,82,86,88,92,97, 9915 log le? (ОВИСИ Binnie, элуу ир уу кеу Аку (ets. Ares Ae 83 Ж ООО АИЛ, О ае бы odes rA 90 и CONE CLM 19/0: oco rof rers erae o ios веке ундан 90 ПАРИ O ОЛ BTOUCTID lOO Scher riae eroe exe tree ү ск p MODERN 90 ОО M THEM T UNTEN RETE 90 СЛОЕ ашай Stearns (1903)... o еен 96,97 DICH UAT CULO Secs Wises изе нике ын Ке T е САМ ү ү EE R Пе ун к eL o ONES азота SD BINGEN Кол E aera К о ста са а а лана RS SLE РВ а с сысы РОСИ ск е Tto TNR EE Spisula (Mactromeris) polynyma .................... а дает x Spisuiaspsindett еы нл ак ese чы ле ра о Итил силен Koldia'(Gnesterium SCISSUT OIG) ce C зы лс ај (бепнде кыылы ы н ыкы куш кл енн ее Сы FRE Oe MONETE Gastropods "Hernntiusshertletnis cw ee cc eR Кы ETT Kee rete О ВА Phe e A CR NE Висстити сЕ cBepIaneti cum ve ree o Ау Кес Е Ж BUGGIILDIESD пае а. ce be e ca a oe ere а E у MEER ERE T аа Bulbusfragiliseeectenc equ и T TC c c MEME e Calyptraea sp. indet. Gancéllaria?sp:o* кы si ы ME ndo red is rel а cett its PER Mg AU E D UU Fusitriton oregonensis Манса (бғурголапеа) сана o.c esc CR TEES Мадеш ао E E gee tape Ern x р ыл I Mu" Мапс аерепо тас e eee cp ES EE MM D cc ape m RE ц СИ Neptunea (Neptunea) sp. D aff. N. (N.) modesta ............ X wan P ern арки ален oe сс сык LM M а D m uh MM MM АРКА АНИНА т у ни они КИ Инона вино MMos. ec E E NeptünPa р Нас toe c MR ecce E ы Oenopota cf. O. candida ОвнорошърсА 2.6 Police (Визріа) азавіоеп чон к EE ыы Кы а-ы: ЖАК НИ АЕ АИ зк И. И ООУ ли С, Folmnicesbuspira) рани он ИОТ PZolnicesPuspira)spzindetue odor RN ЕА Е x GENUS INGCE E aoe me nee n К узе л ДО EUER ERE Lae ы КЕ NS PREPARATION OF MANUSCRIPTS Bulletins of American Paleontology usually comprises two or more sep- arate monographs in two volumes each year. This series is a publication outlet for significant longer paleontological monographs for which high quality photo- graphic illustrations and the large quarto format are a requisite. Manuscripts submitted for publication in this monograph series must be typewritten, and double-spaced throughout (including direct quotations and ref- erences). All manuscripts should contain a table of contents, lists of text-figures and (or) tables, and a short, informative abstract that includes names of all new taxa. Format should follow that of recent numbers in the series. All measurements must be stated in the metric system, alone or in addition to the English system equivalent. The maximum dimensions for photographic plates are 178 mm х 229 mm (7" Х 9"; outlined on this page). Single-page text-figures should be drafted for reproduction as single column (82 mm; 3\4”) ог full page (178 mm; 7”) width, but arrangements can be made to publish text-figures that must be larger. Any lettering in illustrations should follow the recommendations of Collinson (1962). Authors must provide three (3) copies of the text and accompanying illus- trative material. The text and line-drawings may be reproduced xerographically, but glossy prints at publication scale must be supplied for all half-tone illustrations and photographic plates. These prints should be identified clearly on the back. All dated text-citations must be referenced, except those that appear only within long-form synonymies. Additional references may be listed separately if their importance can be demonstrated by a short general comment, or individual annotations. Referenced publication titles must be spelled out in their entirety. Citations of illustrations within the monograph bear initial capitals (e.g., Plate, Text-figure), but citations of illustrations in other articles appear in lower-case letters (e.g., plate, text-figure). Original plate photomounts should have oversize cardboard backing and strong tracing paper overlays. These photomounts should be retained by the author until the manuscript has been formally accepted for publication. Explanations of text-figures should be interleaved on separate numbered pages within the text, and the approximate position of the text-figure in the text should be indicated. Explanations of plates follow the Bibliography. Authors are requested to enclose $10 with each manuscript submitted, to cover costs of postage during the review process. Collinson, J. 1962. Size of lettering for text-figures. Journal of Paleontology, vol. 36, p. 1402. · Gilbert Dennison Harris (1864 - 1952) Founder of the Bulletins of American Paleontology (1895) ISBN 0-87710- SS АЕНА ЕЕ ag 3925 | У ae | \