In the present checklist an attempt has been made to include taxonomic information on all the existing species of both fossil and living ostracods from Japan and its adjacent seas. The area covered is from the northern end of the southern Kuril Islands to the southern end of the Ryukyu Islands; also included are some of the scattered stations of the Dana, the Challenger, and the U.S.S.R. expeditions in the northwestern Pacific off the Japanese Islands.

In determining valid names, we have reexamined all the type specimens deposited both in the University Museum of the University of Tokyo and in the Institute of Geology and Palaeontology, Tohoku University. An effort has also been made to check identifications of species whose type specimens are housed in foreign institutions. Ishizaki has studied the collections of the Challenger Expedition at the British Museum (Natural History), and Hanai the southeast Asian ostracods in the University of Utrecht micropaleontological collection. However, in a number of cases, generic and specific identifications remain doubtful. A generic identification of doubtful status is indicated by a question mark placed after the generic name.

When species are grouped into higher taxa, the species groups and subgeneric levels of classification are adopted without abridgement, for these levels of classification may still reflect the fascinating dynamics of speciation. All the known subspecies are listed in order to avoid the burial of certain geographic relationships among phenotypically similar populations under a cover of species names.

Recently, it has become increasingly apparent that some of the traditional assignments of the ostracods to the higher categories does not adequately express the existing diversity. Thus the traditional classificatory system is tentatively emended. Adamczak's (1966, 1968) opinion that the Palaeocopida includes both Palaeocopa and Platycopa is here adopted and the endings of suborder names emended. The Cavellinidae is placed in Platycopina, as emphasized by Gramm's work (1968, 1972). Following Sohn (1971), the Paraparchitacea is classed in Podocopida. The Halocypriformes is here referred to as the Halocypridina, following Kornicker (1975). For suprageneric clas sification of cytheracean ostracods, references are made especially to Hazel (1967), Benson (1972), Hartman and Puri (1974), and Liebau (1975).

Synonymies for each species provide complete references to each specific name, as far as that name has been applied to materials from Japan and its adjacent seas. Synonyms for foreign materials are not included.

The following abbreviations in this checklist refer to the institutions where types are actually preserved:

BLOSJC:

Biological Laboratory, Okayama Shujitsu Junior College, Okayama.

BMNH:

British Museum (Natural History), London.

FESC:

Institute of Marine Biology, Far Eastern Scientific Center, Academy of Science, Vladivostok.

HMNT:

Hancock Museum, Newcastle-upon-Tyne, Northumberland.

IGPS:

Institute of Geology and Palaeontology, Tohoku University, Sendai.

NSMT:

National Science Museum, Tokyo.

UMUT:

University Museum, University of Tokyo, Tokyo.

ZIANL:

Zoological Institute, Academy of Science, Leningrad.

ZMB:

Zoological Museum in Berlin, East Berlin.

ZMUC:

Zoological Museum, University of Copenhagen, Copenhagen.

In a number of cases no information on the location of type specimens has so far been obtainable from the literature alone for old species which were described by European authors in the 1800s. These instances are indicated as "types unknown." The author of a large number of living species was Kajiyama (1912, 1913). Unfortunately, however, Kajiyama's types are no longer catalogued in the University Museum of the University of Tokyo and are presumed to be lost. No neotypes have been de signated because this case has not been considered to constitute "exceptional circum stances" as defined by the International Code of Zoological Nomenclature.

Type locality is supplemented by type horizon where there is a fossil record. All the information on the geographic and stratigraphic distribution of species hitherto published is listed for each species under the heading of known occurrence. For locating the places listed under known occurrence, refer to text-figures 1 and 2. The old place names used by the original authors are maintained in this checklist. They are, however, supplemented with the modern municipal names where necessary. The names of formations and their geologic ages as adopted by the original authors are given unless otherwise stated. Recent advances in microbiostratigraphy and paleomagnetic surveys have shown that many of the fossiliferous marine sediments along the Japan Sea coast of Japan which had been believed to be Upper Pliocene in age, are actually younger than had previously been thought.

Text-fig. 1. Localities of fossil Ostracoda in Japanese Islands. 1: Hokkaido, 1: Aomori Prefecture, 3: Akita Prefecture, 4: Iwate Prefecture, 5: Miyagi Prefecture, 6: Niigata Prefecture, 7: Chiba Prefecture, 8: Kanagawa Prefecture, 9: Ishikawa Prefecture, 10: Gifu Prefecture, 11: Shizuoka Prefecture, 12: Miyazaki Prefecture, 13: Okinawa Prefecture. St: Setana Formation, Hg: Higashimeya Formation, Sb: Shibikawa Formation, Kb: Kubo Formation, Ts: Tassobe Formation, Tk: Takazawa Formation, Ng: Nagaiwa Formation, On: Onimaru Formation, Iz: Iwaizaki Limestone, Ht: Hatatate Formation, Tt: Tatsunokuchi Formation, Mn: Moniwa Formation, Sw: Sawane Formation, Yb: Yabu Formation, Sk: Sakurai silty sand, Of: Ofuna Formation, Kt: Katase Formation, Ot: Otsu Forrnatidn, Om: Omma Formation, Sn: Sunakosaka Member, Th: Takaharagawa Formation, Sh: Shukunohora sandstone, Fr: Furuya mud, Hk: Heki Formation, Kj: Kounji Formation, Sz: Shinzato Formation, Td: Todorokigawa (Older terrace deposit).

Text-fig. 2. Localities of recent Oatracoda in Japanese Islands. 1: Hokkaido. 2: Aomori Prefecture, 3: Chiba Prefecture, 4: Tokyo Metropolis, S: Niigata Prefecture, 6: Nagano Prefecture, 7: Kanagawa Prefecture, 8: Shizuoka Prefecture, 9: Mie Prefecture, 10: Okayama Prefecture, 11: Shimane Prefecture, 12: Kochi Prefecture, 13: Pukuoka Prefecture, 14: Nagasaki Prefecture, 15: Kumamoto Prefecture, 16: Kagoshima Prefecture, 17: Okinawa Prefecture. Fresh water Nb: Naibo-numa (Iturup Island), Sk: Sakura, Hc: Hachioji, Kj: Kajiyashiki, Ak: Aoki Lake, Tm: Tamagawa, Km: Kamimura-Oike, Hz: Hamazaki, Hn: Hinase, Ng: Nagasaki, Kr: Kiire, Hg: Higashi kaimon. Marine Cr: Cirip Peninsula, Kt: Kasatka Bay, Hrn: Off Hamatonbetsu, Or: Oshoro, Hk: Hakodate, Am: Aomori Bay, En: Enoshima, In: Inamuragasaki, Yg: Yuigahama, Hy: Hayama, Ms: Misaki (Abura tsubo Cove, Moroiso), My: Miyata, Ur: Uraga Strait (St. 2-3), Tt: Tateyama, Ok: Okinose, Nn: Off Nakanogo, Os: Ose-zaki (St. 3708), Mn: Minato, Tr: Toura, Hz: Hamazaki, Sg: Sugashima, Kn: Kumanonada (St. 1, 2, 4), Sh: Shirahama, Nk: Nakanoumi Estuary, Uk: Off Unoko, Sb: Shibukawa, St: Setonaikai (tS. 23 3b), Un: Uranouchi Bay, Ks: Kashiwara, On: Mouth of Onga River, Ty: Tsuyazaki, Ns: Nishikoen, Ts: Off Tsushima, Hr: Off Hiratoshima, Nm: Nagashima, As: Akase, Ch: Challenger St. 231, Dn 1: Dana Ex. St. 3723 (25°30'N, 125°28'E), Dn 2: Dana Ex. St. 3723-II (25°31'N, 125°51'E), Dn 3: Dana Ex. St. 3724 (28°31'N, 125°05.5'E).

Fourteen genera have been described, based on species whose type specimens were collected from Japan and its adjacent seas. To save space, however, illustrations (Plates 1-4) are confined to the type species of the seven genera whose type specimens are preserved in Japanese institutions. All the holotypes of these species are illustrated, along with some paratypes. Details of microstructures of these species are also shown by the use of scanning electron photomicrographs. The type species of four of the remaining genera have their type specimens housed in the collections of either the British Museum (Natural History), London, or the Hancock Museum at Newcastle-upon-Tyne, Northumberland, England. The type of one genus is in the Zoological Museum of the University of Copenhagen, Denmark, and the types of two genera are in the Biological Laboratory of the Far East Research Center, Academy of Science, Vladiovstok, U.S.S.R.

Explanation of Plate 1 Figs. 1, 2. Khataiella ohazamensis (Ishizaki, 1967) 1. Lateral view of right valve. Holotype (IGPS-87080). ×80 2. Interior view of right valve. Holotype. ×80 Figs. 3-7. Parakrithella pseudadonta (Hanai, 1959) 3. Lateral view of right valve. Holotype (UMUT-CA-2901, female). ×88 4. Interior view of right valve. Holotype. × 88 5. Interior view of left valve. Holotype. ×88 6. Normal pore canal opening on exterior surface, located close to the postero-dorsal margin of right valve. Illustrated specimen (UMUT-RA-8404) from the Recent beach sand along the shore in front of the Imperial villa at Hayama-machi, Kanagawa Pref. × 5200 7. Normal pore canal opening on exterior surface, located close to the anterior margin of left valve. Illustrated specimen (UMUT-RA-8405) from the same locality as fig. 6 specimen. ×3280

Explanation of Plate 2 Figs. 1, 2. Parakrithella pseudadonta (Hanai, 1959) 1. Adductor muscle scars of right valve. Illustrated specimen (UMUT-RA-8406) from the Recent beach sand along the shore in front of the Imperial villa at Hayamamachi, Kanagawa Pref. ×384 2. Normal pore canal opening on interior surface, located just above frontal scar of right valve. Illustrated specimen (UMUT-RA-8406). ×3840 Figs. 3-5. Pectocythere quadrangulata Hanai, 1957 3. Lateral view of right valve. Holotype (UMUT-CA-2594). ×l04 4, 5. Interior view of right and left valves. Holotype. × 104 Figs. 6-8. Kotoracythere abnorma Ishizaki, 1966 6. Lateral view of right valve. Paratype (IGPS-87010). × 88 7. Interior view of right valve. Holotype (IGPS-87008). ×96 8. Interior view of left valve. Paratype (IGPS-87007). × 96

Explanation of Plate 3 Figs. 1-7. Howieina camptocytheroidea Hanai, 1957 1. Lateral view of right valve. Holotype (UMUT-CA-2612). ×88 2. Interior view of right valve. Holotype. ×88 3. Interior view of left valve. Paratype (UMUT-CA-2613). × 80 4. Normal pore canal opening on exterior surface, located close to the anterior area of left valve. Illustrated specimen (UMUT-RA-8407) from the Recent Mutsu Bay (Station 14, Lat. 40°58'20"N, Long. 141°04'30"E, depth 40 m), Aomori Pref. ×3840 5. Antero-dorsal area of exterior surface of right valve, showing pot-hole shaped ornamentations and two types of normal pore canal openings. Illustrated specimen (UMUT-CA-8408) from the Setana Formation (Upper Pliocene) at Kaigarazawa, about 500 m W. of Nishinosawa Kuromatsunai-mura, Suttu-gun, Hokkaido. × 880 6. 7. Two types of normal pore canal openings. Illustrated specimen (UMUT-CA-8400). Fig. 6, ×4640; fig. 7, ×4160

Explanation of Plate 4 Figs. 1-5. Kobayashiina hyalinosa Hanai, 1957 1. Lateral view of right valve. Holotype (UMUT-CA-2633). ×88 2. Interior view of right valve. Paratype (UMUT-CA-2634). ×88 3. Interior view of left valve. Paratype (UMUT-CA-2636). ×88 4. Normal pore canal openings on exterior surface, located close to the ventral area of left valve. Illustrated specimen (UMUT-CA-8409) from the Sawane Formation (Upper Pliocene) at the cliff at Mano Bay, Sawane-machi, Sado-gun, Niigata Pref. ×960 5. Normal pore canal opening. Illustrated specimen (UMUT-CA-8409). ×4800 Figs. 6-8. Miia uranouchiensis Ishizaki, 1968 6. Lateral view of left valve. Holotype (IGPS-90286). × 104 7. Interior view of left valve. Holotype. × 104 8. Interior view of right valve. Paratype (IGPS-90287). × 96