The monotypic genus Shako (Crustacea, Stomatopoda) is erected with S. tomidai sp. nov. from the Miocene Ayugawa and Mizunami Groups (Lower Miocene) of Central Japan. This is the second record of the Stomatopoda from Cenozoic deposits of Japan. It appears that S. tomidai preferred a brackish water environment.

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Gastropod fossils from the upper Pleistocene marine sequence in the Oga Peninsula, northern Japan, were analyzed, with special reference to the larval paleoecology and taxonomic relationships of Cryptonatica with two different protoconch types. The frequency of warm-water species increases towards the top of the section, with a gradual decrease in the frequency of cold-water species, suggesting gradual warming of the ambient sea water under the influence of the Tsushima currents from the south during 100-134 Ka. Available data on the relationship between protoconch morphology and mode of development in extant naticids strongly suggest that the two morphotypes of Cryptonatica, whose teleoconch morphologies are comparable to C. andoi, probably underwent different modes of development, i. e. planktotrophy for the type with a smaller protoconch (S-type) and non-planktotrophy for the type with a larger protoconch (L-type). The taxonomic relationships of the two morphotypes of Cryptonatica can be interpreted as closely allied different species (cryptic species) rather than dimorphs of a single species with different developmental modes (poecilogony), since the latter phenomenon is quite rare in modern marine invertebrates. Comparison with type and figured specimens of C. andoi and related species of the same genus shows that specimens of S-type are referable to C. andoi (Nomura), while those of L-type may belong to a new species; here I provisionally treat them under C. sp. aff. C. andoi. According to this interpretation, the transition of developmental modes from non-planktotrophy to planktotrophy may have occurred in association with a speciation event of the "Cryptonatica andoi" lineage at least before late Pleistocene time.

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Well preserved large shrew remains with pigmented teeth were recovered from early Pleistocene fissure sediments at Haimao, Dalian, northeast China. They are assigned to the genus Beremendia on the basis of their morphological characters. The monospecific genus Peisorex previously described from the early Pleistocene of north China is synonymized with Beremendia, because no basic morphological differences indicative of generic distinction exist between them, and its sole species, P. pohaiensis, therefore becomes Beremendia. Comparison with the holotype of this species reveals that the remains from Haimao belong to Beremendia pohaiensis. Moreover, it is newly recognized that "Peisorex pliocaenicus" recently described from the middle Pliocene of north China is conspecific with B. pohaiensis. The remains from Haimao provide us with much knowledge on the morphological characters of B. pohaiensis, which is distinct from other known species of Beremendia. The occurrence of B. pohaiensis is the first reliable record of the genus in East Asia, because previous records of Beremendia from East Asia lack sufficient grounds in identification. Beremendia has been known mainly from the early Pliocene to middle Pleistocene of Europe. B. pohaiensis indicates that Beremendia was distributed both in Europe and East Asia from the middle Pliocene to early Pleistocene. This genus had probably migrated from Europe to East Asia by the middle Pliocene.

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Stable oxygen and carbon isotope profiles of the Early Pliocene fossil Akebiconcha kawamurai from the Tamari Formation, Central Japan, are constructed to obtain environmental and physiological information using a series of samples from the shell surface for a high-resolution record. The δ¹⁸O profile indicates that hydrographic conditions were stable and similar to those of modern bathyal depths. The isotopic temperature was estimated to be around 6 to 8°C with a little seasonal variation. The δ¹³C profile shows an apparently progressive by increasing trend during shell growth, a feature which has been identified from some live mollusks containing symbiotic bacteria. Therefore, the stable isotopic geochemical profiles are regarded as potential indicators of the paleoecological habitat and symbiosis with chemoautotrophic bacteria of fossil mollusks.

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Trochammina hadai Uchio is abundant in brackish water bays around the Japanese Islands and exhibits a biphasic life cycle in natural environments. In the laboratory sexual reproduction, characterized by the release of thousands of gametes, occurred in spring. The release of gametes continued for 1.5 hours. After gametogenesis, parts of the cytoplasm still remained in the mother test. Asexual reproduction took place in the laboratory during autumn and continued for 6 hours. The mother test was not destroyed during asexual reproduction. The geographical distribution of T. hadai in Hamana Lake differs from season to season. This may be explained by the differential dispersal of juveniles during the sexual and asexual phases, which take place at different times of the year.

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Four species of Ancistrolepis and one of Clinopegma are newly obtained and described from Plio-Pleistocene strata in the Japan Sea borderland : Ancistrolepis masudaensis Nomura, A. grammatus (Dall), A. sp. aff. A. hikidai (Kuroda), A. sp. and Clinopegma borealis Tiba. Among the ten species of Plio-Pleistocene Ancistrolepidinae, A. masudaensis. A. peulepsis, A. koyamai and C. fragilis are extinct. The first three species belong to the Ancistrolepis eucosmius group now living in the eastern North Pacific. They suffered extinction during the late Pleistocene cold-climate maxima because of their distribution being restricted to the Japan Sea borderland. On the other hand, in addition to occurring in the Plio-Pleistocene in the Japan Sea borderland, A. grammatus, C. borealis and Bathyancistrolepis trochoideus Dall survive in the Okhotsk and Bering Seas as well as in the subarctic Pacific Ocean. Recent higher water temperatures and a shallower sill depth may prevent the above three species from migrating back into the Japan Sea.

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A large shrew mandible with pigmented teeth obtained from the Pliocene cave sediments of Yinan is referred to a new species of a new genus in the subfamily Soricinae, which is named Lunanosorex Iii. This species belongs to the tribe Beremendiini of the subfamily. Comparisons with large shrews with pigmented teeth such as Beremendia, Blarinoides and Shikamainosorex indicate that Lunanosorex is clearly distinct from all the shrews. In north China, Lunanosorex appeared probably in the middle Pliocene as an indigenous genus, and seems to have been coexistent with Beremendia until it became extinct around the end of the Pliocene.

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