An allozyme analysis of Cryptopecten vesiculosus was conducted to obtain biochemical evidence to determine whether the two discrete morphologic "phenotypes" represent dimorphism or two sympatric species. A total of 17 loci were extracted with polyacrylamide gel electrophoresis from specific tissues of the individuals collected from Sagami Bay, Japan. Of the 17 loci examined, seven (41.2%) were polymorphic, and avarage heterozygosity per individual was calculated at 0.20, indicating a high level of genetic variation in this species. The allozyme patterns are not statistically different between the two "phenotypes", confirming the previous interpretation based on morphologic and ecologic evidence that the two "phenotypes" represent discontinuous intrapopulational variants.

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From the Kawakami Group (the Upper Oligocene to Lower Miocene) of eastern Hokkaido, five new species of Clathromitrinae, including three of Corythomelissa, one of Euscenarium and one of Lithomelissa, are described, placing emphasis on their internal skeletal structure. In addition, one species of Clathromitrinae from the Taiki Formation (the Upper Miocene) of eastern Hokkaido is also examined. Some intraspecific and intrageneric variations are recognized in the internal skeletal structure of Corythomelissa. The intrageneric variations have three tendencies over time : (1) the prolongation of L-Rd; (2) the rising of connecting archers on the dorsal side of the shell; (3) the decline of A'. These intrageneric variations show a general trend through Late Oligocene to Late Miocene time which represents the evolutionary lineage of Corythomelissa.

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A biostratigraphic analysis of the bryozoan fauna of the Upper Paleozoic Copacabana Group in the Lake Titicaca region identified 15 genera and 45 species. Eight of the bryozoan species are new and 14 are presently not assignable to specific taxa. The new species are the cystoporates Fistulipora carrascoi, F. titicacaensis, F. multidiaphragma, the trepostomes Stenodiscus altiplana, Pseudobatostomella micropora, P. yanagidai, the cryptostome Rhombopora kawabei and fenestrate Septopora andeana. Biogeographically, among the 23 formerly described species, eight are endemic to the Andean province, seven are common to the Midcontinent province of North America and eight are found in the Tethyan province. The bryozoan faunas indicate a strong relationship with those of the Midcontinent province although considerable migration from the Tethyan realm presumably occurred.

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Part of the systematic paleontology of Upper Paleozoic bryozoans from the Lake Titicaca region is found in Part 1 of the present article, Part 2 describes two remaining orders, Cryptostomata and Fenestrata. Two new species, Rhombopora kawabei and Septopora andeana, are proposed in the families Rhomboporidae and Septoporidae, respectively.

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Although much work has been done on brackish water foraminifera, this is the first report of modern marsh foraminifera from Japan. Two transects were sampled in marshes of eastern Hokkaido for salt marsh foraminifera. Although these marshes were tidal, salinities were very low as evidenced by the freshwater plants that dominated the transects. Foraminifera present were low in diversity but extremely high in abundance-some of the highest ever recorded for a salt marsh. Miliammina fusca dominated lower areas together with Trochammina macrescens f. macrescens which dominated at all levels in both trasects. In the upper elevations of both transects, Haplophragmoides manilaensis became prominent and thecamoebians occupied the upland regions. Vertical zonation was generally poorly developed in both the foraminiferal and vegetation distributions which is typical of very brackish regions with low tidal ranges. Many typical brackish foraminiferal species observed in the Atlantic marshes are either rare or completely absent here.

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Colonization by an endobyssate bivalve Modiolus kurilensis was possible only in shelly softground conditions, that is, on a soft bottom with the shells being slightly buried with fine sediment. The Pleistocene Omma Formation, Kanazawa, generally exhibits a shelly bottom carpeted by shells (shell pavement) or a shelly bottom covered by soft sediment too thick to allow colonization by Modiolus. The described Modiolus colony was found in the lower unit of the Omma Formation, where sealevel change was relatively small and where shelly softground conditions were present. In contrast, Modiolus is much less common in the shell beds in the cyclothemic middle unit of the formation. An important environmental factor accounting for the uncommon occurrence of Modiolus in cycle-bounding shell beds is their repeated physical reworking followed by deposition of soft sediment too thick to be colonized by Modiolus.

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The fossil Mollusca of the Lower Miocene Yotsuyaku Formation in Iwate Prefecture were studied and 20 species of Bivalvia, 15 species of Gastropoda and 1 species of Scaphopoda were discriminated. They are divided into Type I and II assemblages from a paleoecological viewpoint; Type I is composed of brackish to shallow embaymental elements; Type II indicates middle to lower sublittoral muddy bottom environments. The assemblage generally changes from Type I to II in ascending order. Dosinia (Phacosoma) kawagensis Araki, Ruditapes miyamurensis (Itoigawa), Trapezium (Neotrapezium) modiolaeforme Oyama and Saka, Tateiwaia sp. nov. and Vicaryella "bacula" (Yokoyama) are reported for the first time in the formation. These species seldom occur in Northeast Japan although they have often been reported from the lower part of the First Setouchi Miocene Series. Comparison of Type I with brackish to intertidal elements of the Kadonosawa Fauna of Northeast Japan reveals that characteristic elements of the "Arcid-Potamid fauna" such as Anadara (Hataiarca) spp. are not found in the formation, and several genera are represented by different species. The Kadonosawa Fauna of Southwest Japan has been divided into the Akeyo and Kurosedani Faunas in ascending order. Similar stratigraphic differences in the shallow warm water marine molluscan fauna from upper Lower to lower Middle Miocene sequences have also been recognized in several districts in Northeast Japan. These facts support the conclusion that the molluscan fauna of the Yotsuyaku Formation corresponds to the Akeyo Fauna of Southwest Japan, and the Kadonosawa Fauna in Northeast Japan is also divided into lower and upper portions.

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Twenty species of Bivalvia and 1 species of Scaphopoda, obtained from the Koiwai Mudstone, Sandstone and Conglomerate Member of the Yotsuyaku Formation, are first described herein. Of these, one bivalve, Trapezium (Neotrapezium) ichinohense, is new to science.

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