Bulletin of the Mizunami Fossil Museum

Bulletin of the Mizunami Fossil Museum No. 49

Thirty molluscan species have been recovered from the upper Lower Miocene Higashibessho Formation around Yamada-Nakanose in Toyama Prefecture. Of these, Propeamusium fuganjiense Yamana is the first recorded from this formation and described. Other two interesting species, Myonera osawanoensis (Tsuda) and Liracassis yokoyamai (Kuroda) are also herein described. The deep-sea fauna of the Higashibessho and uppermost part of Kurosedani Formations share some characteristic species with the Lower to Middle Miocene formations in San-in (Shimane and Tottori Prefectures) and Tokai (Aichi, Gifu and Mie Prefectures) areas. Moreover, the vesicomyid Pleurophopsis, the cassid Liracassis and the neilonellid Neilo (Multidentata) migrated southward since the Early Miocene from the west coast of America, Kamchatka and Sakhalin. These data support the extension of a relatively cold-water subsurface current to the Japan Sea side of western Honshu.