Permalink : http://hdl.handle.net/2115/36719

A marine molluscan fauna has been newly found in Tertiary deposits scattered along the western wing of the Hidaka Mountains. This fauna is composed of 40 and over molluscan species in company with some species of brachiopods and others, and is characterized by a considerable number of cold and shallow water elements. The geological age of this fauna is discussed from the stratigraphic viewpoint and the faunal assemblage. The writers come to the tentative conclusion that this fauna may be referable to the middle Miocene "Kawabata" Stage in the provincial Neogene molluscan succession of Hokkaido. In addition to the description of this fauna, the unique plicate species Mytilus (Plicatomytilus) hidakensis, one of the new species, is particularly discussed on its morphological features with relation to its allied species.