Revision of the Genus Inversiunio (Bivalvia : Unionidae)

Abstract

Three species belonging to the genus Inversiunio were briefly redescribed. Shell is elongated and its beak is situated anterior in I. reinianus. It is roundly elliptical with slightly incurved posterior margin in I. yanagawensis. Shell of I. yokohamensis is oblong and resembles to that of I. reinianus. Although it is difficult to distinguish some large shells of I. yokohamensis from those of I. reinianus, their distributions do not overlap. I. yokohamensis is distributed in the eastern part of Japan, whereas I. reinianus is endemic in Lake Biwa. I. yanagawensis is distributed in the western part of Japan.