Sakai, 1934
Front marked by a median groove; the two antero-lateral teeth are well-separated by a wide interval, immediately behind the posterior tooth is a rudimentary one; the basal surface of these teeth are sparingly granulated. (T. Sakai, 1976)
Type locality: Nagasaki, Japan.
Range: Japan - Nagasaki (Sakai, 1934a), Nagasaki and Osaka Bay (Sakai, 1939), Osaka Bay, Tsuyazaki, Nagasaki and Amakusa-shoto (Sakai, 1976a), off Matsuyama, Seto Inland Sea (Takeda et al., 2000).