Three New Species of Hemiliostraca and a Redescription of H. conspurcata (Gastropoda: Caenogastropoda: Eulimidae) from Japan, with a Revised Diagnosis of the Genus

摘要

Three new species of the eulimid gastropod genus Hemiliostraca Pilsbry, 1917, i.e., H. capreolus n. sp.， H. tenuis n. sp., and H. maculata n. sp., are described and H. conspurcata (A. Adams, 1863) is redescribed based on newly obtained material fromJapan. The diagnosis of the genus is also revised. Hemiliostraca capreolus n. sp. was previously misidentified as H. samoensis in museum collections and in literature. This new species was collected from Okinawa-jima Island and Amami-Oshima Island, southern Japan, and can be distinguished from H. samoensis by its distinct color patterns and markings. A recently collected specimen from an unidentified species of ophiuroid from Wakayama Prefecture, central Japan, is herein confirmed to be identifiable with H. conspurcata, which has not been recorded since its originally description from central Japan in1863. Hemiliostraca tenuis n. sp. was collected from an unidentified species of sponge and the ophiuroid Ophiarachnella septemspinosa from Kume-jima Island, southern Japan. This new species is characterized by a slender, oval, transparent shell with indistinct brownish markings. Hemiliostraca maculata n. sp. from the Ogasawara Islands, Amami-Oshima Island, and Okinawa-jima Island, all in southern Japan, is very similar to H. conspurcata in shell appearance, but H. maculata n. sp. is distinguished from H. conspurcata by its color markings consisting of solid lines, and columella-parietal wall that forms very weak angle.