Volume 75 (2017) Issue 1-4 Pages 1-16
We examined specimens which have hitherto been identified as the operculate land snail Metalycaeus vinctus (Pilsbry, 1902) (formerly Chamalycaeus vinctus) in the National Museum of Nature and Science, Tsukuba, Japan. We found among these specimens another morphologically distinct taxon. Field investigation and examination of other newly-collected specimens confirmed that the real Metalycaeus vinctus lives in the northern part of Tanegashima Island, whereas the new species, Metalycaeus minatoi Páll-Gergely n. sp. mainly inhabits the southern part. The two species can be distinguished mainly by the morphology of the body whorl surface along the sutural tube: that of Metalycaeus minatoi n. sp. is more densely ribbed (26–41 ribs, mean: 33.0) and has lower ribs, which results in a nearly smooth shell surface whereas Metalycaeus vinctus (17–23 ribs, mean: 19.6) has elevated and sharp ribs. A third species, also reported from this island, Dicharax (?) tanegashimae (Pilsbry, 1902) was also found by us. The morphology of the penis, radula, operculum, and shell morphology of both Metalycaeus species, and penis morphology of D. tanegashimae are described and illustrated.