A new species of Lyria (Gastropoda: Volutidae) from Southern Japan.

A new endemic species of Volutidae, Lyria (Lyria) ogasawarana sp. nov. is described from Chichijima Island, Ogasawara Islands, Japan. This new species is similar to the other Pacific Lyria: L. (Lyria) cassidula cassidula (Reeve, 1849), L. (Lyria) deliciosa (Montrousier, 1859), L. (Lyria) pattersonia (Perry, 1811) and L. (Lyria) insignata (Iredale, 1940). These different populations of closely related small species of Lyria sensu stricto are scattered in various isolated places of the Western Pacific Ocean. All share the following basic characters of the subgenus: small size (20–30 mm long), tumid purple protoconch, short spire, axial ribs prominent on the spire, swollen body whorl, three anterior columellar plaits adapically followed by small lirae, pattern of fine spiral lines crossing irregular blotches. By all its characters, L. ogasawarana n. sp. belongs to this group. The distribution is broad, widely interrupted, forming isolated ranges: L. cassidula, southern coast of Japan; L. deliciosa, New-Caledonia and eastern coast of Australia; L. pattersonia (= L. nucleus Lamarck, 1811), Norfolk Island; L. insignata, Kermadec Island. Despite the considerable distances between these remote locations, their conchological relationship is preserved. They differ only by slight but stable characters that suggest a genetic isolation in process. Consistent explanation for such geographical dispersion remains speculative pending studies of their respective genetic drift.