SYSTEMATICS OF THE GENERA OF THE ORDER ASCOGLOSSA (GASTROPODA)

Abstract

Abstract List of the genera of Ascoglossa with their distinctive characters. The type species of Cylindrobulla, C. beaui Fischer, 1856, is maintained in the Cephalaspidea Diaphanacea, together with two further species, as subfamily Cylindrobullinae, by reason of their radula. The genus Ascobulla Marcus, 1972, remains in the Ascoglossa, suborder Volvatellacea, family Volvatellidae. The Acochlidiacea Ganitus Marcus, 1953, and Paraganitus Challis, 1968, have ascoglossan teeth. They have no ascus and shed the worn teeth. Their nerve ring lies in front of the pharynx. Therefore they are retained in the Acochlidiacea. Two new genera are introduced: Roburnella, type species Lobiger wilsoni Tate, 1889, and Pattyclaya, type species Elysia arena Carlson & Hoff, 1977; and two new species: Elysia pagenstecheri for Actaeon viridis Pagenstecher, 1863, and Placida babai for Placida dendritica Baba, 1955, from Japan, whose tooth is different from the European dendritica (Alder & Hancock, 1843). The genus type of Costasiella, C. virescens Pruvot-Fol, 1951, is described in detail, and the species belonging to the genus are compared. The characters considered as generic in the diagnoses of Stiliger and Ercolania occur in such varied combinations, that a generic separation is not feasible. Hence, I synonymize Ercolania to Stiliger. Bosellia differs from the elysiids in wanting parapodia and in number of chromosomes. I assign it to the family Boselliidae. Platyhedyle denudata Salvani-Plawen, 1973, with its suborder Platyhedylacea Rankin, 1979, is transferred from the Acochlidiacea to the Ascoglossa.