A NEW SUBFAMILY OF THE ADDISONIIDAE ASSOCIATED WITH CEPHALOPOD BEAKS FROM THE TROPICAL SOUTHWEST PACIFIC, AND A NEW PSEUDOCOCCULINID ASSOCIATED WITH CHONDRICHTHYAN EGG CASES FROM NEW-ZEALAND (MOLLUSCA, LEPETELLOIDEA)

Helicopeltinae, a new subfamily of the Addisoniidae, is proposed for a group of minute deep-sea gastropods found living and feeding on detri tal cephalapod beaks from the Chesterfield Plateau and southern New Ca ledonia. The type species of Helicopelta gen. nov., H. rostricola sp. nov., uniquely combines an operculate, coiled shell similar to that in Choristella Bush, 1987 (Choristellidae), a horseshoe-shaped shell mus cle characteristic of a limpet, a radula similar to that in Addisoniid ae but with more numerous marginal teeth and non-homologous primary ra sping teeth, a large left-centered gill, and a copulatory organ that i s situated on the left side instead of the right as in all other membe rs of the Lepetelloidea. A second (unnamed) species of Helicopelta is recorded from off southern New Caledonia. The opportunity is taken to describe a new limpet of the genus Tentaoculus Moskalev, 1976, from Ne w Zealand that lives and feeds within spent chondrichthyan egg cases, the first record of a pseudococculinid from this habitat. Radulae of T euthirostria cancellata Moskalev, 1976, and of species of Addisonia, C horistella, and Bathysciadium are illustrated and discussed.