ANATOMY AND SYSTEMATICS OF BATHYPHYTOPHILID LIMPETS (MOLLUSCA, ARCHAEOGASTROPODA) FROM THE NORTHEASTERN PACIFIC

Bathyphytophilus diegensis sp. n. is described on basis of shell and r adula characters. The radula of another species of Bathyphytophilus is illustrated, but the species is not described since the shell is unkn own. Both species feed on detached blades of the surfgrass Phyllospadi x carried by turbidity currents into continental slope depths in the S an Diego Trough. The anatomy of B. diegensis was investigated by means of semithin serial sectioning and graphic reconstruction. The shell i s limpet-like; the protoconch resembles that of pseudococculinids and other lepetelloids. The radula is a distinctive,highly modified rhipid oglossate type with close similarities to the lepetellid radula. The a natomy falls well into the lepetelloid bauplan and is in general simil ar to that of Pseudococculinidae and Pyropeltidae. Apomorphic features are the presence of gill-leaflets at both sides of the pallial roof ( shared with certain pseudococculinids), the lack of jaws, and in parti cular many enigmatic pouches (bacterial chambers?) which open into the posterior oesophagus. Autapomorphic characters of shell, radula and a natomy confirm the placement of Bathyphytophilus (with Aenigmabonus) i n a distinct family, Bathyphytophilidae Moskalev. 1978. As revealed by a cladistic study, the Bathyphytophilidae should be classified within the LepeteHoidea close to the Lepetcllidae, Pyropeltidae, and Pseudoc occulinidae. (C) 1996 The Norwegian Academy of Science and Letters.