ANATOMY OF LAEVIPILINA-ANTARCTICA, A MONOPLACOPHORAN LIMPET (MOLLUSCA) FROM ANTARCTIC WATERS

The anatomy of the neopilinid limper Laevipilina antarctica is describ ed on the basis of reconstructions of semithin serial section. In gene ral the anatomy of this small (3.2 mm) species resembles those of Neop ilina galatheae (37 mm) and Vema ewingi (27 mm); small differences occ ur in the alimentary tract. Corrections of the original descriptions o f neopilinid anatomy concern the structure of the mantle margin, the p resence and interpretation of cephalic appendages, and details of the nervous system. The excretory organs are clearly separated from each o ther and there is no connection with the pericardium. The neopilinid c tenidia are considered as ventilatory rather than respiratory organs. These corrections and clarifications of the neopilinid anatomy provide an improved database for discussion on monoplacophoran affinities. In contrast to popular statements about ''living fossils'', the extant T ryblidiida (Neopilinoidea) are regarded as a considerably modified and specialized early conchiferan branch. (C) 1997 The Royal Swedish Acad emy of Sciences.