Pyramidellidae, philinidae et retusidae de la région de roscoff. Etude particulière des protoconques de quelques espèces

Some scanning electron microscopy observations have been conducted on the shells of different species of gastropods from the Roscoff area: Pyramidellidae, Odostomia acuta, 0. unidentata, 0. turrita, 0. plicata, 0. scalaris, 0. lukisi, Turbonilla crenata, T. elegantissima, T. innovata, Chrysallida decussata, C. excavata, C. obtusa, C. spiralis, Evalea obliqua; Philinidae, Philine catena; Retusidae, Refusa mammillata, R. truncatula. The protoconch and the first juvenile spiralial whorls are studied with closer attention.