Frank, John, thank you! Harasewych, in the paper cited below, gave me enough to understand what I have in hands. Olivier http://www.azoresbioportal.angra.uac.pt/files/publicacoes_Aoreana_Sup_6_Separata_121-135%20Mitra.pdf ---------------------------------------------------------------------- [log in to unmask] - a forum for informal discussions on molluscs To leave this list, click on the following web link: http://listserv.uga.edu/cgi-bin/wa?SUBED1=conch-l&A=1 Type your email address and name in the appropriate box and click leave the list. ----------------------------------------------------------------------