Hmmm... At first sight it's tricky! It seems costulata has numerous fine spiral striae, that I can't see there, but which are rather obvious in juvenile specimens: http://www.naturamediterraneo.com/forum/topic.asp?TOPIC_ID=19761 Adult shells progressively loose this spiral sculpture: http://www.naturamediterraneo.com/forum/topic.asp?TOPIC_ID=26999 Thank you, friends, for this help. Olivier ---------------------------------------------------------------------- [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. ----------------------------------------------------------------------