Richard Dawkins wrote a very simple computer program (Blind Snailmaker) which he describes and illustrates in Chap 6 (Museum of All Shells) in 'Climbing Mount Improbable' There seem to be few shells that violate the straight vertical axis but plenty that seem to violate the other axes. If you plotted them, they would show a gradually increasing (and regular) angle away from home, mainly due to the increase in tubular size of the coils. On the other hand, I have plenty of Vermetidae and Siliquariidae that demonstrate no vertical axis discipline at all. ---------------------------------------------------------------------- [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. ----------------------------------------------------------------------