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"If you visualize a coiled snail shell as being a cone of shelly material which is successively wrapped in a spiral way around a central axis, then the columella occupies the space where the geometric axis of the shell is."

Sorry, this is very unclear to me. Which axis is the 'geometric axis'? A diagram or a rewording would help. RedTomato ( talk) 09:30, 21 July 2008 (UTC) reply

Thanks for the note, you are right, it was not very clear. I made an effort to make it clearer. Invertzoo ( talk) 14:40, 7 November 2009 (UTC) reply