Cypraea shells are very smooth (a few genera in the family are not
smooth), and I expect that, combined with the shells' rounded
contours, this is a trait evolved to cause crab chelae and fishteeth
to slip off the shell, reducing the likelihood of shell-crushing
occurring. The labral denticles ("teeth") don't appear to have any
obvious function; a thickened labrum (outer lip) will resist
crab-peeling as well without them. I suspect that if they ever did
evolve to fulfill a function, their continued presence is merely
genetic inertia.

As to the idea of their helping the animal burrow, I seriously doubt
it. The columellar muscle is more than sufficient to keep shell and
animal together.



--
Andrew Grebneff
Dunedin, New Zealand
Fossil preparator
Mollusc, Toyota & VW van nut

<[log in to unmask]>



--
Andrew Grebneff
Dunedin, New Zealand
Fossil preparator
Mollusc, Toyota & VW van nut

<[log in to unmask]>

----------------------------------------------------------------------
[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.
----------------------------------------------------------------------