Back to the archeological Cassis specimens...
 
Two questions:
 
Does Cassis madagascarensis occur in the Gulf of Mexico?
 
Does C. m. spinella really only occur in the Keys as maintained by Johnsonia?
 
And concerning sinistral shells...
 
In the southern hemisphere all sinistral shells are dextral (and vice
versa), and at the equator they are all scaphopods. This also explains why
there are no shells at the North and South Poles.
 
But seriously folks, sinistral shells are more than just reversed dextral
shells, as shown by S.J. Gould. They don't just coil in the opposite
direction, but have different Raupian parameters as well - those
descriptors of how tightly they coil, in what plane they coil, etc. You can
convince yourself of this by holding a sinistral shell of a normally
dextral one up to a mirror - the resulting image does not look quite
"right." So there's more to them than just coiling the wrong way. For more
info:
 
Gould, S. J., Young, N. D. & B. Kasson. 1995. The consequence of being
different: sinistral coiling in Cerion. Evolution 39: 1364-1379.
 
[P.S. for Harry and Kurt - Yes, that's "Wild Bill" Kasson of Captiva fame]
 
 
 
 
*****************************************
 G Thomas Watters
 Ohio Biological Survey &
 Aquatic Ecology Laboratory
 Ohio State University
 1315 Kinnear Road
 Columbus, OH 43212 USA
 v: 614-292-6170  f: 614-292-0181
******************************************
 
"The world is my oyster except for months with an 'R' in them" - Firesign
Theater