Dear all,

I have kept records on sometimes striking L/R discordances (up to
99:1) on segments of the beaches of St. George, Little St. George,
and St. Vincent Is. facing the Gulf of Mexico (not far E of Jim's
Cape San Blas). I only looked at arcids, but all four common species
showed this phenomenon. Sampling at the other end of each island
produced an essentially reciprocal ratio.

There is a significant literature on this taphonomy.

Harry


At 10:52 AM 3/29/2010, you wrote:
>Paul,
>This phenomenon is a frequent occurrence at Cape Blas in Gulf
>County, (FL Panhandle) following storms.  Equally frustrating is the
>large collection of Geoduck right valves that pile up each winter on
>the eastern end of East Pass on St Andrews Bay, PC, FL.
>
>Jim Brunner
>On Mar 29, 2010, at 9:16 AM, Paul Callomon wrote:
>
>>Folks,
>>
>>I'm sure conchlers know all about this, but: the other day I was
>>walking on Bowman's Beach at the outer end of Sanibel Island,
>>picking up shells (we're running out here at the Academy). There
>>were thousands of the big Dinocardium vanhyningi everywhere, but
>>try as I might I could not find one single solitary left valve.
>>I've heard about hydrodynamic sorting of empty shells before, but
>>this was my first encounter with it in such numbers. Has anyone
>>else come across this?
>>
>>PC.
>>
>>
>>Paul Callomon
>>Collections Manager
>>Malacology, Invertebrate Paleontology and General Invertebrates
>>Department of Malacology
>>Academy of Natural Sciences
>>1900 Parkway, Philadelphia PA 19103-1195, USA
>>Tel 215-405-5096
>>Fax 215-299-1170

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