Sorry, Paul, but the Mexican "chocolate clam" is Megapitaria squalida
(Sowerby 1835) -- sometimes also listed as a Callista.  The two are
similar, but it's nearly impossible to confuse them.  The periostracum on
M. aurantiaca (Sowerby 1831) is much lighter and has itself a pinkish tint;
furthermore, M. squalida has a very pretty pattern on the umbones, similar
to the Mediterranean Callista chione L. 1758.
And, Rick, the best book on Southern Baja, in fact the whole Panamic
province, is Keen's "Seashells of Tropical West America", 2nd Edition;
only, it's out of print and VERY difficult to find.

Cheers,

Monika
San Diego, CA
_________________________________
Monika Forner, Ph.D., Linguistics Manager, MT
Bowne Global Solutions

Phone      (+1) 858-737-5221
Fax          (+1) 858-737-5297
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www.bowneglobal.com



                    "Monfils, Paul"
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                    Sent by:               Subject:     Re: Mexican (Baja) chocolat clams
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                    02/12/02 01:02
                    PM
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This is Megapitaria aurantiaca (sorry, I don't have the author name with me
- I'm at work). The brown color is actually a thin, shiny periostracum. The
underlying shell is a rather pretty pink to pink-orange.

Paul M.