Here are some more specimens - most specimens have this compressed part on the middle of the shell,
just a couple don't have like that (one is pictured)

http://www.wonderphotos.com/shellphotos/donax2.jpg

marcus

________________________________________
De: Conchologists List [mailto:[log in to unmask]] Em nome de Paul Mikkelsen
Enviada em: quarta-feira, 4 de julho de 2007 14:21
Para: [log in to unmask]
Assunto: Re: RES: Donax sp. (Happy 4th of July!)

Note that the "pinched" ventral margin shown in Marcus's photo is only indicative of the latest
growth ring...    all other rings seem to be smooth-curved.

Several donacids do have a concavity in their postero-ventral margin, but it is typically indicated
in several post-juvenile rings.
Thus:  I doubt that the "pinch" of only a final(?) adult outer ring (vs smooth curves of several
rings) is a species specific character, but perhaps rather a result of some physical trauma to the
mantle of this particular specimen.

Marcus:  Your photo seems to be a composite of images of a single specimen;   is this single
specimen all that is available in your lot?   If not, do other specimens have a concave portion of
their ventral margin?

Paul


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