In 11.44 02/09/99 +0000, hai scritto:
>Hello all,
>
>Recently I have had a "discussion" (well, just two different points of view,
>that's all...:=) with an exchange partner regarding the extra plates coming
>with Pholas dactylus. In my opinion these plates are really part of the
>shell structure (same material as the rest of the shell) and should be
>collected with the two valves. My partner thinks the origin of these extra
>pieces is cartilaginous, so the plates could be omitted as not being really
>"shell". As I don't have any Pholas with plates right now I can't check this
>on the subject itself.
>
>Are there any specialists who can help us out here ?
>
>Thanks a lot
>
>J. Haspeslagh
>bibliotheek Zwevegem

Hi Jan,

I have two species with extra plates, Pholas dactylus and Barnea candida and
I have kept the extra plates because for me are a part of the shell.
For me the extra plates  aren't cartilaginous pieces even if I haven't
studied the
structure, they are more similar to a piece of shell that to a piece of
cartilage.

The Barnea candida that I have found was alive and I have seen that the extra
plate cover the superior side (near the umbones) of the shell because the
valves leave a small fissure, I don't know if it is the reason of the
presence  of
them, anyone can enlighten about?

Even if the extra plates are cartilaginous pieces why not collect equally
them?
They complete the shell....and some operculum are cartilaginous.. I think...

Bye



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