A very nice sample for white bivalves with periostracum are in the Family
Solecurtidae
Solecurtus scopula
Azorinus chamasolen.

with best shelling greetings
When I go out in winter I'll take my artificial periostracum. It's nearly
black
Helmut, in a cold Innsbruck

Helmut "Helix" Nisters
private:
Franz-Fischer-Str. 46
A-6020 Innsbruck / Austria / Europe
phone: 0043 / 512 / 57 32 14
e-mail: [log in to unmask]
website: www.netwing.at/nisters
office:
Natural History Department of the
Tiroler Landesmuseum Ferdinandeum Innsbruck
Feldstrasse 11a
A-6020 Innsbruck / Austria / Europe
phone: 0043 / 512 / 58 72 86 - 37
e-mail: [log in to unmask]
website: www.tiroler-landesmuseum.at


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>         I can't think of many marine bivalves which have much in the way
of
> pattern in the periostracum, but there are certainly plenty of marine
> bivalves which have a stark white shell under a dark periostracum.  A few
> that come to mind are Nuculidae, Nuculanidae, Arcticidae, Astartidae,
> Mactridae, and Mytilidae.  In the last-named family, some species have a
> dark colored shell under a dark periostracum, while others have a white
> shell.
>
>         Paul M.
>