Kay (Hawaiian Marine Shells, 1979) indicates that the Pteropoda are
pelagic and usually are found world-wide subtropic waters.  Rarely found
on the beach.  Mine all are from dredgings.  Kay indicated Diacria
trispinosa at 9 mm.  My specimens were 6 to 8 mm, now at LA Museum.

I don't know anything about the growth of these molluscs, all I saw were
about the same size.  What is the egg stage and first shell formation
stage.  Do they shed shells as crabs to grow?  The "growth lines" on the
shells indicates that they grow by addint to the anterior somewhat like
a gastropod adds to the lip.

The Southern Synthesis, 1998 has some photos of live animals of
Pteropods in plate 34, near pg 941. Places Diacria in Cavoliniidae and
says the largest species of Cavoliniidae, Clio recurva can reach 30 mm
in length. (mine are smaller)  Cavoliniids develop from males into
hermaphrodites and then into females and more than one male stage can
occur. Identification of juveniles is difficult as the juvenile shells
differ greatly from adults.  Juvelile shells are flexible, and in
Diacria the juvenile breaks off the adult shell.  I don't see a
maximum size for Diacria.
--
                     Aloha from Wesley M. Thorsson
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