Hi Peggy,

The three species of Pteria - colymbus, vitrea, and longisquamosa - are
listed in Abbott's American seashells. Unfortunately, he doesn't give
enough description to be able to differentiate them. As for the small
specimens you have that are very frilly, juvenile Pteria are often
frillier than the adults, as are juvenile Pinctada. So perhaps your
small specimens are juvies of a larger species.

Paul M.