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If you found this in the eastern United States, it is Laevicardium mortoni, Morton's Egg Cockle. Â There may be similar species in other geographic areas however, so locality where collected would be helpful.
Found at Indian Mound Beach , Englewood Florida
Sorry about the lack of location .
OK, so you did. Â With these photos it most certainly is <i>Laevicardium mortoni</i>.
Thank you very much for the reply .