Early Miocene to Late Pliocene; Extinct.
Southern Florida to Maryland.
Note that occurrence of species in St. Marys Fm. of Virginia is mapped as "Middle Miocene"; the actual age of the formation, however, cannot be resolved beyond simply "Miocene."
Original Description (from Conrad, 1832, p. 16):
"Cordate, inequivalve, ventricose, and slightly sinuous; ribs about 25, narrow and crenulated; the crenulations most distinct on the larger valve; beaks very prominant and distant; area with undulated grooves; hinge with the series of teeth contracted in the centre, and a little decurved at the ends.
Locality. St. Mary's River, Md. Upper Tertiary."
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