Late Pliocene to Late Pleistocene; Extinct.
Southern Florida to Virginia.
Original Description (from Conrad, 1832, p. 20):
"Oblong, with about 15 profoundly elevated scaly ribs; dorsal and basal margins parallel; anterior side very short; posterior margin oblique, angular above; inner margin crenate.
Localities. Newbern, N.C. Mr. Nuttall; James River, near Smithfield, and York Town, Va.; near Easton, Md.; Cumberland county, N.J."
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