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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- Late Pleistocene
- Coffee Mill Hammock Formation (S. FL)
- Fort Thompson Formation (S. FL)
- Pamlico Formation (N. FL)
- Middle Pleistocene
- Bermont Formation (S. FL)
- Early Pleistocene
- Bear Bluff Formation (SC)
- Caloosahatchee Formation (S. FL)
- Chowan River Formation (VA)
- Nashua Formation (N. FL)
- Waccamaw Formation (SC, NC)
- Late Pliocene
- Croatan Formation (Lower) (NC)
- Duplin Formation (NC)
- Duplin / Raysor formations (GA)
- Jackson Bluff Formation (N. FL)
- Raysor Formation (SC)
- Tamiami Formation (Ochopee Limestone) (S. FL)
- Tamiami Formation (Pinecrest Beds) (S. FL)
- Yorktown Formation (VA)