Early Miocene; Extinct.
Original Description (from Dall, 1903, p. 1229-1230):
"Oligocene of the Chipola horizon on the Chipola River, Calhoun County, Florida, at Alum Bluff and the silex beds at Ballast Point, Tampa Bay.
Shell rather small and thin, suborbicular, moderately convex, with full, pointed beaks, with fine, sharp concentric grooves having the distal side more abrupt, the interspaces flattish and hardly raised towards the ends of the shell; lunule lanceolate, impressed; beaks sculptured like the rest of the shell; anterior dorsal margin convexly arched; hinge-plate rather short and wide; teeth normal; the adductor scars large; the pallial sinus ample, ascending, acute in front, terminating two-thirds the distance forward from the posterior to the anterior adductor. Height 37.5, length 40.0, diameter 17.0 mm.
The nepionic young of this species have very much the form of the adult and are usually sculptured in much the same way."
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