Late Pliocene to Middle Pleistocene; Extinct.
This species was originally figured in Dall (1898) without a written description.
Original Description (from Dall, 1903, p. 1368-1369):
"Pliocene marls of the Caloosahatchie and Shell Creek; Dall and Burns.
Shell solid, high, short, laterally very convex, longitudinally subcompressed, with large, moderately impressed, cordiform dorsal areas; beaks small, narrow, prosogyrate, with a small, globular, deeply excavated lunule, much larger proportionately and more open in the young shell; ligament very short; surface with little raised, flattish, concentric threads closely adjacent and with only linear interspaces; radial sculpture of four broad ribs separated by narrow, shallow sulci, which become obsolete towards the base, and an impressed line bordering the escutcheon; the middle pair of ribs occupy about one-third of the disk; hinge strong, teeth conical, normal; scars normal, inner margin of the valves entire, except some very minute crenulations near the middle of the base. Alt. 16.5, Ion. 11.0, diam. 15.0 mm.
This is one of the most elegant species of the genus. The young, in which the lunule is apparently much larger and more open, at first would be taken for a distinct species."
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