Late Pliocene; Extinct.
Original Description (from Tuomey and Holmes, 1857, p. 50):
"Description. Somewhat oval, thick, inequilateral, concentrically striate, or grooved; buccal margin rounded; anal side somewhat produced, obliquely truncate; lip crenato.
The teeth extend without interruption around the hinge. The pallial and muscular impressions are well defined, and in young individuals the shell is slightly angular near the umbones. Umbones pointed and closely approximating.
This is the only species of this genus, without radiating ribs, found in our newer Tertiary rocks.
Plate XVII. Fig. 5, Exterior of left, and interior, hinge and teeth of right valve.
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