Late Pliocene to Early Pleistocene; Extinct.
Original Description (from Heilprin, 1886, p. 131-132):
"Shell ovately elevated, moderately ventricose, with the beaks apical, touching (or nearly so), and directed slightly backwards; ribs about 30 to 33, smooth, moderately elevated, teretely rounded, with narrow, impressed interspaces; the ribs on the posterior slope narrower and more crowded than over the general surface, minutely echinated in part.
Hinge-line narrow, acutely curved, with prominent lateral teeth; a prominent triangular cardinal tooth in each valve. Height, from apex to basal margin, 5.3 inches; length (width), 3.7 inches."