Late Pliocene to Early Pleistocene; Extinct.
Original Description (from Dall, 1900, p. 1106):
"Pliocene marls of the Caloosahatchie and Shell Creeks, Florida; Willcox and Dall.
Shell small, plump, oblique, ovate triangular, obtusely carinate behind, with high involute, prosogyrate beaks; body with nine, truncation with eight ribs; on the body the ribs are high, flat-topped, with channelled, cross-striated interspaces narrower than the ribs; on the truncation the ribs are smaller and lower; when intact the ribs carry a row of nodules (rounded in the young, more or less transverse in the adult) which do not extend quite to the sides of the top of the rib on which they are seated; on the truncation the nodules appear to remain hemispherical at all ages; the cross-striation of the channels is close and very elegant; there is a small, smooth space in front of the most anterior rib; the inner margins are fluted and the hinge strong, but more transverse than in many of the species. Alt. 11, Ion. 8, diam. 9 mm.
This elegant little shell is very abundant in the Caloosahatchie marl. It most resembles C. Simrothi Dall, and the Pacific coast recent C. alabastrum Carpenter, but is more elongate, more pointed below, and has no backward wing to the hinge-margin. The large ribs are proportionately smaller and less elevated than in C. alabastrum."
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