Early Miocene; Extinct.
Original Description (from Dall, 1900, p. 1081):
"Oligocene marl of the Chipola River, Calhoun County, Florida; Burns.
Shell small, rotund, plump, nearly equilateral, with moderately full umbones; sculpture of about forty-five close-set, low, nearly flat radial ribs separated by very narrow channelled interspaces; the alternate ribs anteriorly surmounted with prominent hollow spines usually truncate at the ends, their alternates showing low A-shaped spines; behind the middle of the shell the long-spined ribs are less numerous and on the posterior area nearly all the ribs have low spines; there is no smooth area near the hinge-margin; internally the margins are fluted or serrate minutely, and the shell radially sulcate near the margin; hinge normal, delicate. Alt. 7.5, Ion. 7.5, diam. 6 mm.
Only a single valve of this very distinct little species was obtained. Owing to the alternation in the sculpture it has somewhat the aspect of Criocardium."
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