Early Miocene; Extinct.
Original Description (from Dall, 1903, p. 1248):
"Oligocene of the Chipola River, Calhoun County, Florida; Burns.
Shell rounded trigonal, rather thin, subcompressed, the surface finely, evenly, closely, concentrically sulcate, with a few almost microscopically minute radial striulae sometimes visible under a lens in the sulci near the ends of the shell; most of the specimens appear to be without radial sculpture; beaks small, pointed, slightly anteriorly directed over a lanceolate lunule bounded by an incised line; hinge normal; pallial sinus barely indicated; inner margins smooth, the right posterior dorsal margin grooved to receive the bevelled edge of the margin of the opposite valve. Length 8.3, height 7.2, diameter 4.0 mm.
This species is especially characterized by its fine, even, concentric sculpture and nearly total absence of radial striae."
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