Early Miocene; Extinct.
Original Description (from Dall, 1903, p. 1267):
"Oligocene marl of the Chipola horizon at Alum Bluff and on the Chipola River at McDonald's farm; Dall and Burns.
Shell subtrigonal, solid, nearly equilateral, sculptured with fine, close, concentric wrinkles, over and upon which is imposed the faint, close, zigzag sculpture of divaricate lines with numerous angles; anterior dorsal slope nearly straight, posterior gently arched, with one or two faint radial ridges indicated as extending from the umbo to the posterior margin; lunule long, rather narrow; hinge delicate, anterior lateral prominent, compressed; posterior right cardinal bifid near the dorsal end; grooves of the dorsal margin deep; anterior end rounded; posterior end obscurely truncate, base produced a little in the middle. Length 29.2, height 24.0, diameter 17.0 mm.
Young shells were abundant in the marl, full-grown ones comparatively scarce."
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