Early Miocene; Extinct.
Original Description (from Dall, 1903, p. 1382):
"Chipola Oligocene of the Chipola River and of the lower bed at Alum Bluff, Chattahoochee River, Calhoun County, Florida; Dall and Burns.
Shell small, plump, rounded, subequilateral, with small, somewhat prosogyrate beaks; lunule small, lanceolate, moderately excavated; escutcheon linear or none; dorsal areas indicated by the absence of radial sculpture, hardly impressed; disk with twenty-four or more rounded radial riblets, of variable strength, but not bifurcate, crossed by rather sparse, thin, little elevated lamellae which are higher on the dorsal areas; hinge normal, strong; inner margins strongly crenulate. Alt. 4.0, Ion. 4.2, diam. 2.75 mm.
A larger and more solid shell with stronger radials, larger lunule, and less close and regular concentric sculpture than in P. yaquensis."
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