Early Miocene to Middle Miocene; Extinct.
Northern Florida to Georgia.
Original Description (from Dall, 1898, p. 740):
"Oligocene of the Chipola horizon, in the lower bed at Alum Bluff, Chattahoochee River, Florida; Ball.
Shell small, thin, with compressed, flattish umbones and fourteen or fifteen feeble, obsolete ribs on the lower part of the disk separated by equal shallow interspaces; the whole surface marked with fine concentric lines; ears subequal, concentrically striate, not radiated, except the byssal ear, which has five scabrous riblets and a well-marked notch; interior fluted to correspond with the external ribs; the cardinal crura developed. Alt. reaching 15-18 mm. in fully adult shells; figured specimen 8, lat. 7.5 mm.
This small shell is sufficiently distinct in its characters to indicate its specific rank, though it may be that it attains a larger size when adult than any of the specimens obtained. One or two of the specimens have the ribs more rounded and prominent than the majority."
To access this description in its original formatting through the Biodiversity Heritage Library, click here.