Early Miocene to Middle Miocene; Extinct.
Northern Florida to Georgia.
Original Description (from Dall, 1898, p. 783):
"Oligocene of the Chipola beds at the Chipola River and the lower bed at Alum Bluff, Florida; also at Ballast Point, Tampa Bay, Dall, Burns, and Willcox; and at Bowden, Jamaica, Henderson and Simpson.
Shell small, irregular, characterized by a fine, almost microscopic, close-set radial striation covering the whole surface and flaring away from the medial line of the valve in a somewhat wavy manner; the two lower scars on the left valve are subequal and side by side, the major byssal scar larger, opposite the medial line between them; the beak of the left valve is some distance within the margin, and the surface where worn appears smooth; the striation is only visible under a lens in most cases. Alt. 17, lat. 25 mm.
This species is recognizable by its fine, almost divaricate striation, which does not break into pustules near the beaks, as in the larger and more coarsely sculptured A. ephippioides.
The specimens from Bowden have a still finer and often partially obsolete striation. They form the variety indecisa (Guppy, MS.)."
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