Early Miocene to Early Pleistocene; Extinct.
Southern Florida to Maryland.
Original Description (from Say, 1824, p. 134-135):
"Much compressed, with about sixteen striated ribs.
Description. Shell rounded, much compressed; the whole surface covered with scaly striae: ribs elevated, rounded, with about three strife on the back of each; intervening grooves rather profound: ears equal, sinus of the ear of the superior valve profound, extending at least one third of the length of the ear.
Length rather more than four inches and a half; breadth four inches and four-fifths.
In magnitude this shell is justly entitled to compare with the preceding; but it differs in being much less convex, and in having a much more profound sinus in the ear of the superior valve. Three specimens, from which the above description was taken, belong to the Academy, and were presented by Mr. Watson."
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