Middle Miocene to Early Pleistocene; Extinct.
Panama to Virginia.
Original Description (from Lea, 1846, p. 7-8):
"Remarks. -- The longitudinal costae are generally nodulous, but they occasionally seem rather to be cancellated by transverse sulci, which, in other specimens, appear to usurp their place. The two internal laminae are placed at about one-sixth of the circumference apart. They are generally directed towards the centre, and sometimes nearly meet. In some specimens they are much smaller than in others. They rarely or never seem to be continued in the aperture.
This is a very variable shell, both as to the sculpture and internal plates. I at first thought that there were two or three distinct species, but the varieties glide imperceptibly into each other. It appears to be by no means an uncommon shell at Petersburg.
The form figured is a very usual one. I have but few specimens which do not exhibit a decided tendency to form regular revolutions, and in some, the axis is so straight that a pin may be thrust through the umbilicus from the apex to the base.
The second figure is a specimen fractured to exhibit the appearance of the laminae."
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