Late Pliocene to Early Pleistocene; Extinct.
Original Description (from Dall, 1890, p. 103):
This variety may be the result of parasitism or disease, but, however produced, the differences are too marked to leave unnoticed. The fossils resemble the recent F. distans, but have a deeply impressed line in front of the suture and usually on the last two whorls another behind the suture, but less strong. These make the suture much more prominent than in the recent shell and its margin is usually somewhat crenulated. It is possible that this may be due to some annelid building its tube along the suture and so producing an abnormal growth, as is sometimes seen in recent shells; but some young specimens show the gradual progress of this margination from the very apex, which would hardly agree with the above suggestion.
Total length: 88.0 mm. Spire: 33.0 mm. Width: 42.0 mm."
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