Original Combination:

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Original Description:

At the foot of the high bluffs which line the south side of the French Broad river below Paint Rock, just over the line in Tennessee, there occurred a very distinct form of P. tridentata, characterized by its large size, depressed complanata-like form, but closely and regularly striated. The lip is that of the typical tridentata, with rather small marginal teeth. Of twenty specimens the smallest was 19 and the largest 24 mm. in diam., the average being 22 ½. Only two were less than 21. This form is probably the same as that mentioned by Wetherby from Braden mountain, Campbell county, Tenn., and is the same described by Clapp from Oakdale, Morgan county, and Concord, Knox county, Tenn. It is also the same form found at Elizabethton, Tenn., and erroneously by one of us referred to var. complanata. The Elizabethton examples are lighter in color than the Paint Rock specimens and rather smaller, being from 19 ½ to 21 ¼ mm. in diameter, in this respect resembling the Morgan county shells, described by Clapp.