UPPER TENNESSEE DRAINAGE. 553 



Simpson (p. 804) makes U. striatissimus Anthony a synonym 

 of P. estabrookianum (which actually is Fiisconaia barnesiana big- 

 byeiisis). Specimens from Blount Co., Tenn., received from the 

 Alabama Aluseum of Nat. Hist, as striatissimus, and similar ones 

 with the same label in the Walker collection, agree fully with speci- 

 mens collected by myself in Little River in Blount Co., and are 

 this form. 



Walker has four specimens labeled P. sivordianum (Wright) 

 from the Wright collection, which thus are authentic specimens. 

 They are all typical P. oviforme argcntenni. In addition, he has 

 three others from the Sword collection (original lot), of which two 

 are this form, while the third is Fiisconaia pilaris bursa-pastoris. 

 The type of sivordianum has, according to Simpson, the diameter 

 of 40 per cent., and thus would stand under oviforme. This, how- 

 ever, seems to be an extreme specimen. 



This is the compressed form of oviforme, peculiar to the head- 

 waters and other small streams. It also generally attains a larger 

 size than the typical oviforme, and is more rhomboidal in outline. 

 Lea's only type of U. argcnteus (examined by myself in Washing- 

 ton) is not a normal specimen ; it is tapering behind, which is a 

 character of oviforme. U. planior represents the normal shape of 

 this shell, rhomboidal, while U. brcvis is exactly the same thing, 

 only slightly shorter. The color markings are generally less bright 

 than in oviforme, and very often they are obscure or missing, 

 chiefly in old shells. 



This variety is found in Powell River from Big Stone Gap, Wise 

 Co., Va. (where it alone is present), downward (associated with 

 oviforme) ; in the Clinch, from Tazewell Co., Va., down to Kyle 

 Ford, Hancock Co., Tenn. (also associated with oviforme and inter- 

 grading with it). In the Holston drainage it is pure in Big Mocassin 

 Creek, and in the North Fork at Saltville, Smyth Co., and Holston, 

 W^ashington Co., Va. It is also pure in the Middle Fork at Chil- 

 howie, Smyth Co., in the South Fork at Barron, Washington Co., 

 Va., and in Watauga River at Watauga, Carter Co., Tenn. Farther 

 down, it passes into, and is associated with, oviforme, but has not 

 been found in the Holston proper. It is in Little Pigeon River, at 

 Sevierville, Sevier Co., Tenn., but not very well developed here, the 



PROG. AMER. PHIL. SOC, VOL. LVII, KK, OCT. I, I918. 



