UPPER TENNESSEE DRAINAGE. 555 



Type locality: Holston River, Tenn. (Simpson says: Tuscumbia, 

 Ala.) (topotypes examined). 



Note: The group of Pleiirobeina oviforme is also quite abundant 

 in the Tennessee drainage in North Alabama. Also here the hol- 

 stoncnsc-iorra is in the Tennessee proper (also in lower part of Paint 

 Rock River and Limestone Creek) ; in the tributaries, oviforme is 

 the prevailing form, and in some of the headwaters, the argenteiim- 

 form is fully as well developed as in the upper Clinch and Holston, 

 for instance : in Paint Rock River at Princeton, Jackson Co., Ala. ; 

 Dry Creek, Holly Tree, Jackson Co., Ala. (tributary to Paint Rock) ; 

 in Hurricane Creek, Gurley, Madison Co., Ala. (tributary to Flint 

 River) ; in Elk River, Estill Springs, Franklin Co., Tenn., and its 

 tributary : Boiling River, Cowan, Franklin Co., Tenn. 



It should be remarked that in this region also the true Pleuro- 

 benia clava (Lam.) turns up; this species is distinguished by much 

 more anteriorly situated, pointed beaks, swollen anterior part of the 

 shell, and cuneiformly compressed posterior part. The Carnegie 

 Museum has this species from the old Smith collection, labeled Tus- 

 cumbia, Ala., and I have seen it also in the Walker coll. from 

 Florence, Ala. In addition, in the latter collection, are specimens 

 from Sequatchie River, at Jasper, ]\Iarion Co., Tenn. (Wetherby 

 coll.). 



Genus: Elliptic Rafinesque (1820). 



Ortmann, 1912&, p. 265. 



33. Elliptic nicer (Rafinesque), 1820. 



Unio nigra Rafinesque, '20. — Unio crassidcns'Lew[s,'yi. — Unio cras- 

 sidens Pilsbry & Rhoads, '96. — Elliptio crassidens Ortmann. '12b, 

 p. 266 (anatomy). — Unio crassidens Simpson, '14, p. 606. — Unio 

 crassidens Vanatta, '15, p. 555. — Elliptio nigra, LTtterback, '16, 

 p. 88. 



The identity of U. nigra Raf. is now firmly established (Say, 

 Conrad, Kuester, Sowerby, and Vanatta), and it is the species com- 

 monly called crassidens. However, the type of crassidens Lamarck, 

 1819, is not this, but' is the trapecoides Lea (Frierson, '14a, p. 7). 

 Thus Rafinesque's name should be used for the present species. 



