UPPER TENNESSEE DRAINAGE. 561 



Chilhowie, Smyth Co., Va. ; South Fork Holston River, Barron, 

 Washington Co., Va. ; Big Creek (tributary to Holston), Rogerville, 

 Hawkins Co., Tenn. (Walker coll.) ; Little Pigeon River, Sevier- 

 ville, Sevier Co., Tenn. ; Boyd Creek, Boyd Creek, Sevier Co., Tenn. ; 

 Little River, Melrose, Blount Co., Tenn. ; Pistol Creek, Rockford, 

 Blount Co., Tenn.; Conasauga Creek, Monroe Co., Tenn. (Walker 

 coll.) ; South Chickamauga Creek, Ringgold, Catoosa Co., Ga. 



Type locality: Tennessee (and " North Carolina," but no exact 

 locality given). 



41. Alasmidonta (Decurambis) marginata (Say), 1819. 



Alasmodonta marginata Say, '19. — Margaritana marginata Lewis, 

 '71. — Alasmodonta marginata Pilsbry & Rhoads, '96. — Alasm,i- 

 donta marginata Ortmann, '12&, p. 297 (anatomy). — Alasmidonta 

 marginata Ortmann, '13/7, p. 311. — Alasmidonta marginata Good- 

 rich, '13, p. 94. — Alasmidonta (Rugifero) marginata Simpson, 

 '14, p. 504. 



As to the subgenus Decurambis Raf., '31, see Frierson, '14a, p. 7. 

 Generally distributed over the whole upper Tennessee region, but 

 apparently more abundant toward the headwaters. Goes, in the 

 Powell, to dinger, Lee Co., Va. ; in the Clinch, to Richland, Taze- 

 well Co., Va. ; in the Forks of the Holston, to Saltville and Chilhowie, 

 Smyth Co., Va., and is also in Big Mocassin Creek, Scott Co., Va. 

 Pilsbry & Rhoads report it from Watauga River at Johnson City, 

 Washington Co., Tenn. It is also in Ocoee River, at Ducktown, Polk 

 Co., Tenn. (Walker coll.). 



Type locality: Scioto River, Chillicothe, Ohio. 



42. Alasmidonta (Decurambis) raveneliana (Lea), 1834. 



Margaritana raveneliana Lea, '34. — Alasmidonta (Rugifera) ravene- 

 liana Simpson, '14, p. 507. 



Differs from .4. marginata chiefly in the albsence of rugosities on 

 the posterior slope. However, in very young specimens, traces of 

 them are sometimes seen, so that this characteristic feature of the 

 subgenus Decurambis (Rugifera) is still indicated. This form un- 

 doubtedly is an offshoot of the niarginata-siock, separated from the 



