UPPER TENNESSEE DRAINAGE. 581 



dark epidermis with indistinct or no rays, and a deep copper-colored 

 or pnrplish nacre ; rarely the latter is lighter, and even when whitish, 

 it has at least some purple or red. The female is characterized by a 

 very strong dilatation of the postbasal margin, and very often, chiefly 

 in old shells, it has a strong "' constriction " 'behind this dilatation. 



The distribution of this species is very similar to that of E. nebu- 

 losa, preferring also the small streams, and very often the two species 

 are found associated. Also here it is unnecessary to give a list of 

 localities, and it suffices to state that it is found practically over the 

 whole upper Tennessee region. It should be remarked, however, 

 that I did not find it in the headwaters of the Clinch (above Speer's 

 Ferry, Va.), but it may have been overlooked here. While locally 

 abundant in smaller streams, it becomes rare in the larger rivers. 



Also here, local races cannot be distinguished, except that the 

 shell attains, in certain streams, a much greater size than in others. 

 This is the case, for instance, in the Aliddle Fork Holston in Smyth 

 Co., Va., where exceptionally large specimens {U . copei Lea) are 

 found, while the North Fork contains a small race. Specimens of 

 larger rivers are also generally rather large and well developed, and 

 often lack, in the 5, the posterior constriction. Such specimens 

 have a resemblance to U. lienosus Conrad, being more drawn out at 

 the posterior end. U. lienosus is a southern form, not found in the 

 Tennessee drainage. There is no doubt that U. caliginosiis Lea 

 (= lienosus) , recorded by Pilsbry & Rhoads from the lower Clinch, 

 is founded upon such specimens. 



Also this species has a wide distribution in the Cumberland drain- 

 age, the Tennessee drainage in Alabama, and the Coosa-Alabama 

 system, and it is very likely that also the form of the Cumberland, 

 questionably referred to lienosa by Wilson & Clark ('14), is this. 



Type locality: Cumberland River, Tenn. 



■ 69. EuRYNiA (Eurynia) RECTA (Lamarck), 1819. 



Unio rectus Lamarck, '19. — Unio rectus Lewis, '71. — Unio rectus 

 Pilsbry & Rhoads, '96. — Eurynia {Eurynia) recta Ortmann, '12b, 

 p. 344 (anatomy). — Eurynia recta Goodrich, '13, p. 95. — Lamp- 

 silis recta Simpson, '14, p. 95. 

 Abundant in the larger rivers : Tennessee in Knox Co., lower 



