592 ORTMANN— NAYADES OF 



Known from the Cumberland and Tennessee Rivers, from the 

 latter, however, reported hitherto only from North Alabama. I have 

 found it in the Holston, from Knox Co., up to Holston Station, 

 Grainger Co., Tenn., but not in great numbers. 



Type locality: Florence, Ala. (and Cumberland River) (topotypes 

 examined). 



'^j. Truncella walkeri Wilson & Clark (1914). 

 Truncilla zvalkcri Wilson & Clark, '14, p. 46, pi. i, f. i. 



This is practically a large, compressed T. florentina. It agrees 

 with it in every respect, except that it attains a larger size, and is as 

 compressed as T. capscrfonnis. It may be only the headwaters form 

 of T. florentina. 



From T. capsccformis it is distinguished by larger size, and by the 

 absence of any dark green tints (except rays) upon the posterior 

 expansion of the female. Also the denticulations on the margin of 

 the expansion are stronger and more numerous. Wilson & Clark do 

 not mention these denticulations : but his specimens seem to have 

 been more or less mutilated in this region. My specimens, belong- 

 ing to the type set, show only traces of them, while the fine material 

 I collected myself in the headwaters of the Holston shows them well 

 developed. 



The males of T. walkeri and capsccformis are very similar: that 

 of zvalkcri is possibly somewhat larger and of a lighter color, yellow- 

 ish brown, with light green rays, while that of capsccformis is green- 

 ish olive, with dark green rays. But these differences are rather un- 

 certain. However, I was never put to the task of separating them, 

 since I have never found the two species associated. 



T. zualkeri is very local in the upper Tennessee region. I found 

 it only in the South Fork Holston at Emmett, Sullivan Co., Tenn., 

 and at Barron, Washington Co., Va. (Walker has it from Barron) ; 

 and further, I found it in Middle Fork Holston, at Chilhowie, Smyth 

 Co., Va. At the latter place it was not rare. 



In addition, the Carnegie ]Museum has it from Flint River and 

 Hurricane Creek at Gurley and Maysville, Madison Co., Ala. There 

 are also specimens at hand from the type locality. 



