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 ). 
87. TRUNCELLA WALKERI Wilson & Clark (1914). 
Truncilla walkeri Wilson & Clark, ’14, p. 46, pl. 1, f. 1. 
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 7. capseformis. It may be only the headwaters form 
of T. florentina. 
From T. capseformis 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 7. walkeri and capseformis are very similar: that 
of walkeri is possibly somewhat larger and of a lighter color, yellow- 
ish brown, with light green rays, while that of capseformis 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. walkeri 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. 
