532 ORTMANN—NAYADES OF 
Remarkably enough, I have found a single specimen of this form 
in a very small creek tributary to Little River—Pistol Creek, Rock- 
ford, Blount Co., Tenn.—it has the diameter of 50 per cent., and thus 
stands just on the line dividing the two varieties. This specimen is 
rather stunted in growth, and may be only an individual abnormality. 
Type locality: Tuscumbia, Ala. (Tennessee River and Holston 
River, Tenn.) (type examined). 
Note: This type of shell is also present in the Tennessee drainage 
in North Alabama, where again the appressa-form inhabits the larger 
rivers, while in the smaller streams typical cuneolus is found. 
7. FUSCONAIA CoR (Conrad), 1834. 
Unio cor Conrad, ’34——Unio edgarianus Lea, ’40.—Unio obuncus 
Lea, ’71.—Unio edgarianus Lewis, ’71.—Unio andersonensis Lea, 
‘72—Umo edgarianus Pilsbry & Rhoads, ’96—Pleurobema 
edgarianum Simpson, ’14, p. 741. 
According to Frierson (Naut., 29, ’16, p. 102 ff.) the type of U. 
cor Conrad is the same as shells which have been called edgarianus, 
tuscumbiensis, andersonensis. Frierson has sent for inspection a 
specimen, which had been compared with the type of cor, and this 
proved to be edgarianus. This is also supported by Conrad’s descrip- 
tion, which says that cor has rays, some of them broad. 
This species is closely allied in shell and anatomy to F. cuneolus, 
but is distinguished by very smooth and shining epidermis, and by 
beautiful color: upon a brownish or yellowish background are bold, 
dark green to blackish rays, while cuneolus has greenish or yellow- 
ish-olive epidermis, with finer, greenish rays. 
The original cor is a much swollen form, and belongs to the larger 
rivers; but in the smaller streams, it again passes into a more com- 
pressed form (F. cor analoga). I have drawn the line between the 
two at the diameter of 50 per cent. of the length, so that specimens 
with this or a greater diameter fall under cor. 
I have found this form only in Clinch River, at Edgemoor, An- 
derson Co., Tenn., and, according to Pilsbry & Rhoads, it is in the 
Clinch in Roane Co. In the Walker collection, there are specimens 
belonging here from Needham Ford, Union Co., Tenn. (associated 
