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-iovra inhabits the larger 

 rivers, w-hile in the smaller streams typical cuneolus is found. 



7. FuscoNAiA COR (Conrad), 1834. 



Unio cor Conrad, '34. — Unio edgariamis Lea, '40. — Unio ohnncns 



Lea, '71. — Unio edgariamis Lewis, '71. — Unio andersonensis Lea, 



'y2. — Unio cdgarianus Pilsbry & Rhoads, '96. — Pleiirobema 



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 edgariamis, 

 tuscumhiensis, andersonensis. Frierson has sent for inspection a 

 specimen, which had been compared with the type of cor, and this 

 proved to be cdgarianus. 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. cun coins, 

 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, L^nion Co., Tenn. (associated 



