552 ORTMANN— NAYADES OF 



Roan Co., from the Little Tennessee, ^Monroe Co., and Cane Creek, 

 McMinn Co., are labeled ravencUanns. I have found similar ones 

 in Hiwassee River (passing into Iwlstoncnse). I do not think that 

 these are more than individual variations. However, it might be 

 that within the high mountains of North Carolina, P. ovifonne gen- 

 erally assumes these characters (dull color and lack of rays), and if 

 so, we might be justified in calling this form by a varietal name (P. 

 oviforme ravenelianum) . 



The figure of U. conasaugaensis Lea is an ovifonne according to 

 diameter, but is an argentcum according to shape and size. Since 

 topotypes and authentic material of conasaugaensis, examined in the 

 Walker collection, fall partly under oviforme and partly under 

 argentcum, this is a real intergrade, hard to place. 



P. oviforme is widely distributed in all rivers in East Tennessee. 

 Li the Tennessee proper it is rare, and is generally represented by 

 the var. holstonense. It is in Powell, Clinch, Holston, French Broad, 

 Little Tennessee, and in many of their tributaries, passing in the 

 lower parts of the larger rivers into oviforme holstonense, and in the 

 upper parts into oviforme argentcum. It is to be noted that oviforme 

 goes well into the headwaters, and apparently it does not pass into 

 argentenm in some instances. This is chiefly the case in French 

 Broad River, where it goes into the North Carolina mountains (Ashe- 

 ville) without assuming the characteristic features of argentcum. 



Type locality: Tennessee. 



31. Pleurobema oviforme argenteum (Lea), 1841. 



Unio argentens Lea, '41. — Unio striotissimus Anthony, Am. Jl. 

 Conch., I, '65, p. 155. — Unio planior Lea, '68. — Unio brevis Lea, 

 '72. — Unio argentcus Lewis, 'y2. — Unio szufordianus Wright, 

 Naut., II, '97, p. 4. — Pleurobema fassinans Ortmann, 'i^b, p. 

 310 (not fassinans of Lea).- — Pleurobema argentcum Goodrich, 

 '13, p. 94. — Pleurobema szvordianum, argenteum, breve, planins 

 Simpson, '14, pp. 757-802. — Pleurobema fassinans Ortmann, '14, 

 p. 31 (per erroreum). 



The soft parts of this form have been described by me under the 

 erroneous name of F. fassinans. 



