552 ORTMANN—NAYADES OF 
Roan Co., from the Little Tennessee, Monroe Co., and Cane Creek, 
McMinn Co., are labeled ravenelianus. I have found similar ones 
in Hiwassee River (passing into holstonense). I do not think that 
these are more than individual variations. However, it might be 
that within the high mountains of North Carolina, P. oviforme 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 oviforme according to 
diameter, but is an argenteum according to shape and size. Since 
topotypes and authentic material of conasaugaensis, examined in the 
Walker collection, fall partly under oviforme and partly under 
argenteum, this is a real intergrade, hard to place. 
P. oviforme is widely distributed in all rivers in East Tennessee. 
In 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 argenteum. It is to be noted that oviforme 
goes well into the headwaters, and apparently it does not pass into 
argenteum 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 argentewm. 
Type locality: Tennessee. 
31. PLEUROBEMA OVIFORME ARGENTEUM (Lea), 1841. 
Unio argenteus Lea, ’41—Unio striatissimus Anthony, Am. Jl. 
Conch., I, ’65, p. 155.—Unio planior Lea, ’68.—Unio brevis Lea, 
"72.—Unio argenteus Lewis, ’72—Umio swordianus Wright, 
Naut., 11, ’97, p. 4.—Pleurobema fassinans Ortmann, ’13), p. 
310 (not fassinans of Lea)—Pleurobema argenteum Goodrich, 
"13, p. 94.—Pleurobema swordianum, argenteum, breve, planius 
Simpson, ’14, pp. 757-802.—Pleurobema fassinans Ortmann, ’14, 
PisinGper erroretm,)) 
The soft parts of this form have been described by me under the 
erroneous name of P. fassinans. 
