UPPER TENNESSEE DRAINAGE. 537 
associated with bigbyensis. Farther down, barnesiana soon begins 
to prevail, The form bigbyensis has been traced down in the Powell 
to Combs, Claiborne Co., Tenn.; in the Clinch to Clinchport, Scott 
Co., Va.; but a single specimen has been found at Solway, Knox Co., 
Tenn., apparently an exceptional case; in the Holston it has not been 
found below the point where the North and South Fork unite. 
Type locality: Big Bigby Creek, Maury Co., Tenn. (trib. to Duck 
River and lower Tennessee). 
II. FUSCONAIA BARNESIANA TUMESCENS (Lea), 1845. 
Unio tumescens Lea, 745.—Unio crudus Lea, ’71.—Unio radiosus 
Lea, ’71—Unio tumescens Lewis, ’°72—Unio tumescens Pilsbry 
& Rhoads, ’96.—Pleurobema tumescens and P. crudwm Simpson, 
"Td, p. 751, 753.-—Fusconaia barnesiana tumescens Ortmann, 17, 
Pp. 59. 
(Simpson makes radiosus a synonym of tumescens.) 
This is the swollen form of the large rivers, with a diameter of 
50 per cent. of the length, and over. It also generally has higher 
beaks, making the outline of the shell more nearly triangular; but 
higher beaks are also sometimes observed in the typical F'. barnesiana 
(lyoni-type). U. twmescens represents the extreme in obesity, and 
radiosus (type examined!) is very close to it. U. crudus is the much 
eroded form of the French Broad River (topotypes at hand). The 
two former have more or less developed rays, the latter is rayless. 
F. barnesiavia ‘tumescens has its metropolis in the Tennessee 
River at and below Knoxville. But it is also found some distance 
in the rivers above this point. From the Clinch it is known from the 
lower part; the uppermost locality is at Edgemoor, Anderson Co. It 
also has been reported (by Pilsbry and Rhoads) from Emory River 
at Harriman, Roane Co. In the Holston proper I have observed it 
as far up as Noeton, Grainger Co. It is also in the lower French 
Broad, at Boyd Creek, Sevier Co., in the Little Tennessee in Monroe 
Co., and in Hiwassee River, at Austral, Polk Co. (intergrading, at 
these places, with typical F. barnesiana). 
Remarkably enough, a small tributary of Little River, Pistol 
Creek, Rockford, Blount Co., Tenn., contains shells, most of which, 
PROC. AMER. PHIL. SOC., VOL. LVII, JJ, SEPT, 30, 1918. 
