UPPER TENNESSEE DRAINAGE. 589 
Thus this is undoubtedly one of the rarest species of Truncilla, 
and its distribution should be studied more closely. 
Type locality: Holston River, Tenn. (topotype examined). 
82. TRUNCILLA PROPINQUA (Lea), 1857. 
Unio propinquus Lea, ’57—Unio propinquus Lewis, ’71.—Unio 
propinquus Pilsbry & Rhoads, ’96.—Tvruncilla propinqua Simp- 
Son, “Ids 'p. 27. 
‘Reported, by Lewis, from Tennessee River, Knox Co., and from 
the Clinch by Call. Pilsbry & Rhoads give it from the Tennessee at 
Knoxville, the Holston at Boyd Island, near Knoxville, and from the 
Clinch at Patton’s Ferry, Roane Co. The Carnegie Museum pos- 
sesses it from the Tennessee, Knox Co. (Smith coll.),and I found it 
myself in the Clinch at Edgemoor and Clinton, Anderson Co., Tenn. 
Type locality: Florence and Tuscumbia, Ala. (topotypes ex- 
amined). 
83. TRUNCILLA TORULOSA (Rafinesque), 1820. 
Amblema torulosa and gibbosa Rafinesque, ’20.—Unio perplexrus 
Lewis, ’71.—Truncilla perplexa Simpson, ’14, p. 24.—Truncilla 
torulosa Vanatta, ’15, p. 550. 
The identity of torwlosa and gibbosa with perplexus has been in- 
dicated by Conrad (’34), and he selected the name of torulosa. Al- 
though he later (’36) uses gibbosus (and so do Agassiz and Reeve), 
the first selection has to stand. 
The typical T. torulosa has a radial row of prominent knobs 
across the middle of the shell. But these knobs vary greatly, and in 
the upstream direction, they have the tendency to become reduced, 
finally disappearing, thus passing into the condition seen in the next 
form. . 
Restricted to the larger rivers. It turns up in the Tennessee at 
and below Knoxville (Lewis), and continues down the river, but is 
nardly found above Knoxville. The Carnegie Museum has three 
young specimens from near Knoxville (Hartman coll.), which have 
distinct knobs. In addition, there is a specimen from Chattanooga, 
Hamilton Co., Tenn. (Juny coll.), which is typical in all respects, 
