586 ORTMANN—NAYADES OF 
76. TRUNCILLA ARCZFORMIS (Lea), 1831. 
Unio arceformis Lea, ’31—Umio arceformis Lewis, ’71.—Unio 
arceformis Pilsbry & Rhoads, ’96.—Truncilla arceformis Simp- 
son, *I4, p. 12. 
In the larger and medium rivers: Tennessee, Knox Co., Tenn. ; 
French Broad at Boyd Creek, Sevier Co. In the Holston locally 
abundant: Boyd Island, near Knoxville (Pilsbry & Rhoads) ; Mc- 
Millan, Knox Co.; Mascot, Knox Co.; Gant Island near Straw- 
berry Plains, Jefferson Co. (Walker coll.); McBee Ford, near 
Hodges, Jefferson Co.; Turley Mill, Noeton, and Holston Station, 
Grainger Co.; Austin Mill, Hawkins Co., Tenn. In the Clinch at 
Clinch River Station, Claiborne Co.; and Oakham, Grainger Co., 
Tenn. 
Type locality: “Tennessee River.” Lea (Tr. Amer. Philos. Soc., 
1834, p. 86) corrects this, saying that, according to Troost, this 
species is not in the Tennessee, but only in the Cumberland River 
(meaning, of course, the Tennessee of northern Alabama). 
77, TRUNCILLA INTERRUPTA (Rafinesque), 1820. 
Obliquaria interrupta Rafinesque, ’20.—Unio brevidens Lea, ’31 (not 
’24, as given by Simpson).—Unio brevidens Lewis, ’71—Trun- 
cilla brevidens Simpson, ’14, p. 7. 
The identity of Rafinesque’s species with that of Lea has been 
recognized by Conrad, accepted by Kuester and Reeve, and con- 
firmed by Vanatta (15, p. 550). But Vanatta does not use the name 
of interrupta, for reasons which do not hold good, as shown by 
Walker (16, p. 45). The only objection to iterrupta is that it is 
given, originally, from Kentucky and Ohio rivers, while it seems to 
be absent at least from the Ohio. But we must remember that Lea’s 
brevidens also was originally given from Ohio, corrected subse- 
quently, ’34, to Cumberland River. . 
In the larger and medium rivers: Tennessee (Lewis), Holston, 
Clinch, and Powell. In the Powell, up to Rose Hill, Lee Co., Va.; 
in the Clinch, up to Clinchport, Scott Co., Va.; in the Holston up 
to the North Fork at Hilton, Scott Co., Va. 
Type locality: “ Kentucky and Ohio Rivers.” (Probably incor- 
rect; type from Ohio River, according to Vanatta.) 
