17 
south as Erie, the number of species which also 
occur in the Tennessee is considerably increased; 
amongst these are Unio rectus of Lamarck, U. acu- 
lissimus , Lea, U. teres, Raf. U. plicatus, Say, U. 
rejlexus , Raf. JJ. verrucosus , Raf. and U. undatus, 
Barnes. 
Unio interruptus , Say, does not inhabit the Black 
Warrior, and is rare in the Alabama above Clai- 
borne; six miles below this village, it is very abun- 
dant on an extensive bar. 
U. stapes, Lea, inhabits both these rivers, and has 
as yet been found in no other; it is extremely rare. 
Unio arcus, nobis, I have found only in the Ala- 
bama. 
Unio acutissimus, Lea, is very rare in the rivers 
abovementioned, but is abundant in Flint river, a 
tributary of the Tennessee. 
Unio decisus , Lea, has been confounded with U 
scaienius , Raf. but is very distinct. It has, as yet, 
been found only in the Black Warrior and Alabama 
rivers; in the latter very abundantly. 
Unio Alabamensis, nob. The observations on 
B 2 
