18 
the distribution of the preceding species apply equally 
well to this. 
Unio asper, Lea, appears to be confined to the 
same waters. It has been confounded with U. api- 
culatus, Say, a species from Bayou Tercuzp, but it is 
certainly distinct. The tubercles are not disposed 
in regular series as in the apiculatus. 
Unio arctatus,nob. This species is usually found 
on the rocky shores of the Black Warrior and Ala- 
bamarivers; I have not observed it in other streams. 
It is usually white in the nacre, only one specimen of 
the many I obtained being purple. It resembles a 
variety of U. purpureus, Say, which inhabits the 
Delaware, but is much more elongated. 
Unio glans, Lea. I never found it in the Black 
Warrior, yet it is not uncommon in a tributary of the 
Tennessee, which has its source within a few miles 
of the head waters of the Black Warrior. It resem 
bles U. parvus, Barnes, but is purple in the nacre, 
which is not so brilhant asin that shell. Its outline 
is more regularly elliptical than that of the parvus. 
it approaches U. lienosus, nob. but is very distinct. 
Unio teniatus, nob. U. cor, nob. U. maculatus, 
nob. U. subtentus, Say, U.celatus, nob. U: trabalis, 
