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 Teche, 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- 
bama rivers; 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 brilliant as in that shell Its outline 
is more regularly elliptical than that of the parvus . 
It approaches U. lienosus , nob. but is very distinct. 
Unio tceniatus, nob. U. cor, nob. U. maculatus , 
nob. U, subtentus , Say, Uccelatus, nob. U trahalis , 
