18 



the distribution of the preceding species ai)ply equally 

 Aveli to this. 



Unto asjjer, 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 apicidatus. 



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. purpurcus, Say, which inhabits the 

 Delaware; but is much more elongated. 



Unio glans, Lea. I never found it in tlie Black 

 Warrior, yet it is not uncommon in a tributary of the 

 Tennessee, which has its source within a iew miles 

 ofthc 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 disnnct. 



Unio tfpniatus, nob. U. cor, nob. U. macidatus, 

 nob. U suhtentus, Say, Uccelat2cs, nob. U.trahalis, 



