11 



small streams. Rafinesque observes of the U.Jiaviis, 

 that it is "found only in the small rivers falling into 

 the Kentucky, Salt or Green rivers." It occurs, 

 however, in Alabama, where it observes the same 

 peculiarity in the choice of its habitat. Other 

 species prefer the soft muddy shores to the bars, 

 which are the usual localities of the Naiades; amongst 

 these are Unio teres, Raf. (U. anodontoides, Lea.) 

 and U. cariosus? Say: U.fragilis, Raf. ((7. gracilis, 

 Barnes, Syrrvphynota gracilis, Lea,) is abundant on 

 the rocky shores of the Alabama river, at Claiborne, 

 as well as on many of the bars. 



The hmited range of some fresh water shells, and 

 the wide distribution of others is very remarkable. 

 A large Paludhia adheres to the rocks in the vicinity 

 of Claiborne in vast numbers, yet I have not else- 

 where observed it, not even at St. Stephens, on the 

 Tombeckbe, where fragments of the rocky strata 

 strew the margin of the river in the same manner as 

 at Claiborne, and such caka -eous masses appear to 

 be the only resort of the species. In like manner the 

 *FtLsusfiuvialis of Say appears to be limited to the 



* lofusiformisy Lea. It was improper to change the 

 specific name of this shell, for good or bad specific names 

 it is generally conceded, must stand, unless they are pre- 

 occupied in the same genus. The animal of this shell is 



