: : i t 10 



such as the Kentucky, Cumberland, Tennessee, 

 Wabash, Miami, Green, Scioto, Licking, Musk- 

 ingum, Kenhawa, &c. many of which are con- 

 siderable rivers, of from five to eight hundred 

 miles in length. It remains to be ascertained 

 whether they are common to the whole of the 

 valley of the Mississippi, to the Missouri, Ark- 

 ansa, &c. I am certain some have been found 

 there, and think it probable that the shells of this 

 immense basin are analogous, although many 

 particular species may be discovered hereafter in 

 the great western and southern branches of these 

 rivers. 



Among the bivalves of the Ohio, the greater 

 portion of the species belong to the genus Unio, 

 as now established. A number of species, so 

 great as to quadruple this genus, presenting in- 

 finite anomalies in form and structure, is a very 

 remarkable fact, and occasioned doubts respect- 

 ing the annunciation of its characters. Struck at 

 first by some differences in the animals inhabiting 

 these shells, 1 thought I could distinguish a new 

 family or a new genus, which I proposed to name 

 Potamila. I was afterwards convinced, that not- 

 withstanding the slight differences in the animals, 

 these shells accorded entirely with the generic 

 character of the Unio, but at the same time exhi- 

 biting well defined secondary characters, such as, 

 transverse or longitudinal shells, with forms either 



