11 



elliptical, triangular, square, oboval, rounded, &c. 

 and with the lamellar tooth, either horizontal, ob- 

 lique, vertical, straight, curved, flexuous, &c. In 

 my Prodromus of seventy new genera, I proposed 

 to divide them into eight sub-genera. Since that, 

 having increased the number of my species, it 

 seemed proper to construct several genera and 

 sub-genera ; I however give the name Unio, in 

 the second place, to all my new species, in con- 

 formity with the views of naturalists, who hesitate 

 in adopting the changes in nomenclature which 

 discoveries render necessary ; remarking, that by 

 admitting all of them into the genus Unio, which 

 will then consist of more than seventy species, it 

 would be requisite to repeat, in the description of 

 their specific characters, that of the characters of 

 my new genera, which would render the defini- 

 tion of the species prolix. 



Of the Unios of North America mentioned by 

 authors, one was discovered by the younger 

 MICHAUX in the Ohio, and in the account of his 

 travels it is named U. Ohiensis, but as it is not 

 described, I cannot refer it to any of my species : 

 besides, the name is unsuitable ; it is singular 

 that he found but one in that river, which has 

 produced upwards of fifty species ! The Unio 

 Caroliniana of Bosc is imperfectly described ; 

 however, I presume that it is not identical with 

 any species of the Ohio. Among the new species 



