130 AMERICAN JOURNAL 



enough, the North-western States furnish two peculiar species, 

 — P. subulare of Niagara River, and P. Levnsii of Illinois 

 River. 



But two plicate Pletirocerse have yet been discovered, 

 although this form is so very common to the Goniohases in- 

 habiting the same region. These shells are found in the 

 Clinch and Cumberland Rivers. 



Of the smooth species, several extend to the Ohio River. 



ANGITREMA. 



The four species of the first group are inhabitants of the 

 Tennessee River. A. salehrosa has been gathered in the 

 Holston, in East Tennessee, and in the Tennessee at Florence, 

 Alabama. 



A. Jay ana inhabits Cany Fork, Tennessee, 



The five species of the third group are, with the exception 

 of A. rota^ very closely allied. 



A. armigera enjoys an extensive distribution. It was de- 

 scribed from the Ohio River, and has since been found in the 

 Wabash, Indiana, along with several other nodulous and 

 plicate species, whose range is otherwise confined to more 

 southern rivers. Kentucky and Tennessee are also given as 

 habitats for this species; and in the latter State it doubtless 

 originated. A. Duttoniana and Stygia are both reported from 

 Cumberland River, and the former inhabits the Tennessee. 

 The fourth group contains two species not easily distinguished, 

 but differing very much in their range of habitat ; for, while 

 A. lima is confined to the lower waters of the Tennessee, A. 

 verrucosa has a range co-extensive with that of armigera. It 

 occurs in the Holston River and the whole extent of the 

 Tennessee, the Cumberland, the lower parts of the Ohio, and 

 is very plentiful in the Wabash. 



LITHASIA. 



While the Angitremse are essentially a Tennessee group, the 

 subgenus Lithasia partakes of both characters. Its large 

 inflated species, five in number, all occur in the Tennessee 

 River at Florence, Alabama, and vicinity, while the more 

 numerous, compact, heavy species, approaching in form to 

 the typical Goniohases, are almost confined to the Coosa and 

 Cahawba Rivers. The exceptions are a small group of three 

 species, of which ohovata is the type, which inhabit the Ohio 

 River and its Kentucky and Indiana tributaries, and one 

 singular subcylindrical species reported from the Cumberland. 

 Mr. Anthony assigns Tennessee as the habitat of his 

 nucleola; but I think he is mistaken, as I have specimens 

 from the Coosa. 



