xliv 



reported only from the Tombigbee and Chattahoo- 

 chee Rivers respectively. None of the carinate 

 group — inhabitants of Tennessee River — extend 

 northward to the Ohio ; but, strangely enough, the 

 North-western States furnish two peculiar species, — 

 P. siihidare of Niagara River, and P. Lewisii of 

 Illinois River. 



But two plicate PleurocercB have yet been dis- 

 covered, although this form is so very common to 

 the Goniohases inhabiting 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 Caney Fork, Tennessee. 



The five species of the third group are, with the 

 exception of A. rota, very closely allied. 



A. armigera has an extensive distribution. It 

 was described 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 hab- 

 itats 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 sjDCcies not easily distinguished, but 

 differing very much in their range of habitat ; for, 

 while A. lima is confined to the loioer waters of the 

 Tennessee, A. verrucosa has a range coextensive 

 wdth that of armigera. It occurs in the Holston 

 River and the whole extent of the Tennessee, the 



