60 



MEMOIRS OF THE CARNEGIE MUSEUM. 



It is hard to say what the ecological preferences are, but the specimens I col- 

 lected alive always came from riffles with rather coarse gravel and a rapid flow of 

 water. In the Ohio proper it inhabits the shell-banks. However, Baker (1898c, 

 p. 36) says that it is found in the Chicago area in the larger lakes and rivers on a 

 muddy bottom. 



General distribution: Type locality, Ohio River (Rafinesque). 



The range of this species according to Simpson (1900), is "Mississippi-drainage 

 generally; southern Michigan; San Saba Co., central Texas." Call (1885) says: 

 "New River, Virginia, to Tuscumbia, Alabama; to Iowa; to Michigan." 



The area occupied by this species includes the Tennessee, Cumberland, and 

 Ohio drainages; toward the west and southwest, it apparently becomes scarce. 

 It has not been reported from Kansas (Scammon, 1906), but is present in southern 

 Missouri and northwestern Arkansas.*^ Simpson's record from Texas is the 



Fig. 7. 

 ■ Rohmdaria iuberculaln. 

 + Plethohasus cooperianus. 

 • Plcthobasus cyphyus. 



only one in this state, and the list of Singley (1893) does not contain it. Also in a 

 northwesterly direction, the distribution seems to be limited, and barely reaches 

 to Iowa in the Mississippi. Northwards it extends all over Illinois, to southern 

 Cook Co. (Baker, 1898a, 1906) and goes in the Mississippi, Rock, Wisconsin, and 

 St. Croix Rivers, to Wisconsin (Barnes, 1823; Lapham, 1860; Cooper, 1855). 

 In Indiana it has been recorded by Call (1896a) from the Ohio, Wabash, and White 



■" Call (1895) does not mention this species from Arkansas, but, aside from the localities represented 

 in the Carnegie Museum, it occurs also in the Big Buffalo Fork of White River (Meek & Clark, 1912) 

 and W. I. Utterback (1916) reports it from southern Missouri. 



