330 MEMOIRS OF THE CARNEGIE MUSEUM. 



anal and branchial openings). The bottom at these localities generally consists 

 of finer or coarser, closely packed gravel; but I have also found this species in pure 

 sand, when the latter is not kept moving by the current. In Lake Erie, in Presque 

 Isle Bay, of course, this species must live in the fine sand of the bay : but I did not 

 find it alive there. 



General distribution: Type locality, Falls of the Ohio (Rafinesque) (at Louis- 

 ville, Jefferson Co., Kentucky). 



Simpson (1900) gives the following range: "Ohio River-drainage; western 

 New York to southern Michigan; Iowa; eastern Nebraska to Indian Territory." 

 In the Ohio-drainage, this species is generally distributed, not only in the Ohio 

 proper, where it seems to be scarce, but also, and chiefly so, in the tributaries. 

 It goes rather far up in the smaller streams. From Pennsylvania it goes through 

 West Virginia and Ohio to Indiana and lUinois. Here it goes up into the Kankakee 

 River and to Will Co. (Baker, 1906), but is not in the "Chicago area." 



Records from the southern tributaries of the Ohio in Kentucky are scarce, 

 but it is in the upper Cumberland and its tributaries (Wilson & Clark, 1914), 

 and in the Tennessee to northern Alabama and eastern Tennessee, where it reaches, 

 in the Clinch and North Fork of the Holston River, into the state of Virginia. 



Farther to the west, it has been reported from the Mississippi River in Iowa 

 (Pratt, 1876; Witter, 1878; Marshall, 1895), but not farther north. Simpson 

 records it from eastern Nebraska, and it exists in eastern Kansas (Scammon, 1906), 

 and also, according to Simpson, in Oklahoma. However, there are no records 

 from Missouri (see Utterback, 1916) and Arkansas, and southward, and none from 

 the Alabama-drainage. 



T. triquetra has, however, crossed over into the lake-drainage, and it is found 

 in this drainage in Ohio (Sterki, 1907a), in southern Michigan (Walker, 1898), 

 and in Lake Erie (Walker, 1913). Here it goes eastward to the state of New York, 

 and the locality "New York" (Call, 1885; Simpson, 1900) is supported only by 

 definite records from Buffalo and Niagara River (see Marshall, 1895)."'^ 



As in Pennsylvania so elsewhere this species seems to prefer riffles, with rough 

 bottoms and strong currents. 



^'2 It might be in the upper Allegheny in New York, but, as has been said, I never found it in the 

 Allegheny above OO City. 



