158 MEMOIRS OF THE CARNEGIE MUSEUM. 



and into the mountains, farthest in the Susquehanna, where it ascends to Cambria 

 Co., west of the Allegheny Front. Here it is closest to the divide, and it is inter- 

 esting to note, that on the other side in the Ohio-drainage of Indiana and West- 

 moreland Counties, the creek- and pond-forms of A. grandis turn up. 



I collected the pond-form in rather small (artificial) ponds, with very muddy 

 bottoms, and also, but more rarely, in quiet pools in creeks. I obtained the 

 creek-form most commonly, but it is rather erratic in distribution. It seems to 

 avoid the larger rivers (although found under special conditions in the estuary of 

 the Delaware). It favors smaller rivers (Chemung) and creeks. Here it lives on 

 gravelly bottoms, in more or less strongly flowing water (even in riffles), or in more 

 quiet pools in gravel, sand, or mud. The short and high form (tryoni-iype) seems 

 to prefer large rivers with muddy bottoms, but I have not observed it often enough 

 to express a final opinion. 



Probably this species has a more general distribution in eastern Pennsylvania, 

 and the pond-form might especially be found in many other ponds (and lakes): 

 these localities, however, are often not easily accessible, and it is hard to locate 

 this shell in them. 



General distribution: Type locality, not given by Say, but probably is eastern 

 Pennsylvania. 



Simpson (1900) reports this species from "Lower St. Lawrence-drainage; 

 streams draining into the Atlantic south to North Carolina." 



In the St. Lawrence-drainage, it has been reported from Lake Ontario (Hamil- 

 ton Bay, Marshafl, 1895, and Toronto, Latchford, 1914), and this is confirmed by a 

 specimen in the Carnegie Museum. Farther down it is known from various points 

 along the St. Lawrence, and also from the Lake Ontario-drainage in western New 

 York. But there is some doubt whether aU the records given by Marshafl (1895) 

 from this section actually refer to this species. At any rate two of these records: 

 Buffalo Creek in Erie Co. (to Lake Erie), and Ischua Creek, Cattaraugus Co. (to 

 Allegheny River) appear to me very doubtful, and should be confirmed. In this 

 region, indeed, it seems, that the ranges of A. grandis and A. catarada overlap, 

 and on account of the great resemblance of these two species, it is quite possible, 

 that some of the identifications are not correct. This question deserves special 

 study. 



On the Atlantic side this species goes northward to Maine, as is shown by 

 one of our localities, and it has been reported by Jackson (1908) North Haven 

 Island, Knox Co. and Lermond (1909) Cumberland Co. Walker & Coofldge 

 (1908) give it from Keene, Cheshire Co., New Hampshire, Adams (1842) from 



