252 MEMOIRS OF THE CARNEGIE MUSEUM. 



P. fragilis has an immense range, extending from central Texas (Singley, 1893) 

 north to the Red River of the North, and east and northeast over the whole Missis- 

 sippi and Ohio drainages, crossing over into the lake-drainage in Wisconsin, Ohio, 

 and Michigan, and going down the St. Lawrence to the Ottawa River (Call, 1885). 

 In this latter region it has extended also into Lake Champlain, and from western 

 New York (Marshall, 1895) through the Erie canal has reached the Hudson River, 

 thus entering the Atlantic watershed. Li addition it is found in the Alabama and 

 Tombigbee drainages in Mississippi and Alabama (Lea, Obs. X, 1863; Conrad, 

 1836; Marshall, 1895). The latter part of the range is not given by Simpson. 



It is not necessary to mention particular localities, but the western and south- 

 western boundaries, and also the northern boundaries, are rather indefinitely 

 known. The records from Kentucky and Tennessee were meagre hitherto, but 

 the species is present in the Cumberland (Wilson & Clark, 1914) and I found it 

 frequently in the upper Tennessee-drainage. 



The ecological preferences of this species seem to be for large rivers and lakes, 

 and it avoids smaller rivers and creeks. Its absence from the Tuscarawas River 

 in Ohio, according to Sterki (1907a) and from the Beaver in Permsylvania should 

 be noted. Where I found it in small streams, it was generally in eddies and pools. 

 But, as has been stated, it occurs also on riffles, but possibly it has been in such 

 cases washed out of the ' deeper and more quiet pools. Previous authors have 

 made similar observations (Call, 1895, 1900; Baker, 1898a; Scammon, 1906). 



Genus Proptera Rafinesque (1819).'" 

 Ortmann, 1912, p. 332; Simpson, 1914, p. 161 (as subgenus of Lampsilis). 



Type Unio alata Say. 

 Only one species in Pennsylvania. 



Proptera alata (Say) (1817).!'^^ 

 Lampsilis alata (Say) Simpson, 1914, p. 162. 



Plate XV, fig. 7; Plate XVI, figs. 1, 2. 

 Records from Pennsylvania: 



Ham, 1891 (western Pennsylvania). 



Stupakoff, 1894 (Allegheny Co.). 



? Marshall, 1895 (Allegheny River, Warren Co.).i='' 



'" Tliis is the only one of the names proposed by Rafinesque in 1819, which has been properly 

 ■ defined. The alate character of the shell has been mentioned, and a type (alata) has been given. 

 158 Not 181G. 

 ^^^ I have never seen a trace of this shell above Oil City, although it is not easily overlooked, and 



