250 



MEMOIRS OF THE CARNEGIE MUSEUM. 



species, while the lake-environment suits it better. Otherwise there is no difference 

 between the two forms, except that the form from the Ohio river has on the average 

 a somewhat thicker shell and that the lake-form has a stronger tendency to pre- 



serve the wings in old shells. 

 more or less inconstant. 



Fig. 26. 

 • Paraptera fragilis. 

 + Proptera alata. 



But all these peculiarities due to environment are 



Localities in Pennsylvania, represented in the Carnegie Museum: 



Ohio River, Smiths Ferry, Cooks Ferry, Industry, and Beaver, Beaver Co.; Dead Man's Island (Q. T. 



Shafer, A. T. Shafer, R. Foerster), and Edgeworth (G. H. Clapp), Allegheny Co. 

 Allegheny River, Aladdin, Godfrey, and Kelly, Armstrong Co. 

 Monongahela River, Westmoreland Co. (G. A. Ehrmann). 

 Lake Erie, Presque Isle Bay, Erie, Erie Co. 



Other localities represented in the Carnegie Museum: 



Lake-drainage: 

 Lake Erie, Vermilion (C. Goodrich) and Cedar Point (C. Brookover), Erie Co., Ohio; La Plaisance Bay, 

 Monroe Co., Micliigan (C. Goodrich). 



Ohio-drainage: 

 Ohio River, Toronto, Jefferson Co., Oliio; Wheeling, Ohio Co., West Virginia (W. F. Graham); St. 



Marys, Pleasants Co., West Virginia; Parkersburg, Wood Co., West Virginia; Portland, Meigs 



Co., Ohio; Portsmouth, Scioto Co., Ohio. 

 West Fork White River, Riverside, Greene Co., Indiana (J. D. Haseman). 

 Little Kanawha River, Burnsville, Braxton Co., West Virginia. 

 Pocatalico River, Raymond City, Putnam Co., West Virginia. 



