12 MEMOIRS OF THE CARNEGIE MUSEUM. 



the color becomes more uniformly brown, and sometimes blackish. All other 

 characters are like those of the main form. 



L. H. D. Pr.ct. 



Size: Clarksville, Cat. No. 61.3927. .133 mm. 97 mm. 48 mm. .36 (largest at hand). 

 Cochranton, Cat. No. 61.3923.128 " 111 " 51 " .40 



These specimens are superior in size to the largest F. siibrotunda. 



The soft parts and glochidia have been described and figured by Ortmann 

 (19116, PL 89, fig. 1, and 1912, p. 245). 



Breeding season: The only gravid female ever found was obtained on August 2, 

 1908; it had glochidia. Among individuals collected June 25, 1907, and July 10 

 and 19, 1909, none were gravid, although a good many were obtained. This is 

 rather astonishing. The one gravid specimen was the only one among a large 

 number. Many have been collected later in the season, but no other gravid female 

 has ever turned up. 



Remarks: This form passes very gradually into F. suhrotunda, and is positively 

 recognized only by the compression of the shell. In order to distinguish these 

 two forms I was compelled to introduce an artificial and arbitrary dividing line 

 at the diameter of fifty percent of the length. Of course, this does not correspond 

 to the natural conditions, but it is a wonderful help for the practical separation of 

 the forms. 



The other characters are also not reliable, although generally the color and 

 the development of a posterior wing help in the identification. 



The soft parts in kirtlandiana are more frequently of the whitish type, although 

 the orange type is not rare. 



In this form it is likewise impossible to distinguish males and females by the 

 shell. 



Localities in Pennsylvania represented in the Carnegie Museum: 



Ohio River, Indu.stry, Beaver (^o.; Coraopolis (S. N. Rhoads) and Neville Island, Allegheny Co. (W. F. 



Graham). 

 Beaver River, Wampum, Lawrence Co. (G. H. Clapp & H. H. Smith). 

 Mahoning River, Mahoningtown, Coverts, Ediuburg, Lawrence Co. 



Shenango River, Harbor Bridge and Pulaski, Lawrence Co.; Sharpsville and Clarksville, Mercer Co. 

 Pymatuning Creek, Pj-matuning Township, Mercer Co. 



Allegheny River, Natrona, Allegheny Co.; Godfrey, Johnetta, Kelly, and Templeton, Armstrong Co. 

 French Creek, Utica, Venango Co.; Cochranton, Meadville, and Cambridge Springs, Cra^vford Co. 

 Conneaut Outlet, Conneautlake, Crawford Co. 

 Monongahela River, Charleroi, Washington Co. (G. A. Ehrmann). 

 Cheat River, Cheat Haven, Fayette Co. 



