The Crawfishes of Western Pennsylvania. 393 



section of the state (Washington, Greene, Westmoreland, Fayette, and 

 Somerset counties). 



C. bartoni robiistus attains a very large size, even larger than the 

 typical form. The largest male of the first form is from Albion, Erie 

 county : 94 mm.; a male of the second form from the same place is 

 95 mm. The largest female is from Squaw Run, Allegheny county, 

 and measures 94 mm. Hagen gives 3.2 in. = 81 mm., and Faxon 

 86 mm. 



2. Cambarus carolinus Erichson. The Red Crawfish. 



As Hay (Proc. Biol. Soc. Washington, 15, 1902, p. 38) has 

 pointed out, C. carolinus Erichson is identical with C. diihhis 

 Faxon. 



This species is easily recognized in the field by its color. It is 

 of a vivid red, chiefly so on the anterior part of the carapace and on 

 the chelae, the color being hardly subject to any variation, except that 

 it is more brilliant in newly molted individuals. But even in old 

 shells, the bright brick-red of the anterior part of the body is very 

 striking. The sides and abdomen possess often a more or less brownish 

 (leather-brown) tint, and frequently old shells are covered by a black 

 or brown coat of dirt, but even then the chelse and parts of the cara- 

 pace remain clean and red. 



The morphological characters of this species have been well brought 

 out by Faxon (1885, as C. dttbiits). The compressed shape of the 

 carapace is similar to the following species, while in the wide rostrum 

 it resembles C. bartoni. In the shape and the armature of the chelae, 

 aside from the shape of the rostrum, are found the chief differences from 

 C. monongalensis : in C. carolinus the outer margin of the hand is ser- 

 rated, this serration being produced by a series of pits (punctations) 

 forming a regular longitudinal row along this margin. The carpopo- 

 dite of the chela has a single strong spine on the inner side, all other 

 spines on this side being absent. Lower side of meropodite of the 

 chelipeds armed with two rows of spines, the inner row being longer 

 consisting of about 6 spines, the outer one being shorter, and consist- 

 ing of only 3 or 4 spines. 



There is some variation in the shape of the rostrum. Pennsylvania 

 (and Maryland) specimens never have the rostrum as wide as in 

 Faxon's figure (1. c, pi. 4, fig. 3), and generally the margins con- 

 verge a little. But there are specimens in which they are "subparal- 



