396 Annals of the Carnegie Museum. 



reddish-brown. Margins of rostrum generally purple. Tubercles of 

 chelae whitish or reddish. 



Desc7-iption. — Carapace compressed. Abdomen shorter than cara- 

 pace. Rostrum short, not very wide, triangular, margins convergent, 

 suddenly contracted to the triangular, short acumen ; lateral angles at 

 base of acumen not sharp, more or less rounded. Upper surface of 

 rostrum slightly concave. Postorbital ridges short, often indistinct, 

 without spines. No lateral spines on carapace, but sides slightly 

 granulated. Areola narrow, with one or two irregular rows of dots. 

 Suborbital angle indistinct, rounded. Anterior part of epistoma sub- 

 quadrangular. Anterior segment of telson with one spine on each 

 side. Antennae shorter than body, scale small. Large chela ovate, 

 surface punctate. Inner margin of hand serrated by a single row of 

 tubercles. Outer margin rounded and entire, without any serrations. 

 Fingers conical, slightly down-curved, gaping at base, with teeth at 

 their cutting edges. Outer margin of movable finger with deep pits, 

 but without tubercles. Carpopodite with a strong spine on the inner 

 margin, and a smaller spine proximally of it, and further, there are 

 two or three more spine-like tubercles on the lower inner side. Mero- 

 podite with the superior border almost smooth, only with one or two 

 indistinct distal tubercles. Lower side with a row of spines on inner 

 edge, outer edge smooth, with one single distal tubercle. Hooks on 

 third pair of legs of male ; shape of male copulatory organs of the type 

 of the third group. Color always with more or less brilliant blue, 

 tubercles of chelte whitish or reddish, finger tips reddish or orange. 



Largest male of the first form, from Gordons Valley, Edgewood Park, 

 Allegheny county, 67 mm. ; largest female from same locality, 76 mm. 

 (Another female from Monaca, Beaver county, has the same size. ) 



The above characters are constant. The blue color is very strik- 

 ing, and is always present on the anterior part of the body. Pos- 

 terior part of carapace and abdomen sometimes of a purplish hue, and 

 very often there is a blackish or brownish mud deposit on old shells. 

 Shape of rostrum very variable, but always narrower than in C. caro- 

 liuus, and with more convergent margins. The armature of the chelce 

 varies slightly with respect to the number of spine-like tubercles of 

 the carpopodite, but the spines are always more numerous than in C. 

 carolinus. 



This species is geographically entirely isolated from C. caroUmis, 

 and never found associated with it. The boundary between them is 



