CAMBARUS. 89 



According to Mr. P. R. Uhler, C. iiffinis is the common form in the warmer 

 parts of the rivers and creeks of Maryland, underneath stones. In his col- 

 lection are specimens from Montgomery Co., labelled as found in " stagnant 

 pools," and specimens from Alleghany Co., four miles below Cumberland, 

 ■were taken from " holes in the bottom and sides of a canal." 



A female alcoholic siDCcimen of C. affinis in the Academy of Natural Sci- 

 ences of Philadelphia is labelled " Santo Domingo, W. M. Gabb." The locality 

 is doubtless erroneous. 



In young specimens of C affiids the lateral thoracic spine on the cervi- 

 cal groove is single, and the spinules of the hepatic region are reduced to 

 a mere granulation. Very small individuals closely resemble small exam- 

 ples of C. projnnqims, as Hagen observes. The body, however, in the young 

 C. affinis is more pubescent, the rostrum is not cai'inated, and the hand is 

 differently shaped. The specimens in the Museum of Comparative ZoiJlogy 

 from Niagara, referred to C. affinis by Hagen, are all very young (the largest 

 measuring If in.), but I think there is no doubt of the cori-ectness of the 

 determination. 



C. affinis is the common crayfish exposed to sale in the markets of New 

 York and other Eastern cities. 



37. Cambarus Sloanii. 



Plate IV. fis. 5, Plate X. figs. 1. 1 , 1 a, 1 a'. 



Cambarus Sloanii, Bundy, Bull. 111. Mus. Nat. Hist., No. I. p. 24, 1S76. — Proc. Acad. Nat. Sci. Pbila., 



1877, p. 172. 

 Cambarus Sloanii, Faxon, Proc. Amer. Acad. Arts and Sci., XX. 147, 1884. 



Male, form I. — Eostrum wide, subexcavated, plane towards the tip, 

 margins nearly parallel, acumen long, triangular; lateral teeth small in full- 

 grown specimens, in some individuals reduced to an angle merely. Post- 

 orbital ridges with very small anterior spines, or none. Carapace flattened 

 above, punctate, lightly granulate on the sides, lateral spines acute, ante- 

 rior border distinctly angulated, areola wide. Basal .segment of telson two- 

 spined on each side. Antennal scale a little longer than the rostrum, of 

 moderate width. Anterior process of epistoma broad, excavated, emarginate 

 in front. Third pair of maxillipeds hairy within, naked below. Chela short, 

 broad, inner margin with a double series of depi'essed teeth ; outer finger 

 wide at base, furrowed above near the outer and inner margins ; inner finger 



12 



