376 CRAYFISHES. 



tubercles on its surface; the inner border of the hand is furnished with squamoid 

 tubercles disposed for the most in two longitudinal rows; along the distal half 

 of the outer border of the hand there runs a low, but well-marked, carina; the 

 dactylus is tuberculate on its free border, bkmt-toothed (like the immobile finger) 

 along its prehensile edge and ridged longitudinally along its outer face; the 

 carpus is armed with an acute spine on the middle of its internal border, and with 

 a small tubercle at each end of the same border; belo^y, the median carpal spine 

 is well pronounced and there is a small acute spine at the inferior point of articu- 

 lation with the propodus; the two customary spines are present near the anterior 

 end of the upper margin of the merus ; the outer of the two rows of spines on the 

 lower face of the merus is reduced to two at the distal end. The dorsal carina of 

 the inner branch of the last abdominal appendages terminates in a tooth a little 

 distance within the hind margin. 



The gonopods, in the second form of the male, are long and straight, reaching 

 forward, when the abdomen is flexed, as far as the basal segments of the second 

 pair of legs; their rami are rather thick, blunt at the tip, and the outer one is 

 but a trifle longer than the inner one; when viewed from the inner side the two 

 rami are fused up to within a short distance of the end of the organ. 



The annulus ventralis of the female is bituberculate in front, unituberculate 

 behind, the anterior and posterior walls being separated by a transverse fossa 

 which is divided longitudinally by tlie sigmoid fissure. 



Dimensions of a female: — length, 73 mm., length of carapace, 37 mm., 

 length of rostrum from tiji to a level with tlie post-orbital spines, 11 mm., width 

 of rostrum at base, 5 nmi., length of areola, 12 mm., width of areola, 2 mm., length 

 of cheliped, 54.5 mm., length of chela, 27.5 mm., lireadth of chela, 12 mm., length 

 of dactylus, 16 imn. 



This crayfish is closely related to the Cambarus spinosus of Bundy, but is 

 different in the following respects: — the body is more villous, the metacarapace 

 longer in proportion to the procarapace, the anterior process of the epistome 

 is much narrower than in the types of Bundy's species and (what has most 

 weight in regarding it as a subspecies) the external sexual organs are clearly 

 different. The gonopods in C. s. gulielmi being shorter, the rami thicker, blunter, 

 nearly equal in length, and separate for but a short distance from the tip, while 

 in C. spinosus the rami are slender, pointed, the outer one exceeding the inner 

 by a great distance and the split between the two parts involving a large part 

 of the length of the organ. The annulus ventralis of the female, though of the 

 same type as that of the typical C. spinosus, differs slightly in having a more open 

 transverse fossa. 



