North American Species of DicH'ioinus. 145 



curved, but with a sharp angle at the beginning of the distal 

 third ; miiuitely denticulate within. 



Inner ramus of right fifth foot one-segmented, slender, 

 narrowing gradually from base to tip, extending but slightly 

 beyond the proximal third of the second segment of the outer 

 ramus ; hairy at the apex and very delicately denticulate on 

 the outer margin. 



Basal segments of left fifth foot subquadrate, the second 

 slightly longer than the first and both slightly longer than 

 broad; second segment delicately tuberculate on the inner 

 margin. First segment of outer ramus about half as wide 

 and three fourths as long as the basal segment. Second seg- 

 ment about as long as the first, and very similar to the cor- 

 responding segment of D. sicilis Forbes, from which it differs, 

 however, in its armature. This consists of a movable claw, 

 blunt or slightly thickened at the tip, forming a forcipate 

 structure with an inner cushion-like process. The claw 

 usually lies close against this and is difficult to make out. 

 It is hairy on both margins. 



Inner ramus of the left fifth foot one-segmented, hairy at 

 the apex and delicately denticulate on the outer margin, 

 extending to the end of the first segment of the outer ramus 

 or slightly beyond it. 



Second basal segment of the fifth foot of the female with 

 the usual hair at the outer distal angle. First segment of the 

 outer ramus subquadrate, about twice as long as broad. 

 Second segment about as long as the first, tapering to a blunt 

 point ; inner margin denticulate. Third segment wanting, 

 represented by two spines, the inner about twice as long as 

 the outer and smooth, while the outer is delicately hairy. 



Inner ramus of fifth foot of female one-segmented, reach- 

 ing the end of the first segment of the outer ramus ; hairy at 

 the apex and within, and armed at the tip with two long sub- 

 equal delicately hairy spines. 



I have found specimens from the Illinois River at Havana 

 with the inner ramus of the right fifth foot reaching barely 

 beyond the end of the first segment of the outer ramus. The 

 first basal segment of the left foot of the male is provided with 



