North American Species of Diaptomus. 131 



long setae; and 25, four long set 33 and a sense-hair. Some 

 of the setae on the last segments are sparsely hairy. 



Second basal segment of the right fifth leg of the male sub- 

 quadrate, about twice as long as wide ; a delicate hair at the 

 outer margin a short distance above the distal angle. First 

 segment of the outer ramus somewhat narrower than the 

 second basal segment, about twice as long as wide; sec- 

 ond segment very long and narrow, about three times as 

 long as wide. Marginal spine slender, about one third the 

 length of the segment, inserted about half its length above 

 the outer distal angle of the segment. Terminal hook slender, 

 regularly curved, about as long as the preceding segment; 

 distal half of inner margin denticulate. 



Inner ramus of right fifth foot one-segmented, reaching 

 almost to the end of the first segment of the outer ramus ; 

 apex broadly triangular and minutely hairy. 



Second basal segment of the left leg of the male subquad- 

 rate, slightly broader than long ; provided with a delicate hair 

 a short distance above the outer apical angle. First segment 

 of the outer ramus irregular in form, about one and a half 

 times as long as broad, with two rounded protuberances, the 

 one forming the inner apical angle delicately hairy. Second 

 segment long and narrow, almost as long as the preceding 

 segment and a fourth as wide as long; delicately hairy 

 at the inner margin ; armed at the apex with a short, thick, 

 blunt digitiform process, and a long curved spine as long as 

 the segment itself and hairy at the inner jnargin. 



Inner ramus of left fifth leg long and narrow, extending 

 beyond the middle of the second segment of the outer ramus ; 

 margins sinuous ; apex triangular, hairy. 



Second basal segment of the fifth pair of feet in the female 

 with the usual marginal hair. First segment of the outer 

 ramus subquadrate, about twice as long as wide ; second seg- 

 ment narrow, about as long as the first, tapering to a rather 

 blunt point, finely dentate on the inner margin and with a 

 single tooth on the outer, opposite the last tooth on the inner 

 margin; third segment small but distinct, armed with two 

 short sharp spines, the inner slightly longer than the outer. 



