North American Species of Diaptomus. 163 



in the female; upper posterior angle rather acute, lateral 

 angle very obtuse, the spines of both angles thick and short. 

 First abdominal segment slightly longer than the remainder of 

 the abdomen (sette excepted), produced anteriorly into a rather 

 large lateral process with spines pointing obliquely backward. 

 Second abdominal segment very short. Furcal rami short ; 

 sparsely hairy ; about one and a half times as long as broad. 



"First pair of antennae reach to the lateral processes of the 

 first abdominal segment; composed of 25 segments. Ante- 

 penultimate article of the prehensile antenna of the male 

 with a long curved and acuminate process almost surpassing 

 the end of the antenna. 



"Outer ramus of the first pair of feet, especially in the 

 female, pectinately setose. 



"Outer ramus of the fifth pair of feet in the female two- 

 segmented, the second segment with large unguiform process 

 within and heavily spined without. The inner ramus of this 

 foot rather long, clearly not reaching the end of the first seg- 

 ment of the outer ramus ; suture sharply indicated ; pro- 

 vided at the apex with two spine-like setfe and within with 

 minute spines. 



"Eight fifth foot of the male rather robust. Second basal 

 segment dilated within into a rugose lamella ; second segment 

 of the outer ramus with marginal spine placed near the apex. 

 Inner margin of terminal claw slightly sigmoid ; from the 

 middle toward the apex first delicately pectinately spined, 

 and thence tuberculate. Inner ramus small and indistinctly 

 two-segmented, extending slightly beyond the middle of the 

 second segment of the outer ramus ; armed at the apex with 

 a spine, and at the same place and within with thick cilia. 



"Left foot of the fifth pair of the male much smaller than 

 the right. Second or last segment of the outer ramus of this 

 foot with the apex narrowed but obtuse, and within this an 

 acuminate spine ; an emarginate narrow and hairy lamina 

 on the inner margin. Inner ramus slender, rather long, and 

 notably surpassing the middle of the second segment of the 

 outer ramus ; indistinctly two-segmented, the apex similar 

 to that of the right inner ramus. 



