Marsh — North American Species of Diaptomus. 427 



anterior part, and is armed witli hxo very minute spines. The 

 second segment is much shorter than the third, and the two are 

 sometimes only indistinctly separated. The fnrcal rami are 

 about equal in length to the third segment; they are twice as 

 long as broad. The setae are unusually long. 



The antennae are 25-segmented, and reach beyond the end of 

 the furca. The right antenna of the male is swollen anterior 

 to the geniculating joint, but not markedly so; the antepenul- 

 timate segment bears a long, slender process, slightly curved at 

 the end, which reaches, sometimes, almost to the end of the last 

 segment. The setae of the swimming feet are unusually long. 



The spines of the first basal segments of the female fifth feet 

 are rather small. The lateral hair of the second basal segment 

 is of moderate length. The first segTiient of the exopodite is 

 slender, its length being considerably more than twice its width. 

 The hook of the second segment is only slightly curved, and is 

 finely denticulate on the inner margin. There is a short spine 

 on the outer distal angle. The third segment is rudimentary, 

 not completely separated from the second. It is armed with two 

 spines, of which the inner is the longer. The endopodite is 

 acuminate, very suuill and rudimentary. 



The spines of the first basal segments of the male fifth feet 

 are small. The second basal segment of the right foot is quad- 

 rate, longer than broad. The lateral hair is situated at the be- 

 ginning of the distal third. The first segment of the right ex- 

 opodite is of the same form and size as the second basal seg- 

 ment. The second segment is twice as long as the first. The 

 lateral spine is small and situated proximad of the middle. The 

 terminal hook is short, thick, symmetrically curved, and slightly 

 denticulate on the inner margin. Its length is somewhat less 

 than that of the rest of the exopodite. The endopodite is very 

 small and rudimentary. The second basal segment of the left 

 foot is quadrate, and much wider than long. The lateral hair 

 is situated well towards the distal end. The first segment of 

 the exopodite is longer than wide, its inner and outer margins 

 are convex, and it^^ distal cud is only about one-half as wide as 

 the proximal. It is setose on its inner margin. The second 



