Marsh — North American Species of Diaptomus. 459 



The antennae are 25-segmented, and extend a little beyond 

 the fureal rami. The antepenultimate segment of the right 

 male antenna is armed with a small recurved hook. 



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

 armed with rather large spines. The lateral hair of the second 

 basal segment is short and weak. The exopodite is composed 

 of two segments, the third segment being represented by two 

 small spines. The second segment is prolonged into a rather 

 stout hook which is delicately denticulate on the inner margin. 

 The endopodite is slightly longer than the first segment of the 

 exopodite, is composed of one segment, armed on the inner 

 margin of the tip with hairs, and with two rather long terminal 

 spines. The terminal spines are delicately ciliate. 



The fifth feet of the male are rather slender. The first ba- 

 sal segments are aimed with the customary spines. The second 

 basal segment of the right foot is trapezoidal in form, and 

 somewhat longer than broad. The lateral hair is situated at 

 about two-thirds of its length. The first segment of the ex- 

 opodite is also trapezoidal in form, of about half the length of 

 the second basal segment, and is armed on its iuner border with 

 a hyaline lamella which is widened at the distal end and ex- 

 tends beyond the distal angle of the segment. The second 

 segment of the exopodite about equals the combined lengths of 

 the second basal segment and the first segment of the exopo- 

 <iite. The lateral spine is situated at the end of the second 

 third of the segmient. The terminal hook is symmetrically 

 curved, and is somewhat longer than the two segments of the 

 exopodite. The endopodite is broad, acuminate, and shorter 

 than the first segment of the exopodite. 



The second basal segment of the left fifth foot of the male 

 has its lateral hair situated almost at the distal angle of the 

 segment. The first segment of the exopodite is longer than 

 broad, its inner and outer margins are curved, and it is setose 

 on the distal third of its inner margin. The second segment 

 of the exopodite is twice as long as wide, the inner margin ex- 

 panded both at the base and at the distal end, and setose. The 

 distal end of the seoment is setose, and armed with two finger- 



