Marsh—North American Species of Diaptomus. 459 
The antennae are 2 5-segmented, and extend a little beyond 
the furcal 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 armed 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 inner 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- 
dite. The lateral spine is situated at the end of the second 
third of the segment. 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 
fiistal end of the segment is setose, and armed with two finger- 
