Marsh—ISIorth American Species of Diaptomus. 423 
two segments, the third segment being represented by two 
spines. The second segment is prolonged into the customary 
hook, which is very finely denticulate on the inner margin. 
The endopodite slightly exceeds in length the first segment of 
the exopodite, is delicately hairy at the tip, and is armed with 
two rather short terminal spines. 
The first basal segments of the male fifth feet are armed with 
large spines. The second basal segments are rudely trapezoidal 
in form with the inner margins curved, and with the lateral 
hairs situated at about one-third the length of the segments from 
the distal ends; the segment of the right foot is considerably 
larger than that of the left. The first segment of the exopo¬ 
dite is quadrate, its length and breadth being nearly equal. It 
bears upon the outer distal angle a rounded hyaline lamella, 
and another rounded hyaline lamella projects on the posterior 
surface from the distal part of the segment ; this lamella pro¬ 
jects slightly over the second segment of the exopodite. The 
second segment is much shorter than the combined length of the 
first segment and the second basal segment. The lateral spine 
is situated at about three-fourths its length. The terminal hook 
is falciform, and about a third longer than the two segments of 
the exopodite. The endopodite is slender, hairy at the tip, and 
slightly exceeds in length the first segment of the exopodite. 
The two segments of the left exopodite are rudely oval in form, 
about equal in length. The inner margin of the terminal seg¬ 
ment and the distal third of the inner margin of the first seg¬ 
ment are ciliate. The second segment bears two short finger¬ 
like processes. The left endopodite is slender, reaching nearly 
half the length of the second segment, and is indistinctly two- 
segmented. 
Length of male, 1.195 mm. Not enough mature females 
were secured to get an average of lengths. 
This species was found in material collected by Mr. Russell 
T. Congdon in Glen lake, Saskatchewan. 
The noticeable peculiarities which distinguish this from other 
forms are the elongated female abdomen, without lateral spines, 
and the hyaline lamellae of the first segment of the exopodite 
of the right male fifth foot. 
