Marsh—JSJorth American Species of Diaptomus . 465 
than broad. The lateral hair is situated at about two-thirds 
of its length and is rather long. The first segment of the ex- 
opodite is trapezoidal in form, and its length and width are 
about equal. It bears a thin hyaline lamella resembling that 
in signicauda, but it is more pointed at the distal end. This 
hyaline lamella is not inserted on the inner margin, but on the 
posterior surface, so that as viewed from some directions only 
the distal end is visible, although it really extends the whole 
length of the segment. The second segment of the exopodite 
is somewhat shorter than the combined lengths of the first seg¬ 
ment and the second basal segment. The lateral spine is sit¬ 
uated proximad of the middle of the segment. The terminal 
hook is symmetrically curved, and is somewhat longer than the 
two segments of the exopodite. The endopodite is broad, acu¬ 
minate, nearly equaling in length the first segment of the exo¬ 
podite. The second basal segment of the left fifth foot of the 
male has the rather long lateral hair situated almost at the 
distal angle of the segment. The first segment of the exopodite 
is slightly longer than broad, has its inner and outer margins 
curved, and is setose on the distal third of its inner margin. 
The second segment is nearly three times as long as broad, and 
has the inner margin expanded near the base and setose. It 
terminates in two finger-like processes, one of which is much 
larger than the other. The endopodite is long and slender, 
reaching two-thirds the length of the second segment of the 
exopodite. 
Length of female, 0.93 mm. Length of male, 0.9 mm. 
This form was found in material collected by Mr. Chauncey 
Juday in Twin lakes, Colorado, and the name is given in rec¬ 
ognition of the many collections which Mr. Juday has had 
the kindness to send to me. The species in most respects 
bears a very close resemblance to D. signicauda. The male 
fifth foot differs in the proportions of the segments, the form 
of the lamella of the first segment of the right exopodite, the 
position of the lateral spine on the second segment of the same 
exopodite, and in the form of the segment and the terminal 
processes of the second segment of the left exopodite. The 
30—'S. & A. 
