Marsh—North American Species of Diaptorrms. 463 
The fifth feet of the male are slender. The first basal seg¬ 
ments are armed with the customary spines. The second basal 
segment of the right foot is trapezoidal in form and longer than 
broad. The rather long lateral hair is situated at about two- 
thirds of its length. The first segment of the exopodite is 
quadrate, its length considerably less than its width. The 
length of the second segment is somewhat greater than the 
combined lengths of the second basal regment and the first 
segment of the exopodite. The lateral spine is situated beyond 
the middle of the segment. The terminal hook is symmetri¬ 
cally curved and is considerably longer than the first two seg¬ 
ments of the exopodite. The endopodite is triangular in form, 
much longer than the first segment of the exopodite, and is 
sometimes indistinctly two-segmented. 
The second basal segment of the exopodite of the fifth foot 
of the male has its rather long lateral hair situated almost at 
the distal angle of the segment. The first segment of the ex¬ 
opodite is about as long as broad, its inner and outer margins 
curved, the inner margin setose on its distal third. The second 
segment is half again as long as broad, the inner margin ex¬ 
panded at the base and at the distal end and setose. The dis¬ 
tal end is setose and armed with two finger-like processes. The 
endopodite is slender, reaches well towards the tip of the 
second segment of the exopodite, and is setose at the tip. 
Length of female, about 1.187 mm. Length of male, about 
1.137 mm. 
This species was found in material collected for me by Pro¬ 
fessor B. H. Brown in Walla Walla, Washington. 
The close relation of this form to D. signicauda is apparent. 
In the female there are distinctive differences. In the male, 
however, the structure of the antepenultimate segment of the 
right antenna and of the fifth foot are so different that I think 
the validity of the species cannot be questioned. The lateral 
lamella of the antennal segment I have never found in D. sig¬ 
nicauda, while it is characteristic of D. washingtonensis. The 
whole male fifth foot is much shorter and stouter in D. wash- 
ingtonensis, the first segment of the right exopodite has no hya- 
