Marsh—North American Species of Diaptomus. 439 
The second segment is prolonged into the usual hook, which 
is denticulate on the imier margin. The endopodite equals 
the length of the first segment of the exopodite, and the tip is 
armed with hairs and the two terminal spines. 
The fifth feet of the male are slender, and the left foot 
reaches the distal end of the first segment of the right exopo¬ 
dite. The first basal segments are armed with rather large 
spines. The second basal segment of the right foot has the 
lateral hair situated at about two-thirds of its length. The 
length of this segment is about twice its width; it bears upon 
the distal half of its inner margin a thin hyaline lamella, quad¬ 
rangular in form. This projects rather from the posterior 
surface than immediately from the inner margin. The second 
segment of the exopodite is about twice the length of the first 
segment. It bears a small spine on its inner margin at about 
one-third of its length. The lateral spine is small, curved, 
and situated at about two-thirds of its length. The terminal 
hook is falciform, symmetrically curved, and nearly equals in 
length the rest of the foot. The right endopodite is small 
and slender, and reaches about one-lialf the length of the first 
segment of the exopodite. It is armed at the tip with minute 
hairs. The lateral hair of the second basal segment of the 
left foot is situated near the dhtal end of the segment. The two 
segments of the exopodite are about equal in length and are 
oval in form. The first segment is setose on its inner margin. 
The second segment is swollen at the base on its inner margin 
into a cushion which is setose. The tip is setose and armed 
with two short finger-like processes. The endopodite is very 
slender, reaches about one-half the length of the second segment 
of the exopodite, and is hairy at the tip. 
The above description is like that of Lilljeborg with a few 
corrections and additions. In his description he states that 
there is a hyaline appendage of the first segment of the ex¬ 
opodite of the male fifth foot that is “somewhat dilated.” In 
his figure this appendage is made somewhat triangular in 
form. In all the specimens I have seen, the appendage has 
been distinctly quadrangular as I have figured it. I have not 
