68 GEOL. AND NAT. HIST. SURVEY OF MINNESOTA. 
two strong spines. The first segment of the abdomen is much longer 
than the entire remainder of the abdomen and bears a strong spine on 
either side anteriorly. The stylets are short and ciliated internally. 
The antennze reach to the end of the stylets. In the male the ante- 
penultimate segment bears a straight process directed distad and but 
slightly curved at the tip and shorter than the penultimate segment. 
The thickened portion of the geniculate antenna is very much modi- 
fied. The fifth foot of the female has an obscurely two-jointed inner 
ramus much shorter than the first joint of the outer ramus. The 
hook of the penultimate segment of the outer ramus is armed with a 
short series of sharp spines along the middle third of the inner aspect 
or rather nearer the base than the apex. There is a small spine at 
the base of the terminal segment, which is distinct and carries two 
long but unequal spines. The final joint or claw of the outer branch 
of right fifth foot of the male is very strong and gently curved, being 
longer than the whole leg. The accessory spine is also heavy and 
nearer the end than the base of the second segment, and is minutely 
denticulate near its base. The inner ramus of the right foot is one- 
jointed, very short, and slightly ciliate at the tip. The left leg 
reaches to the tip of the inner ramus of the right leg. Its terminal 
segment is of moderate size and ends in one immovable toothed spine 
and abristle; along itsinner aspect a ciliated lamina is situated. The 
preceding segment has a granular area along its inner aspect. The 
inner ramus resembles that of the right leg. 
* Diaptomus lintoni Forbes. 
PLATE V, Fia. 12. 
Forbes ’89. 
‘‘A large red species occurring commonly with D. shoshone, but 
distinguishable from it at a glance by its different shape, its longer 
antenne, its smaller size, and by characters derived from the right 
antenna and fifth foot of the male. The thorax is symmetrically ellip- 
tical in outline, broadest at the middle. The posterior angles are not 
produced nor bifid, but are each armed with a minute spine. The 
first segment of the abdomen of the female is not especially produced, 
but bears at its broadest part a minute spine on each side. The abdo- 
men itself is very short, its length contained about three and one-third 
times in that of the cephalothorax. The antenna of the female is long 
and slender, 25-jointed, reaching a little beyond the tip of the abdo- 
men. The fifth pair of legs in this sex is similar to those of D. sho- 
shone, but much smaller. The inner ramus is not jointed. It is longer 
than the basal joint of the outer ramus, bears two stout plumose sete 
at the tip, somewhat shorter than the ramus itself, and has also at its 
inner tip a patch of small spines or fine hairs. The second segment 
