Cay ae 
Te ise oe 
1(92 GEOL. AND NAT. HIST. SURVEY OF MINNESOTA. 
feet. Theinner ramus of the right fifth foot of the male is slender and 
longer than in sanguineus; this is also true of the inner ramus of the 
left foot. The terminal segment of the outer ramus is provided with 
the same armature as sanguineus and also bears a ciliated plate along 
its inner aspect. The terminal claw of the right leg is toothed. In 
the female the inner ramus is more or less distinetly two-jointed and 
the claw of the outer ramus is toothed. Length of male 1.4 mm. 
Color dark. In the long antenn the species differs from sanguineus, 
which it resembles in the armature of the last thoracic and first ab- 
dominal segment. 
* Diaptomus armatus Herrick. 
Herrick ’82 and 84; De Guerne and Richard ’89. 
The form, which was indicated by only a few points, in the hope 
that it might be subsequently rerecognized, has never again been seen. 
It appears to be allied to sanguineus. The antennz are said to be 
shorter than the body, the caudal stylets narrow, the right male an- 
tenna has a hook upon its antepenultimate joint and is strongly gen- 
iculate. But the one feature which may determine the species is the 
existence of a tooth or spur near the base of the claw of the right fifth 
foot of the male. 
* Diaptomus oregonensis Lilljeborg. 
PLATES IV, Fias. 7-12; 1X, Fie. 3. 
De Guerne and Richard ’89; Marsh ’93. 
This species has been found only in Lake Minnetonka within the 
limits of Minnesota, though Marsh speaks of it as occurring in Wis- 
consin very generally in the smaller lakes. It was first found near 
Portland, Oregon, by Trybom. 
The species is of medium size (1.5 mm. long) and rather graceful 
habit. The antennie extend beyond the caudal stylets and are 
strongly spined. The last two thoracic segments are confluent, and 
bear ope or two small spines laterally. The first segment of the ab- 
domen is as long as the remainder and mucronate. The caudal stylets 
are nearly twice as long as wide. The right male antenna is moder- 
ately modified, its antepenultimate segment being unarmed. The 
apical segmentof the outer ramus of the fifth pair of feet in the female 
is obsolescent with two sharp spines. The claw of the penultimate 
segment is short and slightly curved; the inner rami are one-jointed 
and armed with two large spines and fine bristles apically. The fifth 
feet of the male are sub-equal, the terminal claw of the right foot being 
geniculately curved and rather long. The accessory spine is near the 
end of the preceding segment which also bears a small spine near the 
middle. The inner ramus of the right foot reaches to the spine just 
