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GEOL. AND NAT. HIST. SURVEY OF MINNESOTA. 
Diaptomus gracilis Sars. 
PLATE IX, Fia. 1. 
Sars ’64; Gruber ’78; Rehberg ’80!; Daday ’85°; De Guerne and Richard ’89. 
This very widely distributed species is scarcely over 1.0 mm. long 
and very slender. The antenne are much longer than the whole 
body. The stylets are short, and the first segments of the abdomen are 
armed with strong spines. The inner rami of the fifth feet are one- 
jointed in both sexes, in the female shorter than the basal segment of 
the outer ramus. The apical joint of the outer ramus is well- 
developed and bears two spines, one of which is as long as the claw. 
The inner ramus of the right foot of the male is very long, reaching 
nearly to the base of the claw. There is a curious, conical, ciliated 
process from the inner aspect of the outer ramus of the left foot. 
Diaptomus orientalis Brady. 
PLATE) X, FIG. 5. 
Brady ’86; De Guerne and Richard ’89. 
There seems to be some doubt whether the various collections from 
Ceylon and Australia really pertain to the same species. 
The last thoracic segment is rounded and armed with short spines, 
as is the first abdominal. The second abdominal segment is very 
short. The caudal stylets are short, with long sete. The antenne 
reach the stylets. The antepenultimate segment of the male antenna 
bears a long hook. The terminal segment of the outer rami is distinet 
(not so figured by Sars), the inner ramus as long as the basal segment 
of the outer. Inner rami of male fifth feet very short and one-jointed. 
Length 1.3 mm. 
* Diaptomus stagnalis Forbes. 
PLATES III; XIII, Fias. 11, 13. 
Forbes ’82; Herrick ’82 (D. giganteus), and 194: De Guerne and Richard ’89. 
This species was described by Professor Forbes and the writer at 
almost the same time,, but as the former’s description appeared in a 
periodical it was more promptly distributed and deserves priority. 
A very large species, resembling D. castor, the place of which it 
takes in America. Greatest width in front of the middle. The an- 
tenn scarcely extend beyond the thorax. The first segment of the 
thorax is separated by a suture, as is the last, which is greatly pro- 
duced laterally and bears two spines. The first abdominal segment is 
much longer than the rest of the abdomen. The caudal stylets are 
very short and broad, divaricate, and ciliated externally. The caudal 
setee are large, short and profusely plumose. The egg sac is large and 
spherical. In the male the abdomen is slender and five-jointed. The 
five joints preceding the hinge of the right male antenna are very 
