ENTOMOSTRACA OF MINNESOTA. 57 
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Diaptomus wierzejskii Richard. 
PLATES VIII, Fia. 4; IX, Fie. 13. 
Richard ’88; De Guerne and Richard ’89. 
A rather large species which is obviously very near, if not a 
variety of D. serricornis. The caudal stylets equal the preceding seg- 
ment. The antenn do not exceed the second abdominal segment and 
in the male are armed as described above. The internal rami of the 
fifth feet of the female are one-jointed. The species has been encoun 
tered in Spain and Saxony. Length 2.75 mm. 
Diaptomus pectinicornis Wierzejski. 
PLATE X, Fie. 3. 
Wierzejski ’87; De Guerne and Richard ’89. 
This species can only be separated with difficulty from the other 
members of this section. Making some allowance for the different 
positions and distortions assumed under the microscope some diverg- 
ence is to be expected. The caudal stylets are a little longer than the 
preceding segment. Antennie reach to thestylets. The dentate plate 
on the antepenultimate segment of the right male antenna has about 
fifteen strong teeth on its distal half. 1.8 mm. long. 
* Diaptomus trybomi Lilljeborg. 
PLATES VIII, Fie. 17; 1X, Fie. 4; X, Fie. 13. 
De Guerne and Richard ’89. 
This is a very peculiar and easily distinguished species. It has 
but a few minute denticulations at the extremity of the appendage of 
the antepenult segment of the male antenna, but, in strictness, must 
fall into the present section. Rather small (1.5 mm.). The last tho- 
racic segment with a dorsal projection which extends toward the right 
side. The first abdominal segment in the female also has a large dor- 
sal process. ‘The caudal stylets areshort. The antennz almost reach 
the base of the stylets. The form of the feet may be gathered from 
the figures. Oregon. 
Diaptomus hireus Brady. 
PLATE XXXII, Fias. 6-8. 
Braay ’91. 
FEMALE.—Seen from above the body is widest in front, thence 
tapering backwards to the hinder end of the thorax, which is a little 
wider than the abdomen. The posterior thoracic angles are mucro- 
nate but not very strongly produced. The anterior antennz reach 
backwards as far as the posterior end of the thorax. Inner branch of 
