Cyclops. 
203 
Cephalothorax oval, the first segment being about half its 
total length. Antennae 17-jointed, about as long as first ceph¬ 
alothoracic segment. Abdomen rather slender, the last seg¬ 
ment armed on its posterior border with small spines. All the 
abdominal segments in immature individuals are strongly 
pectinated posteriorly. Furca about three times as long as its 
average breadth, the lateral spine situated well towards the 
end. The first and fourth terminal setae are short, slender and 
plumose, nearly equal in length. Of the internal setae, the 
outer is a little more than three-fourths the length of th^e inner. 
The armature of the terminal joints of the swimming feet is 
as follows: 
FIRST FOOT. 
Outer br. 
ex. 
3 spines. 
Inner br. 
ex. 
1 seta. 
ap. 
2 setae. 
ap. 
1 spine, 1 seta. 
in. 
2 setae. 
in/3 setae. 
SECOND AND THIRD FEET. 
Outer br. 
ex. 
3 spines. 
Inner br. 
ex. 
1 seta. 
ap. 
1 spine, 1 seta. 
ap. 
1 spine, 1 seta. 
in. 
3 setae. 
in. 
3 setae. 
FOURTH 
FOOT. 
Outer br. 
ex. 
3 spines. 
Inner br. 
ex. 
1 seta. 
ap. 
1 spine, 1 seta. 
ap. 
2 spines. 
in. 
3 setae. 
in. 
2 setae. 
Fifth foot two-jointed, basal joint very broad, armed with one 
seta. Terminal joint armed with a seta and a blunt spine. 
Length, 1.2 mm. 
This takes the place in our fauna that is occupied by C. 
viridis Fischer, in Europe. In general form and appearance 
the two forms seem identical, and have been so considered by 
Herrick and Cragin. I have hesitated to propound a new 
species name, but it seems necessary. So far as Uljanin and 
Vosseler have figured viridis it corresponds to our species; but 
