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 the 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. 

 in. 2 setae. 



ap. 1 spine, 1 seta, 

 in. 3 setae. 



SECOND AND THIRD FEET. 



Outer br. ex. 3 spines. Inner br. ex. 1 seta. 



ap. 1 spine, 1 seta, 

 in. 3 setae. 



ap. 1 spine, 1 seta, 

 in. 3 setae.' 



. FOURTH FOOT. 



Outer br. ex. 3 spines. Inner br. ex. 1 seta 



ap 



1 spine, 1 seta, 

 in. 3 setae. 



ap. 2 spines, 

 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 G. 

 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 



