North American FresJi-zvater Cyc'opidce. 53 



The antennae are regularly sixteen-segmented, though 

 Herrick mentions having notes on a similar form in which 

 the antennae are seventeen-lsegmented. They reach to the 

 middle of the second cephalothoracic segment. On the third, 

 tenth, and thirteenth segments are remarkably long, heavy 

 seta?. The antenna (PL XVI., Fig. 1) is given a characteristic 

 appearance by the conspicuous seta on the third segment 

 and a sharp change in direction between the third and fourth 

 segments. The last segment is much shorter than the one 

 preceding. 



The seta? of* the three-segmented legs are long and slender. 

 The distal segments of the third and fourth pairs of legs turn 

 inward in a way peculiar to this species. The legs are armed 

 as follows : — First pair : outer ramus, four spines, four seta' ; 

 inner ramus, six seta?. Second pair : outer ramus, four spines, 

 five seta? ; inner ramus, six seta?. Third pair : outer ramus, 

 three spines, five seta?; inner ramus, six seta?. Fourth pair: 

 outer ramus, three spines, five seta?; inner ramus, one seta, 

 two spines, two seta?. 



The fifth foot (PI. XVI., Fig. 2) has three freely movable 

 segments, though the basal one is small. The second seg- 

 ment bears one seta without, and the third segment bears two 

 seta? — both at the tip. The outer seta is apt to be bent inward 

 across the inner one. These feet are usually large and placed 

 very close together. 



The receptaculum seminis (PL XVI., Fig. 3) is very much 

 as in Cyclops bicuspidatus Claus. It is nearly elliptical in 

 outline, and only a small part of the anterior end extends 

 farther forward than the suture in which the porus is situated. 

 The lateral canals lead from the anterior part. 



The egg-sacs are long and narrow and lie close to the 

 abdomen. 



In length this species does not vary to any marked degree 

 from an average of 1.2 mm. 



The coloring is most beautiful, varying from violet to 

 purple. It is evenly distributed, and is quite persistent in 

 specimens preserved in formalin. 



