1100 Wisconsin Academy of Sciences, Arts, and Letters. 



The abdomen is broad (PL LXXX, iig. 6), its first seg- 

 ment being only slightly smaller than the last cephalothoracic 

 segment. Schmeil states that the second and third segments of 

 the female and the second, third and fourth of the male are 

 serrate on their posterior borders. I find some variations in 

 these serrations in our forms. 



The furcal rami are short, broad and tapering. They are 

 armed upon their surfaces with rows of spines. The lateral 

 setae are well towards the end, with spines at their bases. 

 Of the terminal armature, the outer is a broad, stout spine, 

 the inner a slender, short seta. The median setae are long 

 and stout. The inner margins of the rami are ciliate. 



The first antennae (PL LXXX, fig. 3) reach beyond the 

 middle of the first cephalothoracic segment and, in American 

 specimens are commonly composed of eleven segments. Herrick 

 and Forbes claim to have collected mature specimens with ten 

 segmented antennae. The eighth segment has a sensory hair. 



The second antenna (PL LXXX, fig. 4) is short and broad. 

 Besides the rows of small spines on the surface of the second 

 segment, there is upon the anterior margin a row of curved tooth 

 like spines. Near the end of the second segment is a stout 

 spine, and a similar spine is located near the end of the third 

 segment. 



The spinous armature of the terminal segments of the 

 exopodites of the swimming feet is 3, 4, 4, 3. The outer mar- 

 gins of the segments of the feet are armed with stout spines, 

 and the first basal segment is armed posteriorly with a row 

 of small spines. 



The fifth feet (PL LXXIX, fig. 9) are widely separated from 

 each other and each consists of a broad plate armed with three 

 stout setae. 



The form of the receptaculum seminis is shown in Plate 

 LXXX, fig. 5. 



The egg-sacs lie rather close to the abdomen. 



Length of female about 1.2 mm. according to Schmeil, but 

 American forms average somewhat smaller. 



Cyclops phaleratus occurs in shallow lakes and stagnant 



