North American Fresh-water Cyclopidce. 35 



If the figures as published by Hoek are correct, C. edax differs 

 from ('. leeuwenhoekii in the following particulars : In edax 

 the labrum has eleven teeth; in leeuwenhoekii it has but ten. 

 In edax the seventeenth antennal segment is longer than the 

 sixteenth; in leeuwenhoekii the sixteenth is longer than the 

 seventeenth. In edax the first foot, outer ramus, bears on the 

 distal segment two spines and four sets; in leeuwenhoekii the 

 corresponding segment bears three spines and two sets. In 

 edax the inner margin of the distal segment of the fifth foot 

 is not incurved as in leeutvenhoekii. In edax there are never 

 less than five prominent teeth in the lamella of the seven- 

 teenth antennal segment; in leeuwenhoekii but three are fig- 

 ured. The transverse ridges on the maxilliped of leeuwenhoekii 

 are more prominent, smaller, and more numerous than in 

 edax. 



DISTRIBUTION'. 



This form is very abundant and widely distributed in 

 America. I have found it, among many other places, in col- 

 lections from the Mississippi and Illinois rivers ; from various 

 lakes and ponds of Illinois ; from Sister Lake and Lake 

 Butler in Florida ; from Spirit Lake and Lake Okoboji in 

 Iowa ; and also from lakes Michigan, Superior, Winnebago, 

 and Michigamme, and Yellowstone, Delavan, and Cedar 

 lakes. It was described in 1892 by Wierzejski from the 

 Argentine Republic under the name of C. annulatus. 



SPECIFIC DESCRIPTION". 



The cephalothorax is oval, compact, and broadest before 

 the middle. The first segment is as long as the remainder. 

 The last thoracic segment is scarcely broader than the first 

 abdominal. 



The first abdominal segment is very long, equaling the fol- 

 lowing three. The last segment is the shortest and is bordered 

 by the usual row of spinules. The preceding segments are 

 bordered posteriorly by coarse serrations, more pronounced 

 and regular on the ventral than on the dorsal side. The 

 stylets are one third as wide as long, and in a long series of 

 measurements of individuals from the most widely separated 



