60 Illinois Statv Laboratory of Natural History. 



Delavan Lake, Wisconsin; Quiver Lake, 111.; Green Lake, 

 Wisconsin ; Cedar Lake, 111. ; and a slough at Portage La 

 Prairie, Manitoba. Marsh reports it from Lake St. Clair; 

 and from Twenty-sixth Lake, Pigeon Paver, and Intermediate 

 Lake, Michigan. Cragin describes this species as Ci/rlops 

 pavdiiiutfux from Glacialis Pond, Cambridge, Mass. It is a 

 littoral rather than a pelagic form and where occurring in 

 large bodies of water it is found only in the marginal vegeta- 

 tion. 



SPECIFIC DESCRIPTION. 



The cephalothorax is broad and elliptical. The first seg- 

 ment is longer than the remainder. The chitinous covering 

 of the fifth segment, which in all other species of this genus is 

 composed like the four preceding cephalothoracic segments 

 of a dorsal and ventral plate, is in C. pluderatiis like the 

 chitinous covering of the abdominal segments in that it con- 

 sists of but one piece. The ventral portion of the posterior 

 border of this segment is set with a row of fine teeth, evanes- 

 cent in the middle. About the rudimentary feet are several 

 rows of line spinules. 



The abdomen is large and cylindrical, and very little smaller 

 than the last cephalothoracic segment. The first segment 

 tapers very little. The posterior borders of the first, second, 

 and third abdominal segments of the female are finely serrate. 

 The last segment is very short and the spines on its posterior 

 border are especially long and strong. The profusely spinose 

 stylets are short and broad and taper very rapidly. On the 

 ventral side of each ramus is a row of long spinules, extend- 

 ■ ing from the middle line of the anterior border to the point 

 of insertion of the lateral spine. From this point on, the 

 rami taper much more rapidly. The inner border of the 

 stylets is ciliate* and the whole inner aspect may be spinose. 

 The outermost apical bristle, which is placed high up on the 

 side of the stylet, is short, and plumose on both sides. The 

 inner bristle is very slender and is about as long as the outer. 

 It is plumose on the outside only.* Tlie two median bristles 



♦ Incorrect in figure. 



