North American FrcsJi-'ivater Cyclopidte. 45 



poiul at Wood's HoU, Mass. The most conspicuous dilfference 

 l)et\veeii this form and ( '. t]i<nii<t-^i is a slight one in the shape 

 of the fifth foot. 



In the Illinois River are specimens Avhich hridge over com- 

 pletely the gap between ('. hicui^j)i<h(tii-s and Herrick's C. 

 )ianis, and I see no reason for considering iKinm as a good 

 variety. 



Ci/clopfi iin)niiliis Forbes is distinguished from ('. tliomasi 

 by different proportions alone. It is one of the western rep- 

 resentatives of this species and has been collected in the 

 lakes and rivers of Wyoming. 



C'//^?o;^s• Hcrrdfim Forbes is found in the same situations as 

 C. viiiiiiiliis, from which it is distinguished l)y a slight differ- 

 ence in the armature of the feet and by the fact that the 

 vertical comb of spines of the furcal stylets is but poorly 

 developed. The name scn-<itii.^ l)eing already in use, Herrick 

 renamed the species forbcst. This is the most elongate of 

 the American representatives of the species. 



SPECIFIC DESCRirXIOX. 



This is a long and slender species (PI. XII., Fig. 1) with 

 seventeen-segmented anteniue, oval cephalothorax, slender 

 abdomen, very long and slender caudal stylets, and but two 

 developed set.e to each stylet. The longer of these setae is 

 about twice as long as the shorter. The cephalothorax is 

 widest at about the middle. In specimens from the eastern 

 United States the posterior angles of the cephalothorax are 

 not usually prominent except hi the case of the last segment, 

 where they are laterally produced. In the far western speci- 

 mens the posterior angles of all the segments are prominent. 

 The peculiar appearance of the cuticle caused by circular pits 

 or depressions which Dr. Schmeil mentions, is rarely present 

 in the American form. I have found it in greatly varying 

 degrees of deliniteness in specimens from Lake Superior 

 and from Wyoming. 



The first segment of the abdomen of the female (PI. XII., 

 Fig. 1 ) is emarginate behind the prominent lateral angle. 

 This segment is about as long as all the others together. The 



