214 Marsh — Cyclopidm and Calanidce of Wisconsin. 



FOURTH FOOT. 



Outer br. ex. 2 spines. Inner br. ex. 1 seta. 



ap. 1 spine, 1 seta. ap. 2 spines, 



in. 4 setae. in. 2 setae. 



The fifth foot is three-jointed, the second joint armed with a 

 seta, and the third joint with two terminal setae. 



Cyclops fluviatilis Herrick. 

 Plate V, figs. 14 and 15; plate VI, fig. 1. 



1882. C. fluviatilis Herrick (23), p. 231, pi. VII, figs. 1-9. 



1883. magnoctavus Cragin (24), p. 5, pi. Ill, figs. 14-23. 



1884. " fluviatilis Herrick (26), p. 159, pi. Q°, figs. 1-9. 

 1887. " " " (30), p. 15. 



1891. magnoctavus Brady (36), p. 19, fig. 1-4. 



I see no valid reason for separating fluviatilis and magnoctavus, 

 although they are considered by Brady distinct species. C. pen- 

 tagonus Vosseler is like fluviatilis in the form of the antennae 

 and abdomen, and in the armature of the feet. In the form of 

 the cephalothorax it differs widely from fluviatilis, the first seg- 

 ment being short, broad and angular, while in fluviatilis the 

 first segment is long and rounded, the whole cephalothorax being 

 oval in outline. C. fluviatilis is not likely to be confounded 

 with any other Cyclops, as we have only one other species with 

 twelve- jointed antennae, — C. sermdatus, — from which it is readily 

 distinguished by its smaller size, and the different form of the 

 abdomen and furca. 



I have found C. fluviatilis only in pelagic collections. Cragin 

 and Brady have found it in ditches. But Brady remarks: "It 

 is curious that in both cases the animal was found in ditches im- 

 mediately connected with large sheets of water. " 



Herrick says, " it is one of the most abundant forms in the 

 larger lakes, and especially in streams. " 



