206 Marsh — Ct/clopidce and Ccdanidoe of Wisconsin. 



.•acteristic, and his figure of the furca makes me so certain of 

 the identity of the form, that I have ventured to redescribe the 

 species rather than to propose a new name. It is easily rec- 

 ognized by its short, 17-jointed antennae, and the elongated 

 furca, with the outer terminal seta reduced to a short blunt spine. 



It is widely distributed in lakes and ponds, and is a pelagic 

 species, though sometimes occurring in littoral collections. 



I have had some doubt as to whether this should be consid- 

 ered a distinct species. In most of its structural features it 

 closely resembles americanus, and I have suspected it to be a 

 pelagic variety of that species. I have specimens of amer- 

 icanus with elongated furca like brevispinosus, and I have spec- 

 imens of brevispinosus in which the outer terminal seta of the 

 furca is slender and plumose as in americanus. For the differ- 

 ences in the armature of the swimming feet, however, I have as 

 yet found no intermediate forms, and so must, for the present 

 at least, consider the two distinct. 



Cyclops navus Herrick. 

 Plate IV. Figs. 13-15. 



1882. C. navus Herrick (23) p. 229, pi. V, figs. 6-13, 15-17. 

 1884. » " " (26) p. 152. 



Larger than C. pidchellus, the antennae being about as long 

 as first two segments of cephalothorax, as in that species. 

 Armature of swimming feet as in pulchellus. Fifth foot 

 armed as in pulchellus, but terminal joint more elongated, and 

 its setae more nearly equal in length, the inner being fully two- 

 thirds the length of the outer. The furca is short, with the 

 lateral seta on the posterior third ; of the terminal setae the 

 first and fourth are short, the outer median about three-fifths 

 as long as the inner. 



It is generally reddish in color and occurs in pools. Her- 

 rick considers navus as probably a variety of pulchellus, and I 

 am inclined to agree with him. The principal difference between 

 the two species is in the form of the furca, and the difference is 

 just that which we would expect from the difference of environ- 

 ment. It is just the difference which exists between the 



