214 Marsh—Gy clopidce and Calanidce of Wisconsin. 
FOURTH FOOT. 
Outer br. ex. 2 spines. 
Inner br. ex. 1 seta. 
ap. 1 spine, 1 seta, 
in. 4 setse. 
ap. 2 spines, 
in. 2 setse. 
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. 
(30), p. 15. 
1887. 
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. G. pen- 
tag onus 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. G. fluviatilis is not likely to be confounded 
with any other Gyclops , as we have only one other species with 
twelve-jointed antennae, — G. 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. ” 
