204 Marsh — Cyclopidce and Calanidm of Wisconsin. 



neither gives figures of the swimming feet. From the original 

 description by Fischer our species differs markedly. Accord- 

 ing to his figure the antennas reach to the third cephalothoracic 

 segment, while in americanus they hardly exceed the first. 

 He makes the furca about equal in length to the last abdominal 

 segment; in americanus it equals or exceeds the last two seg- 

 ments. He gives a figure of "a foot," not designating which, 

 but it corresponds to no one of the four in our species. 



Sars says the terminal joint of the external ramus of the 

 ■fourth foot has two external spines; americanus has three. 



Brady's figure of the terminal joint of the outer branch of 

 the fourth foot (18, pi. 20, fig. 7) corresponds to Sars' state- 

 ment. He also figures the terminal joint of the inner branch 

 (18, pi- 20, fig. 8,) which shows a very different armature 

 from that in americanus. 



Schmeil (41, p. 97, pi. VIII, figs. 12-14,) gives a more elab 

 orate description of viridis. His formula for the spines of the 

 swimming feet corresponds to the descriptions of the other 

 European authors. Schmeil, however, does not consider the 

 armature of the swimming feet as constant, and according to 

 his view americanus should be a variety of viridis. In an exam- 

 ination of a large number of specimens from widely separated 

 localities I have found no variation in the number and arrange- 

 ment of the spines and setae of americanus, and until such vari- 

 ation is shown, there seems to be no alternative but to insti- 

 tute a new species for the American form. 



C. americanus is widely distributed. It occurs quite gener- 

 ally in stagnant pools, and is also found to some extent in 

 lakes. 



Cyclops brevispinosus Herrick. 



Plate IV. Figs. 11 and 12. 



1884. C. brevispinosus Herrick (26) p. 148, pi. S, figs. 7-11. 

 Cephalothorax oval, the first segment reaching about half its 



