Marsh — North American Species of Cyclops. 1075 



angle on the distal end is a small, lanceolate spine; in some 

 varieties this spine is separated from the segment by a joint, 

 while in others, this joint does not appear. 



The form of the receptaculum seminis is shown in the figure, 

 Plate LXXIV, fig. 2. 



It varies greatly in size. The common American varieties 

 are 1.25 to 1.5 in length. It may reach, however, as much as 

 5 mm. 



Cyclops viridis seems to be universally distributed in the 

 northern hemisphere. 



Cyclops viridis var. ingens, Herrick. 



This variety, which is also mentioned by E. B. Forbes, is 

 distinguished by three features, first its greater size, sec- 

 ond by the fact that the spine of the second segment of the 

 fifth foot is not separated from the segment by a joint, and 

 third by the ciliated internal margins of the furca. It cor- 

 responds, doubtless to the gigas of Claus. Inasmuch, how- 

 ever, as so good an authority as Schmeil considers that gigas 

 differs from typical viridis only in size, it seems to me wise 

 to retain Herrick's name for the American variety. 



Ingens occurs in pools. 



Cyclops viridis var. brevispinosus Herrick. 



Brevispinosus is rather elongate in form, the furcal rami 

 are long and slender, and the terminal appendage at the outer 

 angles of the furcal rami is a short thick spine, Plate LXXIX, 

 fig. 7, shaped much like the blade of a knife. The formula 

 for the spines of the terminal segments of the exopodites of 

 the swimming feet is 3, 4, 4, 4. The terminal segment of the 

 endopodite of the fourth foot has a spine on its outer margin. 



Brevispinosus is most common in larger bodies of water 

 where it frequently has a limnetic habitat. It is by no 

 means confined to large bodies of water, however, as it is 

 found in many of the smaller lakes of Wisconsin and Michi- 

 gan. 



