North American Fresh-water Cyclopidce. 33 



The egg-sacs are carried at a broad angle from the 

 abdomen. 



In length the female varies, in American specimens, from 

 .95 to 1.5 mm. 



The color is always inconspicuous and may be light blue 

 or gray. 



This is in general a very rare species in America. I have 

 never, until recently, found it in collections in any great 

 numbers, but in twos or threes at long intervals. I lately 

 found it, however, in immense numbers in a collection made 

 in August, 1896, from Fox River, Illinois. It is found in 

 just such situations as is C. edax, but usually in very much 

 smaller numbers. I have seen this species in collections 

 from Lake Harriet, Minnesota; Delavan Lake, Wisconsin ; 

 and from Quiver, Flag, and Dogfish lakes, and the Sangamon 

 and Fox rivers — all in Illinois. It is widely distributed in 

 the lakes and rivers of America, but has not been reported 

 from temporary pools. 



Cyclops edax Forbes. (PI. IX., Fig. 1-3.) 



Cyclops edax. Forbes, '90a, p. 709. PI. III.. Fig. 15; IV.. Fig. 16-19. 

 Cyclops annulatus, Wierzejski, "92, pp. 237. 238. PI. VI., Fig. 14-1S. 

 Cyclops leuckarti, Marsh, '93. pp. 209-211, PI. IV.. Fig. 17: V.. 

 Fig. 2-6. 



SYNONYMY AND COMPARISON. 



This form has been confounded with ('. leuckarti Claus, 

 from which, however, it is very easily separated by a careful 

 comparison of specimens. 



The original description of this species was incomplete in 

 that no mention was made of the sense-club on the twelfth 

 antenna! segment, or of the hyaline plates of the sixteenth 

 and seventeenth segments. As in ('. leuckarti (Pi. VIII., 

 Fig. 2), the plate of the sixteenth segment has an entire edge, 

 though the plate itself is much narrower. The plate of the 

 seventeenth segment (PI. IX., Fig. 2) differs markedly from 

 the corresponding structure in ('. leuckarti. in ('. edax the 

 edge of the plate is cut by a series of deep oblique notches, 

 forming teeth which point strongly backward. These notches 



