778 FRESH-WATER BIOLOGY 



91 (90) With sensory hair on twelfth antennal segment, hyaline plate of 

 seventeenth antennal segment deeply notched, egg sacs 

 lying close to abdomen. . . . Cyclops fuscus Jurine 1820. 



Cyclops fuscus and C. albidus resemble each other very closely, and it is only 

 by a careful examination that they can be distinguished. They are very com- 

 mon, especially in pond collections, Cyclops albidus being found much the more 

 frequently. They are much larger than C. leuckarti and the furcal armature dif- 

 fers in that the lateral seta is placed near the end of the ramus (Fig. 1223). The 

 form of the fifth feet and of the furcal rami will readily serve to show when we 

 have one of these two species, and in most cases it will prove to be Cyclops albidus. 

 Length of female, about 2 mm. 



FIG. 1224. Antennal segments of female Cyclops fuscus. X 13 7- (Original.) 



92 (78, 93) Antennae composed of sixteen segments, fifth feet of three seg- 

 ments Cyclops modestus Herrick 1883. 



This species is comparatively rare altho it has been found in a con- 

 siderable number of places. It occurs as far east as Pennsylvania, as 

 far west as Wyoming, while its northern and southern limits are Wis- 

 consin and Alabama. 



Length of female, 1.2 to 1.25 mm. 



FIG. 1225. Cyclops modestus. A, abdomen of 

 female. X 170. B, fifth foot. X 448. 

 (Original.) 



93 (?8, 92) Antennae composed of twelve segments, fifth feet of one segment. 



94 



94 (97) Fifth feet armed with three setae, swimming feet composed of 

 three segments 95 



