North American Fresh-water Cyctopidce. 49 



one spine, four seta?. Second and third pairs : outer ramus, 

 four spines, five seta ; inner ramus, one seta, one spine, four 

 setas. Fourth pair: outer ramus, three spines, five setge; 

 inner ramus, one seta, two spines (inner naked and movable), 

 two setae (distal one minute). 



The fifth foot is two-segmented. The basal segment is two 

 thirds as wide as long, its outer margin straight, its inner, 

 convex and minutely hairy. The distal end is truncate, with 

 a very long seta at the outer distal angle. The second seg- 

 ment is about as long as the preceding is wide, lobed in the 

 middle and trisetose, the outer seta shorter than the inner, 

 and the latter about half as long as the median. 



The anterior portion of the receptacuhim seminis is kidney- 

 shaped and the posterior is two-lobed. The lateral canals 

 are attached to the lower portion. 



The usual length of the female in America is from 

 1.26-1.4 mm., but it seems to be much greater (2.5 mm.) in 

 the European representatives of the species. 



The color, which is blue or green, is distributed in dark 

 bands with nearly colorless intervals on the thorax, the last 

 abdominal segment and stylets, and on the second, third, 

 ninth, and tenth antennal segments. 



This species is very generally distributed, having been 

 found in all the localities in America from which collections 

 have been examined. It is not common in temporary ponds, 

 but I have several times noted its occurrence in wells. 



Subgenus Homocyclops n. subgen. 



Cephalothorax very robust. Antennas seventeen-segmented. 

 Eami of swimming feet three- segmented. Fifth feet one- 

 segmented, bearing one spine and two seta'. 



Cyclops ater Herrick. (PI. XIV., and PI. XV., Fig. 1-3.) 



Cyclops ater, Herrick, "82a, p. 228, PJ. III.. Fig. 9-12. 

 Cyclops ater, Marsh, '95. pp. 13, 14, PJ. VI., Fig. 1-4, 6, 12. 

 Cyclops ater, Herrick and Tinner, '95, pp. 89, 90, PL VII., Fig. 

 11. 12; XII., Fig. 9-12; XXL, Fig. 13-15, 17, IS. 



The cephalothorax is peculiarly short and broad. Its first 



