North American Fresh-water Cyclopidcc. 51 



body of the segment. Neither the seta? nor the spine seem 

 to be provided with hairs or spinules. 



The receptaculum seminis (PL XV., Fig. 3) is of an unusual 

 and very characteristic shape. The anterior part is small, 

 and its outline is marked by two anterior and two lateral 

 rounded prominences. The posterior part consists of a 

 median lobe, partially divided posteriorly, and two curved 

 lateral lobes from which lead the lateral canals. The porus 

 is in the median part connecting the upper and lower divisions. 



The egg-sacs are of the usual size and shape. 



In length the female varies from 1.77 to 2.88 mm. 



The color is unusually variable. It is commonly dark blue 

 or green but may be gray or red. The deep color and large 

 size make this a conspicuous species. 



Herrick says that it is widely but sparingly distributed over 

 the Mississippi Valley. Marsh reports it from Rush, Round, 

 St. Clair, Intermediate, Twenty-sixth, and Susan lakes in 

 Wisconsin. I have noted its occurence in collections from 

 Thompson's, Quiver, Flag, Phelps, and Dogfish lakes near 

 Havana, Illinois. 



Subgenus Orthocyclops n. subgen. 

 Antenna? sixteen-segmented. Rami of swimming feet, three- 

 segmented. Fifth feet three-segmented, distal segment bear- 

 ing two apical seta?. 



Cyclops modestus Herrick. (PI. XV., Fig. 4, and PI. 

 XVI., Fig. 1-3.) 



Cyclops modestus, Herrick, '83a, p. 500. 



Cyclops modestus, Herrick and Turner, '95, pp. 108, 109, PI. XXI., 



Fig. 1-5. 

 Cyclops modestus, Marsh, '93, pp. 213, 214, PI. V., Fig. 10-13. 

 Cyclops capilliferus, Forbes, '93. pp. 248. 249. PI. XL., Fig. 14-17: 



XLL. Fig. 18. 



SYNONYMY AND DISTRIBUTION. 



By a study of the type specimens of Cyclops capilliferus I 

 find that they agree almost completely with Herrick's descrip- 

 tion of C. modestus. The descriptions differ with respect to 



