Marsh — North American Species of Cyclops. 1089 1 



In the second antenna, the inner margins of the first two 

 segments are usually setose. The third segment is short, but 

 little exceeding the second in length. (PL LXXVI, fig. 7.) 



The spinous armature of the terminal segments of the ex- 

 opodites of the swimming feet is 4, 4, 4, 3. 



The distal seta on the inner margin of the endopodite of 

 the fourth foot is rudimentary, being represented by a small 

 spine; very rarely there is a short seta in this place; I have 

 never found a seta of full length. (PL LXXVI, figs. 1, 3.) 



The fifth foot is of two segments (PL LXXVI, fig. 6). The 

 first segment is longer than wide. It has a patch of spines on 

 the inner margin near the base, and a few spines about midway 

 of its inner margin which may extend over part of the surface 

 of the segment in a curved line. The distal margin is armed 

 with small spines. On its distal outer angle is a long seta. 

 The length of the second segment about equals the breadth of 

 the first. It bears a long median seta and two stout serrate 

 setae, one at each distal angle; the inner of these lateral setae 

 is the longer. 



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

 (PL LXXVI, fig. 9). 



The egg sacs of the female stand out from the abdomen al- 

 most at right angles. 



The females measure upwards of 1.5 mm. 



Cyclops albidus is universally distributed in Xorth America 

 It belongs to the litoral rather than to the limnetic fauna. 



Under C. fuscus there is a brief discussion of the distinguish- 

 ing points between these two species. 



C. annulicornis Sars, 0. tenuicornis var. distinctus Richard, 

 and C. gracillicornis Lande are doubtless identical, and the 

 names have been given to separate a form supposed to be in- 

 termediate between albidlus and fuscus. Brady (1906) and Lill- 

 jeborg (1901) make a distinct species using the name distinc- 

 tus of Richard. Nothing has appeared in our American co- 

 pepod fauna which seems to need a distinct species name, and 

 I am inclined to agree with Schmeil that there is no good 

 reason for separating this form from albidus. Accordingly I 

 have placed them in the synonomy. 



