Marsh—North American Species of Cyclops. 1089 
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. (PI. 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. (Pi. LXXVI, figs. 1, 3.) 
The fifth foot is of two segments (Pi. 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, 
(PI. 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, C. tenuicarnis 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 albicllus 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. 
