Marsh—North American Species of Cyclops. 1083 
lateral hyaline lamella. The lamella on the seventeenth seg¬ 
ment is serrate on its margin, and has besides either a single 
deep depression near its distal end, or four or five snch de¬ 
pressions. The figure (PI. LXXIV, fig. 10) shows a common 
form. I do not find, in our American forms the spines spoken 
of by Schmeil on the antennal segments. 
The segments of the second antenna (PI. LXXV, fig. 3) are 
elongated. The lower margin of the second segment of the 
outer maxillipede always has a number of shallow depressions, 
giving it a more or less crenulated appearance. This appear¬ 
ance is described by the German authors under the term ge- 
perlte. While, in some of our forms, this term could he prop¬ 
erly applied, more frequently crenulated would describe the ap¬ 
pearance more accurately. The figures (PI. LXXIV, figs. 4, 
5, 6) show the extreme forms as they occur in America. In one 
(PI. LXXIV, fig. 4) this appearance is confined to only a small 
part of the margin, hut is there very distinct, while in the other 
(PL LXXIV, fig. 6) it is not so marked but extends through 
the greater part of the length of the margin. PI. LXXIV, fig. 
5 shows another form intermediate between the others. 
The second segment of the inner maxillipede has on its 
anterior margin a number of scattered and rather long setae 
(PI. LXXIV, fig. 11). This seems to he a constant character¬ 
istic of this species; I think it was first mentioned by Brady 
(Brady 1891) in his description of Scourfeldi. It is not men¬ 
tioned by Schmeil hut it is shown in his figure of the inner max¬ 
illipede. 
The spinous armature of the terminal segments of the ex- 
opodites of the swimming feet is represented by the formula, 
2, 3, 3, 3. The membrane connecting the feet of the fourth 
pair is armed on the posterior border with two blunt spines. 
(PI. LXXV, fig. 1.) Each segment of the rami is armed on 
the distal border with a row of spines. 
The fifth feet (PI. LXXIV, figs. 8, 9) are two-segmented. 
The first segment is short and broad and bears upon its distal 
outer angle a plumose seta; this seta is ordinarily long as in 
PI. LXXIV, fig. 9, but sometimes it is quite short, as in PI. 
LXXIV, fig. 8. The second segment bears a long plumose seta 
