Turner—Ecological Notes—Cladocera and Copepoda. 155 
the basal joint of the outer ramus is a trifle over twice as long as 
wide; the second segment is slightly shorter than the first, it tapers 
to a sharp point and curves inward (towards the inner ramus); about 
half way up the concave margin, there is a prominent tooth, between 
this tooth and the tip there are numerous fine serrations. [This tooth 
is a constant feature, but is not to be seen in mounts that show a 
cephalic rather than a lateral view.] There is the merest trace of a 
third joint, this bears two long setae, which are finely pectinated, and a 
shorter seta. The inner ramus, which is about as long as the first 
joint of the outer ramus, is of about uniform width throughout and 
terminates in two sub-equal setae, which are usually hairy. 
Viewed from the side, the dorsal margin is feebly but uniformly con- 
vex, 
Male.—The inner distal angle of the geniculate antenna is extended 
into a straight, pointed, process, which is longer than the penultimate 
joint. 
On the inner border of the basal segment of the larger fifth leg there 
is a hyaline plate which is more than half as long as the segment, and 
bears on its inner distal angle a prominent tooth. The inner margin of 
the second basal segment is strongly convex and bears a narrow hyaline 
flange. The proximal fourth of the inner margin of the distal joint of 
the outer ramus of this leg is convex; the next two fourths concave; 
near the convexity, in the proximal portion of this concavity, there is a 
prominent spine. This distal segment is about twice as long as broad 
and its broadest part is its distal border; from its outer angle, springs 
a stout, pectinated, lateral spine, which is about half as long as the 
segment; from the inner angle of this border arises a sickle-like seta, 
which is longer than the outer ramus of the leg. The inner ramus 
of the leg is sub-clavate and extends to about the middle of the distal 
joint of the outer ramus; its free blunt end bears, at about its middle, 
a small tooth. 
The smaller fifth leg reaches to a little beyond the base of the last 
segment of the larger leg. 
This form was found in only one locality, which was a 
temporary pond in a marsh. The depth of the water 
was from two to six inches, the bottom was covered with 
plants (dead), the temperature of the water was 4° C. 
4. DrIAPTOMUS MISSISSIPPIENSIS Marsh. 
Diaptomus mississippiensis, Marsh, ’94, p. 15; pl. I., fig. 1-3. 
Diaptomus mississippiensis, Herrick & Turner, ’95, p. 78; pl. 
XLVII., fig. 1-3. 
Diaptomus mississippiensis, Schacht, ’97, pp. 173-176; _ pl. 
XXXIII., fig. 1-4. 
This was found in only one pond; but it was abundant 
in both shallow and deep water. The temperature of the 
