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. Diaptomus mississippiensis Marsh. 



Diaptomus mississippiensis, Marsh, '94, p. 15; pi. I., fig. 1-3. 

 Diaptomus mississippiensis, Herrick & Turner, '95, p. 78; pi. 



XLVIL, fig. 1-3. 

 Diaptomus mississippiensis, Schacht, '97, pp. 173-176; pi. 



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 



