412 Wisconsin Academy of Sciences, Arts, and Letters. 
DIAPTOMUS REIGHARDI Marsh. 
Plate XV, figs. 2, 6, 9. 
1895. Diaptomus Reighardi Marsh, p. 9; pi. I, figs. 1-4. 
1897. Diaptomus Reighardi Schacht, p. 169; pi. XXVIII, 
%. i. 
Of moderate size. The first cephalothoracic segment nearly 
equals in length the rest of the cephalothorax; the suture of 
this segment is very distinct. The last cephalothoracic segment 
is armed on each side with a minute spine. 
The first segment of the female abdomen is elongated, nearly 
equaling in length the remainder of the abdomen and the furca. 
It is dilated laterally and in front. The lateral dilatations are 
slight, and are armed on each side with a minute spine. The 
second segment is about one-third shorter than the third. The 
third segment is slightly shorter than the fureal rami. The 
furcal rami are ciliate on the inner margin. 
The antennae are 25-segmented and reach to the end of the 
furca. The right male antenna is swollen anterior to the genic- 
ulating joint; the antepenultimate segment has no appendage. 
The spines of the posterior surface of the first basal seg¬ 
ments of the female fifth feet are very small. The first seg¬ 
ment of the exopodite is twice as long as wide. The second 
segment is prolonged into a sharp hook which is denticulate on 
the inner margin. The third segment is represented by two 
spines. The endopodite is one-segmented, slightly longer than 
the first segment of the exopodite, is setose at tip, and armed 
with two rather long spines. 
The spines of the first basal segments of the male fifth feet 
are moderately prominent. The second basal segment of the 
right foot is about one-half longer than broad. The lateral 
hair is situated at about two-thirds of its length. The length 
of the first segment of the exopodite is about equal to its width. 
It bears a slight fold on its posterior surface near the distal 
end. The second segment is more than twice as long as wide. 
