416 Wisconsin Academy of Sciences, Arts, and Letters . 
diaptomus pallidus Herrick. 
Plate XVI, figs. 1, 2, 3. 
1879. Diaptomus pallidus Herrick, p. 91; pL II, figs. a-d. 
1883. Diaptomus pallidus Herrick, p. 383; pi. VII, figs. 1-6. 
1884. Diaptomus pallidus Herrick, p. 142; pi. Q, fig. 17. 
1889. Diaptomus pallidus DeGueme and Richard, p. 62; fig. 
34. 
1893. Diaptomus pallidus Marsh, p. 196; pi. Ill, figs 6, 7, 9. 
1895. Diaptomus pallidus Herrick and Turner, p. 73; pi. IV, 
figs. 1-6; pi. V, fig. 10; pi. XIII, fig. 17. 
1897. Diaptomus pallidus Schacht, p. 144; pi. XXVII, fig. 3. 
1905. Diaptomus pallidus Pearse, p. 147. 
A slender species of medium size. First cephalothoracic 
segment considerably longer than the three following; the last 
cephalothoracic segment bears two small lateral spines. 
The first abdominal segment of the female nearly equals in 
length the rest of the abdomen, is slightly dilated laterally, and 
bears two minute lateral spines. The second segment is slightly 
Shorter than the third, and the third slightly shorter than the 
furcal rami. The furcal rami are ciliate on the inner margin. 
The antennae are 25-segmented and reach slightly beyond 
the end of the furcal rami. The right antenna of the male is 
swollen anterior to the geniculating joint, and without special 
armature. 
The female fifth feet are short and stout, the spines of the 
first basal segments small. The lateral hairs of the second 
basal segments are rather long. The exopodite is composed of 
two segments, the third segment being represented by two 
spines. The second segment is prolonged into a rather long 
hook, and serrulate on the inner margin. The endopodite is 
slightly longer than the first segment of the exopodite; the tip 
is setose, and armed with two rather long spines. 
In the male fifth foot the spines of the posterior surface of 
the first basal segments are small. The second basal segment 
