458 Wisconsin Academy of Sciences } Arts, and Letters. 
order of the other descriptions, was received while this paper 
was going through the press. Consequently the author has not 
seen the type specimens, and there has been no opportunity to 
prepare figures. Pearse speaks of it as related to Lintoni, and 
it is evident that it falls into the leptopus group, being closely 
related to stagnalis as well as Lintoni. The form f the endo- 
podite of the left fifth foot of the male is a distinctive charac¬ 
teristic. 
diaptomus sigxicauda Lilljeborg. 
Plate XXI, figs. 8, 10, 11. Plate XXII, fig. 3. Plate XXIII, 
fig. 3. 
1889. Diaptomus signicauda DeGuerne and Pichard, p. 55; 
pi. I, figs. 15, 16, 31; pi. Ill, fig. 22. 
1895. Diaptomus signicaudatus Herrick and Turner, p. 63; 
pi. VIII, fig. 13; pi. IX, fig. 10. 
1897. Diaptomus signicauda Schacht, p. 164; pi. XXIX, figs. 
3-6. 
A small species. The cephalothorax is broadest in front 
of the middle at the second segment. The first segment is 
about twice the length of the second. The last two segments 
are confluent, and the last segment has rather broad projecting 
lateral lobes with acute posterior angles ending in small spines. 
The fourth thoracic segment has a slight dorsal gibbosity. 
The first abdominal segment of the female is expanded in 
front and laterally, and is armed laterally with minute spines; 
on the posterior end on the right side it bears a finger-like proc¬ 
ess which projects backward. This process is somewhat vari¬ 
able in length. The second abdominal segment varies in length. 
In some cases it is hardly to be distinguished from the first 
segment (PI. XXI, fig. 11), while in others it equals in length 
the third segment (PI. XXIII, fig. 3). The fureal rami vary 
in length from one and a half times the breadth to twice the 
breadth. They are setose on the inner margin. 
