Marsh—North American Species of Diaptomus. 449 
my collections have been made, although it is reported as oc¬ 
curring not only in Illinois and Minnesota, hut in Ohio, Ken¬ 
tucky and Alabama. 
The segmentation of the fifth feet of the female would indi¬ 
cate that this is one of the least specialized of the members of 
the leptopus group. 
DIAPTOMUS CONIPEDATUS Sp. nOV. 
Plate XX, fig. 4. Plate XXI, figs. 2-4. 
A rather large species. The first cephalothoracic segment is 
nearly as long as the succeeding three segments. The last 
cephalothoracic segment has two minute spines on each lateral 
lobe. 
The first abdominal segment of the female is somewhat less 
in length than the rest of the abdomen and the furca. It is 
dilated in front, and slightly dilated at the sides. The lateral 
dilatations are armed with small spines. The second and third 
segments are about equal in length, and are broader than long. 
The rami of the furca are somewhat longer than the third seg¬ 
ment and are ciliate on the inner margin. 
The antennae hardly reach the end of the furca. The right 
male antenna is much swollen anterior to the geniculating joint. 
The antepenultimate segment is armed with a hook-shaped proc¬ 
ess, which is not strongly recurved; it is rather less than half 
as long as the penultimate segment. 
The first basal segment of the female fifth foot has the usual 
spine upon its posterior surface. The second basal segment has 
the customary lateral hair. The first segment of the exopodite 
is short and stout. The second segment is stout and prolonged 
into the usual hook which is denticulate on the inner margin. 
The third segment is represented by two spines. There is also 
a third spine situated outside these two. The endopodite is 
much longer than the first segment of the exopodite, is armed 
with short hairs on the inner margin of the tip, and has two 
rather long terminal spines. 
29—S. & A. 
