Marsh—'New Species of Diaptomus from Colorado. 197 
ON A NEW SPECIES OF DIAPTOMUS FROM COLORADO. 
C. Dwight Marsh. 
DIAPTOMUS COLORADENSIS SP. NOV. 
Plate X, figs. 7, 8 and 9. 
Of medium size. The suture between the first and second 
cephalothoracic segments is quite distinct, and these two, form¬ 
ing the first apparent segment, are together somewhat shorter 
than the three following segments. The last cephalothoracic 
segment is expanded into large lateral processes, each side being 
armed with two small spines. 
The first segment of the female abdomen (Plate X, fig. 8) 
slightly exceeds in length the rest of the abdomen. It is broad, 
dilated ventrally, and moderately dilated laterally. The lateral 
processes bear large spines which are turned towards the pos¬ 
terior end of the animal. The second segment is shorter than 
the third and the two together are considerably longer than the 
furca. The fureal rami are stout and ciliate on both the inner 
and the outer margins. The antennae reach beyond the end of 
the furca. The antepenultimate segment of the right male an¬ 
tenna is without any special appendage. 
The fifth feet of the female (Plate X, fig. 9) are slender. 
The spines of the first basal segments are large and prominent. 
The lateral hairs of the second basal segments are of moderate 
length. The first segment of the exopodite is more than twice 
as long as wide. The second segment is long and slender, ex¬ 
ceeding in length the first segment. The hook is slightly curved 
and denticulate on, the inner margin. It is armed with three 
spines of which the inner is the longest. The two inner spines 
represent the third segment. The endopodite is slender and 
