AQUATIC INVERTEBRATE FAUNA OF WYOMING AND MONTANA. 
247 
COPEPODA. 
Cyclops minnilus, n. sp. 
A small slender species, with seventeen-jointed antenn*, with narrow and loosely 
articulated cephalothorax and salient thoracic angles, slender abdomen, long and 
narrow furca, and but two well-developed caudal seta; for each ramus. The antennae 
reach to the posterior margin of the second distinct segment, and are of very nearly 
the length of the abdomen (including furca, but excluding the caudal setae). The 
greatest width of the thorax is contained two and one-third times in its length, and 
the furca is very nearly half the length of the remainder of the abdomen. The diam- 
eter of a ramus is about one-seventh its length. 
The rudimentary inner caudal seta is a trifle longer than the outer, and about 
a third the length of the ramus; the longest seta as long as abdomen and furca; the 
next in length less than half the longest. 
The last segments of the thoracic legs are armed as follows: 
First pair: outer ramus, one spiue and two set* at tip, two set* within, and one 
seta without; inner ramus, one spine and one seta at tip, three set* within, and one 
seta without. 
Second pair: outer ramus, one spine and one seta at tip, three set* within, and 
two spines without; inner ramus, one spine and one seta at tip, three set* within, and 
one seta without. 
Third pair: outer ramus, two spines and one seta at tip (second spine twice as 
long as first), three set* within, and one spine without ; inner ramus, one spine and one 
seta at tip, three set* within, and one seta without. 
Fourth pair: outer ramus, two spines and one seta at tip (second spine twice as 
long as first), three set* within, and one spine without; inner ramus, two spines at 
tip (one twice as long as the other), two set* within, and one seta without. 
Rudimentary legs of fifth pair distinctly articulated, basal article with a long seta 
at its outer distal angle, and second article with two set* at its blunt tip, the outer 
the longer. 
Duck Lake. 
Cyclops serratus, n. sp. 
A very long, narrow, loosely articulated species, with strikingly salient thoracic 
angles; cephalothorax broadest far forward and lobed in front, between the seventeen- 
jointed antenn*. * 
Abdomen long and slender, with very long and narrow caudal rami, and but two 
developed caudal set* to each ramus. The first segment is but little longer than wide 
(eight to seven), is broadest across the middle, and excavate in front at the base of 
each antenna, leaving a thick, median, projecting lobe. The second segment is nearly 
a fourth as long as the first, and but little narrower, broadest across its posterior 
angles, which, though blunt, are so strongly salient that the lateral margins are 
decidedly sinuate. The third segment is as long as the second, but narrower, and 
with its sides more nearly parallel. The fourth and fifth segments are progressively 
shorter and narrower, the latter being trapezoidal, as seen from above, and separated 
from the first abdominal segment by a deep acute emargination. 
