AQUATIC INVERTEBRATE FAUNA OF WYOMING AND MONTANA. 247 



COPEPODA. 



Cyclops minnilus, n. sp. 



A small slender species, with seventeen-jointed antennae, with narrow and loosely 

 articulated ceplialothorax 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 setee). 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 spine and two setae at tip, two setae within, and one 

 seta without; inner ramus, one spine and one seta at tip, three setae within, and one 

 seta without. 



Second pair: outer ramus, one spine and one seta at tip, three setae within, and 

 two spines without; inner ramus, one spine and one seta at tip, three setae within, and 

 one seta without. 



Third pair: outer ramus, two spines and one seta at tip (second spine twice as 

 long as first), three setae within, and one spine without; inner ramus, one spine and one 

 seta at tip, three setae within, and one seta without. 



Fourth pair: outer ramus, two spines and one seta at tip (second spine twice as 

 long as first), three setae within, and one spine without; inner ramus, two spines at 

 tip (one twice as long as the other), two setae 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 seta? at its blunt tip, the outer 

 the Jonger. 



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 antennae. 



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. 



