1070 Wisconsin Academy of Sciences, Arts, and Letters. 



KEY TO SPECIES OF CYCLOPS FOUND IN NORTH AMERICA. 



Antennae composed of 17 segments 



Fifth foot composed of one segment, armed with one spine and 



two long setae, — a large species of dark color, ater 



Fifth foot composed of two segments, 



Second segment of fifth foot armed with seta and short 



spine viridi* 



Second segment of fifth foot armed with two setae, 

 The second segment of the fifth foot is elongate, its length 

 as much as twice its width, the seta of the inner 

 distal angle spine-like, less than one half the length 

 of the outer seta, bia.ixpidatus 



The second segment of the fifth foot is shorter, length 

 less than twice its width, armed with two nearly 

 equal setae, 

 The seventeenth antennal segment is armed with a 



serrate hyaline plate, Leuckarti 



The seventeenth antennal segment is not armed with 

 a hyaline plate, tenuis 



The second segment of the fifth foot is armed with three 

 setae 

 The twelfth antennal segment has a sensory club, the 

 egg-sacs stand out from the abdomen, the hyaline 

 plate of the seventeenth antennal segment is ser- 

 rate, or smooth, albidu$ 

 The twelfth antennal segment has a sensory hair, the 

 egg-sacs lie close to the abdomen, the hyaline plate 

 of the seventeenth antennal segment is deeply 

 notched, fuscus 

 Antennae composed of sixteen segments, fifth foot of three seg- 

 ments, modestus 

 Antennae composed of twelve segments, fifth foot of one segment. 

 Fifth foot armed with three setae, rami of swimming feet of 

 three segments. 

 Furca of variable length, armed externally with a row of 



spines, found almost everywhere. xerrulatut 



Furca short, without spinous armature, a small limnetic 



species, prasinus 



Fifth foot armed with one seta, rami of swimming feet of 



two segments, raricans 



Antennae composed of eleven segments, 



Rami of swimming feet composed of three segments, phaleratus 



Rami of swimming feet composed of two segments, bicolor 



Antennae composed of eight segments, fimbriatus 



Antennae composed of six segments, aequoreu* 



