Copepoda Found in the Vicinity of Lincoln, Nebraska. 133 



Cyclops navus Herrick. 



This form is considered a variety of C. pulchellus, by 

 Herrick, but given specific value by Marsh. It seems quite 

 distinct in habitat and form. It is slenderer than C. fuscus 

 or C. leuckarti, but nearly the same length. The first seg- 

 ment is less than half of the cephalo-thorax. The second 

 segment is shorter than the third. The first abdominal seg- 

 ment is a little longer than the two following. All the 

 abdominal segments are dentate on their posterior margins. 

 The furcae are four times as long as broad. The lateral spine 

 is at the end of the second third, and is plumose. The two 

 median setae are nearly equal, the first and fourth are as 3 : 2. 

 The seventeen jointed antennae reach to the middle of the 

 second segment. There is, on the first joint, a transverse 

 row of very fine teeth. The fifth foot is two-jointed. The 

 first joint is broader than long, and bears a plumose seta. 

 The terminal joint is much elongated, and broadest at its 

 distal end. It bears a plumose seta and smooth spine half as 

 long as the seta. 



The armature of the terminal joints of the swimming feet 



is as follows : 



Outer ramus. Inner ramus. 



First foot.. . ex. 2 spines 1 seta. 



ap. 2 setae 1 spine, 1 seta. 



in. 2 setae 3 setae. 



Second and ex. 2 spines 1 seta. 



Third feet. . ap. 1 spine, 1 seta t spine, 1 seta. 



in. 3 setae 3 setae. 



Fourth foot. ex. 2 spines 1 seta. 



ap. 1 spine, 1 seta 2 spines. 



in. 3 setae 3 setae. 



This form was found twice beside at the place mentioned 

 in the table, each time in marshy shallow ponds. 



Cyclops pulchkllus Koch. 



A slender species 1.25 mm. long. Broadest at about the 

 middle of the first cephalo-thoracic segment. Somewhat 



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