STATE GEOLOGIST. 151 



** The two median setae much longer than the external. 



The species of this section are the most perplexing of the genus. 

 The best that I can now do is to indicate the relations of the nom- 

 inal species and express the conviction that most are of varietal 

 value simply. 



Sp. 16. Cyclops pulcliellus, Koch. 



C. bicuspidattLS, claus- 

 t Terminal joint of outer ramus of feet with two spines outwardly. 

 16 a. C. ihomasi, Forbes. 

 16 b. C iiavus, Herrick. 

 ft With three spines. 

 16 c. C. bisetosus, Rehberg^. 



= C. bicuspidatus, Sars. 

 = (?) C. insectus, Forbes. 



There are at least three well marked varieties in America, which 

 may probably rank as species and have been ranked as such by 

 Forbes. I give verbatim Forbes' description. 



(16a) Cyclops tlioinasi, Forbes. 



(Plate U. Figs. 4, 5, 7 and 8.) 



"Elongate, slender, broadest in front and tapering backward, 

 antennae 17-jointed, reaching the middle of the third segment. 



The first abdominal segment in the female is broad in front and 

 slightly emarginate on each side before the anterior angles, and the 

 last segment has a terminal circlet of small spines. The rami of 

 the furca are more than half as long as the abdomen, and each bears 

 two short rows of transverse spinules outside, one at the anterior 

 the other at the posterior third. With the latter a spine occurs 

 about as long as the outer terminal seta. The inner seta at the tip 

 of the ramus is about half the length of the furca, the outer still 

 shorter. The inner median seta is as long as the abdomen and 

 furca, and the outer about half as long. 



In the outer ramus of the first pair of legs the terminal joint 

 has one spine and two setae at the tip, one spine on the outer mar- 

 gin and two setae within. 



In the second, third and fourth pairs the last joint has one spine 

 and one seta at tip, two spines externally and two setae within. 

 The inner rami of the second and third pairs terminate in one spine 

 and one seta, that of the fourth pair in two spines, the inner of 

 vrhich is only half as long as the other. 



The legs of the fifth pair are two-jointed, with the basal joint 



