STATE GEOLOGIST. 161 



Sp. 28. Cyclops phaleratus, Koch. 



(Plate R. Figs. 6—10.) 



(rar. a.) 



C. canthocarpoides, fischer, claus, lubbock, frig. 

 C. phaleratxis, koch, sars, ul.janix, brady, rkhbebg. 



C. afflnis, sabs. "^^ 



C. py(7m<:EUJ*. rehberg. ^ 



C. adolescent, hebrick.(==(7. pera/rmatus, cragix.) 'i' 



fC. laSCiVUS, POGGENPOL. -•'. 



That the two varieties here united are very closely allied must 

 be admitted; that they are merely age forms is possible. Glaus in 

 figure 2 of his plate II (Freilebenden Copepoden) figures some 

 other species than the one described as C canthocarpoides, as can 

 be gathered from the elongated stylets and the eight-jointed an- 

 tennse. Our Minnesota specimens combine the eleven-jointed an- 

 tennse of C. affinis with the short stylets and peculiar form of the 

 filth feet of the first mentioned. Rarely one is found with ten- 

 jointed antennae and at the same time sexually mature. The char- 

 acteristic oblique lines of spines at the base of the stylets may be 

 absent. Rehberg's figures of C. pygmseus agree very well with our 

 species, but he has decided that it is not specifically distinct from 

 C. affinis. 



It appears to me undesirable to institute a new species for the 

 American form, neither is it possible to sufficiently identify it with 

 any of the above. 



I here append a brief description of Cyclops adolescens^ Herrick 

 (^C. perarmatusj Cragin,) for comparison with the description of 

 C. affinis as transcribed below. Thorax oval, broad, acute anterior- 

 ly ; last segment large and separated by a constriction from the 

 anterior ones. The head is beaked below; first throacic segment 

 large and long (.36 mm.): last thoracic segment wide, united 

 closely with the first abdominal segment, armed with series of 

 teeth. Abdomen short, especially the last segment, which is 

 toothed behind ; stylets very short. The antennae are much 

 shorter than the first segment, eleven-jointed. The maxillipeds 

 are very small. All the feet are armed with a row of very large 

 teeth or lanceolate spines down one side; fifth foot one-jointed, with 

 three spines, the outer being smooth, the others spiny; egg-sacs 

 variable, narrow, appressed; eggs large, color usually dark. The 

 animal moves like Canthocamptus, and is able to progress out of 

 water better than other species. The following measurements will 

 give an idea of the proportions: Length 1.26 mm.; thorax, 0.76 

 11 



