NOTES ON THE COPEPODA OF WISCONSIN. 



BY C. D WIGHT MARSH, RIPON, WISCONSIN. 



In the waters of Wisconsin and in the adjacent lakes are found 

 the following twenty-one species of free-swimming copepods : 

 Diaptomus sanguineus, Forbes; D. leptopus, Forbes; D. ^alli- 

 dus. Herrick; D. sicilis, Forbes; D. ashlandi sp. nov ; D. mi- 

 nutus, Lil!j. ; D. oregonensis, LilJj. ; Epischura lacustris, Forbes; 

 LimnocaJanus macrurus, Sars; Cyclops americanus, sp. nov.; 

 C. brevispinosus, Herrick; C. pulchellus. Koch; C. navus, Her- 

 rick; C. parens, Herrick; C. leucarti, Sars; C. signatus, Koch; 

 C. modestus, Herrick; C. fluviatdis, Herrick; C. serrulatus, 

 Fischer; C. phaleraius, Koch; C fimbriatus. Fischer. 



Although two of these, D. ashlandi and C. americanus, are 

 new species, it is not probable that they are peculiar to the Wis- 

 consin fauna. The copepods of America have thus far received 

 very little attention, the only important publications on the sub- 

 ject being by three men, Professor Cragin, Professor Herrick and 

 Professor Forbes. If more were known of our copepods it is 

 probable that it would be found that there are few local differ- 

 ences in the faunae of our northern States. The copepods are 

 readily transported from one body of water to another and, 

 without change of structure, stem to endure great changes in 

 their environment. In fact, half of our species of cyclops ate 

 not only widely distributed in America, but are identical with 

 those of Europe. Those that may be considered distinctly Amer- 

 ican are closely allied to well-known European forms. 



C. leucarti is found in nearly all parts of the world where col- 

 lections have been made and, so far as can be inferred from the 

 published descriptions, varies but little, even in the minute de- 

 tails of its structure. 



C. americanus closely resembles C. viridis, and is probably the 

 species which has by other American authors been identified 

 with viridis. Although there seems to be good reason for sepa- 

 rating it from the European species, the similarity of the two 

 forms is so great that it is only by a close examination that the 

 structural differences become apparent. 



It is very possible that C. brevispinosus should be considered 

 a pelagic variety of C. americanus, thus reducing by one the 

 number of species peculiar to America. There is some reason, 

 too, for supposing that C. navus is not specifically distinct from 

 C. pulchellus. 



C. pulchellus is the common pelagic form of the Great Lakes. 

 Although found in smaller lakes, it is more commonly replaced 

 by C. brevispinosus. which is a species of wide distribution. 



C. navus is found only in stagnant pools. 



The most common of all our species is C. serrulatus. Earelv 

 is a collection without this form, which seems to adapt itself 

 easily to very different surroundings. It has. however, wide 



