1068 Wisconsin Academy of Sciences, Arts, and Letters. 



ton with all the species of this genus grouped together has very 

 little value so far as Entomostraca are concerned. It may be 

 a matter of doubt whether the general student of Zoology is 

 ever likely to determine the species of Copepoda easily, as 

 special training is almost necessary for such work. But, even 

 if one had patience and a willingness to do the necessary work, 

 authoritative publications have not been available. Probably 

 the majority of students of North American Entomostraca refer 

 to Herrick and Turner's work because it is more comprehensive 

 than any other work published. This is now, however, pretty 

 thoroughly out of date, and it is very aggravating to a student 

 to feel that his book of reference is unreliable. 



A much more accurate paper is that of E. B. Forbes (Forbes 

 '97) and it seems to me that the real value of this paper has 

 never been recognized. It is now ten years since Forbes's 

 paper was published and additions have been made to our 

 knowledge of the genus, and facts which lead to a reconsidera- 

 tion of some of his statements. 



It has seemed to the author that the time has come when a 

 paper which would accurately present our knowledge of the 

 genus today, would be of real assistance to those students who 

 have anything to do with Entomostraca. There is really very 

 little to add that is new from the standpoint of the species 

 maker, only one new species is suggested, but it is worth while 

 to know what it is best to call the old species which have been 

 recognized under different names. 



In preparing this paper we have accepted the work of 

 Schmeil as authoritative for European species. Sometime it is 

 to be hoped that equally thorough work can be done for our 

 American species, but it does not seem wise to undertake it at 

 present. Our knowledge of the distribution of species in 

 America has been very much enriched in the past few years, 

 but nothing like thorough work has been done. The present 

 paper is based on collections made from the northern Canadian 

 provinces to Mexico and the West Indies, and from the At- 

 lantic to the Pacific, but vastly the most complete collections 

 have been made in the Mississippi Valley. 



