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thoroughly out of date, and it is very aggravating to a student 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