SCIE 



limits of variation, and it is, perhaps, due to this fact that it is 

 so universally distributed. The littoral and pelagic forms are so 

 different that they have been considered specifically distinct. 



C. modestus is a rare form. Thus far it has been found in 

 only a single locality in Wisconsin. 



None of the American species of Diaptomus is identical with 

 those of Europe, although in some cases the relationship is very 

 close. 



D. sicilis is the common pelagic form of the Great Lakes, but 

 occurs also in smaller bodies of water. D. ashlandi has been 

 found only in the Great Lakes. 



The most common species in the smaller lakes is D. oregon- 

 ensis. This was described by Lilljeborg from specimens col- 

 lected in Oregon, and probably is common through our northern 

 States. D. minutus is common in Newfoundland, Greenland 

 and Iceland. It occurs in some of the small lakes in northern 

 Wisconsin and in Green Lake. It is likely that it occurs quite 

 generally through the northern part of North America, and pos- 

 sibly central Wisconsin is near its southern limit. 



Especial interest attaches to the fauna of Green Lake. This is 

 about seven miles long, with a maximum depth of nearly two 

 hundred feet. While the pelagic fauna of the Great Lakes is 

 quite distinct from that of the smaller lakes, we find in Green 

 Lake both sets of faunae. D. sicilis and Limnocalanus macrurus 

 I have not found outside the Great Lakes except in Green Lake. 

 But besides these species the pelagic fauna of Green Lake in- 

 cludes C. brevispinosus and C. fluviatilis, which are the charac- 

 teristic species of the smaller lakes. 



A more detailed account of the Wisconsin copepoda will soon 

 appear in the Transactions of the Wisconsin Academy. 



