North American Species of Diaptomus. 99 



salinus, D. coeruleus, and D. zachariasi, and for specimens 

 of Heterocope and Temorella, — all of which, however, arrived 

 too late to be of service to me in connection with this paper. 

 From Herr Poppe I received the following species : D. tyrrelli, 

 D. gibber, D. incongruens, D. deitersi, D. drieschi, D. zacha- 

 riasi, and Limnocalanus sinensis. 



The material at my command was nearly complete, includ- 

 ing all but two of the known North American forms (D. 

 novamexicanus and D. birgei), and the collection of the liter- 

 ature of the group to which I have had access is probably as 

 ample as that to be found in any library in this country. 

 In compiling the bibliographical list appended to this paper, 

 Schmeil's monograph on the Ccntropag'uhe ('96) was taken 

 as a basis and was especially helpful, while a great deal was 

 also gained from the works of de Guerne and Eichard. 



By far the greater part of the collections examined are the 

 property of the Illinois State Laboratory of Natural History. 

 They represent localities distributed over the entire continent, 

 from Massachusetts in the East to Oregon in the West, as far 

 south as Florida and as far north as Canada, and including the 

 following states : Massachusetts, Florida, Mississippi, Ohio, 

 Indiana, Illinois, Iowa, Minnesota, Michigan, Wisconsin, 

 Oregon, Washington, Montana, Wyoming, California, Idaho, 

 and Nevada. In addition to the above I have examined 

 specimens from Manitoba, Newfoundland, and Greenland. 



The localities represented by these collections vary widely 

 in character, ranging from temporary pools on the Illinois 

 prairies to Lakes Michigan and Superior; from the warm 

 lakes of the Florida swamps to the cold mountain lakes of 

 the Eockies ; and from the small head-water streams of the 

 Kaskaskia to the sluggish Illinois and the mighty Mississippi. 

 The collections were made at all seasons of the year and at 

 nearly all times of the day and night. 



Although no very complete data for any single locality are at 

 hand, it is found that in ordinary years the spring and early 

 summer are the most favorable seasons for collecting in our 

 latitudes. Individuals are found, however, at all times ; and 

 in some cases the normal habitat is a lake whose waters are 



