98 Illinois state Laboratory of Natural History. . 



have been made by Claus, Schmeil, Poppe, Imhof, Zacliarias, 

 and others, in Germany ; by Brady, in England ; by Nord- 

 qvist, in Finland; by Bars, in Norway; and by Lilljeborg in 

 Sweden, the latter especially having described a number of 

 American species. Perhaps the finest work yet published 

 on Copepoda in general is Giesbrecht's monograph on the 

 " Pelagischen Copepoden des Golfs von Neapel" ('92), the 

 general classification of which is followed in the present 

 article. 



It has been my purpose in preparing this paper to do for 

 the students of American Centropagidce a service similar to 

 that which de Guerne and Richard have rendered to students 

 of this group as distributed throughout the world. I am 

 under especial obligation to my instructor, Prof. S. A. Forbes, 

 to whose encouragement and aid any value this paper may 

 have is to be largely attributed. I am indebted also for 

 specimens or other favors to Dr. Wilhelm Lilljeborg, of 

 Upsala, Sweden ; to Dr. Otto Schmeil, of Magdeburg, Ger- 

 many; to Herr S. A. Poppe, of Vegesack, Germany; to Prof. 

 C. Dwight Marsh, of Ripon College, "Wisconsin ; to Prof. L. 

 S. Ross, of Drake University, Des Moines, Iowa; to Mr. 

 Adolph Hempel, now of the Museu Paulista, Sao Paulo, Bra- 

 zil ; to Prof. Frank Smith, of the University of Illinois ; to Mr. 



C. E. Phillips, of Millington, 111. ; and to my friend and fellow 

 student, Mr. E. B. Forbes. I have also to call attention to 

 the fact that most of the figures accompanying this paper 

 were drawn by the Artist of the State Laboratory, Miss 

 Lydia M. Hart. 



From Dr. Lilljeborg I received specimens of Diaptomus 

 signicauda, D. minutus, 1>. trybomi, D. eiseni, I). francisca- 

 nus, Epischura nevadensis, and K. nordenskibldi. Prof. Ross 

 and Mr. Hempel kindly loaned me their personal collections, 

 the former thus furnishing me D. siciloides, I >. piscina, and 



D. clavipes sp. nov., and the latter, D. mississippiensis and 

 D. albuquerquensis. Prof. Marsh has sent me slides or entire 

 specimens of D. ashlandi, 1 >. mississippiensis, and D. reighardi. 

 To Dr. Schmeil I owe thanks for several kind letters, for the 

 European species 1>. gracilis, I>. graciloides, I>. castor, D. 



