44 Illinois State Laboratory of Natural History. 



dependence can be placed upon it for purposes of distinction. 

 This variety may be wholly red or blue or greenish or it 

 may even be colorless. 



It is found everywhere in the United States and Canada 

 where Cyclops have been collected, and no situation seems to 

 be free from them. In Illinois by far the greater portion of 

 the Cyclops of the small ponds and temporary pools and 

 puddles belong to this species. 



Cyclops bicuspidatus Claus. (PL XII. , Fig. 1-4.) 



Cyclops bicuspidatus, Claus, '57, p. 209. 



Cyclops pulchellus, Sars, '63, pp. 246,247, PI. XI., Fig. 6 and 7. 



Cyclops navus, Herrick, "82a. p. 229, PI. V.. Fig. 6-13, 15-17. 



Cyclops tfwmasi. Forbes. "82a. p. 649. 



( 'yclops bicuspidatus, Suhmeil, '92, pp. 75-87, PJ. II., Fig. 1-3. 



Cyclops minnilus, Forbes, '93, p. 247. 



Cyclops serratus, Forbes, '93, pp. 247, 24S. 



Cyclops Jbrbesi, Herrick and Turner, '95, p. 104. 



SYNONYMICAL DISCUSSION. 



This immensely variable and widely distributed species is 

 represented in the United States by a number of forms which 

 have been described by our most reliable zoologists as species 

 new to science. As more complete series of collections from 

 the United States have been studied, it has become evident 

 that these forms are so closely connected in series, that dis- 

 tinctions which a few years ago were considered as specific 

 must be cast aside and the whole group united under the 

 name of the European form. 



With regard to Cyclops thomasi Forbes, I must agree with 

 Dr. Schmeil that there is no need of considering this form as 

 even a variety. A close study of the type specimens of 

 ( 'yclops tli mil <i si reveals a number of small differences between 

 it and Cyclops bicuspidatus as described by Dr. Schmeil, but 

 they agree almost exactly with other descriptions, by European 

 investigators, of forms included in Dr. Schmeil's synonymy of 

 C. bicuspidatus Clans. Only a single specimen of the form 

 as described by Dr. Schmeil has been found by me in collec- 

 tions from this country. This single individual came from a 



