North American FrcsJi-ivatcr Cyclopidce. 57 



Ordinarily the egg- sac tapers to a sharp point at the lower 

 end, and stands out from the abdomen at a wide angle. 



The size is remarkal)ly variable. In Enrope, the length 

 varies from .883 to 2.2 mm. In America I have measured 

 specimens varying in length from .54 to 1.47 mm. A com- 

 mon length is .*,) mm. 



Cyclops prasinus Fischek, (PI. XIX., Fig. 1 and 2, and 

 ri. XX., Fig. 1 and 2.) 



Cxjclops prasinus^ Fischer, 'GO, pp. 052-054. PI. XX., Fig. 10-'2Ga. 

 Cyclops fliiinalills^ Ilerrick, '82 a, p. 231, PI. VII.. Fig. 1-9. 

 Cyclops magnoctavus, Cragin, '83, pp. 70,71, PI. III.. Fig. 14-23. 

 Cyclops prasinus, Sehmeil, *92. pp. 150-150, PI. V., Fig. 1-5. 

 Cyclops fluviati lis, Herrick and Turner. '95, pp. 114,115, PI. XXVI., 

 Fig. 1-8; XXX., Fig. 1. 



SYNONYMY AND DISTKIBUTION. 



On account of the great difficulty in determining the struc- 

 ture of the rc'ct'])t((riibiiii sc in hi is of C ^yrasiniis, this organ 

 has escaped study in the American representatives of this 

 species, and although Marsh had noted a general resemblance 

 of Herrick's ('. jJiiridfUis to Vosseler's C. pciitdfioiius (C. 

 2im-'ii)ni-'^ Fischer), he did not consider these as identical. By 

 a careful study of a large number of specimens of C. Jiuvuit- 

 tlis from Illinois, Florida, and "Wisconsin, I find a complete 

 agreement in the characters of the rcccptunduiu scininis of C. 

 jirdsiiiiis and C. tiiir'uifilis and in all other specific characters 

 as well. 



I have noted the occurrence of C. jirdsinns in collections 

 from Sister Lake, Florida ; Long Lake, Adams county. 111. ; 

 ponds and temporary pools at Urbana, 111. ; Illinois Kiver at 

 Havana, 111. ; Phelps, Flag, and Thompson's lakes in Ful- 

 ton county, 111. ; Dogfish and (Quiver lakes in ^lason county, 

 111. ; and from Lake Geneva, Wisconsin. Herrick reports it 

 from Lake Minnetonka, Minn., and from an estuary of the 

 Mississippi, Marsh finds the species in Lakes Erie, Michi- 

 gan, and St. Clair, and in fifteen smaller lakes of Michigan 

 and Wisconsin. Cragin found it in ditches at Cambridge, 

 Mass. 



