THE WATER FLEAS (CLADOCERA) 



717 



Only one American species. 



Eurycercus lamellatus (0, F. Mtiller) 1785. 



Body stout, heavy. Post-abdomen very large, 

 flattened, general form quadrangular; anus terminal, 

 in depression; dorsal margin, with very numerous 

 — over 100 — saw-Uke teeth. Claws on spiniferous 

 projection, with 2 basal spines and denticulate. Six 

 pairs of feet. Intestine with hepatic ceca and con- 

 volution. $ hke young 9 : hook on first foot; vas 

 deferens opens at base of claw on ventral (anterior) 

 side. Color yellowish-brown, opaque. Length, 9 , 

 to 3.0 mm. or more; 3 . to 1.4 mm. The largest 

 member of the family. Found everywhere; in per- 

 manent pools or margins of lakes among weeds. 



Fig. II 18. Eurycercus lamellatus. Post-Abdomen. 



119 (118) Anus on dorsal side of post-abdomen, whose post-anal portion bears 



denticles. No hepatic ceca. Two summer eggs; one 

 ephippial egg. $ with strong hook on first foot. 



Subfamily Chydorinae . . 120 



120 (247) Eye present 121 



121 (246) Eye and ocellus of ordinary size; antennules do not project beyond 



rostrum, though olfactory setae may. . . .... 122 



122 (171) Posteriormarginof valves not greatly less thanmaximumheight. 123 



No species of Pleuroxus belong in this section, though some individuals of 195 and 199 may 

 seem to do so. 



123(135) Body compressed; claws with secondary tooth in middle. . . 124 



124 (129, 132) Crested; post-abdomen narrow/ with marginal and lateral 

 denticles ' 125 



' Terms denoting relative size are to be understood with reference to the section in 

 which they occur. 



