THE WATER FLEAS (CLADOCERA) 



701 



54 (55) Head and valves strongly reticulated and covered with numerous 

 short spinules Ceriodaphnia acanthina Ross 1897. 



General shape rotund with well-developed spine. Head much depressed, not angulated in 

 front of antennules or at vertex. Antennules short and thick with sense-hair near apex. Post- 

 abdomen narrow, much like quadrangula, with 7-9 anal spines. Claws denticulate, the denticles 

 in the proximal two-fifths of the claw obviously longer than the remainder. Color whitish- 

 transparent to very dark. Length, 9> to i.o mm., $ unknown. 



Manitoba, in weedy slough. 



FIG. 1080. Ceriodaphnia acanthina. FIG. 1081. Details of valve, much enlarged. 



55 (54) Valves not spinulated 56 



56 (57, 62) Post-abdomen abruptly cut into near apex, serrate above, 



spines below Ceriodaphnia megalops Sars 1861. 



Head angulated before antennules; valves striated. Anten- 

 nules with sense-hair near apex. Post-abdomen broad, with 

 an angle near apex, cut into below angle, finely serrate above 

 and with 7-9 slender anal spines below. Claws not pectinate. 

 Length, 9 1.0-1.5 mm.; $ , 0.6-0.8 mm. 



Widely distributed but not common. 



FIG. 1082. Ceriodaphnia megalops. 



Post-abdomen not cut into; of ordinary form 58 



57(56,62) 

 58 (59) 



Fornices projecting into spinous processes. Eye small. 



Ceriodaphnia lacustris Birge 1893. 



Head angulated in front of an- 

 tennule; vertex with fine spinules. 

 Fornices very broad, triangular; 

 with spines at tip. Valves with 

 stout, short posterior spine, some- 

 times divided, but usually with 

 3-4 spinules. Post-abdomen like C. 

 quadrangula. o" unknown. Color 

 yellow, transparent. Length, 9, 

 0.8-0.9 mm. 



Wisconsin, Michigan; limnetic 

 in lakes. 



FIG. 1083. Ceriodaphnia lacustris. 



