THE WATER FLEAS (CLADOCERA) 



709 



large, some distance from apex of rostrum. Intestine convoluted, with small hepatic ceca. 

 $ with hook on first foot; vas deferens opens near claws. Length, 9 , to 1.2 mm. Color 

 transparent-yellowish. 



Maine, New Hampshire; among weeds in lakes. The difference in antennary setae of 6* and 

 9 holds for all specimens hitherto seen. 



;&2 MM. 



FIG. noi. Parophryoxus tubulatus. (After DoolittleJ 



QO 



StreUocerus Sars 1862 



89 (88) Setae - =-& ; animal small, spherical. 



11-3 



Body round-oval, not compressed or crested. Labrum with large, serrate, acute process. 

 Antennules large, flat, bent, or rather twisted, broadened in distal part; with lateral sense- 

 hair near base, several hairs on posterior face, rows of fine hairs, and subequal olfactory setae. 

 Post-abdomen bilobed; the pre-anal part compressed, semi-circular; the anal part rounded, 

 with fine spines or hairs. Claws small, curved, with several equal minute denticles on con- 

 cave edge. Five pairs of feet. Intestine convoluted, with small hepatic ceca. $ (European, 

 of S. serricaudatus) small, triangular, much like 9 ; first foot without hook. 



90 (91) Dorsal margin of valves smooth. 



Streblocerus serricaudatus (Fischer) 1849. 

 0.1 MM. ' Pre-anal part of post-abdo- 



men with serrate margin and 

 bearing rows of fine hairs. 

 Anterior margin of antennule 

 somewhat toothed. Color 

 whitish-opaque to yellowish. 

 Length, 9> ca. 0.5 mm.; $, 

 ca. 0.25 mm. 



Rare but widely distributed 

 in weedy pools and margins of 

 lakes. Reported from New 

 England, Wisconsin, Nebraska, 

 Louisiana, Colorado, Califor- 



FIG. 1102. Streblocerus serricau- 

 datus. 



gi (go) 



Valves reticulated, the edges of the reticulations making scale-like 

 ridges, which give the dorsal margin a serrate appearance. 

 O.05 MM i t Streblocerus pygmaeus Sars 1901. 



Pre-anal part of post-abdomen not serrate, with 4-5 rows 

 of fine hairs. Color grayish white, opaque, to nearly black 

 in ephippial 9 $ unknown. 



Length, 9 0.2-0.25 mm. The smallest member of the 

 family and one of the smallest of the group. Louisiana, in 

 weedy pools, with S. serricaudatus. 



FIG. 1103. Streblocerus Pygmaeus. 



