THE WATER FLEAS (CLADOCERA) 



737 



243 (238) Claws with 2 basal spines; posterior margin of valves excised near 



infero-posteal angle 244 



244 (245) Post-abdomen fairly long; angled at apex; valves reticulated and 



with fine striae Alonella excisa (Fischer) 1854. 



General appearance Pleu- 

 roxus-like. Rostrum moder- 

 ate to long, never as pro- 

 longed as in A. rostrata nor 

 recurved; longer in southern 

 forms. Infero-posteal angle 

 marked, sometimes produced 

 into a point; posterior mar- 

 gin above it excised, some- 

 times crenulated. Post-ab- 

 domen long, narrow, not nar- 

 rowing much toward apex; 

 apex angled; with about 9- 

 10 small marginal denticles. 

 Color yellow to brown. 

 Length, 9> to 0.5 mm.; $ t 

 0.28 mm. 



Not uncommon in all lo- 

 calities; in weedy pools and 

 lakes. 



0.1 MM. 



FIG. 1165. Alonella excisa. Entire specimen and details of 

 markings of valve. 



245 (244) Post-abdomen short; rounded at apex; valves without fine striae. 



Alonella exigua (Lilljeborg) 1853. 



Much like preceding species but smaller. About 6-8 small 

 marginal denticles. Color yellow, not very transparent. 

 Length, 9, 0.35 mm.; $, 0.28 mm. 



Maine, Wisconsin, Michigan; rare. 



FlG. 1 1 66. Alonella exigua. 



O.I MM. 



246 (121) Eye and ocellus very large; antennules project far beyond rostrum. 



Dadaya Sars 1901. 

 Sole species Dadaya macrops (Daday) 1898. 



Form rounded-oval; not compressed. Head 

 small, much depressed; tumid above eye; ros- 

 trum short and broad. Antennules long, mod- 

 erately stout, projecting far beyond rostrum. 

 Post-abdomen of moderate size, compressed, 

 somewhat broadened behind anus, slightly 

 narrowing toward apex; angle rounded; about 

 14-18 marginal denticles. Claws small, one 

 small basal spine. Eye very large, with few 

 lenses; ocellus nearly as large, crowded down 

 into rostrum. $ unknown. Color dark 

 brown. Length, 9 > ca- -3 nun- 



A single specimen of this species was found 

 in a collection from a weedy pool at Smith- 

 ville, Texas. 



FIG. 1167. Dadaya macrops. 



