THE WATER FLEAS (CLADOCERA) 



157 (156) With marginal and lateral denticles 



158 (161) Size large; 14 or more marginal (kninK:-. 



159 (160) Cluster of fine spinules at base of claw. 



723 



^■S\^<. 



■•^^.-,'r^'C-^-J 



0.1 MM. 



Mouii ajjinis (U-ydig) i860. 



Greatest hi-i^ht usually near ti.i.lflr 

 valves. \'alvcs IcmKituMinally • 

 ticulatod, often not plainly miir. 

 with rhomboidal keel; its torn. • 

 lated, sometimes n)un(lc<J. i 

 large, not widened behind ant; 

 serrate marginal dentitl«-s an' I 

 of small S(iuamaf. Claws Ion, 

 with long ba.sal spine and 45 ; 



r; 



mentary. Length, 9. t" « o mm.; ^ . to 0.7 

 mm. 



The largest species of the gcnuA; very abun- 

 dant in all regions, in maririn of jinnd* and 

 lakes, among weeds. 



Fig 1130. Alotui r-,nf 



160 (159) No spinules at base of claws. 



Alona quddrangularis {O. V . Miiilcr) 1785. 



Greatest height usually posterior to middle of valves. Valves usually plainly striated. 

 sometimes conspicuously so, with a reticulated area in infero-anterior region (var. /<-/>iJu Hirifr). 

 Labrum with large keel of variable form; often quadrate or with rounder! angles. Post aWo- 

 men large, flattened, dorsal margin dilated; with 15-18 serrate marginal denticles and row o( 

 lateral squamae. Claws large, with long basal spine; no spinules on inside of basal ^%T^e. 

 Length, 9. to 0.9 mm.; <? , to 0.6 mm. See Fig. 1129, a. In similar KKalitii's to prrcnlinjc 

 species; also on bottom of open water. 



161(158) Size moderate or small. Fewer than 14 denticles. 



This section of the genus needs much additional study. There are s|K'iics .md numerous 

 varieties beside those listed. 



162 (163) Lateral fascicles or squamae do not extend beyond dorsal marpin 

 of post-abdomen ^loun costatu Sars iSO:. 



Evenly arched or greatest height behind middle; posterior margin ranvcx. Valve* «ri*ted 

 or smooth. Post-abdomen short, broad; with straight dorsiil (lower) manan tapenng toward 

 apex; with about 12 subequal denticles and a row of fine squamae. rost-alMl.>mcn of J taper- 

 ing; no marginal denticles; very fme squamae; vas deferens ojK-ns at 

 extending out ventral to (above) claws; claws without basal spme. I 

 more; ^ , 0.4 mm. See Fig. 11 29, c. 



Found everywhere and very abundant. 



163(162) Lateral fascicles long, extending beyond dorsal ma r^nn. if*; 



164 (165) Post-abdomen not broadened toward ape.\. 



AloHii rcctiin'^-M.i : 



Body evenly arched; general form like A. guttata. Valves striate*!, rrtin.l.ntcl. 

 rarely tuberculate; ventral margin usually somewhat a'"vex 1' ■; 

 enlarged toward apex, angle rounded; with 8-0 marginal ( enticles or 

 as many fascicles, the distal long enough to project beyond margin *'' i 

 without cecum, enlarged at junction of intestine and rectum. s*.incwh.ti a-s .» 

 Length, 9, 0.35 to 0.42 mm. See Fig. 1129, c. /. x ; t. . ii..ii:rK 



Common everywhere. Most specimens found belong to var. puUHra nciuai. 



\\itx of pfucrsa 

 ngth. 9.05 nim or 



' '-ly 



it 



■ uc 



