THE WATER FLEAS (CLADOCERA) 



721 



(141) 



About 16 marginal denticles. 



Oxyurclla longUaudis (Birgc) igio. 



Between Alona and f .' ' 

 Valves with conccntrii : 

 marginal dentiiles. lar^ • 

 nullimate much larger, an.: 

 larKer still and serrate on 



Basal spine stout, attai lutl aL....; .,.,, . 



way from base- of daw. ^ unknown 

 Length, 9 . 0.5-0.6 mm. 



Rather rare amon^ wec<ls. Lake CliArlcs. 

 La. 



Fig. 1 1 26. OxyurtlU Umtuaitdn. 



143 (140) Post-abdomen not noticeably narrow; distal denticles not conspicu- 



ously larger. Basal spine small. Alomj{miJsis\H:ck-s) . . 151 

 Take up the key at the number indicated where the genus is discussed a^ a unit. 



144 (139, 147) Post-abdomen with marginal denticles only. ... ; ; 



145(146) Post-abdomen large, denticles very small. Alondladiaphdr.i 

 Turn to the key at the number indicated where the species named is discu.sscd. 



146 (145) Post-abdomen of moderate size; denticles of usual size. 



Alona guttuUi 

 Turn to the key at the number indicated where the species named is discussed. 



147 (139, 144) Post-abdomen with numerous clusters of large spines. 



Lcydigia Kurz 1874 

 General shape oval, much compressed but not crested. Head small, extendcl; V-' •' 

 labrum rhomboidal with angles blunt or rounded. Post-abdomen very large, com; • 

 semi-elliptical in form; post-anal part much expanded, with numerous clusters of 

 spines in distal clusters very long. Claws long and slender. Kye smaller than wcIIun (J 

 with blunt rostrum; process on upper (ventral) side of post-abdomen on which vas deferens 

 opens; post-abdomen with spines. Color yellow. 



148 (149) Valves without markings. Leydigia quadrangular is (Lcydig) i860. 

 Keel of labrum with minute setae. Claws with basal spine. Length. 9 • to 0.9 mm ; ' 



0.7 mm. 



In all regions of the country; not common; found singly among weeds. 



149 (148) Valves striated longitudinally. 



Leydigia acanthoccrcoidcs (Fischer) 1854. 



Keel of labrum with long cilia. Claws without basal spine. Length. 9 1 to 10 dmu. or more; 



d (European), 0.7 mm. 

 Rare: Louisiana. 



I^O 



148 



0.2 MM. 



Fig. 1 1 2 7 Leydigia acatUkocercoides. 



