THE WATER FLEAS (CLADOCKRA) 



171 (122) Posterior margin of valves considerably Kss llian maximum height. 



All species of Pleuroxus belong here; also AloncUa excisa an<l <-.ri\'M<j. 



172 (204) Body elongated, form not spherii al. 



173 (174, 175) Lower part of posterior margin excised or crenulalwl. 



AloncUa excisa, A. cxigwi • ; ; . . 



Turn to the key at the numbers indicated where two species are discusv ; 



174 (173, 175) Posterior margin with numerous teeth along whole length. 



Pleuroxus procurvatus, P. trutUiitus iK,s. i,ji 



Turn to the key at the numbers indicated where two sik-cIcs are disrusM<i 



175 (173, 174) Teeth (if any) only at infero-jHjslcal angle. \-h 



176 (179) Infero-posteal angle well marked, ordinarily with trcth 177 



177(178) Rostrum long /7<'//r<u;o- most s{K'nes 186 



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



178 (177) Rostrum short UoticUa dctUiifra . . 



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

 N.B. If the rostrum is broad, semi-circular at vnd, see 167. 



179 (176) Infero-posteal angle rounded 180 



180 (185) With well-marked tooth or teeth 181 



181 (182) Rostrum long, recurved Pleuroxus striatus . 



Turn to the key at the number indicated where the species named is di.scusse<i. 



182(181) Rostrum short D u )i /lanl la Kiuf; iS-~,^ ..-, 



General shape rounded. Valves tumid, gaping below; obscurely reticulatc<!; infcn>-i»i»Mc«l 

 angle rounded, with i or 2 teeth on ventral margin in front of angle. I'ost-aiH!. tm n l-cnt 

 abruptly behind anus; post-anal part thick, somewhat foot-shajx'd as strn from d 



(lower) margin lying parallel to ventral margin of valves; with many fine dcnti' 

 Claws short, curved, with i basal spine. $ with usual characters; ixjst-alxionuu >-i. 

 as 9 > with fine hairs only. 



183 (184) Form short and high, as dorsal margin is much arched. 



Dunhrccdi,! srHi'cr,: (Hirire) 1S77. 



^ ^ V"; ' ^ X,^ Keel of labrum pro(iuce<i into a stmicwhat tm . 



^^.^ I ' ' ^ • ^ v^^ form, its ventral margin sm(H)th. Color yellow. 1 



^: \ 9, to 0.5 mm.; /, ca. o..^f) mm. 



\ New England and Wisconsin to Colorado, l^ 



; " " ^ Jl, and Texas. Not common; among wcttls. I'crhap 



. , , cal with D. crassa King. 



■''^■<- . ^ 



aiMMf. . . f- 



