. Fresh-water biology. Freshwater biology. THE WATER FLEAS (CLADOCERA) 725 171 (122) Posterior margin of valves considerably less than maximum height. 172 All species of Pleuroxus belong here; also Alonella. excisa. and exigua. 172 (204) Body elongated, form not spherical I73 173 (174, 17s) Lower part of posterior margin excised or crenulated. Alonella excisa, A. exigua . 244,245 Turn to the key at the numbers indicated where two species are discussed. 174 (173, 17s) Posterior margin with numerous teeth along whole length. Pleuroxus procurvatus, P. truncatus . 188, 191 Turn to the key at the n
. Fresh-water biology. Freshwater biology. THE WATER FLEAS (CLADOCERA) 725 171 (122) Posterior margin of valves considerably less than maximum height. 172 All species of Pleuroxus belong here; also Alonella. excisa. and exigua. 172 (204) Body elongated, form not spherical I73 173 (174, 17s) Lower part of posterior margin excised or crenulated. Alonella excisa, A. exigua . 244,245 Turn to the key at the numbers indicated where two species are discussed. 174 (173, 17s) Posterior margin with numerous teeth along whole length. Pleuroxus procurvatus, P. truncatus . 188, 191 Turn to the key at the numbers indicated where two species are discussed. 17s (173, 174) Teeth (if any) only at infero-posteal angle. . 176 176 (179) Infero-posteal angle well marked, ordinarily with teeth. . 177 177 (178) Rostrum long. . Pleuroxus most sptds?, . 186 Take up the key at the number indicated where the genus is discussed as a unit. 178 (177) Rostrum short . Alonella dcntifera . 233 Take up the key at the number indicated where the genus is discussed as a unit. If the rostrum is broad, semi-circular at end, 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 . 195 Turn to the key at the number indicated where the species named is discussed. 182 (181) Rostrum short Dunhevedia King 1853 . 183 General shape roimded. Valves tumid, gaping below; obscurely reticulated; infero-posteal angle rounded, with i or 2 teeth on ventral margin in front of angle. Post-abdomen bent abruptly behind anus; post-anal part thick, somewhat foot-shaped as seen from side, its dorsal (lower) margin lying parallel to ventral margin of valves; with many fine denticles and setae. Claws short, curved, with i basal spine. $ with usual characters; post-abdomen same shape as 5, with fine hairs only. 183 (184) Form short and high, as dorsal margin is much arched. Dunhevedia setigera (Birge) 1877. Keel of labrum produced i
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectfreshwa, bookyear1918
