25 



dd. With shell ; paired eyes sessile. 



e. Shell resembling that of a small clam. CONCHOSTRACA. 



f. Shell spheroidal without lines of growth. Limnetid.E. Limnetis. 



ff. Shell with concentric lines of growth. Limnadiid.^. 



g. Shell with 4 to 5 lines of growth. Eulimnadia. 



gg. Shell with 18 to 22 lines of growth. 



h. Pediculated dorsal organ on front of head ; 18-22 pairs of limbs. 



Linmadia. 



hh. No dorsal organ present ; 24 to 28 pairs of limbs. Esthcria. 



ee. Shell not clam like. NOTOSTRACA. 



cc. With 4 to 6 trunk limbs ; shell bivalved, generally covering body but 



leaving head free. CLADOCERA. 



d. Shell restricted to the brood chamber ; feet flattened and jointed. 



GYMNOMERA. 

 Polyphemus pediculus (fig. 13) and Leptodora kindti (fig. 15). 

 dd. Shell covering the body ; feet not distinctly jointed. 



CALYPTOMERA. 



e. Six pairs of feet ; foliaceous. CTENOPODA. 



f. Swimming antenna of female two branched, the dorsal with many 



lateral and terminal setae. Sididae. 



g. Dorsal ramus 3-jointed, ventral ramus 2-jointed ; beak present 



(fig. 2). Sida. 



gg. Dorsal ramus 2-jointed, ventral ramus 3-jointed. 



h. Dorsal ramus with interior process or expansion on basal joint. 



Latona. 

 hh. Dorsal ramus without process. 



i. Posterior margin of shell valves with several long setse. 

 j. Eye dorsal far from insertion of antennule. Latonopsis. 



jj. Eye ventral or in middle of head. Pseudosida. 



ii. Posterior margin of shell valves without set£e. (fig. 12). 



Diaplianosoina. 

 ff. Animal enclosed in a large globular, transparent, gelatinous case 

 open ventrally and forming two valves. Antennae of female with 

 single ramus. HoIvOpedidae. Holopediuin. 



ee. Five or six pair of trunk limbs, first two pairs more or less pre- 

 hensile. ANOMOPODA'. 

 f. Second antennae with superior branch 4-segmented ; inferior branch 

 3-segniented. 

 g. With five pairs of feet ; first antennae small, if rarely large, (as in 

 Moina) then not inserted at anterior end of head ; intestine with 

 2 hepatic csca. Daphnid^. 

 h. Head of female with a beak, 

 i. Head keeled above ; no transverse suture on neck ; shell with 

 polygonal marks and with posterior spine (fig. i). Daphne. 

 ii. Head not keeled ; neck suture present, 

 j. Spine on shell produced in a straight line with the ventral mar- 

 gin ; shell with indistinct net like markings. Scapholeberis. 

 jj. Spine absent or very short and blunt ; markings of transverse 

 lines (fig. 5). Simocephalus. 



