334 CRUSTACEA 



L. setifera (0. F. Milller). Body and appendages very setose; color 

 yellowish, often with spots; length 3 mm.: among weeds in clear lakes; 

 widely distributed; Europe. 



3. Daphnella Baird. Ventral branch of second 



antennae with 3 segments; dorsal branch 2 segments; 



I beak absent; no teeth on the abdomen; first antennae 



Fig. 515 short in female: several species. 



Daphnella 



hrachmra D. brachyura (Lievin) (Fig. 515). Length .7 mm.: 



(Siissw. F. Deut.). . , .\ , 



1, second antenna m clear water; widely distributed; Europe. 

 2, first antenna 7 ^ , r- 



Family 2. DAPHNIDAE. 

 Body oval; head rounded, usually with a short beak; first antennae 

 usually minute, consisting of a single segment; the 2 branches of the 

 second antennae consisting of 3 and 4 segments respectively; 5 pairs of 

 legs, the last pair separated from that next to it; intestine not coiled 

 and with a pair of liver sacs : about 12 genera. 



/O 



^ ^ / /5 ^T"^ i3 



Fig. 516 — Paphnia pulex (Kingsley). 1, first antenna ; 2, second antenna ; 3, eye ; 

 4. optic ganglion; 5, brain; (j, liver sac; 7, intestine; 8, kidney; 9, heart; 10, brood 

 sac with two eggs ; 11, abdomen ; 12, anus ; 13, ovary ; 14, legs ; 15, mouth ; 16, 

 exopodite ; 17, endopodite. 



Key to the genera of Daphnidae here described : 

 Ci Head terminating ventrally in a beak. 

 &i Head not separated from body by a dorsal notch ; shell with a caudal 



spine at the upper posterior angle 1. Daphnia 



&2 Such a notch present. 

 Ci Shell abruptly truncated behind, with a short spine at the lower 



posterior angle 2. Scapholeberis 



c. Shell rounded below, with a blunt spine above 3. Simocephalus 



«2 No beak, or a rudimentary one. present. 



hi Abdomen not enclosed by shell 4. MoiNA 



tj Shell enclosing the whole abdomen 5. Ceriodaphnia 



1. Daphnia 0. F. Miiller. A sharp caudal spine, extending from 

 the upper posterior angle of shell; head not separated from the body by 

 a dorsal notch: about 50 species. 



D. minnehaha Herrick. Caudal spine less than half the length of 

 the shell; general form oval, tapering behind; length 1.8 mm.; a project- 



