334 



CRUSTACEA 



L. setifera (0. F. Miiller). 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; 

 beak absent ; no teeth on the abdomen ; first antennae 

 short in female: several species. 



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

 in clear water; widely distributed; Europe. 



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. 



Pig. 515 



Daphnella 



"bracliyura 



(Siissw. F. Deut.). 



1, second antenna 

 2, first antenna 



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

 I. optic ganglion; 5, brain; 6, 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 : 

 o x Head terminating ventrally in a beak. 

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



spine at the upper posterior angle 1. DAPHNIA 



6, Such a notch present. 

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



posterior angle 2. SCAPHOLEBEBIS 



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



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



&! Abdomen not enclosed by shell 4. MOINA 



&a Shell enclosing the whole abdomen 5. CEEIODAPHNIA 



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, tapexing betindj length 1.8 mm.; a project- 



