entom6straca and phyll6poda. 265 



c. Reticulated; spine or tooth on the upper angle; 



antennae long, with two branches. Cerioddph- 

 nia, 4. 



d. Beaked in front {e). 



d. Not beaked; oval, both ends rounded; smooth or 



hairy. Cypris, 5. 



e. Posterior border with from one to four small 



teeth. Camptocdrcus, 6. 

 <f. Posterior border without teeth (/). 

 /. Shell nearly spherical; posterior border truncate. 



Chydorus, 7. 



f. Shell no't spherical; posterior border convex; an- 



tennse small. Alondpsis, 8. 

 /. Shell not spherical; posterior border truncate; 

 antennae large, long, and branched. Sida^ 9. 



g. Body long and narrow; antennae long, twenty- 



five jointed. Didptomus, 10. 



g. Body long and narrow; antennae short, from four 

 to ten jointed. Canthocdmptus, 11. 



g. Body racket (battledore) shaped, with two exter- 

 nal ovaries. Cyclops, 12. 



h. Body enclosed in a bivalve shell (t). 



h. Body not enclosed in a shell (7). 



i. Shell nearly spherical, smooth. Limnetis, 13. 



i. Shell oval or oblong, flattened, amber-colored, 

 with longitudinal lines. Estheria, 14. 



j. In brine pools and salt lakes; eyes black, on 

 stalks. Artemia, 15. 



j. In fresh water; males with large frontal append- 

 ages; females without frontal appendages, but 

 with an external and posterior, broad, short, 

 bottle-shaped egg-sack (k). 



k. Frontal appendages much twisted and coiled; 

 body slender. Chiroc^phalus, 16. 



