ENTOMOSTRACA AND PHYLLOPODA. 247 



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, posterior, broad, short, and bot- 

 tle-shaped egg-sack (&). 



k. Frontal appendages much twisted and coiled ; body 

 slender. Chirocephalus, 16. 



k. Frontal appendages not twisted nor coiled ; body 

 stout, granchipus, 17. 



ENTOMOSTRACA. 

 1. DAPHNIA (Fig. 159). 



There are several species of Ddphnia, all of which 

 may be known by the presence on the posterior border 

 of a sharp spine, which is never 

 on the lower angle. It varies in 

 length in the different species, 

 sometimes being nearly as long as 

 the shell, and extending oblique- 

 ly upward. It also varies in length 

 and in position on the same indi- 

 vidual, being longest in the young, 

 and becoming quite short with 

 age. In the species figured (Ddph- 

 nia pulex) it is usually on the 

 upper angle, but not rarely as shown in the cut. In 

 very old specimens it may be entirely absent, but it is 



