ENTOMOSTRACA. 41 



as Branchinecta schcefferi, the last segment of the abdomen having become divided 

 into two. Nor is this change produced by artiiicial means alone. The salt pools near 

 Odessa, after a number of years of continued washing, became converted into fresh- 

 water pools, and with the gradual change in character Artemia salina produces first a 

 species known as Branchinecta spinosus, and at a still lower density Branchinecta ferox, 

 and another species described as B. medius. "We have already referred to partheno- 

 genesis in this genus. 



There are only two other genera of this family which need to be mentioned, 

 Chirocephalus and Thamnocephalus. In these genera the frontal process, which is 

 small in Branchipus, acquires a great development, branching in the latter genus, 

 which is peculiar to America, in a manner recalling the limbs of a tree, whence the 

 scientific name of the genus, — bushy head. Thamnocephalus also differs from all the 

 other genera of Phyllopoda in the absence of appendages to the telson. 



Several species of Phyllopoda are known in a fossil condition, four being found in 

 American strata. JEstheria occurs in the Devonian of Europe, while Beaia, a more or 

 less problematical form, occurs in the lower carboniferous of both Great Britain and 

 Pennsylvania. Apus first appears in the Triassic, while Branchipus dates back to the 

 Eocene. 



J. S. KiNGSLBY. 



