CRUSTACEA. 



155 



genus Lepas or Anatifa has as yet been certainly detected in a 

 fossil condition (Darwin), though D'Orbigny states that he has 



B 



Fig. 99. A, Turrilcfias Wrightii. Upper Silurian. (After Woodward.) a A plate 

 of the same magnified. B, Loricula pulchella. Chalk. (After Darwin.) 



discovered a representative of this genus in the Miocene 

 Tertiary. 



CHAPTER XV. 



CR US TA CEA Continued. 

 SUB-CLASS ENTOMOSTRACA. 



THE Entomostracous Crustaceans are defined by Professor 

 Rupert Jones as follows : " Animal aquatic, covered with a 

 shell, or carapace, of a horny consistency, formed of one or more 

 pieces, in some genera resembling a cuirass or buckler, and in others 

 a bivalve shell, which completely or in great part envelops the 

 body and limbs of the animal ; in other genera the animal is in- 

 vested with a multivalve carapace, like jointed plate-armotir ; the 

 branchifB are attached either to the feet or to the organs of mastica- 

 tion; the I i tubs are jointed, and more or less setiferous. The 

 animals, for the most part, undergo a regular moulting or change 

 of shell, as they grow ; in some cases this amounts to a species of 

 transformation. " 



The orders commonly included in the sub-class Entomostraca 

 are the Ostracoda, Copepoda, Cladocera, Phyllopoda, Trilobita, 

 and Merostomata (comprising the sub-orders Xiphosura and 

 Eurypterida). Of these, the Copepoda and Cladocera may 



