THE CLASSIFICATION OF CRUSTACEA 37 



dorsal shield, or carapace, covering the greater part of 



the body, which consists of a large number of seg- 



ments (about twenty- 



eight), and ends be- 



hind in a pair of 



long antenna-like fila- 



ments. The fin-like 



feet are also very nu- 



merous (about sixty- 



three pairs). The eyes 



are not stalked, but 



are set close together 



on the upper surface 



of the carapace. 



The third order of 

 the Branchiopoda, 



the CONCHOSTRACA 



(Fig. n), are not re- 

 presented in Britain, 

 though several 

 species occur on the 

 Continent of Europe. 



j , , FIG. 12 Daphnia pulex, A COMMON 



tne cara- SPECIES OF "WATER-FLEA." MUCH 



(Fr m British Museum 



Female carrying eggs in the brood- 



chamber 



pace forms a bivalved 



shell, Completely en- 



closing the body and 



limbs, and closely resembling that of a small mollusc. 



The fourth order, the CLADOCERA, comprises the 



so-called " Water-fleas," which are abundant every- 



