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. 11), are not re- 

 presented in Britain, 

 though several 

 species occur on the 

 Continent of Europe. 

 In these the cara- 

 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- 



FlG. 12 



Daphnia ptilex, a Common 

 ' Water-flea. ' ' Much 

 (From British Museum 



Species of 



enlarged 



Guide.) 



Female carrying eggs in the brood- 

 chamber 



