350 



ARTICULATA: CRUSTACEA. 



FIG. 476. 



Cephalo-thorax. 



Hind body or 

 abdomen. 



A Crustacean young Crab magnified. (Natural size indicated by the 

 marks at the left.) 



the cephalo-thorax and the abdomen only the latter 

 showing distinctly the rings or segments of which it is 

 composed. 



Normally, the body of a Crustacean consists of 

 twenty-one rings or segments fourteen belonging to the 

 cephalo-thorax and seven to the abdomen' but in the 

 adult state these segments are not apparent in the 

 forward portion of the animal, nor always in the hind 

 portion. 



The external appendages of Crustaceans are numerous, 

 and all these appendages have the same fundamental 

 structure, and all are regarded as locomotive organs, 



