XII 



PHYLUM CHORDATA 



529 



The Cetacea (Fig. 298) among which are the largest of 

 existing Mammals, are characterised by the possession of a 

 fusiform, fish-like body, tapering backwards to the tail, which 

 is provided with 

 a horizontally ex- 

 panded caudal fin 

 divided into two 

 lobes or " flukes," 

 and a relatively 

 large head, not 

 separated from the 

 body by any dis- 

 tinct neck. A dor- 

 sal median fin is 

 usually present. 

 The fore - limbs 

 take the form of 

 flippers, with the 

 digits covered over 

 by a common in- 

 tegument and de- 

 void of claws ; the 

 hind-limbs are ab- 

 sent. The mouth 

 is very wide ; the 

 nostrils are situ- 

 ated on the sum- 

 mit of the head, 

 and the auditory 

 pinna is absent. 



Hairs are completely absent, or are represented only by a 

 few bristles about the mouth. In the Whale-bone Whales 

 the nostrils have two external slit-like apertures ; in the 



Man. Zool. M M 



