9 8 A BOOK OF WHALES 



limb are imperfect. The phalanges of the second 

 and third digit always exceed in number the number 

 (three) normal in the Mammalia. The pelvis is 

 represented by a pair of horizontally-placed styliform 

 vestiges of the ischia. Teeth may be absent and 

 their place taken by sheets of baleen or whalebone ; 

 when present they may be very numerous and homo- 

 dont, or less numerous and heterodont, or reduced to 

 a single pair. The epiglottis and the arytenoids are 

 prolonged, and embraced by the soft palate, so as 

 to form a continuous tube for the passage of the air 

 from the nasal cavities to the trachea. The brain 

 is large, and the cerebral hemispheres are richly con- 

 voluted. The testes are abdominal. The teats are 

 two, and are posterior in position. The uterus is two- 

 horned ; the placenta diffuse and non-deciduate." 



This definition is more comprehensive, but it still 

 does not state all those features in which whales 

 differ from other animals, which are not clearly con- 

 nected with the need for a fish-like form and life at 

 times in great depths of the ocean. 



It seems possible to extract from what has been 

 said here, as essential characteristics of the group, 

 the following facts of structure : 



In the Skull. -The separation of the two parietals 

 by the intervention of the supra-occipital, or their 

 concealment by its overlapping. 



The overlapping of the muzzle generally by the 

 premaxillse. 



The loose attachment between the various bones 

 surrounding or connected with the organ of hearing. 



