18 MANUAL OF NATUKAL HISTORY. 



swimmers, and spend the greater part of their 

 time in the water. 



VI. OBDER— Cetaceans (Cetacea). 



External appearance somewhat fishlike; body ge- 

 nerally covered with a smooth skin ; anterior limbs 

 in the form of paddles ; no posterior limbs ; tail 

 expanded horizontally into a fin of greater or less 

 breadth. 



I. SUB-ORDER — Carnivorous Cetaceans (Carnivora). 



Skin smooth, shining, generally destitute of hairs ; 

 nostrils in the form of spiracles and pierced on sum- 

 mit of head ; mammae placed near vent ; teeth coni- 

 cal or wanting. 



1. Family. — Baleen- Whales (Balsenidae). Head 



large ; upper jaw much arched ; no teeth, but 

 from each side of the upper jaw is suspended 

 a series of plates of baleen or whalebone, the 

 edges of which are formed into a loose fringe 

 of fibres which fill cavity of mouth ; spiracles 

 on upper part of head; with or without a 

 dorsal fin. 



2. Family. — Sperm-Whales (Physeteridse). Head 



very large, with an extremely obtuse snout ; 

 lower jaw narrow, corresponding to a groove 

 in upper, and furnished with a row of conical 

 teeth which fit into cavities on edge of palate 

 when the mouth is shut, there being no teeth 

 in upper jaw ; blow-hole situated on anterior 

 part of head. 



