VB11TBBRATE ANIMALS MAMMALIA DIAGRAM 3. 



and instead of running, 

 they take great leaps. 



9th. The last order of 

 mammals is that of Ce- 

 tacea, and these are ani- 

 mals which at first sight 

 have altogether the ap- 

 pearance of fish ; such as 

 the whale and the dol- 

 phin. They have no hair ; 

 they have fins instead of 

 arms, ^and a tail behind 

 instead of hind limbs. 

 Nevertheless we after- 

 wards perceive a great 

 difference from fish . 

 While the tail of the 

 latter is vertical, and they beat the water on the right and 

 left to advance, that of the cetacea is horizontal; and they 

 move it up and down. Lastly, the cetacea have no gills ; 

 they have lungs, and breathe air like other mammals, and are 

 obliged to return frequently to the surface to take breath. 

 They have a nose called the blow holes, by which they blow 

 out water, which rises in a jet from the sea. 



An Opossum and young. 



Skeleton of a Whale. 



The order Cetacea includes various animals of moderate size 



