VERTEBRATE ANIMALS MAMMALIA DIAGRAM O. 



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 JJ "V 

 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, 



