CHARACTERISTICS OF BIRDS. as 
being but six or seven feet long, and on its paddles are 
short nails, by which it can drag its unwieldy body on 
the land to bask in the sun or to get food. All the ani- 
mals of this tribe are like the Whales in their paddles, 
their oily skin, their horizontally flattened tail, and their 
fish-like shape. 
Questions. —What is said of the size of animals living in water? 
How do the Whale tribe compare in size with terrestrial animals ? 
How do the Cetacea differ from all other Mammals? What group 
of Mammals are somewhat like them? How does the tail of Whales 
differ from that of Fishes? What is the breadth of it? What is 
the chief office of the flippers? What is said of their frame-work ? 
What is the blubber? What purposes does it serve? Explain the 
provision which enables the Whale to stay under water so long. 
What is said of the nostrils? Describe the spouting apparatus. 
What are the two families of Whales? Describe the Cachelot Whale. 
What is said of its spermaceti? How much is obtained from one 
Whale? What is Ambergris? What is said of the habits of Sperm 
Whales? What is said of the Whalebone Whales? What are in- 
cluded in the Dolphin family? What is said of the Porpoise? 
What of the Dolphin? What of the Narwhal? Whai of the Du- 
gong family? What are the animals of this family commonly called ? 
Where are they found? What is said of the structure of the species 
represented ? 
CHAPTER XII. 
CHARACTERISTICS OF BIRDS. 
196. Brrps form the second grand division of warm- 
blooded Vertebrates. This division is separated from 
the first division, the Mammals, by very marked charac- 
teristics, which I will point out. 1. They are oviparous 
($23). 2. They do not suckle their young. 3. They are 
covered with feathers. 4. They are constructed for flight, 
with some few exceptions. 5. They have no teeth, which 
is true of only a few species of Mammals. 6. They have 
bills, which is true of only one species of Mammals, the 
Duck-billed Platypus of Australia (§ 183). 7. They have 
