GENERAL CHARACTERISTICS OF CETACEANS 139 



pletely enveloped in a thick layer of fat, called "blubber," 

 which lies under the skin, and is impervious to cold. It is 

 as if a man had a layer of felt an inch thick under his skin. 



All Cetaceans are destitute of hair, and in most cases the 

 skin is as smooth as plate glass. The great majority of them 

 have teeth, but many are toothless. Except the whales of 

 greatest commercial value, little is known of the habits of 

 Cetaceans generally. It is very difficult to study creatures 

 that make their home in the sea and that can be closely 

 studied only when killed. Nevertheless, quite a number of 

 interesting facts regarding these strange animals have been 

 brought together, chiefly by observing whalers. Their four 

 Families are as follows: 



1. BALEEN 



WHALES : 

 (without teeth) 

 Balaenidae. . . . 



%. SPERM 



WHALES : 

 (with teeth) 

 Physeteridae. . . 



3. DOLPHINS 



and 



PORPOISES: 

 Delphinidae . . . 



4. FRESH-WATER 

 DOLPHINS : 

 Platinistidae . . 



CETACEANS 

 Cete 



"Whalebone" Whales, of large size, without teeth. 

 The mouth is provided with "baleen," commercially 

 called "whalebone." This group includes the Sul- 

 phur-Bottom, largest of all whales, and about fifteen 

 other species. 



Whales with a narrow, beak-like lower jaw, and formi- 

 dable teeth. There are four species, varying in size 

 from the Pygmy Sperm Whale, 12 feet long, to the 

 great Sperm Whale, 80 feet long. 



This Family includes about thirty species of Dolphins, 

 Porpoises, Grampuses, Blackfish and Narwhals. They 

 vary in size from the five-foot common Porpoise to 

 the thirty-foot Orca, or "Whale-Killer." All save a 

 very few are harmless, but the Killer is the most sav- 

 age and dangerous creature that swims the seas. 



The narrow-beaked dolphins of the Amazon and 

 Ganges. 



