GENERAL CHARACTERISTICS OF CETACEANS 139 
pletely enveloped in a thick layer of fat, called ‘“‘blubber,” 
which lies under the skin, and is dmpervious 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: 
CETACEANS 
Cete 
FAMILIES 
1. BALEEN “Whalebone’’ Whales, of large size, without teeth. 
Wuates:| The mouth is provided with “baleen,” commercially 
(without teeth) { called “whalebone.” This group includes the Szl- 
Balaenidae....| phur-Bottom, largest of all whales, and about fifteen 
other species. 
2. SPERM Whales with a narrow, beak-like lower jaw, and formi- 
Wuates:| dable teeth. There are four species, varying in size 
(with teeth) from the Pygmy Sperm Whale, 12 feet long, to the 
Physeteridae...| great Sperm Whale, 80 feet long. 
This Family includes about thirty species of Dolphins, 
3. DOLPHINS Porpoises, Grampuses, Blackfish and Narwhals. They 
and vary in size from the five-foot common Porpoise to 
PorpoisEs: the thirty-foot Orca, or “Whale-Killer.” All save a 
Delphinidae...| very few are harmless, but the Killer is the most sav- 
4, FresH-WATER 
DoLpuHins: 
Platinistidae. . 
age and dangerous creature that swims the seas. 
The narrow-beaked dolphins of the Amazon and 
Ganges. 
