Whalebone Whales 
and constitute the largest known animals. The whales and their 
allies are grouped in several families as follows: 
I. Whalebone whales (Family Balenide). Size very large 
(length 30-85 feet), mouth enormous, no teeth, but the 
upper jaw provided with long strips of whalebone. 
Il. Sperm whales (Family Physeteride). Teeth all along the 
lower jaw, but absent entirely from the upper. Length 
10-80 feet. 
III. Bottle-nosed whales (Family Ziphiidev). One tooth on each 
side of the lower jaw or with no visible teeth at all; 
a narrow projecting snout. Length 20-30 feet. 
IV. Dolphins and porpoises (Family De/phinide). Teeth nume- 
rous in both jaws (or with one long horizontal tusk in 
the narwhal). Head in some species rounded in front 
while others have a projecting snout. Length 5-15 feet. 
WHALEBONE WHALES 
Family Balenide 
This family includes all of the true whales or toothless whales, 
as they are variously called, and the only large ‘‘whale” not 
included here is the sperm whale which is really more closely 
allied to the porpoises and dolphins. The whales are charac- 
terized by their immense size, enormous head, and total absence 
of teeth. Small teeth are, it is true, formed very early in their 
development, but they are entirely absorbed before birth. 
Another peculiarity of the family is the presence in the mouth 
of ‘‘baleen” or whalebone. This consists of thin, flexible, horny 
plates, somewhat triangular in outline, which are attached cross- 
wise down each side of the roof of the mouth. The inner 
edges of these plates are much split up and frayed so that the 
slender filaments form a sieve reaching from the top to the bot- 
tom of the mouth, by which the water is strained away from 
the small marine animals that are scooped up by the whale and 
which constitute its food. By raising the tongue in the nearly 
closed mouth the water is expelled from the lips and the food 
remains. 
There is a popular idea that the water taken into the mouth 
is discharged through the nostril or “blow hole’ situated on 
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