322 VERTEBRATE ANIMALS. 
ing” consisted in the whale ejecting through the nose the water 
which had previously been filtered through the baleen-plates of 
the mouth; but it appears to be quite certain that this view, 
at any rate, is not the correct one. The Rorquals or Finner 
Whales resemble the Greenland Whale in most respects, but 
the skin is furrowed with deep plaits or folds, and there is a 
dorsal fin, placed on the back. Some of these attain a gigantic 
size (eighty feet or more), but they are seldom captured, as their 
commercial value is small. 
The Toothed Whales (Odontocet?) are best known by the 
Sperm Whale, an animal as large or larger than the Greenland 
Whale, but distinguished by having numerous conical teeth, 
a single blow-hole, and a curiously truncated head. They yield 
an excellent oil, and the singular fatty substance which is known 
as “‘spermaceti.” They also yield the substance called ‘‘amber- 
gris,” which is used as a perfume ; but this is probably a pro- 
duct of disease. 
The last family of the Ce/acea is that of the Delphinide, com- 
prising the Dolphins (fig. 174) and Porpoises. They have nume- 
rous conical teeth in both jaws, and the nostrils open by a single 
aperture on the top of the head. The Dolphins are inhabitants 
of the sea, but two species live in rivers,—one in India, and the 
other in America. The Porpoises are also marine, and occur 
in all seas. The most remarkable of the Delphinid@e is the 
Narwhal or Sea-Unicorn, which is found in the Arctic seas, and 
which attains a length of as much as fifteen feet in the body 
alone. Thechief peculiarity of the Narwhal is in the dentition. 
The females, as a rule, have no teeth, the upper jaw alone 
having two rudimentary incisors which never cut the gum. In 
the males, however, whilst the lower jaw is without teeth, one 
of the two central incisors of the upper jaw is enormously 
developed, and grows throughout the life of the animal. It 
forms a tusk of from eight to ten feet in length, the whole sur- 
face of which is spirally twisted. The function of this extra- 
ordinary tooth is doubtless offensive. 
ORDER VI. UNGULATA.—This order is often spoken of as 
that of the Hoofed Quadrupeds, and is one of the largest and 
most important of the orders of Mammalia. The order is 
characterised by having all the four limbs and by having that 
portion of the toe which touches the ground encased in a greatly 
