350 
COMPARATIVE ZOOLOGY. 
Fig. 343.—Troop of Dolphins, with Manatee in the distance. 
one. They have a narrow brain; bristles scantily cover¬ 
ing the body; and nostrils placed on the snout, which is 
large and fleshy. The living representatives are the Ma¬ 
natee, of both sides of the tropical Atlantic Ocean, and the 
Dugong, of the East Indies. 
9. Proboscidia. — This race of giants, now nearly ex¬ 
tinct, is characterized by two upper incisors in the form of 
tusks, mainly composed of dentine (ivory). In the extinct 
Dinotherium the tusks projected from the lower jaw; and 
in the Mastodon, from both jaws. Canines are wanting. 
The molars are few and large, with transverse ridges (Ele- 
. phant) or tubercles (Mastodon). The cerebrum is large 
and convoluted, but does not cover the cerebellum. The 
skull is enormous, the size arising in great measure from 
the development of air-cavities between the inner and 
outer plates. The nose is prolonged into a flexible trunk, 
which is a strong and delicate organ of prehension. There 
are four massive limbs, each with five toes incased in 
