CLASS I. MAMMALIA: OEDEE 12. CETACEA. 
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distinguished by the fish-like form of its members, which are thus adapted for passing their exist- 
ence in the water. The}' are generally very bidky creatures, the head being often of an enor- 
mous size ; the body tapers off posteriorly, and is terminated by a broad tail-fin, which, like 
that of the fishes, is the principal agent in swimming, but is set on in the contrary direction, being 
horizontal instead of perpendicular. This caudal fin is supported upon a fii'm cartilaginous basis, 
but has no trace of rays or bones. The anterior limbs are converted into powerful fins, com- 
pletely inclosed in a uniform skin ; but beneath this we find the usual bones of which the arm 
of a vertebrated animal is composed, although considerably shortened. In some instances the 
phalanges are very nimierous, but the fingers rarely exhibit any traces of nails. The posterior 
limbs are entirely wanting. 
The head is not separated from the body by a neck, although the cervical vertebrae are dis- 
tinctly marked in the skeleton ; the great bulk of the head is made up of the facial bones, the 
cranial portion being often very small. The nostrils are sometimes, as in other vertebrated ani- 
mals, placed on the fore part of the nose ; but in the typical forms, these orifices are brought quite 
to the top of the head, constituting what are called the hloiv-holes of the whale. The external ear 
is entirely wanting, and the mode in wliich the auditory of the organs of the Cetacea are adapted 
for the perception of sounds, both in the water and in the air, is very interesting. The external 
aperture of the ear is exceedingly small, so as to prevent any injury to the organ from the rush 
of water when the creature is progressing rapidly through that element, although it apparently 
allows of sufiicient access of water for the communication of any sounds that may be transmitted 
by its means. The air penetrates into the ear through the Eustachian tube, which is of large 
size, and opens into the blow-hole; and thus, when the whale is at the sniface of the water and 
breathing, aerial sounds can find their way into the ear. The eye is of very small size wben 
compared with the bulk of the animal, and, from the immense development of the facial bones, 
it often appears to be placed nearly in the middle of the body. 
The skin is naked, or only sparingly covered Avith scattered bristles; but to make up for the 
want of the ordinary clothing of the Mammalia, the whole surface of the body beneath the skin 
is covered with a thick coating of fat, or blubber as it is termed, which forms a most efiicieut agent 
in preserving the temperature of the body, at the same time that it reduces its specific gravity. 
It is this blubber, which is often present in enormous quantity, that forms the principal object for 
which these creatures are pursued. The Cetacea are all inhabitants of the sea. They are divisi- 
ble into two very distinct groups, the Cete, which include the Whales, JVarwhals, Porpoises, 
Dolphins, &c. ; and the Sibenia, which include the Manatee, Dugoncj, &c. The great distinction 
between these two groups or sub-orders is, that the former lives on animal food, and the latter is 
herbivorous. 
THE CETE. 
The animals of this division were anciently regarded as fishes, but they are true members 
of the class Mammalia. Some of them are the largest of known animals. They have a large 
head, forming nearly one-half the body; the mouth is wide and armed with conical teeth, 
except in one family, the Balcenidce; the mammae are two, and placed on the belly ; the nostrils, 
sometimes two and' sometimes one, are on the top of the head. These do not serve as organs of 
smell, but only as respiratory openings, through which the water, taken in while the animal^ is 
beneath the surface, is ejected. Though living on animal food, the stomach is complex, consist- 
ing of four apartments, and sometimes of as many as seven ; the skin is naked. These animals 
have no voice; the period of gestation is nine or ten months; they produce the young alive, and 
suckle them for a considerable period ; they are sociable creatures, and live in large shoals, often 
sporting on the surface of the water. They are most abundant in the Arctic and Antartic Seas. 
The Cete are divided into three families, the Whalebo7ie Whales, the Sperm Whales, and the 
THE WHALEBOI^E WHALES OR BAL^NID^. 
In these, which constitute the true whales, the upper teeth are deficient, but in their place there 
are several longitudinal rows of horny plates called Baleen or Whalebone, set cross-wise, and 
