CETACEA. 183 
united; the teeth implanted in the incisive bone are permanent, and grow 
to such a size as to become true pointed tusks, but of which the greater 
portion remain covered by thick fleshy lips, bristled, and with mustachios. 
The body is elongated, and the tail terminated by a crescent-shaped fin. 
One species only is known, the 
Hal. dugong; Siren; Sea-Cow, &c.; Renard, Poiss. des Indes, 
pl. xxxiv, f. 180; Home, Phil. Trans. and F. Cuy. Mammif. (The 
Dugong). It inhabits the Indian Ocean, and is frequently con- 
founded by travellers with the Manatus. 
STELLERus, Cuv.—Rytina,* Lllig. 
The Stelleri appear to have but a single compound grinder on each 
side, with a flat crown, and bristled with plates of enamel. Their fins 
have not even the little nails observed on those of the Manatus. Accord- 
ing to Steller, the first, and hitherto the only one who has described them, 
their stomach also is much more simple. 
One species only is known, which is confined to the northern part 
of the Pacific Ocean. + 
FAMILY II. 
ieee 
CETACEA ORDINARIA. 
The Ordinary Whales are distinguished from the preceding by the 
singular apparatus from which they have received the name of Blowers. 
(Souffleurs). As a large quantity of water passes into their huge mouths 
along with their prey, some way was necessary by which they could get 
rid of it; accordingly, it passes through the nostrils by means of a peculiar 
disposition of the velum palati, and is accumulated in a sac situated at the 
external orifice of the cavity of the nose, whence, by the compression of 
powerful muscles, it is violently expelled through a narrow opening on the 
top of the head. It is in this way they produce those jets d’eau observed 
by navigators at so great a distance. Their nostrils, continually bathed 
by waves of salt water, could not be lined with a membrane sufficiently 
delicate to enable them to detect odours, and accordingly, they have none 
of those projecting lamine found in the nasal cavities of other animals; 
the olfactory nerve is absent in several, and if there be any which enjoy 
the sense of smell, they must have this nerve mostly in an obliterated 
state. Their larynx, of a pyramidal form, penetrates into the posterior 
nares to receive air and conduct it to the lungs, without compelling the 
* Rytina, wrinkled. 
t+ Nov. Comm. Petrop. IT., 294, et seq. It has never been figured. 
