206 Manatid.e. MAMMALIA. Maxatid.®. 
of ribs. One of the most interesting visceral modifica- 
tions is that of the heart (fig. 82), which may be said 
to have two apices, seeing that the ventricles are par- 
tially separated from one another, and independent at 
their lower ends. In the annexed cut the letters of 
reference indicate as follows : — a, light auricle, h right 
ventricle, c, pulmonary artery, cl, left auricle, <?, left 
ventricle, /, the aorta. In most particulars the skeleton 
strictly conforms to the cetacean type ; but in the head 
and neck we notice several departures, the cervical 
ng- S2 
Heart of the Diignng (llalicore Diigong). 
vertebrae remaining quite distinct, whilst the head is 
sliortened and comparatively massive in some species. 
In the Dugong — Plate 34, fig. 139 —the intermaxillary 
bones are enormously developed for the implantation 
of its incisive tusks, whilst the lower jaw is remarkably 
broad and deep. Tliese cranial peculiarities are not 
present in other allied genera. Tlie several bony 
elements of the fore-limbs are more perfectly formed 
than in the zoophagous cetaceans, the would-be posi- 
tion of the hinder extremities being indicated by an 
attenuated V-shaped bone, constituting a rudimentary 
pelvis. True V-shaped bones also exist along the 
hoemal aspect of the caudal vertebra?. In conclusion, 
we have only to observe that all the klanatida? are 
found near the sea-coast, and near estuaries and mouths 
of riv'ers, up which they occasionally wander to a con- 
siderable distance, feeding on marine fuci and other 
kinds of aquatic vegetation. 
THE MANATEE [Manatus australis) — Plate 36, 
fig. 84 — is an inhabitant of the shores and great o{)en 
rivers of the South American continent, being particu- 
larly abundant off the coasts of Guyana and Brazil, 
where it is commonly known as the Sea-cow. The 
term Lamantin is sometimes applied to it as well as 
to another species. The IManatees are gregarious in 
their habits, and like other Cetacea are devotedly 
attached to their young, which they defend with great 
vigour. In the adult state the skin presents a greyish- 
black colour, whilst, in common with other species of 
the same genus, the ilippers are each provided with 
four flattisli nails, that of the thumb being wanting. 
They have thirtj'-two molar teeth, that is, eight on 
either side above and below, their crowns being irregai' 
larly fiat, square-shaped, and dir ided transversely by 
a central groove. There are no canines or incisors 
except in extremely young individuals. Under ordi- 
nary circumstances the habits of the Manatee are mild 
and inoffensive. It is readily taken with the harpoon, 
and is chiefly valued on account of its flesh, which is 
stated to be excellent eating. Though formerly very 
plentiful, the Sea-cow hunters have greatly reduced 
their numbers. When these animals raise the anterior 
half of the body out of the water, they display a fanci- 
ful resemblance to a human figure, and this circum- 
stance induced our ancient navigators to believe in the 
existence of sirens, mermen, and mermaids. 
Two other species of the genus Manatus are also 
j known — the Lamantin, properly so called {M. Senegdl- 
ensis of Adanson), which is a native of the western 
coasts of tropical Africa, and the Mexican Sea-cow {M. 
latirostris), a very large species, upwards of fifteen 
feet in length, found on the shores of Florida, Mexico, 
Surinam, and some of the West Indian islands. 
THE INDIAN DUGONG [llalicore Ducjong)—YMQ 26, 
fig. 85 — is a species of very considerable interest, though 
much smaller than the foregoing, seldom measuring more 
than seven or eight feet from the tip of the abrupt and 
flattened snout to the end of the broad crescentic tail. 
On turning to the drawing given at Plate 26, fig. 85, 
it will be seen that the flippers are not furnished with 
nails, but their margins are thickened and tubercuLated. 
One of the most characteristic features of this animal 
arises out of the presence of two large incisors or tusks 
in the upper jaw, a ( fig. 83), the molars being flat, and 
varying numerically from eight or ten to twenty, ac- 
cording to age and other circumstancco. “ In the female 
Dugong,” says Professor Owen, “ the growth of the per- 
manent incisive tusks of the upper jaw is ai-rested before 
they cut the gum, and tliey remain through life con- 
cealed in the premaxillaries. The tusk is solid, is 
about an inch shorter, and less bent than that of the 
male ; it is also irregularly cylindrical, longitudinally 
Skull of the Indian Dugong (Halicore Dvigong). 
indented, and it gradually diminishes to an obtuse 
rugged point. The base is suddenly expanded, bent 
obliquely outwards, and presents a shallow exca- 
vation.” Speaking of other peculiarities, the same 
authority also observes that the external form of the 
Dugong is “ not so well calculated for moving rapidly 
through the water as that of the dolphin and other 
carnivorous cetacea, which subsist by a perpetual pur- 
