_Propithecus_, Bennett, P. Z. S., 1832, p. 20; Milne-Edwards and
Grandid., Hist. Nat. Madag., Mamm., i., p. 288 (with full synonymy).
{97}The characters which distinguish this genus from _Avahis_ and _Indris_
are the following: The fur with which they are covered is more silky than
woolly, and in general appearance is white, more or less washed with
yellow, varying to red or black. The head is very slightly longer than it
is broad, with a black and almost naked muzzle; the ears, half buried in
the fur, are flatter and wider than in _Indris_, the inner surface being
naked and black, and the outer haired. The nostrils are large and semilunar
in shape. The tail is long. The index-finger is not united by a membrane to
the others; their hands and feet are in a much less degree organs of
prehension than in most of the other Lemurs.
The skull in proportionate length is intermediate between that of _Avahis_
and _Indris_. Compared with _Avahis_ it is less vaulted, its muzzle is
longer, and the orbits are smaller. The space between the eyes is high, and
not depressed, on account of the presence of a large air-cavity in the
underlying bone. Their nasal bones do not reach as far forward in front as
the level of the incisor teeth. In the dentition of the upper jaw, the
incisors protrude somewhat in front, and are dilated laterally in a regular
series--thus distinguishing the genus _Propithecus_ from _Lemur_,--the
inner incisors being larger than the outer ones, with their tips
approximating. Between the canine and the anterior pre-molar there is a
short gap. The anterior and median molars have the cusps of the crown
alternate; the posterior has them opposite. In the lower jaw the incisors
are shorter and stronger than in _Avahis_, and the molars are four-cusped.
The genus _Propithecus_ contains three species; (1) The Diademed Sifaka
(_P. diadema_), (2) Verreaux's Sifaka (_P. {98}verreauxi_), both having
numerous very marked varieties; and (3) the Crowned Sifaka (_P.
coronatus_).
These species are found all round the coasts of Madagascar; as well in the
luxuriant forests on the east side as in the arid deserts and the
sparsely-wooded plains of the south-western and western coasts. Of the
three species of the genus, one (_P. diadema_) is confined to the eastern
and southern coasts, the other two (_P. verreauxi_ and _P. coronatus_) are
found only on the west coast. More or less distinctly coloured varieties or
races of these three species occur, and it is very remarkable that each of
them is rigorously restricted to localities distinct from that of the
typical species.