THE SIFAKAS. GENUS PROPITHECUS.
Propithecus, Bennett, P. Z. S., 1832, p. 20; Milne-Edwards and Grandid., Hist. Nat. Madag., Mamm., i., p. 288 (with full synonymy).
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. 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.
I. THE DIADEMED SIFAKA. PROPITHECUS DIADEMA.
Propithecus diadema, Bennett, P. Z. S., 1832, p. 20; Milne-Edwards and Grandid., Hist. Nat. Madag., Mamm., p. 296 (with full synonymy), Atlas, pl. 1-3.
Characters.—Fur long, silky, the muzzle naked. Head shorter and rounder than in the other species of the genus; thumb slender, like the toes, set far back, free; great toe very strong, and in the same plane with the other digits; a marked depression exists in the skull behind the orbits. Body, 21 inches; tail, 19 inches in length.
Forehead crossed by a broad white bar; cheeks in front of the ears, and the under side of the chin, white or fulvous white; face black, with a few short black hairs. Back of head, neck, shoulders, sides of body, outer sides of arms, sometimes grey, but generally very dark brown, merging into dark grey on the lower back. Tail at its root washed with orange-yellow, paler in the middle, greyish-white at its extremity. Fore-arm, lower part of arm, sacral region, and external face of hind-limbs, bright orange-yellow. Hands black-haired to the ends of the fingers, but with long and yellow tufts of hair at the tips. Feet pale orange and haired to the nails. Chest dark brown. Under surface white, or white tinged with yellow, or dark brownish-grey. Internal face of the fore-limbs grey, from the intermixture of black hairs; that of the hind-limbs pale yellow.