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 {99}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. YOUNG.--Similar in colour to the adults, but lighter; the frontal band yellow, not white; limbs light yellow. VARIETIES.--Several varieties of this species--the "Simpona" of the natives--have been described, of which the following deserve special notice:-- THE SILKY SIFAKA. PROPITHECUS SERICEUS. Face black, with flesh-coloured spots; the body entirely white, faintly washed with yellow; the base of the tail washed with rust-red. It is of the same size as the type-form, and appears to be only an albino variety. Specimens showing every gradation in coloration between that of the type and the absolute albino are now well known. This form, however, is more or less restricted to the narrow belts of forest on the eastern side of the mountains in the north-east of Madagascar, between the rivers Lokoi and Bemarivo, a region conterminous with that inhabited by the typical species. MILNE-EDWARDS' SIFAKA. PROPITHECUS EDWARDSI.