HABITS.--Nothing is known of the habits of either of these two species of _Opolemur_. {64}THE TRUE LEMURS. SUB-FAMILY III. LEMURINÆ. The third sub-family of the _Lemuridæ_ contains the True Lemurs, which are characterised by the possession of a soft, thick, and woolly fur, the head rounded behind, with a specially elongated muzzle. They have small and oval ears, with the exterior aspect covered with long hair, but the inside naked, except round the margin. Their hind-limbs do not show so great a disproportionate length compared to that of the fore-limbs, as in the next sub-family, the _Indrisinæ_. The ankle-bones (_tarsus_) are only slightly elongated, and their toes are not united by a membrane. Their long and bushy tail is sometimes longer and sometimes shorter than the body. The females produce one or two, nearly naked, young at a birth, the mammæ being either two or four in number. The skull presents a central ridge on the frontal bone, and its facial portion is much elongated, the inter-orbital space being depressed and wider, and the orbits also directed somewhat outward and less straightforwardly than in several of the genera already noticed. The maxillary bones are generally much reduced, and the incisor teeth carried by them not unfrequently entirely aborted. The teeth in this Sub-family vary in number from 32 to 36, the dental formula being I(0-2)/2, C1/1, P3/3, M3/3. The foot is slightly elongated by the lengthening of the _naviculare_ bone of the ankle, the others being short. In the wrist (_carpus_) the central bone (_centrale_) may be present or absent; its absence, however, is a character which is met with otherwise only in Man, the Chimpanzees, and the Endrina and some other Lemurs, to be described later on. The cæcum is not markedly developed. {65}The external coloration of the species of this Sub-family is remarkably variable, the variation being chiefly in the upper portion of the hairs, as their base is generally slate-grey.