A naked black gland on the undersurface of the tail exudes small beads of moisture that have a musky odor, especially in the males. The pelage, which is soft, is lacking in the rump region. The nostrils are located at the end of the snout. The eyes and ears are well developed, and there is a pale eye ring in most species. The hind leg is much longer than the forelimb.
Females have two or three pairs of mammae.
The penis is divided into three forks. When the dental formula is complete, the first upper incisors are larger than the others and the lower incisors are about equal in size. The front incisors are rather widely separated from each other. The hard palate extends behind the molars and has large openings through it near the median line, in the muzzle region, and between the back teeth. The braincase is relatively large.