The Order PRIMATES, therefore, comprises two very homogeneous sub-orders--(1) The Lemur-like animals (LEMUROIDEA) including the Aye-Aye, the Tarsier, and the True Lemurs; and (2) the Man-like animals (the ANTHROPOIDEA), which embrace the Marmosets, the Baboons, the great Apes, and Man. In common with all other Mammals, the Primates are furnished with an epidermal covering, which, except in Man, consists of a woolly or hairy fur. They possess four limbs and a tail, which may be long, short, or concealed, and which is often used as a prehensile organ. The young are born in a condition of greater or less helplessness, with their eyes, as a rule, unopened, and the framework of their bodies incompletely ossified, and consequently requiring protective care and entire nourishment from the mother, for a considerable period. At maturity this skeleton consists of a skull, a breast- and a back-bone of many pieces, ribs, jointed limbs, and a pair of collar-bones. As a knowledge of many of these bones and some of the more prominent organs of the body are necessary for an accurate comprehension of the description and classification of the animals discussed in this volume, a few of the more important must be briefly referred to. The _cranium_, formed of many bones firmly united together, consists of a cerebral region, or box, containing and guarding the brain, and a facial region, in which are situated, besides the mouth, the organs of sight and smell. The bones connected with the {4}mouth are the two maxillæ, along the margins of which are placed the grinding- or cheek-teeth; the two pre-maxillæ, in which are set the cutting- and the eye-teeth; and lastly, the palatine bones which form the roof of the mouth. Hinged on to the sides of the cranium is the toothed mandible, or lower jaw, composed of two halves, which may be solidly or loosely joined together in the mid-line, or symphysis. Along the under surface of the skull, there are, besides the great (often posterior) orifice for the entrance of the spinal cord, numerous _foramina_, or openings, for the passage of blood-vessels for the nourishment of the brain, and of nerves which bring all parts of the body into relation with the supreme directing centre. Conspicuous near its posterior part, on each side, is an ivory-like capsule, the periotic bone, containing the essential organ of hearing. Lying beneath the lower jaw is the hyoid arch, a slender framework of bones, supporting the tongue and the upper end of the windpipe with the organ of voice. In a few of the Monkeys and Apes certain of the bones of this arch are much enlarged and hollowed for increasing the volume of sound emitted by them. On either side of the great opening which is so conspicuous at the hinder part of the skull, for the reception of the spinal cord, is a smooth kidney-shaped surface, called a "condyle." These two condyles serve for the articulation of the first