In the Orang or "Mias" (Simia satyrus) there are neither cheek-pouches nor natal callosities, and the hips are covered with hair. As in the Gibbons, the arms are excessively long, reaching considerably below the knee when the animal stands in an erect posture. The hind-legs are very short, and there is no tail. When full grown the Orang stands about four feet high. It never progresses with the help of a stick, or walks erect at all, except along the branches of trees, supporting itself by a higher branch, or when attacked. When young, the head of the Orang is not very different from that of an average European child; but, as the animal grows, the facial bones become gradually produced, whilst the cranium remains in a tolerably stationary condition; great bony ridges are developed for the attachment of the muscles of the jaws and face; the incisors project; and ultimately the muzzle becomes as pronounced and well-marked a feature as in the typical Carnivora (fig. 453, A). The Orangs are inhabitants of Sumatra and Borneo. They are arboreal in their habits, and form for themselves a sort of nest or shelter amongst the trees. The forehead is rounded, the cerebrum is greatly convoluted, and the canine teeth of the full-grown males are very large.
The genus Troglodytes contains the Chimpanzee (T. niger) and the Gorilla (T. Gorilla), with some other imperfectly known forms. The Chimpanzee is a native of western Africa, extending its. range eastwards to Abyssinia; and has the arms much shorter, proportionately, than in the Gibbons and Orangs; still they are much longer than the hind-limbs, and they reach beneath the knee when the animal stands erect. The ears in the Chimpanzee are large, and the body is covered with dark-brown hair. The animal can stand erect, but the natural mode of progression is on all-fours. The hands are naked to the wrist, and the face is also naked, and is much wrinkled. The Chimpanzee lives in society in wooded districts, constructs huts, and can defend itself against even the largest of its foes.
Fig. 453. - A, Skull of the Orang-utan. B, Skull of an adult European.
The Gorilla is in most respects the same as the Chimpanzee, but is much larger, attaining a height of between five and six feet. The hind-limbs are short, and the ears are small. It is an enormously strong and ferocious animal, and is found in Lower Guinea and in the interior of equatorial Africa. It possesses a laryngeal sac, has a most appalling voice, and is polygamous. Its habits are mainly arboreal, and the male builds a kind of nest in the trees, in which the female brings forth the young. The Gorilla has been often regarded as the most human of the Anthropoid Apes, but many of the highest authorities believe that the Gibbons have a greater claim to occupy this position.
As regards the distribution of the Quadrumana in time, the earliest representatives of the order appear to be found in the Eocene Tertiary. In deposits of this age in Wyoming, Professor Marsh has discovered several forms apparently related to both the Lemuroids and the Platyrhines. They form the two families of the Lemuravidae, of which the principal genus (Lemuravus) has forty-four teeth, and Limnotheridae, in which there are only forty teeth. Remains of Lemuroids have also been found in the Eocene of Europe. The first remains of the higher Quadm-mana appear in the Miocene. The two most important of these are Pliopithecus (fig. 454) and Dryopi-thecus, both of which are European, and both of which belong to the section of the Catarhine Monkeys, which are at present characteristic of the Old World; the former being most nearly allied to the living Semnopitheci, the latter to the Gibbons. It is interesting to notice that the South American fossil Monkeys - from the later Tertiary deposits of South America - belong to the division of the Quadrumana now peculiar to that continent - to the section, namely, of the Platyrhine Monkeys.
Fig. 454. - Lower jaw of Pliopithecus antiquus. Miocene.