In this family are included the Gibbons, the Orangs, the Gorillas, and the Chimpanzees, the most highly organised and the nearest to Man in structure of all the _Anthropoidea_. To {144}these groups the term "Ape," has been by many writers chiefly restricted, the remaining families of the Old World, and all of the Western Hemisphere, being designated "Monkeys" as a convenient method of nomenclature. The outward resemblance of the _Simiidæ_ to Man has made the various members of the family objects of the greatest interest, not alone to the naturalist, but to every intelligent person; and has naturally suggested a constant inter-comparison between the characters of both. They are all essentially arboreal climbing animals, yet when they come to the ground they progress in a semi-erect position of their own accord. Their front-limbs are always so much longer than their hind-limbs, that when walking on a level surface their fingers reach the ground, without stooping lower than their semi-erect attitude. Their front-limbs vary in length in the different genera; so does the thumb; but their great-toe is always smaller in proportion to the foot than it is in Man, and, unlike his, is opposable to the other toes. As they belong to the Catarrhine group, their nose has a narrow partition between the nostrils, which are directed downwards. In all, an external tail, cheek-pouches, and (except among the Gibbons) ischial callosities are wanting. All are covered with hair, some more thickly than others, but no Ape has on its head the long abundant locks which Man possesses. The form of the skull varies very greatly in the _Simiidæ_. It is, however, always longer than broad. In its frontal region it is never so rounded and elevated as in Man. The roof of the eye-sockets projects into the fore part of the brain-cavity, and considerably reduces its capacity. The pre-maxillary bones (carrying the incisor teeth) are relatively more distinct and much larger than in Man, "the sutures {145}separating them from the maxillary bones remaining visible after the adult dentition has been obtained." (_Mivart._)[1] The _Simiidæ_ have a bony meatus or canal to the ear. The back part of the head, which among the Guenons is flat, is convex among the _Simiidæ_. The palate is long and narrow, and the margins of the jaws nearly parallel. The lower jaw is always in one piece, the two halves being firmly ossified in the middle. The dental formula of the Man-like Apes is I2/2, C1/1, P2/2, M3/3 (_i.e._, 32 teeth in all); their inner upper incisors are larger, and the lower are smaller than the outer pair; the canines are large, and between them and the neighbouring incisor above there is a vacuity (or diastema), and, below, between them and the nearest pre-molar. The upper pre-molars have three roots, and the lower, two; the upper molars have four tubercles, their crowns being relatively wide; the lower molars have five tubercles, but the posterior has no hind talon.