The bulk of the brain is less in comparison with that of the Orang, and the hind part does not quite cover or overlap the cerebellum, and the whole skull is long and low, and slightly broad behind. The most striking parts about it are the cavities for the eyes (the orbits), which are nearly circular in outline, deep, open, and swollen behind; moreover, they are wide apart, and there is no brow ridge connecting them. They, the face and the lower jaw, occupy only one-half of the skull, and the brain case is composed of the usual bones, which are extremely faintly ridged, the ridges extending on either side from the outer part of the orbit on to the frontal and parietal (or side) head bones. The back of the skull is rough, for the attachment of muscles, and the opening for the spinal cord and the joints for the top of the neck are far back, so that the head is set, as it were, forward in respect of the spine. There is a long and narrow roof to the mouth, and the diastema, or space in the line of the teeth, in front of the upper eye or canine teeth, is very distinct. These teeth are long, thin, and grooved, and project rather outwards as well as far below the other upper teeth. Yet, in all probability, this is not a bloodthirsty sign, but one which may have to do with sex, the males of many of the Monkeys possessing these great teeth only, or having them larger than the females. The first, or incisor teeth, occupy a very small space, and they and the two front molars are like those of man. An examination of the three true crushing molars shows the last, or that nearest the back of the jaw, to be the largest. They have four cusps or projections, which are small but decided, and somewhat resemble those of insect-eating animals. The lower jaw is very remarkable, for it has a good straight chin; and the joint and the part which passes from it to the body of the jaw, or the “angle,” resembles that of man more than that of the rest of the Apes. The lower teeth are very unlike the upper, and the canines are smaller; the first false molar is pyramidal, and has a cutting surface in front and behind. The true molars have at least five cusps or projections, and are admirably suited for the creature’s diet. [Illustration: SKELETON OF THE SIAMANG. (_From the “Cyclopædia of Anatomy and Physiology.”_)] One of the most curious points about the Siamang is that the broad breast-bone, the blade-bone, and large chest, and the ribs present human resemblances, but there are fourteen pairs of these last. The hip-bones are long and do not curve far in front, but the joint of the thigh is situated more after the manner of that of man than is the case in the other great Apes.