Hence the Baboons, found as they are in the separated districts, existed as a united genus before those vast changes. If the Black Baboon is a forest dweller--and there appears to be good reason to believe that this is the case--there is something more than simple conjecture in the suggestion that the whole of the Baboons once lived in forest lands. [Illustration: BLACK BABOON.] * * * * * The Cynomorpha, or Dog-shaped Quadrumana, include the genera Semnopithecus, Colobos, Macacus, and Cynocephalus, and their distinctions and some of their anatomical peculiarities have been noticed, and they may be summarised as follows:--As a group, the Cynomorpha are more fitted for running on all-fours than for any other method of progression, and their construction relates to that of such running animals as the Cats as well as to that of the Monkeys. Thus the arm-bone (humerus) is unlike that of the man-shaped Apes; it is bent so as to be slightly convex forwards, and the top where the round joint is--the head of the bone--look upwards and backwards, and not upwards and inwards as it does in the Gorilla. The forearm bones, longer than the arm-bone, are modified, and the most movable of them (the radius) is so much jointed to the arm-bone that the power of moving the lower part of the forearm upwards and downwards (of pronation and supination) is much diminished. There is the extra bone in the wrist, making nine, and one of the bones sticks out behind (pisiform), so as to form a kind of heel to the hand. The thumb is complete except in the Colobi, but it is short in proportion to the other fingers; and in some the third and fourth fingers are equal in length, thus departing from the Ape, whose third finger is always longest, resembling rather that of beasts of prey. The blade-bone differs much from that of the Anthropomorpha, being longer and narrower, and the portion above its spine, instead of being large, as it is in such ponderous climbers, is small. All these arrangements relate to the running on all-fours, the palms of the hands being applied to the ground. Moreover, in order that the hand should thus resemble a foot in its duties, some of its muscles simulate those of the foot and fore-leg. Thus a muscle which extends the metacarpal bone of the thumb (the bone between the wrist and the thumb under “the ball”), and keeps the thumb flat on the ground in running, and tends to pull it up, has a slip which is attached to the bone of the wrist, called trapezium, and which is at the wrist end of the metacarpal bone. It extends the wrist as well as the thumb. Now this is an arrangement seen in the foot, where a muscle extends the great toe’s metacarpal bone and the ankle bones also. In order to carry out this extension of the fingers, so as to prevent downward bending (or flexing), they have a complete double set of extensor muscles. [Illustration: SKELETON OF THE MANDRILL. (From the _Cyclopædia of Anatomy and Physiology._)]