Both these animals, although lively and tolerably good humoured when young, become mischievous in their dispositions and disgusting in their habits as they advance in age. The voice of the latter closely resembles the bark of a dog.
In the true Baboons the facial angle of the adult varies from 30° to 35°, and the superciliary crests are for the most part considerably elevated, as is also the ridge on the back of the head formed by the attachment of the temporal muscles, which, as well as the canine teeth, are large and powerful. The cheeks are furnished with pouches capable of much distension; and the muzzle terminates in a flattened extremity like that of the dog, on which the openings of the nostrils are situated. The tail is generally as long as, and sometimes even longer than, the body; but in several of the species it is extremely short. The callosities are frequently of large size and disgustingly conspicuous. This genus is generally considered as the lowest in organization, and consequently in capacity and intelligence, of the tribe to which it belongs.
The colour of the common Baboon is reddish brown; his face and hands are black, and his upper eyelids white. The hair of his cheeks forms a considerable tuft on each side; and the under surface of his body is but sparingly covered. In bulk he is equal to a middle sized dog; his proportions are thickset and inelegant; but he is by no means dull or inactive. When young, he is gay, playful, and docile; but as he grows older he becomes untractable, malicious, and ferocious. He is sometimes even dangerous, his muscular strength and agility, together with the great power of his teeth and jaws, rendering him a formidable opponent. On this account it is absolutely necessary to keep him strictly confined. He is a native of Africa, and more especially of the tropical parts of its western coast.
Belonging to a different tribe of the same grand division with the true Monkeys, from which they are more readily distinguished by their general form and habit than by any very remarkable deviation in their structure or organization, these agile and playful little creatures form a group which naturally follows in immediate succession. The technical peculiarities on which their separation from the Monkeys is founded are usually deduced from their teeth and nails; but other and more obvious characteristics are afforded by the form of their heads, of their tails, and of their hinder extremities, and these assist in confirming a distinction which might otherwise be regarded as arbitrary and unnecessary. The teeth of the Lemurs are, like those of man and of the Monkeys of the Old World, thirty-two in number, and consist of four incisors, two canines, and ten molars in the upper jaw, and of six incisors, two canines, and eight molars in the lower. Such at least is the usual statement with respect to their dentition; but M. Geoffroy maintains, on the other hand, that the number of incisors is equal in both jaws, and coincides with that of the Monkeys; the two outermost of the six, which are larger than the rest, being in his opinion the true canines; while the canines, commonly so called, are in fact only the first of the series of molars. This conjecture unquestionably derives considerable strength from the fact that, when the animal closes its mouth, the supposed canines of the lower jaw pass behind those of the upper, a position directly contrary to that which they uniformly assume in every other animal that is furnished with that kind of teeth. On each of their four hands they have four fingers of moderate length, and a thumb which is capable of being opposed to them almost equally well with that of the other Quadrumana; they are consequently enabled to grasp whatever they seize with the greatest precision. The peculiarity of their nails consists in the shape of that of the index of the hinder hands, which forms an elongated, curved, and pointed claw, approaching in some degree to those of the carnivorous quadrupeds. All the rest of their nails are broad and flat like those of the Monkeys. Their posterior extremities are longer than their anterior; and their body and limbs are light, graceful, and well proportioned. The tail, which is of uniform thickness throughout, is longer than the body, and, in common with it, is clothed with long, soft, and woolly hair. The head is long, triangular, and gradually tapering into a slender and pointed muzzle, which, in proportionate length, far exceeds that of any of the Monkeys; the ears are short and rounded; and the whiskers but little developed.