used in climbing or in balancing, determined naturalists to rely but little upon that member in this group, and to join those with tails and without tails in one genus, called _Macacus_. Those with long tails, the _Macacus cynomolgus_, for instance, cause the group to resemble the Guenons; or, in other words, link and ally the two genera, it being difficult in the case of this Monkey to say to which one it should belong. On the other hand, the Barbary Ape, which managed to get to Gibraltar and live there in some numbers, and which has but the very stump of a tail, connects the whole group, or genus, with the Baboons without tails. Then there is one with a fine head of hair, and a long snout (_Macacus Silenus_), which lives in Malabar, and which has a longish tufted tail; and it links some Baboons with long tails to the group now being described. The Macaques live in India, Tibet, North and South China, Japan, and southwards, and in some of the great islands of the Archipelago, Formosa, in Africa, in Barbary, but not south of the Atlas range, and in Europe, on the Rock of Gibraltar. They all have cheek-pouches and callous pads, or callosities, on their seat, and thus resemble the Guenons; moreover, most of them have throat or laryngeal sacs, which open into the membrane above the vocal organ and below the base of the tongue (in the thyroid membrane). On examining their jaws it will be noticed that there is the same number of teeth as in the other Monkeys already described, and that the upper eye or canine tooth on each side is very strong and long. Now, these teeth are not for killing or stopping living prey, although their possessors do not hesitate to snap up a good-sized Beetle, a small Lizard, or even a Frog, but they make, with the first false grinder of the lower jaw, a capital nut-opener. The canine, when the mouth is shut, fits just in front of this tooth, which is usually called the first pre-molar, and which is pressed back and made to slant in the jaw by the constant pressure and movements of the canine. The back of the canine is sharp, and comes in contact with the equally sharp edge of the slanted pre-molar below, so that when a nut comes between the two it is cut and crushed at the same time. The canine does not thus fit into a diastema, or vacant space, but is of great use to the animal. This arrangement is interesting, because it produces a distortion of the front back teeth of the lower jaw for a definite and useful purpose: it is noticed in some of the Guenons, and is particularly seen in mouths of the great Baboons, which will be noticed further on. The other back teeth resemble somewhat those of the Guenons, but the last one of the lower jaw has five cusps, or prominences, on it.