The mona has pouches on each side of his jaws, and callosities on his posteriors. His tail is about two feet long, which is longer by six inches than both his body and head. The head is small and round, and the muzzle thick and short. The colour of his face is a bright tawney; a stripe of grey hairs on the forehead, another of black from the eyes to the ears, and from the ears to the shoulders and arms. He has a kind of grey beard formed by the hairs on his throat and breast, which is longer than in any other part. His hair is of a reddish black on the body and whitish under the belly. The outside of his legs and thighs are black, and its tail of a dark ash with two white spots on each side of its insertion. He walks on all fours, and his length, from the snout to the origin of his tail, is about a foot and a half. The female is subject to periodical emanations. THE CALLITRIX, OR GREEN MONKEY. Callitrix is a term made use of by Homer to express in general the beautiful colour of the hair of animals. It was not till many ages after Homer's time, that the Greeks applied this name to some particular kinds of monkeys, and which, from the propriety of such application, we must suppose to be the animal in question (_fig. 208._). The body is of a fine green colour, the neck and belly white, and the face of a beautiful black. He is found in Mauritania, and in Ancient Carthage; so there is reason to suppose he was known to the Greeks and Romans; and that he was one of the long-tailed monkeys, to which they gave the name of _callitrix_. There is also a species of white monkeys in the adjoining provinces of Egypt, both on the side of Ethiopia and of Arabia, which the ancients have also described by the name of callitrix. Prosper Alpinus and Pietro della Valle, speak of this white monkey, but we have never seen this species, which, perhaps, is only a variety of the green monkey, or the mona, which is very common in those countries. The callitrix, or green monkey, appears to be known in Senegal, as well as in Mauritania and in the Cape Verd islands. M. Adanson relates, that the woods of Ponor, along the river Niger, are filled with green monkeys. "I discovered these animals, (says this author) only by their breaking off the branches of trees, and throwing them down; for they were so very quiet and nimble in their tricks, that it was scarcely possible to perceive them. I did not walk far, before I killed three of them without in the least terrifying any of the rest: however, when numbers felt themselves wounded, they began to retreat; some concealing themselves behind large branches, and others descending to the ground and running away; but the greatest number leaped from the top of one tree to another. During this bustle I kept firing at them and killed about twenty-three in less than an hour, without any of them uttering a single cry, although they several times assembled together, and made an appearance of attacking me."