Another species of Howlers is the Preacher Monkey (_Mycetes Beelzebub_), an animal about the size of a fox, with long black glossy hair, a round beard beneath the chin and throat, black glistening eyes, short round ears, and a long tail. A native of Brazil and Guiana, he derives his name from the following circumstance: one of these creatures will climb to the summit of a lofty tree, while numbers gather about the lower branches. The monkey perched above the rest then raises a loud howl--a howl so shrill and keen that it is audible at a very great distance; after a while he pauses, and gives a signal with his hand, whereupon the entire assembly join in chorus; another signal, and the discord ceases, while the preacher or singer concludes his inharmonious exercitation.[174] It is said that this howling faculty is due to the peculiar conformation of the _os hyoides_, or throat-bone, which, communicating with the larynx, increases the resonance of the voice. The Paters, or Red Monkey (_Cercopithecus ruber_), so called from the bright bay colour of his upper parts, is a native of Senegal. In Congo and Guinea is found the frolicsome Spotted or Diana Monkey (_Cercopithecus Diana_), the upper parts of whose body are of a reddish colour, besprinkled with white spots. The Mandrill, or Variegated Baboon (_Cynocephalus maimon_), is, undoubtedly, the most notable of his genus, for various and brilliant colours. When standing upright he measures fully five feet. His body is thick and robust, his limbs are firm and muscular; scarcely any forehead relieves the flatness of his long face; the eyes are small and deeply sunken in the large head; the projecting cheek-bones are marked with several deep furrows of purple, scarlet, and violet blue; both the abrupt muzzle and the lips are large and protuberant. The hair of the forehead and temples rises in a kind of pyramid, which gives to the head a triangular appearance; and from the chin hangs a small pointed orange-yellow beard. His strength, moroseness, and ferocity, render him a formidable opponent; and as he prowls about in large bands, it is dangerous for the natives to penetrate into the woods, unless well-armed, and in numerous companies. The Derrias (_Cynocephalus hamadryas_), a native of the mountains of Arabia and Abyssinia, measures upwards of four feet when standing erect, and about two feet and a half in a sitting posture. The hair of the head and neck gathers in a long mane, which falls back over the shoulders; the broad whiskers incline backwards so as to cover the ears. The long face is of a dirty flesh-colour; long, shaggy, brownish hair covers the head, neck, shoulders, and all the fore-part of the body. The tail terminates in a long tuft of brown hair.