CHARACTERS.--MALE.--Snout tapering, longer than the upper lip; face, ears, palms and soles of feet naked; whiskers bushy, directed backwards, nearly hiding the quadrangular ears; tail of the form usual in this genus, shorter than the body. Hair on back of the neck longer than on the body; facial ridges present, but not very prominent; hinder part of belly, inside of limbs, and chin, throat, and breast very scantily haired. Face, ears, naked parts of hands and feet, black; upper eyelids white; fur of head, back, and limbs in general brownish-yellow--the hairs being ringed with alternate bars of black and light-brown; cheeks and whiskers fawn-coloured; throat and under side of body paler. Scrotum, callosities, and naked parts of buttocks bright flesh-coloured, but not so bright as in _C. hamadryas_. Length of body (in young male), 27 inches; of tail, 20 inches. FEMALE AND YOUNG MALE.--Similar to adult males in coloration; but less thick-set, and with a shorter muzzle. DISTRIBUTION.--The Guinea Baboon inhabits West Africa from Senegal and the Niger to Central Africa. In East Africa, Mr. H. H. Johnston observed it in the inhabited region of Kilimanjaro. HABITS.--Little is known of the habits of this species; but it is improbable that it departs widely from those of the other {271}members of the genus. In regard to the bright coloration of the callosities and posterior parts of this and other Baboons, Mr. Darwin remarks: "In the discussion on sexual selection in my 'Descent of Man,' no case interested and perplexed me so much as the highly-coloured hinder ends and adjoining parts of certain Monkeys. As these parts are more brightly coloured in one sex than the other, and as they become more brilliant during the season of love, I concluded that the colours had been gained as a sexual attraction.... I had, however, at that time no evidence of Monkeys exhibiting this part of their bodies during their courtship.... I have lately read [in an article by J. von Fischer, of Gotha, published in April, 1876] an account of the behaviour of a young male Mandrill when he first beheld himself in a looking-glass, and it is added, that after a time he turned round and presented his red hinder end to the glass. Accordingly I wrote to Herr J. von Fischer to ask what he supposed was the meaning of this strange action. He says that he was himself at first perplexed ... and was thus led carefully to observe several individuals of various other species of Monkeys, which he has long kept in his house. He finds that not only the Mandrill (_C. mormon_) but the Drill (_C. leucophæus_) and three other kinds of Baboons (_C. hamadryas_, _C. sphinx_, and _C. babuin_) ... turn this part of their bodies, which in all these species is more or less brightly coloured, to him when they are pleased, and to other persons as a sort of greeting.... From these facts von Fischer concludes that the Monkeys which behaved in this manner before a looking-glass ... acted as if