their reflection were a new acquaintance.... It deserves especial attention that von Fischer has never seen any species purposely exhibit the hinder part of its body, if not at all {272}coloured.... With respect to the origin of the habit, it seems to me probable that the bright colours, whether on the face or hinder end, or as in the Mandrill, on both, serve as a sexual ornament and attraction.... The fact that it is only the Monkeys (with those parts brightly coloured), which as far as at present known, act in this manner as a greeting towards other Monkeys, renders it doubtful whether the habit was first acquired from some independent cause, and that afterwards the parts in question were coloured as a sexual ornament; or whether the colouring and the habit of turning round were first acquired through variation and sexual selection, and that afterwards the habit was retained as a sign of pleasure, or as a greeting, through the principle of inherited association." X. THE ARABIAN BABOON. PAPIO HAMADRYAS. _Simia hamadryas_, Linn., Syst. Nat., i., p. 36 (1766). _Le tartarin_, F. Cuvier and Geoffr., Mamm., vol. i., livr. 5 (1819). _Cynocephalus hamadryas_, Fr. Cuvier, Hist. Nat. Mammif., p. 129, pl. 46 ([male]). _Papio hamadryas_, Geoffr., Ann. Mus., xix., p. 103 (1812); Schl., Mus. Pays Bas, vii., p. 129 (1876, in part). _Hamadryas ægyptiaca_, Gray, Cat. Monkeys Brit. Mus., p. 34 (1870). CHARACTERS.--MALE.--Size of a large Pointer Dog; muzzle long; nose slightly longer than the upper lip; nostrils terminal, separated by a furrow above and in front; face naked, the ridges parallel to the nose, and far less prominent than in the Mandrill or Drill; eyes deep-set; brows overhanging; ears naked; a large mane, mantle-like, on the throat, neck, {273}shoulders and middle of the back; whiskers long, directed backwards, almost concealing the ears; hair on the lower back, arms, thighs and legs short; callosities large, and the surrounding part of the buttocks nude; tail slightly shorter than the body, arched at the basal third, then descending perpendicularly to its termination, which is tufted; under surface of body and inner aspect of limbs thinly haired; fourth finger and second toe strongly clawed.