272 ALLEN’S NATURALIST’S LIBRARY. 
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., 1., p. 36 (1766). 
Le ¢artarin, F. Cuvier and Geoffr., Mamm., vol. i. livr. 5 
(1819). 
Cynocephalus hamadryas, Fr. Cuvier, Hist. Nat. Mammif., p. 
129, pl. 46 (2). 
Papio hamadryas, Geoffr., Ann. Mus., xix., p. 103 (1812) ; 
Schl., Mus. Pays Bas, vii., p. 129 (1876, in part). 
Hamadryas egyptiaca, 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, 
