1900.] MAMMALS FROM S.AV. ARABIA. 97 



common throughout the Mammalia. Naturally every craniologisfc 

 is more or less familiar with this fact, but in describing a new 

 species on such material as the present it is necessary to emphasize 

 the value of the size of the teeth as a criterion of species, irre- 

 spective of sex. 



Taking for comparison a good adult skull of a male Hamadryad 

 from Abyssinia we find, in marked contrast to those given above, 

 the following dimensions (in millim.) : — 



Combined lengths of 



Total length 5 upper cheek- 4 posterior Length of 

 of skull. teeth. lower cheek- last lower 



teeth. molar. 



6. Abyssinia .. 174 50-4 48 17'4 



$ . Arabia 140 41-5 39-5 13-1 



Such a difference in the size of the teeth evidently indicates 

 specific distinction. 



In its general physiognomy the skull is, as might be expected, 

 much less prognathous than that of the male of P. Jiamadryas, the 

 orbits are similarly high and rounded, the facial ridges are less 

 marked, the chin is much developed, and the shape of the coronoid 

 is different, being more vertical and less slanted backwards. The 

 complete measurements of the skull are as follows (in millim.) : — 



Greatest length (gnathion to occiput) 140, basal length (gnathion 

 to basion) 98 ; zygomatic breadth 90 ; gnathion to lower edge of 

 orbit 61 ; tip of nasals to orbit 32 ; orbits, width 24, height 22-5 ; 

 brain-case, length from occiput to nasion 91, breadth on squamosals 

 67 ; interorbital breadth 46 ; palate length 57, breadth outside 

 tooth-row 44; lower jaw, length from condyle 101, height at 

 coronoid 50. 



In its external characters the skin may be described as follows: — 



Pur thin and scanty, rather wavy in texture across the back, 

 the hairs across the shoulders but little lengthened beyond the 

 rest. General colour dull greyish ; the hairs on the crown and 

 those of the middle line of the loins annulated, blackish with a 

 buffy subterminal ring, those on the temples, sides of neck, shoulders, 

 and flanks unannulated, dull grey. Hairs on the rump above the 

 callosities with a strong rufous suffusion. Under surface and inner 

 side of limbs practically naked. Hairs of arms and legs scanty, 

 dull greyish, gradually passing into annulated black and whitish 

 hairs on the hands and feet. Tail-hairs annulated above, pale 

 greyish below, those at the tip forming a small dull whitish tuft. 



Measurements of a remade skin, approximate: — 



Head and body 590 mm., tail 410, hind foot 135. 



Considering the former extension of the genus into India, it was 

 quite to be expected that the Arabian Baboon should prove different 

 to that found on the African side of the lied Sea. But it may 

 be noted that the two Siwalik species, Papio eubhimalayanus and 

 P. falconeri, both have teeth as large as (or larger than) any of the 

 African Baboons. 



Proc. Zool. Soc— 1900, No. VII. 7 



