4 SIMIID^. 



wlaicli are generally black, and the persistence of the former colour throughout 

 life in some females, and perhaps also in some males, are facts of considerable 

 interest, and should not be lost sight of in studying the various species of Se^nno- 

 pitheci. Some of the species of tliis tailed group appear only to be distinguish- 

 able from each other by differences of colour, some of them being deep black and 

 others bright red. The dark-coloured species have their young born yellow 

 or red. 



The leading features of the skull of H. lioolock as compared with H. lar are its 

 less prominent orbital ridges, longer muzzle, more elongated nasal orifice, and 

 considerably larger teeth, associated with a much longer palate than in S. lar. 

 Such a series of structural characters occurriag in the skull along with peripheral 

 distinctions by which alone it is possible to separate S. hoolocJc from H. lar clearly 

 indicate the two as distinct species. 



On the other hand, the skull of S. agilis has the prominent ridges surrounding 

 the orbits, the short snout and palate and small teeth of JI. lar, to which in 

 external characters it is closely alHed. The skulls also of H. leuciscus and of 

 S. miilleri do not appear to me to present any very marked structural modification 

 on the skuU of S. lar. 



There is occasionally considerable asymmetry between the two sides of the facial 

 bones of S. hoolock, due to a lateral twisting which I have generally observed to be 

 towards the right side. It is quite apparent in life, and sometimes produces a 

 most ludicrous appearance. This asymmetry does not appear to affect the rest of 

 the skull. 



The canine teeth, unUke those of the higher anthropoid apes, appear to be 

 equally well developed in both sexes of all the species, if the specimens on wliich 

 these observations are founded have been correctly sexed, which I have no reason to 

 doubt, as I have as far as possible personally verified the sex in each instance. 



Dahlbom, in his comparatively recent revision of the genus, has placed, it 

 appears to me, undue stress on the character of the absence or presence of a tuber- 

 cle on the clavicle, for the existence of such a nodule can hardly be regarded in the 

 Mglit of a structural character, as it simply, indicates that the muscle has had a 

 more powerful attachment to the bone than in those cases in which the nodvde is 

 only feebly developed. Such a character would be largely influenced by the Hfe 

 the animal led, and unless all the individuals on which his observation rests were 

 thoroughly ferine, its value is much lessened. Dahlbom accepts S. agilis as distinct 

 from S. rafflesii, and H. entelloides as separable from S. lar. 



I append a synopsis of the species after a careful comparison and study of 

 the various types in Europe and the examination of a very extensive series in 

 India. 



