I THE ORANQ 57 



offer differences as decided as those existing between the most 

 strongly marked forms of the Caucasian and African crania in 

 the human species. The orbits vary in width and height, the 

 cranial ridge is either single or double, either much or little 

 developed, and the zygomatic aperture varies considerably in 

 size. This variation in the proportions of the crania enables us 

 satisfactorily to explain the marked difference presented by the 

 single-crested and double-crested skulls, which have been 

 thought to prove the existence of two large species of Orang. 

 The external surface of the skull varies considerably in 

 size, as do also the zygomatic aperture and the temporal 

 muscle ; but they bear no necessary relation to each other, a 

 small muscle often existing with a large cranial surface, and vice 

 versd. Now, those skulls which have the largest and strongest 

 jaws and the widest zygomatic aperture, have the muscles so 

 large that they meet on the crown of the skull, and deposit the 

 bony ridge which separates them, and which is the highest in 

 that which has the smallest cranial surface. In those which 

 combine a large surface with comparatively weak jaws, and small 

 zygomatic aperture, the muscles, on each side, do not extend to 

 the crown, a space of from 1 to 2 inches remaining between them, 

 and along their margins small ridges are formed. Intermediate 

 forms are found, in which the ridges meet only in the hinder 

 part of the skull. The form and size of the ridges are therefore 

 independent of age, being sometimes more strongly developed in 

 the less aged animal. Professor Temminck states that the series 

 of skulls in the Leyden Museum shows the same result." 



Mr. Wallace observed two male adult Orangs 

 (Mias Kassu of the Dyaks), however, so very 

 different from any of these that he concludes 

 them to be specifically distinct; they were 

 respectively 3 feet 8J inches and 3 feet 9| inches 

 high, and possessed no sign of the cheek ex- 

 crescences, but otherwise resembled the larger 

 kinds. The skull has no crest, but two bony 



