174 THE SKULL. [chap. 



contour of the face a totally different appearance from that 

 presented by the skull. 



In the Elk (Alces), and a small Abyssinian Antelope 

 (Neotragus saltiana), the nasal bones are very much shorter 

 than they are in ordinary ruminants. 



The Tylopbdd (Camels and Llamas) and the Tragulina 

 differ from most of the Pecora, and resemble the non- 

 ruminating Artiodactyles in having the tympanic bulla 

 filled with cancellated bony tissue. 



The skull of the Pig shows in section that the axis of the 

 face is bent down upon the basicranial axis almost as much 

 as in the Sheep, a disposition which increases with age. 

 Though the form of the cranial cavity is not very different 

 from that of the Sheep, the external appearance of the 

 hinder part of the skull is greatly changed by the elevated 

 and backward sloping occipital crest, formed by the union 

 of the supraoccipital (concave from side to side posteriorly) 

 and the parietals. The latter have their outer and inner 

 surfaces widely separated in the adult Pig by .large air-cells. 



The frontal is broad and flat between the orbits, and 

 sends out a small postorbital process, which does not join the 

 zygoma. The face is greatly elongated, tapering forwards, 

 and compressed laterally. The nasals are long and narrow, 

 and the apertures of the nares small and nearly terminal. 

 The premaxillae send up long processes on each side of 

 the nasals, which, however, do not meet the frontals. The 

 lachrymal has a considerable facial portion ; and, as in 

 other Ungulata, the malar encroaches considerably on the 

 face, uniting with the lachrymal. 



At the anterior extremity of the mesethmoid a peculiar 

 ossicle {prenasal) is developed, which strengthens the cartila- 

 ginous snout. 



