THE SKELETON IN MAMMALIA. THE SKULL. 465 



the Ungulata from the other groups of mammals are drawn 

 from the skull. But in the Ungulata vera as opposed to the 

 Subungulata a distinguishing feature is found in the fact that 

 the lachrymal and jugal form a considerable part of the side 

 of the face, and that the jugal always forms the anterior part 

 of the zygomatic arch, the maxilla taking no part in it. 



UNGULATA VERA. 



ARTIODACTYLA. The skull in Artiodactyla differs from that 

 in Perissodactyla in the fact that the posterior end of the 

 nasal is not expanded and there is no alisphenoid canal. 



The skulls in the different groups of Artiodactyla differ 

 considerably from one another. 



The skull of the Pig 1 will be described as illustrative of the 

 skull in the Suina. In the Pig as in most Artiodactyla the 

 face is bent sharply down on the basicranial axis, the com- 

 mencement of the vomer being situated below the mesethmoid 

 instead of in front of it as in most skulls. The occipital region 

 of the skull is small, and the line of junction of the supra-occi- 

 pital and parietals is raised into a prominent occipital crest. 

 The parietal completely fuses at an early stage with its fellow, 

 and the exoccipital is drawn out into a long paroccipital process 

 (fig. 94, A, 8). The frontal is large and broad and drawn out 

 into a small postorbital process. The lachrymal too is large and 

 takes a considerable part in forming the side of the face in front 

 of the orbit, as does also the jugal, though to a less extent. 

 The face is long and tapers much anteriorly. The nasals are 

 long and narrow, as are the nasal processes of the premaxillae, 

 which do not however reach the frontals. A prenasal ossicle 

 is developed in front of the mesethmoid. The palate is long 

 and narrow, the pterygoid (fig. 94, A, 10) is small, but the 

 pterygoid process of the alisphenoid is prominent. The 

 squamosal is small and has the tympanic fused with it ; the 

 tympanic is dilated below, forming a bulla (fig. 94, A, 9) filled 



1 See W. K. Parker, "On the Structure and Development of the Skull 

 in the Pig." Phil. Trans, pp. 289336, 1874. 



R. 30 



