THE SKELETON IN MAMMALIA. THE SKULL. 471 



only in the male) bearing a pair of blunt bony outgrowths, 

 Between these two elevated regions the skull is much de- 

 pressed. The cranial, cavity is very small, the orbit confluent 

 with the temporal fossa, and the zygomatic arch massive. 



In Tapirus the orbit and temporal fossa are confluent. 

 The nasals are small, wide behind and pointed in front, and 

 are supported by the mesethmoid ; the anterior nares are 

 exceedingly large and their lateral boundaries are entirely 

 formed by the maxillae. The postglenoid and post-tympanic 

 processes of the squamosal are large. The periotic is not fused 

 to the squamosal or to the small tympanic. The mandible is 

 large and has the angle much developed and somewhat inflected. 



Palaeotherium, which lived in early Tertiary times, has a 

 skull much like that of the Tapir, especially as regards the 

 nasal bones. 



In the Horse and its allies (Equidae) the facial portion of 

 the skull is very large as compared with the cranial portion, 

 the nasals and nasal cavities being specially large. In the 

 living species of the genus Equus there is no fossa between the 

 maxilla and lachrymal, but it occurs in some extinct species. 

 The lachrymal and jugal form a considerable part of the side 

 of the face ; and the orbit though small is complete and pro- 

 minent. The postorbital bar is formed by a strong outgrowth 

 from the frontal, which unites with a forward extension of the 

 squamosal. The squamosal may extend forwards and form 

 part of the wall of the orbit, a very unusual feature, as in most 

 mammals the squamosal stops before the postorbital bar. The 

 palate is narrow and excavated behind as in Rhinoceros ; the 

 palatines take very little part in its formation. The glenoid 

 surface for the articulation of the mandible is very wide. The 

 squamosal gives rise to small postglenoid and post-tympanic 

 processes, and the exoccipital to a large paroccipital process. 

 The tympanic and periotic are ankylosed together, but not to 

 any other bones. 



In the SUBUNGULATA, the lachrymal and jugal do not form 



