

xi.] UNGULATA. 167 



cess parallel with, and equalling, or sometimes exceeding, 

 in length, the paroccipital process. The meatus auditorius 

 lies in a deep groove between the postglenoid and the post- 

 tympanic processes of the squamosal ; the latter articulates 

 with the exoccipital, completely excluding the mastoid from 

 the external surface of the skull. 



The tympanic and periotic are ankylosed together, but 

 not with the squamosal. They are both very small. The 

 under surface of the tympanic is rough, forms no distinct 

 bulla, and is much encroached upon posteriorly by the very 

 large tympanohyal, which presents a circular, flat, rough, 

 inferior surface, half an inch in diameter (in an adult 

 Sumatran Rhinoceros). Externally, the tympanic is pro- 

 duced into a rough, irregular, inferior wall to the auditory 

 meatus. The periotic internally shows the internal auditory 

 meatus near its lower part, but no distinct depression for 

 the flocculus ; it is prolonged upwards and outwards into 

 a small mastoid portion, which, as before said, does not 

 appear on the outer surface of the skull. 



The mandible has a very wide condylar articular surface, 

 and slender recurved coronoid process, a rounded, somewhat 

 incurved angle, a compressed, rather narrow, horizontal por- 

 tion, and a shallow depressed symphysis. 



The hyoid is much like that of the Horse, and has a 

 glossohyal process from the middle of the basihyal. 



The Tapirs present some singular modifications of the 

 same type of skull. 



As in the Rhinoceros, there is no separation between the 

 orbit and temporal fossa, but the anterior nares are of 

 immense size, and extend backward above the orbits, being 

 separated from them only by a thin plate of bone, instead 

 of a broad, flat surface, as in the Horse and Rhinoceros. 



