xi.] UNGULATA. 177 



cancelli, as in the Pig. As in that animal, there is a long 

 narrow meatus auditorius, directed upwards and backwards 

 in a fissure between the postglenoid and post-tympanic 

 processes of the squamosal, the floor being formed by a 

 compressed, ridged prolongation of the tympanic, which 

 is at a very early age completely fused with the squamosal. 

 The periotic is very small, remains longer distinct, though 

 ultimately ankylosing with the conjoined squamoso-tym- 

 panic, and has only a rudiment of a mastoid portion, which 

 is quite confined to the interior of the cranium. 



The tympanohyal is slender, ankylosed to the back of the 

 tympanic, and in the adult skull sunk in a deep fossa, 

 between that bone and the exoccipital, which also gives exit 



io the facial nerve. 

 The mandible is of immense size and weight. The 

 :ondyles rise very little above the level of the molar teeth. 

 The coronoid process is small and much recurved. The 

 angle is greatly expanded and everted, rounded behind, and 

 terminating below in a distinct process, projecting down- 

 wards and forwards. The horizontal rami are compressed 

 in their middle portion, but widen anteriorly into a very 

 broad and massive truncated symphysial portion, which 

 supports the huge incisor and canine teeth. 



In the hyoid apparatus, the basi- and thyro-hyals ankylose, 

 and are something like those of the Pig. The anterior arch 

 consists of three well-ossified pieces of subequal length. 



Order Hyracoidea. — The skull of the Hyrax presents 

 many affinities with that of the Perissodactyla, others with 

 the Rodentia, and some characters peculiar to itself. 



The cranium is high and truncated behind, the occiput 

 nearly vertical, the tentorial and olfactory planes oblique, 

 the olfactory fossa rather small. 



