202 THE SKULL. [CHAP. 



are long and slender. The glen old fossa is wide transversely, 

 and with a considerable postglenoid process. The periotic 

 and tympanic are ankylosed together, but usually remain 

 distinct from the squamosal. The tympanic forms a 

 moderate-sized bulla, and a spout-like floor to the external 

 auditory meatus, between the glenoid and post-tympanic 

 processes of the squamosal. The periotic has a very slight 

 floccular depression, and sends backwards no distinct mas- 

 toid process. The pituitary fossa is very shallow, without 

 clinoid processes. The foramen rotundum and foramen 

 ovale are distinct perforations through the alisphenoid. The 

 optic foramen pierces the large orbitosphenoid near its 

 hinder margin. 



The mandible has a high and exceedingly broad ascending 

 portion, its hinder margin being produced far behind the 

 condyle, but the angle is rounded, and without any distinct 

 process. The condyle is much extended transversely, and 

 narrow from before backwards, especially in its inner half, 

 for externally it is somewhat rounded. The coronoid pro- 

 cess is small and recurved. 



The hyoid apparatus of the Hyrax s unlike that of any 

 other known Mammal. The basihyal is oval, transversely 

 extended and flat, with a small median eminence on its 

 anterior border, and an emarginate posterior border, only 

 ossified in the centre, and prolonged laterally, without any 

 definite segmentation, into broad, flattened, slightly curved 

 cartilaginous thyrohyals. Articulated to the anterior and 

 external angles of the basihyal are two large, triangular, 

 flattened bones (ceratohyals), each with a long process 

 projecting forwards and meeting in the middle line, so 

 as to enclose (with the anterior margin of the basihyal) a 

 triangular space. There is no other cartilage or bone in the 

 anterior arch, unless a very minute pyramidal bone, described 



