xi.] ARTIODACTYLA. 195 



the skull, between the hinder border of the squamosal and 

 the exoccipitaL The tympanohyal is very large, cylindrical, 

 curved, and almost completely embedded in the tympanic, 

 between the inferior wall of the meatus and the outer wall 

 of the bulla. 



The extracranial portion of the hyoid consists of large 

 compressed stylohyals (sh), with a prominent posterior 

 process near the upper end, short but well-ossified epi- 

 hyals (eh] and ceratohyals (ch), and a basihyal represented 

 by a small rounded nodule of bone, to which the straight 

 thyrohyals (//*) are not ankylosed. 



The mandible has a broad flat condyle (cd], a long slender 

 coronoid process (r/), a rounded angle, a rather slender 

 horizontal portion, contracted and with a sharp upper edge 

 in front of the molar teeth, and expanded anteriorly for the 

 lodgment of the incisors. 



The Ox agrees generally with the Sheep in its cranial 

 characters. The face is bent down on the basicranial axis 

 almost in the same manner. The occipital surface is flat, 

 and terminates above in a broad transverse ridge, which 

 extends between the horn cores. The parietals are ex- 

 tremely narrow above, and placed almost entirely behind 

 this ridge. They unite very early with the interparietal and 

 supraoccipital. The intercornual ridge of the frontals is 

 excavated by large air-cells, communicating with those of 

 the horn cores, and is especially developed when the horns 

 are large. Unlike the parietals, the frontals are of very 

 great extent, and have a broad and flattened upper surface. 



The tympanics are compressed and scarcely at all bullate. 

 They end anteriorly in long compressed styliform processes, 

 and become firmly ankylosed with the periotic and squa- 

 mosal. The under surface of the meatus auditorius has a 



o 2 



