103 COMPARATIVE OSTEOLOGY 



There are eight small alveoli in front for the incisors and canines, the latter 

 being close up to the former ; the condyles are small and convex in their 

 short, but slightly concave in their long diameter, permitting considerable 

 lateral motion to the joint. The coronoid processes are long, and the sigmoid 

 notches very deep. 



The OS hyoides has a cornu and two cornicula on each side — the former 

 (stylchyals) are suspended from the temporal bone. The spur process is small 

 and blunt. 



VERTEBRA. 



The true vertebral column is made up of 26 segments— 7 cervical, 13 dorsal, 

 and 6 lumbar. The bodies of the cervical vertebrae are shorter than those of 

 the horse ; the transverse processes consist of a superior, small, and an 

 inferior, large portion, pierced by the vertebral foramina ; the neural spines 

 are large, and increase from before backwards ; the inferior spines unite the 

 anterior and posterior articular ends. The atlas, smaller than that of the 

 horse, has its alse more horizontal and slightly turned up at the external 

 borders. The spinal foramen is large, and the posterior lateral one absent. The 

 condyloid articulations are wide, that for the dentata being small and flat. 

 The dentata is short, the odontoid process being broad, bounded below by a 

 prominent articular ridge, which is not excavated in the inferior median line ; 

 the neural spine does not bifurcate nor become continuous with the posterior 

 articular processes. The pedicles on either side are perforated by a circular 

 foramen. 



The sixth cervical vertebra has long superior spinous and transverse pro- 

 cesses, but no inferior spine. The seventh neural spine is the longest, and 

 points backwards and upwards; the transverse processes are single, and ter- 

 minate in rough tuberosities ; there is no inferior sj)ine, and seldom a vertebral 

 foramen. 



The centra of the dorsal vertebrae are longer than in the horse, but have 

 the same general form ; the pedicles are almost always pierced by foramina in 

 place of the posterior notches. The transverse processes are large, decreasing 

 in size, and assuming an arched form from before backwards ; all but the 

 last, or last two, present distinct articular surfaces for the costal tubercles. 

 The neural spines are broad, long, and smooth : the five or six anterior ones 

 incline backwards, then upwards, the remainder simply backwards ; the 

 fourth is usually the longest, but the first four or five vary little in length. 

 The rest gradually become shorter backwards to the last. This gives the 

 back when viewed laterally a very different form from that of the horse. The 

 lumbar vertebra? are longer and thicker than in the horse, their bodies being 

 more convex on the lateral and inferior surfaces ; their transverse processes 

 are long, the fourth being the longest, and they are almost at right angles to 

 the body, concave anteriorly, convex posteriorly, the first four being inclined 

 backwards; they never articulate with each other, nor does the last with the 

 sacrum. The articular processes are small, the posterior being overlapped by 

 the anterior ones. 



The sacrum is large and more arched, and the superior surface more convex 

 than in the horse ; the spinous processes are united by more complete ossifi- 

 cation. The superior groove is narrow and uneven, and the superior forauuna 

 not so regular ; the under surface is more concave, the promontory being 



