SKELETON OF THE CROCODILE. VERTEBRAL COLUMN. 241 



The second or axis vertebra also differs a good deal from 

 the other cervicals. The centrum is massive, and is terminated 

 in front by a very large slightly concave articulating surface 

 formed by the odontoid process (fig. 41, 3) which is united 

 with the centrum by suture only, and is really the detached 

 centrum of the first vertebra. The cervical rib (fig. 41, 9) 

 articulates with two little irregularities on the odontoid pro- 

 cess. The posterior surface of the centrum is convex. The 

 neural arch is strongly developed and terminated dorsally 

 by a long neural spine (fig. 41, 5), its sides are notched, 

 slightly in front and more prominently behind for the exit ofr 

 the spinal nerves. It is drawn out in front into two little 

 processes bearing a pair of upwardly and outwardly directed 

 prezygapophyses, while the postzygapophyses are similar to 

 those of the other cervical vertebrae. 



The last two cervical vertebrae resemble the succeeding 

 thoracic vertebrae, in the increased length of the transverse 

 processes, and the shifting dorsalwards of the facet with which 

 the capitulum of the rib articulates. 



THE THORACIC VERTEBRAE. 



The thoracic vertebrae commence with the first of those 

 that bears ribs reaching the sternum. They are ten in 

 number, and the first eight are directly connected with the 

 sternum by ribs. 



The third of them may be taken as a type. It has a 

 thick cylindrical centrum, concave in front and convex behind, 

 there is a slight hypapophysis, and the centrum is suturally 

 united with a strong neural arch enclosing a narrow neural 

 canal. The neural arch is drawn out dorsally into a wide 

 truncated neural spine, and laterally into two prominent 

 transverse processes, with the ends of which the tubercula of 

 the ribs articulate, while the capitulum articulates in each case 

 with a step-like facet (fig. 42, A, 3) on the anterior face of the 

 transverse process. The prezygapophyses (fig. 42, A, 2) are 

 R. 16 



