The Skeleton 51 



v 



five vertebrae, which may be separated into the 

 usual regions; there are nine cervical, ten dorsal, five 

 lumbar, two sacral, and about thirty-nine caudal. It 

 is likely that the number of caudals may be sub- 

 ject to frequent variation; one complete skeleton 

 had sixty-five vertebras in all, another had sixty- 

 eight. A complete skeleton of the crocodile (species 

 not known) had sixty vertebras. A thirteen-foot 

 skeleton at Western Reserve University had only 

 sixty-one vertebras, but some of the caudals were 

 evidently missing. Two skeletons of C. porosus in 

 the museum at Singapore had sixty and sixty-three 

 vertebras respectively. A skeleton of Tomistoma 

 schlegali in the same museum had sixty vertebras. 



The Cervical Vertebra. Since all of the cervical 

 vertebras bear ribs, we shall assume the distinction 

 between them and the dorsal vertebras to be that 

 the ribs of the latter meet the sternum, while those 

 of the former do not reach to the sternum. As- 

 suming this distinction, there are, as was said 

 above, nine cervical vertebras. 



With the exception of the first two, to be dis- 

 cussed later, these are all essentially alike and the 

 fourth will be described as a type (Fig. 17). Its 

 centrum is cylindrical or somewhat hourglass 

 shaped, concave anteriorly and convex posteriorly; 

 it is not completely. fused with the neural arch but 

 is united with it by sutures. From the anterior 

 end of the ventral surface of the centrum projects 

 downward and forward a small plow-shaped process, 



