CROCODILES, ALLIGATORS, G A VIALS. 585 



sacral, and caudal vertebrae, all procoelous except the first two cervicals, 

 the two sacrals, and the first caudal. In most of the pre-cretaceous 

 Crocodilians, however, the vertebrae were amphicoelous. The centra of 

 the vertebrae are united by fibro-cartilages, and the sutures between the 

 neural arch and the centrum persist at least for a long time. Chevron 

 bones are formed beneath the centra of many of the caudal vertebrae. 



Many of the ribs have two heads capitulum and tubercle by which 

 they articulate with the vertebrce. From seven to nine of the anterior 



at 



" y ; 



FIG. 202. Crocodile's skull from dorsal surface. 



^p.mx., Pre-maxilla ; mx., maxilla; /., lachrymal ; pr.f., pre-frontal ; 

 /> jugal ; p.f., post-frontal; q.j., quadrato-jugal ; g., quadrate; sq., 

 squamosal ; pa., parietal ; e.pt., epi-pterygoid ; /., frontal ; pt., ptery- 

 goid (on lower surface); o.t., os transversum (on lower surface); ., 

 nasal. 



dorsal ribs are connected with the sternum by sternal ribs, and from 

 several of these anterior ribs cartilaginous or partially ossified uncinate 

 processes project backwards. The so-cal led abdominal ribs have nothing 

 to do with ribs, but are ossifications in the fibrous tissue which lies 



