CROCODILES, ALLIGATORS, GAVIALS. 



5S5 



sacral, and caudal vertebrse, all proccelous 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 vertebrce 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 vertebra;. 



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

 they articulate with the vertebrce. P'rom seven to nine of the anterior 





'^y 



Fig. 202. — Crocodile's skull from dorscil surface. 



p.77ix., Pre-maxilla ; 7ux.-, maxilla ; /., lachrymal ; pr.f.^ pre-frontal ; 

 y., jugal ; p./., post-frontal; g-j-, quadrato-jugal ; (/., quadrate; sq.^ 

 squamosal ; /a., parietal ; c.pt.^ epi-pterygoid ; /., frontai ; pt.^ ptery- 

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

 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 



