CHARACTERS OF CHELONIA. 5 



noid is unossified or small, a downward prolongation 

 of the parietal taking its place. There is no bony pre- 

 sphenoid or orbito-sphenoid. The mesethmoid carti- 

 lage largely persists. The orbito-temporal fossa is 

 covered by a bony arch. The dentary pieces of the 

 mandible are anchylosed together. 



8. The pectoral arch is ossified in such a way that 

 scapula and precoracoid form one bone, but the cora- 

 coid remains distinct. 



9. The heart has a single ventricle. 



10. There are no teeth, but the jaws are provided 

 with horny cutting-plates. 



