314 CLASSIFICATIOX OF VERTEBRATES. 



teeth or are toothless, and occasionally teeth occur on the ossi- 

 fied palatines (Fig. 171). The feet are either fitted for walking 

 or for swimming. 



Sub-Order i. SPHENODOxxiyA. 



Small terrestrial forms with amphicoelous vertebrae. Here belongs the 

 living Sphenodon. The fossil forms, HojncEosaurus, Hyperodapedon, Pro- 

 terosaurus, PalcEokatteria. Telerpeton. etc., have been found only in 

 Europe. 



Sub-Order 2. Choristodera. 



.A^quatlc reptiles with flattened vertebra ; teeth 011 the palatines and 

 pterygoids. Large forms from the upper cretaceous of North America 

 (Champosaurus) and lower eocene of Europe (Simcedosaurus). 



ORDER VI. DIXOSAURIA. 



Extinct, mostly terrestrial reptiles, frequently of enormous 

 size, with long tail, ambulator}- feet, and a skin either naked or 

 covered with large dermal spines, plates, and ossicles. Vertebrae 

 solid or hollow ; flat, amphiccelous. or opisthocoelous, the latter 

 predominating ; sacrum of 3 to 6 vertebrae ; ribs bicipital ; ab- 

 dominal ribs occasionalh" present ; quadrate fixed ; supra- and in- 

 fratemporal fossae present. Teeth in alveoli or alveolar grooves ; 

 no episternum or procoracoid ; sternum partially ossified ; ilium 

 elongate in front of and behind the acetabulum, the acetab- 

 ulum itself open ; pubis with frequently a well-developed post- 

 pubic branch ; toes with claws or hoofs. 



As the name implies, the dinosauria were enormous reptiles, 

 remains of which have been found in all continents except Aus- 

 tralia, but which were especially developed in western America. 

 In many respects they resemble the lizards ; in others some 

 were decidedly bird-like. In size they varied between forms a 

 3 ard in length up to giants over a hundred feet long. Some 

 were herbivorous, some carnivorous, and thev were largelv in- 

 habitants of swampy places ; some, like Atnphicixlias and the 

 Megalosaurs, having bones so hollow and light that it seems as 

 if the)- could only support the weight of the body when it was 

 immersed in water. 



An exoskeleton occurred only in some orthopoda, and pos- 



