CLA SSIFICA TION OF I r ER TEBR. I TA 23 



Hadrosaurus and Diclonius. Upper Cretaceous, U.S.A. 



?Ornithomimus. Upper Cretaceous, Colorado. 

 4. Order Ceratopsia, Marsh. Tubes simple, with sym- 

 physis. Pentadactyle, quadrupedous. Maxilla and mandible 

 with a toothless rostrale and predentale. With dermal armour. 



Ceratops and Tricerato ps. Cretaceous, Europe and U.S.A. 



7. Sub-CLASS PTEROSAURIA, Kaup 



Stereospondylous. Quadrate fixed. Anterior limbs trans- 

 formed into wings, the enormously elongated ulnar finger 

 carrying the patagium. 



1. Sub-order PTERODACTYL! With alveolar teeth. 

 Dimorphodo n. Lias, England. 



Pterodactylus and Rhamphorhynchu s. Upper Jurassic, 



Europe. 

 Ornithocheirus. Cretaceous, England. 



2. Sub -order PTERANODONTES. Without teeth. 

 Scapula articulating with spinous processes of dorsal vertebrae. 



Pteranodon. Cretaceous, Kansas. 



8. Sub-CLASS PLESIOSAURIA, Fitzinger 



Quadrate fixed. Alveolar teeth. Thoracic ribs without 

 tuberculum. Strong abdominal ribs. One or more sacral 

 vertebrae. No sternum. Neck mostly long. Aquatic. 



1. Order Mesosauri, Boulenger. Pentadactyle, not more 

 than five phalanges. Vertebrae with persistent notochordal 

 canal. Four sacral vertebrae. 



Mesosauru s. Trias, S. Africa and Brazil. 



2. Order Nothosauri, Boulenger. Pentadactyle walking 

 and swimming limbs, with not more than five phalanges. 

 Vertebrae solid. 



Nothosaurus. Muschelkalk, Germany. 

 Lariosaurus. Upper Trias, fresh water, Lombardy. 



3. Drder "Plesiosauri. Limbs transformed into hyper- 

 phalangeal paddles. Vertebrae solid. Europe, from the 

 Rhaetic to the upper Chalk, Marine. 



Plesiosaurus, Pliosaurus, Polyptychodon. 



