JVVi.] COPE ON HOEIZONS OF EXTINCT VERTEBRATA. 35 



Streptospondylus. Beyond this no comparisons can be made, and we 

 therefore pass to the rich fauna of the Kimmeridge. North America 

 cannot show such records of this epoch as have been found in Europe. 

 There are no Archceopteryx, WmmpliorJiynchus, nov FterodaGtylus ; no Lep- 

 tolepis, Thrissops^ nor otlier of the numerous fishes of Solenhofen. The 

 Omosaurus has, however, some very close relatives in the supj)osed Da- 

 kota beds of the Eocky Mountains. Ij^o remains of that primitive Mar- 

 supial fauna which occurs in the Purbeck have yet been detected in 

 the Western Continent. A partial representation of the Wealden fauna 

 of Europe is found in the beds of the Rocky Mountains mingled with 

 the types of the Oolite and Kimmeridge already mentioned. The rela- 

 tionships of this fauna to those of the European Jurassic series may be 

 thus exhibited : 



American. !Euroi>ean. 



Camabasatjrus Beds. Wealden. 



9 Iguanodon. 



f Hypsilophodon. Sypsilophodooi. 



SylcBosaurus. 

 f Cetiosaurus. Cetiosaurus. 



Camarasaurus. Eucamerotus.* 



OrnitJwpsis. 

 AmpMccelias. 

 f GoniopJiolis. GoniopJiolis, 



Kimmeridge. 

 HypsirJiopJius. Omosaurus. 



Caulodon. f Caulodon.\ 



OXPORD. 



Upanterias. Streptospondylus. 



Oolite 

 " Cetiosaurus." 

 f Megalosaurus. Megalosaurus. 



From the above table it will be seen how difficult it is at the present 

 to parallelize the related beds of the Jurassic periods of the two conti- 

 nents at the present time. All that can be said is that many types re- 

 sembling | nearly those of different horizons of the European Jurassic 

 are found to have lived together or near together in the Eocky Mount- 

 ain region of ISTorth America. 



That the Cretaceous fauna of ISTorth America was the richest in the 

 cold-blooded Vertebrata is indicated by the present state of discovery. 

 The ocean of the interior of the continent deepened from the beginning 



* Chondrosteosaurus Owen. 



t Iguanodon prcBCursor Sauv. 



t A near affinity has been shown by Professor Owen to exist between Eucamerotus 

 and Camarasaurus. Professor Owen believes these genera to be identical; but the 

 neural spuie» of the anterior dorsal vertebrsB are very different, being single in the 

 former, and double in the latter. 



