1902.] AND ANCIENT GEOGRAPHY. 365 



the present boundaries of South America, which is formed by the 

 Chilian- Fuegian coast range, once a part of Antarctica. 



2. North America was separated during the Lower Cretaceous 

 from Central America. During the Upper Cretaceous it was divided 

 into an eastern and a western portion ; the western was definitively 

 connected at this time with Central America. In the beginning of 

 the Tertiary the eastern portion was reunited with the western, and 

 thus the whole of North America, from the Arctic Ocean to the 

 Gulf of Mexico and the Caribbean Sea, became a unit. 



3. Central America existed as a continental mass up to the end of 

 the Cretaceous. Being originally separated from North America, it 

 became united with it in the Upper Cretaceous. By the formation 

 of the Caribbean Sea it was broken up and consisted, in the begin- 

 ning of the Tertiary, of two main parts : a northern, belonging to 

 North America, and a southern, which became united with South 

 America, then undergoing the process of construction. Both parts 

 were separated by the Old Tertiary interoceanic connections at 

 Panama and Nicaragua. 



The southern part of Central America was originally (Lower 

 Cretaceous) bounded on the south by sea, which occupied the 

 region from the Orinoco valley westward. In the Upper Cretaceous 

 Guiana was connected with Venezuela, and thus Central America 

 was connected also with Africa. To the south of these parts was 

 the Upper Cretaceous interoceanic connection of the Amazonas 

 valley. In the àegimting of the Tertiary, what was left of Central 

 America in the south (Venezuela and Guiana) was united with the 

 Brazilian mass by the beginning of the upheaval of the Cordilleras, 

 by which parts of Colombia, Ecuador and Peru became land. 



In the middle of the Tertiary (Miocene) the interoceanic connec- 

 tion in the isthmian region became land, and thus North America 

 and the northern remnants of Central America were united with the 

 southern remnants of Central America and South America. 



4. South America consisted in the beginning (Jurassic and Lower 

 Cretaceous) of the Brazilian mass (Archiplata), which included 

 Guiana, and a smaller part which is perhaps of Cretaceous age, rep- 

 resented now by the Chilian coast range. Archiplata was con- 

 nected with Africa up to the middle of the Cretaceous. In the Upper 

 Cretaceous, Guiana was separated from Brazil by the interoceanic 

 connection of the Amazonas valley and Archiplata became an 

 island. At the end of the Cretaceous, and chiefly during the 



