220 GEOLOGY. 



marine origin also occur in Patagonia. 1 Both marine and non-marine 

 Eocene may be much more widely distributed. 



Eocene beds, not always distinctly separable from the Oligocene, are 

 extensively developed in the West Indies, where limestone is the domi- 

 nant type of rock. In Cuba, 2 the Eocene beds (together with the Oligo- 

 cene) occupy the surface of about half the island. In Jamaica 3 the 

 Eocene is distinct from the Oligocene. Eocene beds grading up into 

 Oligocene without interruption are present on the island of Trinidad, 

 and are extensively developed on the eastern side of Panama, 4 and in 

 Central America. They are partly clastic, and partly limestone. Ma- 

 terial derived from igneous rocks enters largely into their composition, 

 and extensive extrusions of basic rocks occurred in this region during 

 the period. Some idea of the changes of later times may be gained 

 from the fact that the Early Tertiary formations of the Caribbean 

 region occur up to elevations of 5000 feet on the mainland, and up to 

 elevations of 10,500 feet in Hayti. 5 The date of the principal deforma- 

 tion was later than the Eocene. 



It was formerly thought that the Atlantic and Pacific oceans con- 

 nected freely across Panama during the early Tertiary, but the work 

 of Hill renders it doubtful whether there were more than shallow and 

 restricted connections in the Eocene, and whether there were connec- 

 tions of any sort at a later time. 



General geography of the Eocene. — From what has been sajd it is 

 clear that Eocene geography was very different from that of the present 

 time, and differences still greater than those already indicated are con- 

 jectured. North America was perhaps connected with Asia on the 

 west, via Alaska, and with Europe on the east, via Greenland and Ice- 

 land. 6 Land seems to have failed of making a circuit in the high lati- 

 tudes of the north only by the strait or sound east of the Urals. 



In the southern hemisphere, it has been surmised that Antarctica 

 was greatly extended, connecting with South America, Australia, and 



1 Ameghino, L'age des Formations Sedimentaires de Patagonia, Anales de la 

 bociedad Crentipica Argentina, 1903. 



2 Hill, Cuba and Porto Rico. 



3 Hill, Geology and Physical Geography of Jamaica, 1899. 



4 Hill, Geological History of the Isthmus of Panama and Portions of Costa Rica. 

 Bull. Mus. of Comp. Zool., Cambridge, 1898. 



6 Idem. 



8 Neumayr, Erdegeschichte Bd. II. 



