254 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 



ous rocks along the northernmost coast of South America and in the 

 Great Antilles is directly in harmony with the east and west trend of 

 the same phenomena upon the mainland, 1 and we cannot escape the con- 

 clusion that they are the product of the same great orogenic revolution, 

 the age of which was Mid-Tertiary, for rocks of early and late Eocene 

 age everywhere as exposed along the Caribbean coast, and in the Great 

 Antilles, are folded by these mountain making processes, while the Plio- 

 cene and Pleistocene are more horizontally laid down against the sea- 

 ward margin of the mountain masses. 



There is a remarkable suggestiveness in the age, character, and trend 

 of these late Tertiary movements with those of the Pacific coast of 

 North America, especially of California and Lower Californian regions. 

 An imaginative mind could easily draw a long sweeping curve along 

 the Pacific coasts of Oregon, California, Lower California, and Mexico, 

 across the continent in Central America and the Antilles, and state 

 that it represented the trend of the great orogenic revolution of the 

 Tertiary time, — a revolution which perhaps produced the greatest 

 known modification of Central American and Antillean topography, and 

 largely established the present shapes of the land areas. 



T7te Epeirogenic Movements of Post-Miocene Time. — We have de- 

 scribed in detail the character of the swamp lands in the vicinity of 

 Colon, composed of littoral debris of the ocean, showing that they 

 represent elevation of marginal sea deposits which had been deposited 

 against a greatly eroded pre-existing land. We have shown the exist- 

 ence of the same phenomena upon the Pacific slope of Panama, though 

 of a less marked extent. From the wide distribution of this phenom- 

 enon I am inclined to believe that the whole region has undergone uni- 

 form elevations in comparatively recent (Post-Pleistocene) time, whereby 

 the shallow margins of the sea have been elevated into low lying coast 

 lands. 



The Monkey Hill level at Panama, which rises from 50 feet at the 

 sea to 100 feet a few miles inland, seems to be a widely distributed 

 topographic feature. This level is the result of the degradation of the 

 land down to marine base level, followed by subsequent elevation to 

 its present height. This level is well defined along the Limon coast 

 of Costa Rica, where are seen the same low-topped hills projecting 

 above the swamp plain as at Colon, presenting exactly the same charac- 

 ters of composition and topography. While I could not trace these 



1 In this connection the reader is referred to an admirable chapter on this sub- 

 ject in Professor Suess's "Das Antlitz der Erde," Vol. I. pp. 692-710. 



