GEOLOGY OF CENTRAL AMERICA 237 



laid down, a foundation of granitic rocks, occurring in an east 

 and west arrangement, existed on the site of Central America. 

 Apparently parallel granitoid ridges extended from the longi- 

 tude of Trinidad directly across the path of the main con- 

 tinental trends through forty degrees, as far north as Acapulco 

 in Mexico. These fragmentary data, he says, are sufficient to 

 indicate that in pre-Tertiary times there may have been a 

 basement barrier of granitic rocks forming an east and west 

 arrangement which outlined the Central American region, and 

 constituted an ancient buttress against or upon which the 

 higher mountain folding has originated. Professor Suess,* 

 too, speaks of the mountain chains of Yucatan and Guate- 

 mala as the western continuations of the Antillean system, 

 contending that North and South America are to be looked 

 upon as two radically distinct continents, separated from one 

 another by a third element, that of Central America and the 

 Antilles. All this agrees to some extent, as we shall see later 

 on, with the conclusions we can draw from a study of zoogeo- 

 graphy. Central America and the Antilles, which are collec- 

 tively spoken of sometimes as the remnants of an ancient 

 " Antillean Continent," possess a distinct and peculiar fauna 

 quite apart from the South American one which has invaded 

 this area. 



Towards the end of the Mesozoic Era parts of this Antillean 

 continent must have begun to subside. About that time signs 

 of the coming volcanic activity appeared all along the Central 

 American region. During the successive igneous eruptions in 

 early Tertiary times, which have been continued with varied 

 intensity to the present day, the Atlantic Ocean seems to have 

 invaded the existing area of Central America and submerged 

 portions of it. At any rate, Professor Hill f states that 

 biological and geological evidence led him to the con- 

 clusion that a shallow marine transgression must have existed 

 somewhere in Central America during Eocene times, although 

 there is nothing to show with certainty that the isthmus 

 of Panama was the exact site of this inter -oceanic con- 

 nection. All the same, Professor Schuchert J seems to be 



* Suess, E., " Antlitz der Erde," Vol. I., p. 700. 



t Hill, E. T., " Geological History of Panama," p. 265. 



| Schuchert, 0., " Paleogeography of North America," pp. 96 97. 



