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 tier Erde,” Vol. I., p. 700. 
t Hill, R. T., “ Geological History of Panama,” p. 265. 
J Schuchert, C., “ Paleogeography of North America,” pp. 96—97. 
