DEVELOPMENT OF SOUTH AMERICA 
845 
America, and some contend that Chile has been wholly or par¬ 
tially above the surface of the ocean since very early geological 
times. As Professor Suess * has pointed out, the extreme 
south of the continent is composed of a peculiar and probably 
very ancient system of rocks. This Patagonian mountain 
chain is quite independent of the Andes, of which it does not 
form a continuation. Further north in Chile it lies outside or 
westward of the Andes, constituting the coast Cordillera. 
Still further north, in Peru, only fragments of this Cor¬ 
dillera are recognisable here and there close to the coast, 
while in Ecuador the ancient coast Cordillera again appears 
to be more clearly represented. There is some evidence, 
therefore, of the existence of a very old land-mass not only on 
the eastern but also on the western side of the continent. And 
it seems as if .the Mesozoic rocks f orming a large part of the 
Andes had been deposited in a great trough along the eastern 
shores of this ancient land. When the Andes were subse¬ 
quently raised, the older western land presumably subsided, 
leaving only here and there along the coast some traces of its 
former existence. 
Let us now pursue this subject from a purely zoogeo- 
graphical point of view, and endeavour to utilise groups with 
whose distribution we are fairly well acquainted, in elucida¬ 
ting the more obscure points in the geological history of 
northern South America. Groups of animals of which we 
have reason to believe that they are very ancient, possibly 
of Mesozoic age, will be best for this purpose. Such a one for 
example is that of the Onychophora (Protracheata). It 
contains creatures caterpillar-like in appearance, with a beau¬ 
tifully soft skin and unjointed limbs. Internally they contain 
air-tubes so characteristic of insects; at the same time, their 
excretary organs resemble those of worms. These very pri¬ 
mitive features, taken together with a wide and most discon¬ 
tinuous distribution, have always caused these creatures to 
be looked upon as survivors or relicts of very remote geological 
ages. Formerly they were all classified under the genus 
Peripatus. In recent years many new forms have been dis¬ 
covered and subjected to careful study, with the result that 
Suess, E., “ Antlitz der Erde,” I., pp. 666—690. 
