DEVELOPMENT OF SOUTH AMERICA 345 



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 forming 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," L, pp. 666690. 



