334 OKIGIN OF LIFE IN AMERICA 



but the two have many forms of mollusks in common, and 

 should be regarded perhaps as sub-divisions of one faunistic 

 marine area. According to Dr. von Ihering,* Chile received, 

 in early Tertiary times, certain tropical genera of mollusks 

 which never succeeded in attaining the North American 

 coasts, yet are represented also in Patagonia, while others, 

 such as Conus, Purpura, Oliva, Concholepas, Cassis, Cypraea 

 and Bissoa are absent from the latter country. They are 

 supposed to have travelled along the north coast of South 

 America to Ecuador, Peru and Chile by means of a Central 

 American marine channel. Certain species even of that an- 

 cient marine migration have persisted to the present day, 

 not only on the coast of Chile, but on the west coast of Africa 

 and in the Mediterranean. Even in Miocene times the in- 

 fluence of the Caribbean and European marine faunas was 

 felt on the coa-st of Peru, according to Dr. Ortmaam.f 

 Certain northern species of the genera Saxidomus and 

 Chlorostoma, says Dr. von Ihering (p. 524) did not reach the 

 coast of Chile until the Pleistocene Period. Thus it seems 

 manifest that during practically the whole of the Tertiary 

 Era there was no Humboldt current sweeping northward 

 along the west coast of South America, as it does at present. 

 On the contrary, there is sufficient evidence to show that 

 whatever current there existed flowed in the opposite 

 direction. 



This investigation has resulted in two very important 

 results, viz., firstly, the demonstration that the Humboldt 

 current formerly did not exist, and secondly, that its absence 

 must have been caused by profound differences in the condi- 

 tions of land and water from those now prevailing. Of the 

 nature of these changes I have foreshadowed already enough 

 to enable anyone to reconstruct them. When the currents 

 issued from the Caribbean Sea into what is now the Pacific, 

 they must have been faced by land westward and northward. 

 They could only have flowed southward. But the land which 

 lay south-westward between Central America and the Gala- 

 pagos islands extended probably far southward, parallel to 



* Ihering, H. von, " Mollusques fossiles de 1' Argentine," pp. 514516. 

 t Ortmann, A. E., " Tertiary Invertebrates of Sta. Cruz," p. 320. 



