450 Evolution and Distribution of Fishes 



Mexico to Cape Horn. For the flora and fauna of each 

 Island group indicate direct derivation from the nearest 

 continental land, as well as a derivation of that flora and 

 fauna from a Central or even North American source. 



It seems highly probable therefore that before elevation 

 of the Andes, and during later Cretaceous time, a wide and 

 easy pathway existed for passage of northern seed-plants, 

 of the later reptiles, and of primitive mammals of early 

 polyprotodont type, down into western S. America. In 

 this latter region the San Martin and Lower Lignite beds, 

 at least in the southern part of the continent, indicate great 

 freshwater deposits that may be 5000 to 6000 feet thick. 

 The pathway probably continued throughout Eocene and 

 Oligocene times, in more or less changing state, as progres- 

 sive elevation of the Andes proceeded. During this time 

 also migration from South America across the Southern or 

 Antarctic continent proceeded most actively, so that even 

 freshwater fishes of northern ancestry not only reached 

 Magellan; they were carried eastward with plants and 

 with many land or freshwater animals, to New Zealand, 

 Tasmania, and Australia. 



Possibly during Miocene time the climax of Andean 

 mountain building was reached, and coeval with this or later, 

 extensive faults and downthrows of wide areas took place, 

 so as to submerge a large part of the former land-bridge. 

 For the long "deep" or "trench" that runs parallel to the 

 Chilean-Peruvian coasts as "the Atacama trench," is from 

 12,000 to fully 20,000 feet deep, and has been v.Iewed by 

 some geologists as a gigantic fault that depressed the land 

 almost as greatly, as were the Cretaceous and other strata 

 folded and uplifted to constitute the Andean ranges. 



Taking all of the above facts into account, the writer 

 would put forth what may to many seem an unlikely and 

 far-fetched suggestion, but which undoubtedly has many 

 distributional facts in Its favor, and which Is Illustrated in 

 Figure 35, p. 240. It is that a wide western area of land 

 extended during Cretaceous times from Southern Mexico 

 southward by, as well as Including the Galapagos and Juan 

 Fernandez Islands to Magellan, that then was of wider 

 westward expanse than now. This region constituted the 



