328 OKIGIN OP LIFE IN AMEEICA 



to. If a Pacific continent existed, and I quite concur with 

 those who are of that opinion, it must have largely subsided 

 before the Tertiary Era. It seems to me as if the central 

 ^ part of it had broken down gradually, the margins slowly 

 following suit, both on the eastern and western Pacific, only 

 leaving here and there a few remnants which either remain 

 as isolated pillars far out in the ocean or have become joined 

 to more recent land-masses. I imagine that the latest pre- 

 Pliocene land Connection between North America and Asia was 

 not the Pacific Continent, but merely its margin, which per- 

 sisted probably until Oligocene or Miocene times. In a geo- 

 logical sense, remarks Dr. von Drasche,* it is more correct 

 to draw the western boundary of the Pacific Ocean through 

 Kamchatka, Japan, the Philippines, New Guinea and New 

 Caledonia, because they all possess old crystalline or ancient 

 sedimentary rocks. But the oceans, as Professor Walther f 

 has pointed out, are areas of depression surrounded by folds or 

 flexures which give rise to extravasation of eruptive material. 

 The chain of the volcanic Aleutian islands lie in. such a fold. 

 Near the east coast of Japan the depth greatly increases. On 

 the eastern side of the Pacific, in western North America, 

 the igneous rocks skirt the coast for some distance, whereas 

 in the south-west the volcanic centres lay far inland, justi- 

 fying the assumption that the Tertiary coast-line extended 

 some distance inland, which is fully established by geological 

 observation. Although the Pacific is known to have invaded 

 Californian territory, there is no evidence that the coast hills 

 and outlying islands were covered by the sea ; and these pro- 

 bably remained as part of the marginal land which skirted the 

 west coast of North America. It is from this old land, I think, 

 which contained Asiatic immigrants, that North America 

 received its ancient Tertiary fauna from Asia. I suggest, 

 therefore, that in early Tertiary times a belt of land, possibly 

 representing the margin of the more ancient Pacific Continent, 

 extended from the south-west coast of North America in a 

 great curve to Japan and further south (see Pig. 14). The 

 extraordinary similarity of the east Asiatic, Mesozoio and 



* Drasche, E. von, " Palaeozoische SoMchten auf Eamtschatka," p. 268. 

 t Walther, J., " tjber den Ban der Flexuren, &c." 



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