02 2 t'. SKOTTSBERG 



growing accumulation of evidence that the Pacific basin shows unique features which 

 are not duplicated in any other oceanic or continental area of the earth. 'J'here is no 

 feature on the surface of the earth which compares in dimensions and importance with 

 the Marshall line, within which the younger eruptive rocks are basaltic rather than 

 andesistic. This discontinuity in the material of the crustal layers is called here the 

 boundarv of the Pacitic l>asin. 



This is in conforniit}- with what I have quoted above from other sources. 

 However, 



certain areas of the I'acific Ocean (near its borders, for example), at least part of the 

 region between South America and the Easter Island rise, or between the Marianas 

 and the Asiatic continent, show indications of continental layers. For the latter, petro- 

 graphical and geophysical evidence agree. 



As seen on the niaj), (il TKXHKRC] goes a good way beyond the Juan Fer- 

 nandez-San Anibrosio rise, but the blaster Island shield which, excepting the vi- 

 cinity of this island, is covered by very deep water, belongs to the wide basaltic 

 centre, where continental layers are lacking — in contrast to the Atlantic where 

 "granitic la\-ers of the continents continue far out under the bottom . . . probably 

 at least some continental rocks underlie its bottom throughout its area". 



Turning to tiie speculations of biologists I shall quote some representatives 

 from the two op|)osite camps. Arldt [6') did not draw his conclusions merely 

 from facts of distribution but compiled a wealth of geological, palaeontological, 

 bathymetrical dates and so on, and constructeci a series of maps illustrating the 

 distribution of land and sea through earth's history. A Cretaceous Oceania united 

 South America with Australia + New Zealand, it disappeared during F^ogene and 

 left the west coast of South America in the same position as to-day. F>om what 

 he sa)-s about Juan Fernandez it appears that he regarded these islands as con- 

 tinental 'see below p. 376), while still admitting the possibility of oversea migra- 

 tion from the coast. Camphkll was for a long time a supporter of the land-bridge 

 theorv. He regarded the Hawaiian Islands as formerly much larger and more closely 

 connected with land masses to the southwest, having become isolated during 

 early Tertiary time coincident with the ui)lift of the great Cordilleras (</./). Later, 

 when discussing the Australasian element in the Hawaiian flora he expresses him- 

 selt very positively: "We are justified in assuming the former existence of land- 

 masses of consideral)le size, connecting more or less directly both Australia and 

 New Zealand with Hawaii' (./-r. 22i); and when, for the third time, he took up 

 the history of the Hawaiian flora, he expressed himself as follows (46. l8l): 



We may assume that the Hawaiian Arc hij)elag(), as it now exists, is but a remnant of 

 a much larger landmass which has been in subsidence for a long period, and that extensive 

 subsidence has also o( ( urrcd throughout Polynesia, and to a lesser degree in Australasia. 

 One argument tor this assumjition is the great development of coral reefs in the Pacific, 

 espec iaily in Polvuesia and northeastern Australia. The existence of active coral reefs 

 involves continuous subsidcMKc and the absence of large land-masses in mid-Pacific, with 

 the innumerable small coral islands and reefs, can be explained most satisfactorily on the 

 theory that the latter are remnant of sul)mergcd land-masses of large size — possible even 

 of continental dimensions. 



