408 
PACIFIC EXPLORATION: C. SCHUCHERT 
possession of by the oceans, a history which none exhibits better than 
the Australia-New Zealand region. 
We have learned from the several deep-sea expeditions something of 
the rare and strange Hfe of the oceanic abysses. An analysis of these 
organisms shows that no Paleozoic forms occur among them, and very 
little of the Hfe indeed is ancestrally traceable even to the stocks of 
Triassic times. It is with the Jurassic and later life that the organisms 
of the abysses have their affinities. This seems to indicate that the 
oceans have been progressively deepened only since the Triassic. As 
one of the most marked crustal deformations, however, began in the 
Coal Measures of the Paleozoic and continued, though with pauses, 
well into the Triassic, it therefore appears that the oceans have been 
progressively enlarged and deepened ever since Permian time. This is 
in keeping with the theory that the earth's radius has been gradually 
diminishing and that the compensation therefor has been greatest in 
the oceanic basins, the areas of greatest rock densities. 
It is now more than fifty years since James D. Dana began to teach 
that the rising continents and the sinking oceanic basins have been, in 
the main, permanent features of the earth's surface. He did not mean, 
however, that the continents have always had essentially the same shape, 
elevation, and areal extent that they have today. Still, Dana did not 
fully appreciate the amount of continental fragmenting that has taken 
place in the course of geologic time, though he clearly pointed out the 
foundering of Australasia, speaking of it in his famous Manual of Geology 
(p. 797) as "a fragment of the Triassic world. " The teachings of Dana 
as to the permanency of continents and oceanic basins have been accepted 
in some form by all geologists, and lie at the basis of all zoogeogra.phy and 
evolution as well. Geologists are holding more and more to the hypoth- 
esis that the earth periodically shrinks, and each time it does so some 
parts or all of the continents may rise, but that in the main there is 
subsidence of the ocean bottoms, that the water of the hydrosphere is 
constantly increasing in amount, and that even though the continents 
are in the main permanent, yet they are partially breaking down into the 
oceanic basins. 
From this we conclude that the enlarging oceanic basins are the most 
permanent features of the earth's surface. On the other hand, along 
with the progressive subsidence, the bottom of the Pacific is also built 
up into many local volcanic cones by outpourings of lava, and, further, 
it rises into more or less long mountain ridges. Some of these elevations 
of the bottom appear at the surface of the ocean as groups or lines of 
dead or active volcanoes. Another general conclusion is that most of 
