THE OZARKIAN AND ITS SIGNIFICANCE 527 
The Ozarkian has heretofore attracted little attention, because 
until very recently geological history was supposed to be 
recorded only in stratified rocks and their contained fossils; but 
this being a period of continental elevation and enlargement, it 
has left no strata exposed to view. Geological history was at 
that time recorded only by erosive work. So far as stratified 
rocks and fossils are concerned, this is a period of lost record— 
it is a lost interval. 
I said that the real importance and significance of this epoch 
is best seen on the western part of the continent. I must justify 
this assertion by a comparison of the phenomena in different 
parts of the continent. 
1. The eastern part—I\n the eastern part of the continent, the 
work of erosion of this time is seen in the so-called old river- 
beds deeply underlying the present beds and extending beyond 
their limits on each side, and especially continuing beyond the 
limits of the present continent, as submerged channels trenching 
the submerged continental shelf, notching deeply its margin and 
opening out into the abyssal waters of the true oceanic basin. 
It is shown also not only in the deep gorges of the Ozark region, 
not only in the deep and widespread erosion of the Lafayette 
gravels in the south, but also in the highly emphasized topog- 
raphy underlying the drift all over the glaciated region of the 
north. By means of the submerged channels the amount of ver- 
tical elevation of the eastern portion of the continent has been 
estimated as certainly not less than 3000-5000 feet and may 
have been much greater. Similar evidences of elevation are 
found on the Pacific coast and also on the coasts of Europe and 
of Africa. We have every reason to believe that it was a time 
of almost universal continental elevation and enlargement. 
Heretofore these old rivers of the east have been referred, 
like those of the west, to the Tertiary times and called Tertiary 
river-beds; although it is admitted that they were occupied and 
deepened by the ice of the Glacial times. The Tertiary erosion 
was supposed to have graded insensibly and continuously into 
that of the Glacial, but the greater part was attributed to the 
