220 Tht American Geologist. October, 1894 
Spread of lowland conditions. 
Since baseleveling by meteoric agencies does not necessarily 
bring about the drowning out of lowland species by the en- 
croachment of the sea, those forms which originally possessed 
the coastal belt will find a wider field opened to them by the 
degradation of the interior. If they migrate into this wid- 
ening field, they may be brought into contention with those 
forms which have followed the surface downward. Other 
things being equal, the endemic lowland forms will have an 
advantage over those organisms which are living under the 
trial of altered environment with the added stress of a con- 
test against hitherto unmet species. The new conditions 
comprising wider range will affect the lowland fauna and 
flora : it seems as if these forms should dominate over the less 
favored species forced down from the fading uplands. 
'Tin peneplain mi open, field for land life. 
We have here to note perhaps the most important respect 
in which the new view of the origin of the ancient plains of 
denudation differs from the hypothesis of marine erosion. So 
long as it was held that plains of denudation and the great 
unconformities in the geological section were formed alto- 
gether or essentially by the action of the surf-mill advancing 
over their surface, animals and plants inhabiting the land 
must have undergone extermination or have sought refuge on 
islands, on the remaining territory, or have migrated to some 
land before unoccupied by them. Such even are the effects 
of bare submergence without actual baseleveling, stated by 
De La Beche* as early as 1837. By submergence, he says. 
''the area of dry land would be much diminished ami the same 
amount of animals could not find room in it; there would be 
a considerable collision of species against species The 
weaker would give way. and thus some species might be ex- 
terminated so far as the islands were concerned." 
Where the process of planing off the lands was complete in 
the old view all land life must have been extinguished. The 
new view leaves the land open as a theater for land life: and 
the slow, gradual change in environment brought about by 
erosion is much more nearly in accord with the rate of alter- 
*Researches in Theoretical Geology, New York. 1837, \>. 2\7. 
