SUMMIT PLAIN OF ROCKIES 
361 
into details it suffices to note that at the present time it coincides 
closely with the crest of the Rockies. Only the very highest peaks 
stand above it. Manifestly the position of the younger peneplains, 
if remnants could be retained to mark their levels, is far above the 
existing high points. 
In the attempt to refer the remnantal Summit Plain of the 
Rocky Mountains to any one of the four peneplains of the region 
about, or even to a hypothetical Fifth plain which might have 
once stood high above the adjoining Great Plains tract, the Raton 
peneplain and the Maya peneplain may be at once dismissed from 
serious consideration. Their elimination is due mainly to the fact 
that their normal positions are so far distant beyond the tops of the 
highest peaks. The hypothetical Fifth plain may also be passed 
over, since its calculated position is really that of the Maya pene¬ 
plain. The present Great Plains surface seems to be out of ques¬ 
tion for reason of the fact that it is represented not by a warped 
surface following closely the broader contours of the Rocky Moun¬ 
tain uplift but by the beds of the existing mountain streams with¬ 
in the elevated area. 
Alone there now remains for consideration the possibility of the 
Comanchan peneplain. As indicated by the attitude of the Da¬ 
kotan sandstone which rises so steeply out of the Great Plains on 
the flanks of the Rockies and by the position of the remnantal 
