284 The American Geologist. November, 1905 
In no sense then can the extensive bolsons of New 
Mexico be grouped into a common class and referred to as 
remnants of the early Cretaceous peneplain preserved 
"merely by lack of erosion agencies." We must then take 
sharp issue with Dr. Keyes, when he says of the bolsons 
of New Mexico: "Bolson plains may be considered as sec- 
tions of an upraised peneplain surface in its earliest infancy, 
in the stage when they are as yet untouched by stream 
action." 
As a bolson plain is a constructional form and is not 
confined necessarily to any period of time it must be recog- 
nized that the bolson plain passes through a history of con- 
struction and destruction similar to that of any other con- 
structional topographic form, and the various stgaes of its 
formation and destruction should be carefully noted. After 
the formation of the bolson plain the region may become 
subjected to intense erosion, which would eventually leave 
but remnants of the old plain, while a neighboring plain not 
subjected to such treatment might persist or even continue 
to develop its characteristics as a distinct physiographic 
type. 
It seems to the writer that the bolson plain will find its 
proper place and recognition in the literature of topographic 
forms. 
