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ANNALS NEW YORK ACADEMY OF SCIENCES 
should be interpreted in that way with faunas so much nearer geographically. 
I myself was expecting an east-west fault which would put the northern area 
out of relationship with the southern, or a southward dip which would bring 
only the lower beds to view in the noijth. 
This summer, however, while I was detained in Idaho, Mr. Richardson 
was able to make a hurried trip into what we had considered the critical area 
and with results important in their bearing on the problems in question. 
His facts will perhaps make it necessary to dismiss the hypothesis from 
which the relations of the Guadalupian to the Kansas section were tenta¬ 
tively considered and to conclude that the remarkable facies of the Guada¬ 
lupian fauna is to a large extent, if not wholly, the result of environmental 
causes. 
The chief facts of immediate importance, which Mr. Richardson has 
kindly permitted me to summarize on this occasion, but which he will present 
in full in another place, are these: The Guadalupian formations in passing 
northward from Guadalupe Point are not interrupted by east-west faults 
and the prevailing dip is eastward. In its northward extension the massive 
Capitan limestone merges along the strike into thin-bedded limestone and 
sandstone, the limestone element finally disappearing altogether or being 
represented only by thin local beds. Still farther to the north, the strata 
take on a red color and become part of the “Red Beds” series. Northward 
from Guadalupe Point fossiliferous horizons become rare in the Capitan 
and the collections which Mr. Richardson brought in tend to show that with 
the change in lithology the fauna also changes character, so that practically 
nothing of the typical Guadalupian facies is left. This feature I shall refer 
to more in detail below. 
The fossiliferous limestone capping the Sacramento Mountains on their 
western rim and exposed at Cloudcroft northeast of Alamogordo, New 
Mexico, has been known to me for a good many years. The first collections 
were made by Mr. R. T. Hill in 1900. I visited the locality two years 
afterward and collections have been brought in subsequently by other 
members of the Survey. The presence of faulting renders it difficult to 
measure the section from Cloudcroft to the valley below, but the limestone 
at Cloudcroft is underlain by perhaps 3,000 feet of “Red Beds” and 1,500 
feet of shales, sandstones and limestones, all of upper Carboniferous age. 
The limestone at Cloudcroft I have been tentatively correlating with the 
upper part of the Hueco limestone of western Texas because of certain 
faunal resemblances with a collection made at the Corundas Mountains, 
the horizon of which is in the upper part of the Hueco. The Hueco in the 
typical area consists of limestone throughout, even shale beds being usually 
wanting, and the approximate thickness is 5,000 feet. Inferentially, there- 
