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For reasons which will appear later, I believe the Guadalupe mountains to be carboniferous in age contrary to the opinion of the Shumard Brothers, the only other geologists who have ever studied the mountains

The lower rocks are yellow, clayey sandstone, with beds of black limestone, in places almost a slate. The middle beds are thick bedded fossiliferous white magnesian limestone and the upper beds sandstone chiefly. These will be described in more detail later. No Permian beds appear between the Guadalupe mountains and the Pecos in the section studied, but wherever the Carboniferous is covered by later formations these deposits are either Quarternary or Cretaceous. In the mountains proper, the rocks are all Carboniferous, but on the northern end in New Mexico Cretaceous beds exist in the foot hills, and from this point a scarp of Cretaceous rocks covers the Carboniferous at a progressively increasing distance toward the southwest being, at the head of Delaware creek, about twenty miles from the base of the mountains. Quarternary conglomerate appears both on the Carboniferous and Cretaceous at places.

The chief part of the Guadalupe mountains lie in New Mexico, and this end was visited only in so far as was necessary for a correct understanding of certain general features.

The general form of the Guadalupe mountains is prow shaped. Commencing in New Mexico, at a moderately low elevation and more than twenty miles wide, they become progressively higher followed southward, at the same time becoming narrower until the point of the mountain is reached. This, the southern part, is just south of Guadalupe Peak the highest point, which is eight thousand feet above sea level. The point of the mountains is a precipice in the white magnesian limestone fully two thousand feet high which suddenly terminates the mountains. South of this the line of disturbance is continued in the form of foot hills with an abrupt face to the west.

On the northern end in New Mexico the mountains continue for many miles becoming progressively lower until they are really no more than foot hills. The dip of the strata in the mountains is very "

Mr. W. P. Jenney speaks of them as carboniferous, but without giving reasons. Mr. Jenney's report to the railway company has never been published, and merely a brief mention of the mountains appears in his paper Am. J. Sci., 1874, previously mentioned.