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hills are made has not been definitely determined, nor just why they have arranged themselves in a belt extending from north to south at this particular locality.

GEOLOGY OF THE STAKED PLAINS.

Heretofore very little has been known of the geological formation of the Staked Plains. It has been generally supposed to be Cretaceous. The observations of this year disclose the fact that the Cretaceous does not appear as the upper strata of the Staked Plains anywhere north of the line of the Texas and Pacific Railroad, except it be a very narrow strip along the eastern edge where the overlying strata has been eroded.

The strata forming the upper part of the Staked Plains belong to the later Tertiary, and were described by this writer under the name of " Blanco canyon beds " in the First Annual Report of the State Survey, 1889.

This formation thickens towards the northwest. At Big Springs the formation is less than twenty feet thick, while at Amarillo it is three hundred feet thick, and at the extreme northwestern extension of the Plains it has attained a thickness of over four hundred feet. It is the lower portion of the beds that thin out towards the southeast; the upper beds of white, chalky, indurated limestone is continuous, and found at the top everywhere over the entire area, except in such places as are covered by soil. The beds vary somewhat in composition at different localities, but everywhere they have the same general characteristics, and are easily identified.

The Tertiary of the Staked Plains is underlain partly by the Cretaceous and partly by the Triassic.

All that part of the country situated southeastward from a line beginning at a point on the Double Mountain Fork of the Brazos river, about where the eastern line of Garza county crosses the river, and running thence southeast to the Pecos river, is underlain by the Cretaceous, and all that part of the Plains situated northwestward from that line, except a very small area at the head of Fossil creek in New Mexico, southeastward from Tucumcari Mountain, is underlain by the Triassic. At that place mentioned, the Tucumcari beds, which are Cretaceous, extend under the Tertiary and over the Triassic.

The Tucumcari beds are Cretaceous, but belong to a different horizon in the Cretaceous series from that at Big Springs and elsewhere along the eastern escarpment of the Staked Plains.

The reason for believing these beds Cretaceous will be more fully set out in the Annual Report, when I shall have had time to study more closely the collections made at that locality. It is enough to say now that my conclusions are based upon the character of invertebrate fosssils