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They are of a fine consistency, unconsolidated, and apparently unlaminated until exposed to weathering, when their laminated character is developed.

They are light blue before atmospheric exposure, but rapidly change into a dull yellow, owing to the oxidation of the contained pyrites of iron. Their chief accessory constituent is lime in a chalky condition, and they are more calcareous at their base than at the top. Near the top of these and other ex- posures there is to be seen a rapid transition into the black calcareous clay soil, characteristic of chalk and chalky clays, whenever their excess of lime comes in contact with vegetation.

The details of these clays have not been yet ascertained, and from the nature of the problem it is not evident that they can be discovered speedily, but the following facts are apparent:

• (1) That they are more calcareous and fossiliferous at their base, where they probably gradate into the Austin chalk.
• (2) That their middle portion is apparently void of well preserved fossils, yet impressions are abundant in places.
• (3) Toward the top, as seen one mile north of Webberville, ten miles east of Austin, they become slightly arenaceous and concretionary and very fossiliferous, indicating a gradation into the Glauconitic division.

The fauna of these concretionary clays at Webberville, Corsicana, and elsewhere begins to partake of the character of that of the Glauconitic division, and yields an abundance of species.

The Webberville beds are practically the uppermost exposure of the Upper series along the Colorado section, for they are overlaid at that point by the Lignitic or Basal division of the Eocene Tertiary. In East Texas, where the rivers have cut through these overlying Tertiary beds, and in Southwest Arkansas, which is but the northeastern termination of the Texas section, the Glauconitic or Arenaceous division is highly developed. This division is the upward continuation of the Ponderosa marls, its chief lithologic difference being that the clays gradate into sands and glauconite as we ascend, and there are conspicuous changes in the fossils, which become more plentiful, and the species assume a sub-littoral aspect, partaking of the same faunal characteristics that distinguish the Cretaceous of the New Jersey and Alabama regions. This division as it occurs in Southwest Arkansas has been minutely described in my Arkansas report, but its whole detail remains to be developed in Texas, its occurrence having only been affirmed in one or two places without specific detailed study .

The Upper Cretaceous series, including all the Cretaceous strata in Arkansas "

See Am. Journal Science and Arts, December, 1889.