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paper as t². These sands are easily recognizable in the drill sections, at least, in the samples from the San Marcos well, showing the typical red color of the clays that they exhibit at their outcrop at Travis Peak post-office. Westward the Hensell sands lose their identity by merging into the general Basement sands of the western border.

The Travis Peak formation as a whole records a subsidence of the land during its deposition. As the waters deepened the deposits changed from coarser to finer material, becoming more comminuted and calcareous at the top of the beds, until the sand grains are so fine as to be almost imperceptible to the eye, the whole mass becoming chalky and "magnesian" in appearance.

At the top of the sandy beds (No. 1 of the Glen Rose section, Nos. 12 and 13 in the Colorado section) a yellow, arenaceous, fossiliferous limestone appears. This marks the first or lowest appearance of the peculiar fossils Monopleura and Requienia (Caprotina), and indicates the beginning of the Glen Rose formation.

The typical Glen Rose formation consists largely of even-bedded strata of argillaceous, arenaceous, chalky limestones, alternating with thin strata of marly, arenaceous clay. The beds are of different thicknesses. The thickness of each individual bed is remarkably uniform throughout its extent when traced along the outcrop. From the alternation of limestone and clay the beds were provisionally called the "Alternating beds" when first differentiated by the writer, and were included in the Fredericksburg division.

The Basement beds of the Comanche series have been described as arenaceous in character. The Glen Rose formation, on the other hand, is calcareous, with clays and sand as accessory material. Each of these formations is accompanied by the material of the other as a minor accessory. Thus the calcareous rocks of the Glen Rose formation are partially arenaceous, especially at their base, the siliceous grains being so finely triturated that they are an almost impalpable powder. This siliceous material gradually diminishes upward in the reds, and the lime increases proportionately in both the indurated beds and the marls. Toward the top of the Glen Rose the limestones are again slightly arenaceous.

The indurated beds consist of strata of brecciated crystalline, arenaceous, magnesian, or chalky texture. They are white, yellow, and "

It is important to note that the Sycamore and Hensell sand beds are strikingly analogous to the water-bearing beds denominated t¹ and t² on the deep-well descriptions, and that the Cow Creek bed corresponds in position to great thicknesses of limestone between the sands in the Austin, Belton, and waco wells.

See Bull. No. 1, Geol. Survey of Texas, Austin, 1889, p. xiv.