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extension are no doubt fully developed coastward beneath the Grand Prairie.

No outcrop of the Glen Rose beds is known in Indian Territory, where the entire Trinity division, so far as known, is made up of sand.

The greatest thickness of the Glen Rose beds exposed in the Colorado section is about 435 feet, of which probably 100 feet at the top may be considered the equivalent of the Paluxy sands. The rocks are exposed in many sections from the Colorado northward about 130 miles to Glen Rose. Near the latter place, as shown in the Comanche Peak section, the Glen Rose beds have an exposure of 236 feet, which, together with the overlying Paluxy sands, show a thickness about equivalent to that of the Round Mountain section of the Colorado Valley.

The Glen Rose formation decreases in thickness from east to west, and passes from limestones into clays and sands toward the western border region, as is shown by various general and local sections and described in detail later under the head of Structure. (See figs. 8, 41, and 44.), Obversely stated, in going south-southeast, perpendicular to the strike, from any point on the western border of the Grand Prairie, the rocks of the Glen Rose rapidly increase in thickness along the line of dip and change from sands into clays and limestones, thus thickening coastward from the interior border region at a varying rate, to be explained later, but averaging 8 feet to the mile.

In the sections of the western border the Basement sands pass upward into reddish clays, sandy clays, and impure limestones; proceeding coastward, the limestones become more frequent and abundant and the sands and clays less important.

As shown in the discussion of the transgression of the beds of the Trinity division upon the Paleozoic rocks of the old Cretaceous shore line, the Glen Rose beds are largely represented along the western border by pack sands which herein have been included under the general name of the Basement or Trinity sands. There is little doubt that a large part of the Basement sands of the western border from Burnet to north of Nix, Lampasas County, as well as of the Antlers sands of the northwestern and northern border regions is synchronous with the lower portion of the Glen Rose formation. It is also certain that the uppermost calcareous Glen Rose beds of the southern sections represent the southern equivalent of the Paluxy sands of the northwest, as will be more fully set forth under the head of Paluxy sands.

There are but few places within the area of the Grand Prairie proper where the entire thickness of the Glen Rose beds is exposed, notably between the village of Paluxy, Erath County, and the higher slopes of Comanche Peak in Hood County, around Lampasas and in the Colorado