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represented in the Brazos or Parker County section by the basal sands near Lambert and the Hiner and Bluffdale sands, which occupy analogous positions below the Glen Rose formation.

The Glen Rose beds in their broadest development, as shown in the bluffs of Colorado, Paluxy, and Lampasas rivers, are limestone beds with alternations of yellow and white marls and sandy marls. The beds are of various thickness, and sometimes make steep bluff formations. The Glen Rose beds are best exposed in the valley sections of the Lampasas Cut Plain between the Brazos and the Colorado. They do not outcrop north of Trinity River.

The Paluxy sands in their greatest development are thick beds of "pack sand." They are found in greatest extent between the thirty-first and thirty-third parallels, dying out in the southern counties of the Grand Prairie or changing in lithologic character to yellowish limestones and marls, there included in the Glen Rose beds.

In the Paluxy section the Paluxy sands and Glen Rose beds are well exposed in juxtaposition, but the equivalents of the Travis Peak beds are only partially if at all shown, being largely concealed by embedment. The details of these various beds will be brought out in the local descriptions of the sections. Explanation of certain conditions of the Trinity division as a whole is necessary to a clear understanding of the details of their occurrence, stratigraphic variation, and relations.

Whether along the western outcrop or where penetrated 2,000 feet or more beneath the surface the Basement beds of the Lower Cretaceous system adjacent to the underlying Paleozoic floor everywhere. consist of friable conglomerate and sand sparsely accompanied by reddish and pale-green clays; these sands are next to and above the. rocks of the Paleozoic floor upon which the Cretaceous rocks were deposited, and between the latter and overlying calcareous deposits.

These sands are more or less fine grained, very friable, and so slightly compact that they are readily cut with pick and spade; hence they are generally known throughout the region as "pack sands." They are accompanied in places, usually at their base, by fine pebble conglomerate, locally varying according to the material of the adjacent preexisting rocks. Thin beds and laminae of red and blue clay occur in the sands, and often the residual surface has a reddish color.

These Basement sands are undoubtedly of, shallow-water or near-shore origin and represent the ancient marginal deposits of the sea as it encroached upon the land. Everywhere next to the Paleozoic floor