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Some of the creeks and rivers that have their source w; thin the main Cretaceous area near the eastern boundary of the Trinity have cut down into the sand by their rapid erosion, yet they are not able to maintain their position, because of the steep dips of the rock, which carry them down to the stream beds again. By this process of erosion ribbons of the Basement sands are exposed in the deeper stream valleys in the western portion of the Lampasas Cut Plain. Such is the case in the region of Paluxy, Bosque, and Lampasas rivers and other small streams.

In some cases these streams have cut across the Trinity-Glen Rose border, stolen finally the drainage of other creeks, and still hold their sources in the Trinity sands. The valley of the Paluxy in Erath, Hood, and Somervell counties presents an excellent illustration of an