Paleontology and geology
During the Cambrian, Texas lay under a shallow sea. Sediments, mostly sands, were carried into this sea from land lying to the northwest of the state. Further out to sea, limestones and dolostones were being deposited. Although not visible on this map, these rocks can be found today in the Llano Uplift area of Texas. Within these deposits, we find fossils of trilobites, brachiopods, bivalves, sponges, gastropods, and bryozoans.