The Upper Cretaceous or Gulf series of Texas is separated from the Comanche series below, and from the Eocene series above, by pronounced unconformities. Unconformities within the series have not heretofore been generally recognized, although several of them have been indicated in previous publications. These stratigraphic breaks are recognized in part by physical features at the contacts, and in part by the absence of lithologic members and paleontologic zones which would be expected to be present in the sections had there been no emergence and erosion. The stratigraphic relations of the formations composing the series in central Texas are shown in a generalized chart. Descriptions and illustrations are given of an ideal typical Coastal Plain unconformity, and of several specific localities at which unconformities have been observed within the series. These unconformities, and numerous minor interruptions to sedimentation (diastems), record differential warping off the flanks of, and between, the Llano-Burnet and Ouachita uplifts, and resultant transgressions and regressions of the sea.