The stratigraphic relations of the formations of the Gulf series (Upper Cretaceous) in Texas and Arkansas are briefly described in the text and are graphically represented in a correlation chart. Two new units, the Tokio and Ozan formations, are recognized (in collaboration with C. H. Dane) in the Arkansas section. A new name, Gober, is proposed for a tongue of the Austin chalk, which was previously incorrectly correlated with the Annona chalk. A new formation name, Olmos, is given to the "coal series," in the Rio Grande section in Maverick County, Texas. Several important unconformities are recognized in the Gulf series. The Gulf series is shown to be separated from the Comanche series below, and from the Midway (Eocene) above, by important unconformities.

An attempt is made to show the age relations of the formations by means of heavy numbered lines. The divergence of these lines shows the thickening, and their convergence the thinning, of the series. The thinning of the series is attributed in part to actual thinning of the deposits and in part to the presence of unconformities.