The Tascotal Mesa quadrangle is in southeastern Presidio and southwestern Brewster counties, Trans Pecos Texas. Bandera Mesa and Tascotal Mesa are reached most easily from Marfa, 50 miles north, by the Marfa-Lajitas road which traverses the quadrangle from north to south. Green Valley in the northeastern part of the area is most easily reached from Marfa by the 02 Ranch road in Paradise Valley; an alternate route is from Alpine by the Terlingua highway and the 02 Ranch road.

New information concerning the ancestry of the later Tertiary horses, Calippus, Protohippus (in the original sense), Hipparion, Neohipparion, and Nannippus, has been obtained from a restudy of the various mammalian farmas of the Coastal Plain in Texas, based in the main on the extensive collections of the Bureau of Economic Geology, The University of Texas. The age, stratigraphic correlation, and composition of these faunas have been reevaluated, and the results provide new evidence that has important bearing on Miocene and Pliocene intercontinental correlations of mammalian faunas.

The Blacklands Experimental Watershed, a hydrologic research project of the Soil Conservation Service located about 15 miles southeast of Waco, Texas, is underlain by marls and chalks belonging to the Taylor group of the Gulf series of the Cretaceous system, which, in conformity with the general structure of the Gulf Coastal Plain, dip east-southeastward at an angle a little steeper than the general slope of the land surface.The lowest strata cropping out in the experimental watershed are part of the Wolfe City member of the Taylor marl and consist of about 110 feet of sandy marl containing