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.

The fossils described in this paper substantiate the Permian age of the Rustler formation. The Rustler fauna is largely molluscan and has a Whitehorse aspect.

Rocks of Cretaceous age crop out along the western margins of the deeper playa basins and along the southern and southeastern margins of the Llano Estacado.

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 collectio

The Squaw Creek quadrangle is partly within the Llano region and partly within the Edwards Plateau province.

The Hazel mine is one of the oldest mines in Texas and has been the largest copper-producing property in the State.