The Barrilla Mountains, in the northeastern part of the Davis Mountains of Trans-Pecos Texas, are composed of Tertiary volcanic materials. Five tuffs and five lava flows, 1500 feet thick occurring throughout the mountains, persist in thickness and lithologic characteristics.

Steeply dipping shales and interbedded sandstones presumably of the Ouachita facies have been discovered along the Colorado River in Burnet and Travis counties, Texas. Previously the Ouachita facies was known in Texas only from bore-hole samples.

The occurrence of sulphur in the vicinity of Rustler Springs in northeastern Culberson County, Texas, has been known since 1854 when, according to Phillips (1902, pp. 13, 71), the mineral was recognized by William P. Blake, a geologist attached to a U.S.