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which is called the Permian and the upper the Triassic. The former (which constitute an overwhelming proportion of the whole) is subdivided by Cummins into three divisions-Wichita, Clear Fork, and Double Mountain, in ascending series-while the few feet of strata of the alleged Triassic are called the Dockum formation.

.-This is described as being composed of sandstones, clays, and a peculiar conglomerate. There are no limestones in it from bottom to top. The sandstones are of various colors. The clays are red and bluish. Red clays or iron concretions exist in great abundance. The peculiar conglomerate is composed of clay or clay ironstone in a ferruginous matrix. The Wichita formation does not extend south of the Brazos, and its thickness is placed at 2,000 feet.

.-This is the name given to the middle division of the Permian strata. It is composed of limestones, clays, shale beds, and sandstones. The limestones are mostly magnesian and carbonaceous. The sandstones are not so abundant as in the Wichita beds and are not so massive, but are generally thin bedded. The clays are blue or red, the red occurring in thick, heavy beds. The conglomerate is similar to that found in the Wichita, formation, but not so abundant. Toward the top the sandstones become more shaly and the clays more sandy. There are also some beds of gypsum, but not in so great abundance as found in the Double Mountain formation. The formation occurs immediately west of the Wichita formation as far south as the Brazos, and is then found resting upon the Coleman or Permo-Carboniferous throughout its continuation to the south of the latter stream.

.-The Double Mountain formation is composed of sandstones, limestones' sandy shales, red and bluish clays, and thick beds of gypsum. The limestones are generally of an earthy variety, containing casts of fossils. The gypsum beds are numerous, and many of them are very thick. All the clays and shales are impregnated with gypsum, and many of them carry a large percentage of the sandstones, and are generally very friable and of various colors-red, white, and spotted. These beds have a thickness of about 1,900 feet.

These divisions do not appear to be clearly marked stratigraphically, and probably represent continuous sedimentation. The Double Mountain beds are preeminently the great gypsum formation, although this mineral appears in the underlying divisions.

These beds cross Red River into southern Indian Territory, where they surround the Wichita Range. In this vicinity they are composed of the débris of the rocks of the Wichita Mountains, as shown by Mr. Vaughan. They pass north around the western and eastern termini