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• Marbled magnesic limestone, unfossiliferous.
• Gryphaea Pitcheri (?) beds.
• Unfossiliferous limestone much discolored by iron.
• Very fosiliferous limestone, rusty.
• Sandy limestone.
• Sand, yellow and red in places.

The total thickness from one to five inclusive, is about 150 feet, but the thickness of the sand was undetermined. The fossiliferous limestone beds, except the gryphaea beds were not detected farther east, but this is not strange since the greater part of the country is covered with a deep residual soil.

From the base of the mesa bluff just east of Metz to beyond Monahan, a distance of nearly twenty miles, the Trinity sands cover the surface in the form of sand dunes. This strip of sand extends many miles north and south averaging in width from twelve to fifteen miles. It is a striking development of blown sand and with every breeze the sand is shifting position. The conical hills, and crater like pits so typical of similar aeolian deposits, are strongly developed here where they are rendered possible by the aridity of the climate and the presence of an abundant supply of sand furnished by the Trinity beds, as the bluff recedes and partly protected from removal to the eastward by this high bluff. The sand is chiefly white, having been bleached during its long exposure to sun and wind and is scantily clothed in places by such native plants as greasewood, sagebrush, mesquite, cactus, soapplant and sandgrass. These in part hold the sand in place, but only partially so, since in this region every moderate breeze carries along clouds of sand before it.

Carboniferous.

COLEMAN BEDS.—Where the Trinity beds disappear, northwest of Coleman, the Coleman beds of the Carboniferous are found beneath them. At this point there is a blue, very much rusted, clayey limestone containing many specimens of a large Pinna, Myalina, Bellerophon and Bryozoa. One Pinna on a slab near the road had a length of 23 inches, with a greatest width of 3 inches. A portion of the small end was gone.

The region hereabout is but recently uncovered by the erosion of Jim Ned creek. In the valleys the Carboniferous rocks are exposed, but to the north and west, as well as south, hills and buttes are found. Some of the hills from which most of the Cretaceous has been removed are still partly covered by small patches of Trinity Sand.

The character of the Carboniferous rocks is identical with that described in the report on the Carboniferous under the head of the Coleman beds. There seems to be very little clay, but its apparent absence may be due to the talus covering formed by the down dropping of the limestone on the hill sides. This feature is quite typical of the