1. Flaming Gorge Group; arenaceous shales or bad-land sandstones, purple and white at top and red below 1,200 feet. 2. Gray Cliff Group; massive cross-laminated sandstone, buff to red in color 500 feet. 3. Vermilion Cliff Group; massive cross-laminated sandstone, red, with a purple band at the top 500 feet. 4. Shin-ar´-ump Group; consisting of— _a._ Variegated clay shale; purple and white above and chocolate below, with silicified wood 300 feet. _b._ Gray conglomerate, with silicified wood; the “Shinarump Conglomerate” 30 feet. _c._ Chocolate-colored shale, in part sandy 400 feet. ————— Total Jura-Trias 2,930 feet. The rock of the Flaming Gorge Group is of a peculiar character. It is ordinarily so soft that in its manner of weathering it appears to be a shale. It is eroded so much more rapidly than the Henry’s Fork conglomerate above it, that the latter is undermined, and always appears in the topography as the cap of a cliff. Nevertheless, it is not strictly speaking a shale. The chief product of its weathering is sand, and wherever it can be examined in an unweathered condition it is found to be a fine-grained sandstone, massive and cross-laminated like those of the Gray and Vermilion Cliffs, but devoid of a firm cement. In a number of localities it has acquired, locally and accidentally, a cement, and it is there hardly distinguishable from the firmer sandstones which underlie it. In the immediate vicinity of the Henry Mountains it varies little except in color from summit to base, but in other localities not far distant it is interrupted near the base by thick beds of gypsum and gypsiferous clays, and by a sectile, fossiliferous limestone. The Gray Cliff and Vermilion Cliff sandstones are often difficult to distinguish, but the latter is usually the firmer, standing in bold relief in the topography, with level top, and at its edge a precipitous face. The former is apt to weather into a wilderness of dome-like pinnacles, so steepsided that they cannot often be scaled by the experienced mountaineer, and separated by narrow clefts which are equally impassable.