mainly crossbedded white to pale red sandstone with thin beds of cherty limestone. Forms needles, arches and other erosional features. Thickening southwestward is the White Rim Sandstone Member of white crossbedded sandstone. 800-1,000 Cutler Creek, Colo. White Rim Sandstone Member White Rim, Wayne Co., Utah Organ Rock Tongue Organ Rock, Utah Cedar Mesa Sandstone Member Cedar Mesa, S. E. Utah Rico Formation Buff, red, and purple arkosic sandstone and conglomerate containing several thin beds of marine fossiliferous limestone. Forms moderately steep slopes. 250-585 Rico, Colo. 300 Pennsylvanian Hermosa Formation Hermosa Creek, Animas River Valley, Colo. Unnamed upper member Blue, greenish, and gray fossiliferous limestone interbedded with white, gray, and greenish sandstone and gray to green shale. Lower part known only from deep wells. Forms steep canyon walls. 900-1,800 Paradox Member Salt, gypsum, and anhydrite with interbedded black and brown shale; some limestone. ? Paradox Valley, Colo. Last but far from least among the factors responsible for the grandeur of the canyon country is the desert climate, which allows us to see virtually every foot of the vividly colored naked rocks and has made possible the creation and preservation of such a wide variety of fantastic sculptures. A wetter climate would have produced a far different and smoother landscape in which most of the rocks and land forms would have been hidden by vegetation. In the canyon lands the vegetation is mainly on the high mesas and on the narrow flood plains bordering the rivers, but scanty vegetation does grow on the gentle slopes or flats. The desert climate has combined with the nearly flat lying layers of sediments of different character, hardness, and thickness to produce steep slopes having many cliffs and ledges and generally sharp to angular edges rather than the subdued rounded forms of more humid regions. This has led geologists to refer to such terrain as having “layer-cake geology,” and this is brought out by the profile in the rock column (fig. 9), by the cross section (fig. 10), by figure 15, and by many of the other photographs. But the baker of this cake was rather careless—not only do the layers range widely in thickness and character, but some are wedge shaped, thick on one side of the cake but thin or absent on the other. Then too, when he ran out of icing in the midst of a layer, he was apt to finish with a different kind or color, for no inspector was on the job to insure orderly construction.