I am grateful to several colleagues and friends for the loan of photographs, for geologic help and data, and for reviewing this report. I am also deeply grateful to my wife, Ruth, for accompanying me on all the fieldwork and for her help and encouragement. Selected References Abbey, Edward, 1971, Desert solitaire, a season in the wilderness: New York, Ballantine Books, 303 p. Baker, A. A., 1933, Geology and oil possibilities of the Moab district, Grand and San Juan Counties, Utah: U.S. Geol. Survey Bull. 841, 95 p. Baker, Pearl, 1971, The Wild Bunch at Robbers Roost: New York, Aberlard-Schuman, 224 p. Beckwith, Frank, 1934, A group of petroglyphs near Moab, Utah: Santa Fe, N. Mex., El Palacio, v. 36, p. 177-178. Breed, Jack, 1947, Utah’s arches of stone: Natl. Geog. Mag., p. 173-192, August. Case, J. E., and Joesting, H. R., 1972, Regional geophysical investigations in the central Colorado Plateau: U.S. Geol. Survey Prof. Paper 736, 34 p. Cater, F. W., 1970, Geology of the salt anticline region in southwestern Colorado: U.S. Geol. Survey Prof. Paper 637, 80 p. —— 1972, Salt anticlines within the Paradox Basin, _in_ Geologic atlas of the Rocky Mountain region, United States of America: Denver, Colo., Rocky Mtn. Assoc. of Geologists, p. 137, 138, fig. 4. Cleland, H. F., 1910, North American natural bridges, with a discussion of their origins: Geol. Soc. America Bull., v. 21, p. 313-338. Crandell, D. R., 1969, The geologic story of Mt. Rainier: U.S. Geol. Survey Bull. 1292, 43 p. Dane, C. H., 1935, Geology of the Salt Valley anticline and adjacent areas, Grand County, Utah: U.S. Geol. Survey Bull. 863, 184 p. Dellenbaugh, F. S., 1902, The romance of the Colorado River: New York, G. P. Putnam’s Sons, 399 p. [reprinted 1962 by Rio Grande Press, Chicago, Ill.] Everhart, W. C., 1972, The National Park Service, Praeger Library of U.S. Government Departments and Agencies No. 13: New York, Praeger Publishers, p. i-xii, 1-276. Follansbee, Robert, 1929, Upper Colorado River and its utilization: U.S. Geol. Survey Water-Supply Paper 617, 394 p. Gilluly, James, Waters, A. C., and Woodford, A. O., 1968, Principles of geology [3d ed.]: San Francisco, W. R. Freeman & Co., 685 p. Hansen, W. R., 1969, The geologic story of the Uinta Mountains [with graphics by John R. Stacy]: U.S. Geol. Survey Bull. 1291, 144 p. Herron, W. R., 1917, Profile surveys in the Colorado River Basin in Wyoming, Utah, Colorado, and New Mexico: U.S. Geol. Survey Water-Supply Paper 396, 6 p., 43 pls. Hite, R. J., 1972, Pennsylvanian rocks, _in_ Geologic atlas of the Rocky Mountain region, United States of America: Denver,