pages 149-173 : illustrations, maps (3 folded in pocket) ; 24 cm
At head of title: United States Department of the Interior, J. A. Krug, Secretary. Geological Survey, W. E. Wrather, Director.
"Prepared in cooperation with the Secretaría de la Economía Nacional de México, Dirección General de Minas y Petróleo and the Universidad Nacional Autónoma de México, Instituto de Geología, under the auspices of the Interdepartmental Committee on Scientific and Cultural Cooperation, Department of State."