From introduction: This report is based on investigations carried on by the Geological Survey (U. S. Department of the Interior) under the auspices of the Interdepartmental Committee on Scientific and Cultural Cooperation (U. S. Department of State) and the Foreign Economic Administration. The function of the last two agencies is presently carried on by the International Cooperation Administration. Roberts is responsible for the text of this report and for the compilation of the geologic map. He was in Central America from January to April 1942 under a program of scientific and technical cooperation with the American Republics sponsored by the Department of State, and mapped manganese deposits in Costa Rica and manganese and antimony deposits in Honduras.