1 Received for publication September 6, 1938. Approved for publication by the Director of the South Dakota Agricultural Experiment Station. The first two authors are in the Dept. of Experiment Station Chemistry of the South Dakota State College, Brookings; the third is in the Dept. of Geology, UTniversity of South Dakota, Vermillion; the fourth was in the S. D. State Planning Board at Brookings and is now geologist with the Bureau of Agricultural Economics, Land Utilization Division, U. S. Dept. Agric., Lincoln, Nebraska. The authors wish to thank Dr. E. P. Rothrock, State Geologist of South Dakota, for making available the samples from the Irish Creek well core, and Mr. Morris Rhian and Mr. George Stanford for their assistance with the analysis of the samples for selenium. associated with soils derived from Pierre shale. Beath and his coworkers have reported on extensive investigations of the geological distribution of selenium in Wyoming formations (Beath et al., 1934a, 1934b, 1935, 1937a, 1937b; Knight and Beath, 1937). Byers (1935, 1936) has reported on the selenium content of formations from various parts of the Great Plains