There has been much discussion recently relative to the geologic age of Yuma and Folsom artifacts. The writers submit the following palaeontological and geological data which may aid in a better interpretation of the subject. This paper deals with three localities in Nebraska where Yuma and Folsom implements have been found with extinct mammals; namely, the Scottsbluff Bison Quarry, the Sand Hill blow-out sites, and the Sioux County artifact sites
