Henry Irwin No description specified. 1-4 (4 Records) Documents Archaeology of the Agate Bluff Area, Colorado Plains Anthropologist (No. 8:15-38) (1957) Archaic Complexes of the Foothills Region of Colorado Archeology of the Agate Bluff Area, Colorado (1957) Hell Gap: Paleoindian Occupation On the High Plains (1973)