In early life he was in business as a merchant, but his leisure hours were devoted to collecting fossils and studying the rocks of the neighborhood of Madison. Being unsuccessful in business he turned his whole attention to science, and in 1848 he gained employment on the United States Geological and Geographical Survey of the Territories in Iowa, and subsequently in Wisconsin and Minnesota. In 1852 he became assistant to Professor James Hall at Albany, New York, and worked at palaeontology with him until 1858.
Meanwhile in 1853 he accompanied Dr FV Hayden in an exploration of the badlands of Dakota and brought back valuable collections of fossils. In 1858 he went to Washington, D.C., where he devoted his time to the palaeontological work of the United States geological and geographical surveys, his work bearing the stamp of the most faithful and conscientious research, and raising him to the highest rank as a palaeontologist. About this time, both he and Hayden joined the Megatherium Club at the Smithsonian Institution.
Besides many separate contributions to science he prepared with WM Gabb (1839-1878), two volumes on the palaeontology of California (1864-1869). And also a Report on the Invertebrate Cretaceous and Tertiary Fossils of the Upper Missouri Country (1876). He died of tuberculosis at Washington in 1876.
National Academy of Sciences.