American palaeontologist and marine biologist. BS, Harvard, 1862. Studied marine fossils with Louis Agassiz. Served in the army, 1862–5, during the American Civil War. Curator, Essex Institute, 1867. Co-founder and editor, American Naturalist, 1867–71. Custodian, Boston Society of Natural History, 1870–81; curator, 1881–1902. Taught zoology and palaeontology at the Massachusetts Institute of Technology, 1870–88; Boston University, 1877–1902. Founded a natural history laboratory at Annisquam, 1879; the laboratory was moved to Woods Hole, 1888, and incorporated as the Marine Biological Laboratory, with Hyatt as first president of its board of trustees. Palaeontologist to the US Geological Survey from 1889.