Millard was a relative of Philip and William Sclater, Secretaries of ZSL
Letters from Morton Allport to Philip Lutley Sclater about the introduction of salmon to the waters of Tasmania
Letters from Spencer Fullerton Baird of Washington to Philip Lutley Sclater regarding ornithology
Letters from Henry Walter Bates to Philip Lutley Sclater regarding his research and animals collected by Paul Du Chaillu
Letters from Herbrand Arthur Russell to Philip Lutley Sclater regarding the purchase of animals, his election as member of the council of the Zoological Society, his attendance at meetings and the appointment of a veterinary surgeon at the Zoological Society
Letters from A de Borre of the Musee Royal d'Histoire Naturelle Brussels, to Philip Lutley Sclater
Letters from Frederic Brine to Philip Lutley Sclater regarding the living conditions of a gorilla, a sacred white elephant which was said to have been in Siam but which he refuted, and the height and weight of Jumbo and Jenny
Letters from Bennet Burleigh to Philip Lutley Sclater regarding the donation of two turtles
Letters from Arthur Cates to Philip Lutley Sclater regarding the proposed Regent's Canal Railway
Letters from Sir Percy Zachariah Cox to Philip Lutley Sclater regarding specimens of Oryx Beatrix, Dik Dik skeletons, snakes and antelopes. Also letters regarding his election and membership of the Zoological Society of London