Material related to the Otis T. Mason collection can also be found in the Bureau of American Ethnology records and the Department of Anthropology records, including the Division of Ethnology Manuscript and Pamphlet file. The following materials in the National Anthropological Archives series of Numbered Manuscripts are also pertinent:
A.S.W./Anthrop., Hist. of, 4821 (pt.): Box 4. "Anthropology in the District of Columbia..." (39 pages, dated 1906) and two letters pertaining to it.
Anthrop., Hist. of, 49033: "Diary of Otis T. Mason.." from 1 July 1884 to 23 May 1891 (approximately 100 pages).
Arch., U.S., 2431: notes, sketches, and letters used in Smithsonian Annual Reports for 1876-1879 and 1881-1883.
Athapaskan, 173 and Tinne (Kutchin), 169: translation and notes from works of Petitot (total of 68 pages).
Choctaw, 666: revision of Byington's grammar of Choctaw (ca. 1872).
Census, 4289: report on Indian education for the 10th census.
Africa, Morocco, 7083: Choctaw, 4056; Fewkes 4408 (5-a); Mohaven 7036; and Pamunkey, 2218: various letters to Mason containing ethnographic or linguistic information (dated from 1891 to 1893).
In the United States National Museum Manuscript and Pamphlet File, Boxes 4, 14, 20, 35-40, and 70, is material on the topics represented in the Mason papers as well as other material produced by Mason.
The Smithsonian Institution Archives has a small series of copies of letters which Mason wrote to the Smithsonian in 1889 while on a trip in Europe to study museum practices (SIA 7086).