Mrs. Abigail F. Sias, 66, of 173 Buckingham street, died late Sunday night, after a continued illness. Mrs. Sias was the wife of Chauncey R. Sias. She was formerly Miss Abigail Flint of Wilmington, where she was born, the daughter of Kendall and Cynthia Beard Flint. She was descended from Gov. John Winthrop of early colonial days. She spent her early life in North Reading, Woburn, and later in Boston. She came to this city 21 years ago and was among the first families to locate in the McKnight district. She was a member of Rev. W.R. Alger's Unitarian church in Boston. She leaves besides her husband, two children, a son, Chauncey K. Sias, and a daughter, Miss C. Augusta Sias; also a sister, Mrs. Alden Knights of Woburn, and two grandchildren. The funeral will be held Thursdayafternoon at 2.30. Burial will be in Woburn.