Merle Britt Petterson, 89, of Pensacola died Saturday, December 27, 1997, following a short illness.  Mrs. Petterson was a native and lifelong resident of Pensacola.  She was a member of The Cathedral of the Sacred Heart, the Catholic Daughters of Americus and a 27 year member of The Mother Seton Guild of Sacred Heart Hospital.  She was a retired Escambia County School teacher.  She was preceded in death by her husband, T. Sigurd Petterson.  Survivors include her brother, Ray H. Britt of Ellicott City, MD; nieces, Josephine Britt Alexander, Patricia Britt Fendlay and Elizabeth Britt Shea; nephew, Robert Britt; three grandnieces; and three great-grandnieces, all of Maryland.  Funeral services will be held at 10 a.m. Tueday in The Cathedral of the Sacred Heart, with the Rev. Father Michael Shaw officiating.  Burial will be in St. John's Cemetery.  Waters & Hibbert Funeral Home is in charge of arrangements.  Friends may call at the funeral home from 5 to 7 p.m. Monday.  The rosary will be recited a 6:30 p.m. Monday at the funeral home.  In lieu of flowers, memorial contributions may be made to Sacred Heart Children's Hospital.