Mr. Frank Markoe Jr. of Far Hills, N.J. announces the engagement of his daughter, Ritchie Harrison to Charles Scribner III, son of Mr. and Mrs. Charles Scribner Jr. of Far Hills and New York. Miss Markoe is also the daughter of Mrs. Margaret McCormack Anderson of Palm Beach. An August wedding is planned.

Miss Markoe, a teacher at Christ Church Day School in New York, will join the teaching staff at The Buckley School in September. A 1971 debutante presented at the New York Assemblies and the Bachelors Cotillion in Baltimore, she was educated; at the Foxcroft School and received a BA in art history from the New York University and an MA from the the Bank Street College of Education. Her father is vice-chairman of the Board of Directors and a member of the Office is Chairman of the WarnerLambert Company, and is also president of the New Jersey Ballet and a member of the Board of International Broadcasting (Radio Free Europe/Radio Liberty).He was a partner in the Baltimore law firm Cable and McDaniel. Miss Markoe is the granddaughter of Mrs. Nathan Ryno Smith and the late Mr. and Mrs. Margaret Smith Schumann, and the great-granddaughter of Dr. and Mrs. Nathan Ryno Smith and the late Mr. and Mrs. John S. Markoe, all of Baltimore. She is a direct descendant the first flag that incorporated the 13 stripes of the American colonies.

Mr. Scribner graduated in 1969 from St. Paul's School, Concord, N.H., and received his AB in 1973 from Princeton University where he earned his PhD in art history in 1977 and was a member of the faculty in the Department of Art and Archaeology. He is a director of the family publishing house of Charles Scribner's Sons, of which his father is Chairman and his great-great-grandfather, Charles, founded in 1846. Mr. Scribner is also a trustee of Westminster Choir College. He is a grandson of Mrs. Charles Scribner of Far Hills and the late Mr. Scribner and of the late Mr. and Mrs. Edwin Sunderland of Morrison, N.J. Mr. Sunderland was a partner in the New York law firm of Davis, Polk and Wardwell and a director of the Illinois Central Railroad. CAPTION: Picture, no caption, Bachrach