NATION

Courtney F. Jones, treasurer of General Motors for more than three years and a veteran of 22 years with GM, was named executive vice president and chief financial officer of Merrill Lynch & Co., New York, supervising treasury, controller and credit operations. Jones assumes responsibilities borne temporarily by Stephen L. Hammerman, chief administrative officer, since the resignation in March, 1984, of Gregory Fitz-Gerald. A GM spokesman said no decision on a replacement as treasurer has been made.