The Boards of Directors of Harleysville National Bank & Trust Company, and the Citizens National Bank of Lansford, jointly announced that an agreement in principle has been approved and signed by the two institutions calling for their merger. Citizens National Bank will become a wholly-owned subsidiary of Harleysville National Corporation. The current employees and board of directors will continue to operate the bank, making local decisions affecting the marketplace, said Walter E. Daller Jr., president of Harleysville National Corporation.