A. The membership of this retirement system shall be composed of all persons who are employees on December 31, 1946, except those hereinafter specifically excluded, provided that before July 1, 1947, any such employee files with the board of trustees on a form prescribed by such board a notice of election to be covered in the membership of the system and also files enrollment as a member on a form prescribed by the board of trustees. Except as hereafter provided, after June 30, 1948, no person who has attained the age of fifty years shall be eligible to become a member.
B. Any person who was not employed on December 31, 1946, by a parish or city school board, but who prior to that time has been so employed, may become a member of the system and shall be entitled to receive credit for such prior service upon entering the system, provided he applies for membership on or before July 31, 1955.