Section 518 - Election of coverage under articlea. Except as provided in subdivision c hereof, a member of a public retirement system of the state on June thirtieth, nineteen hundred seventy-six who is not subject to the provisions of article eleven of this chapter may elect to become subject to this article by submitting such election on or before June first, nineteen hundred seventy-eight. An election hereunder shall be made in the form and manner prescribed in rules and regulations promulgated by the head of the retirement system to which such member belongs at the time of election. Such election shall be irrevocable thirty days after it is received by the system involved. Provided, however, that an election may not be made by any employee who is not employed by a participating employer, or who is employed by a participating employer described in subdivision c of section five hundred of this article.b. Contributions made by a member prior to an election pursuant to subdivision a of this section, together with any interest thereon through the date of election, shall thereafter become subject to the provisions of section five hundred seventeen of this article.c. On and after the date on which this act shall take effect, no member of a public retirement system of the state shall elect to become subject to this article.N.Y. Retire. and Soc. Sec. Law § 518