A supernumerary judge of a circuit court who desires that his spouse receive, after his death, the benefits provided in subsection (c) of Section 12-18-10 must, at the time of the filing of the instrument showing his election to come under the provisions of Article 1 of this chapter, pay into the judicial retirement fund an amount of money equal to the largest sum heretofore paid into that fund by a now retired circuit court judge between September 18, 1973, and the date of his retirement.