§ 15-a. Marriages of minors under eighteen years of age. Any marriage in which either party is under the age of eighteen years is hereby prohibited. Any town or city clerk who shall knowingly issue a marriage license to any persons, one or both of whom shall be at the time of their contemplated marriage actually under the age of eighteen years, shall be guilty of a misdemeanor and on conviction thereof shall be fined in the sum of one hundred dollars.