The legislative authority of a municipal corporation shall, by ordinance, fix the salary of its members which shall be paid in equal monthly installments. For each absence from regular meetings of the legislative authority, unless authorized by a two-thirds vote of all members thereof, there shall be deducted a sum equal to two per cent of such annual salary. Absence for ten successive regular meetings shall operate to vacate the seat of a member, unless such absence is authorized by the legislative authority.