The commissioners of the county commission, the county assessor, the county clerk, and those sitting as members as may otherwise be provided, who are now or may hereafter be compensated by salary shall not be entitled to additional compensation for the performance of their duties as members of the county board of equalization. The county surveyor shall be present and sit as a member of the county board of equalization and shall receive as compensation a fee as agreed upon by the county commission. Citizens who are not officers of the county, but who sit as members of the county board of equalization, may receive compensation if agreed upon by the county commission.