N.M. Stat. § 6-10-8
The board of county commissioners in each county in the state shall, ex officio and without additional compensation, constitute a county board of finance and as such shall, subject to the limitations of this act, have supervision over the determination of the qualifications and selection of banks, savings and loan associations and credit unions, whose deposits are insured by an agency of the United States, to receive the public money of their respective counties and of independent rural school districts, rural school districts and municipal school districts of municipalities having less than twenty-five thousand population according to the next preceding United States census and of any special or other districts in their respective counties for which the respective county treasurers of such counties act as ex-officio tax collectors. The county clerk in each county shall, ex officio and without additional compensation, act as clerk of such county board of finance. Every county board of finance shall hold meetings whenever necessary for the discharge of its duties, and the chairman shall convene such board whenever necessity therefor exists or when requested so to do by two of its members or at any time when the county treasurer shall advise the chairman that he has in his custody public money in excess of the aggregate amount which depositories qualified by law are entitled to hold. A majority of the board shall constitute a quorum for the transaction of business.
The county treasurer of each county in the state shall have supervision of the deposit and safekeeping of the public money of his county and all the money which may at any time come into or be in his possession as county treasurer and ex-officio tax collector for the use and benefit of the state or of any county, municipality or district or of any subdivision of any county or of any state or public institution and by and with the advice and consent of the respective boards of finance having jurisdiction over the respective funds shall designate banks, savings and loan associations and credit unions, whose deposits are insured by an agency of the United States, to receive on deposit all moneys entrusted in his care.
NMS § 6-10-8