The director of finance of each county may, with the approval of the council, deposit securities owned by the county in mainland depositories. The securities shall be subject to all the terms, conditions, and authorizations of the depository agreement which the director of finance may have or may make with any such mainland depository. Further, the director of finance of each county may, with the approval of the council, and with the consent of the state director of finance, place such securities under the control of the state director of finance for safekeeping in mainland depositories. The securities shall be subject to all the terms, conditions, and authorizations of any depository agreement which the state director of finance may have or make with any mainland depository, and all expenses thereof shall be borne by the county. Moneys received by any mainland depository, on behalf of the county, or on behalf of the state director of finance for the county, from the sale or redemption of securities, or as interest, shall not for a period of thirty days after the receipt thereof by the depository be considered as deposits within the meaning of chapter 38, and moneys placed with the depositories for the purchase of securities shall not be considered as deposits within the meaning of chapter 38.