For the purposes of acquiring non-Federal lands within the boundaries of said park as established by this section and , the Secretary of the Interior is authorized, in his discretion, to exchange federally owned lands within sections 1, 12, and 13, township 148 north, range 100 west, and sections 6, 7, and 18, township 148 north, range 99 west. Reserving, however, to the stockmen of the surrounding area a perpetual right-of-way through the park for the trailing of livestock, to and from the railroad, along and adjacent to the Little Missouri River, being the same trail or route which has been used by the stockmen for that purpose since the beginning of the livestock industry in the area. Administrative jurisdiction over any of such lands that the Secretary of the Interior finds are not required for exchange purposes as herein provided may be conveyed to other Federal agencies by the Secretary of the Interior without exchange of funds, or if such lands are not required by other Federal agencies they may be conveyed to the State of North Dakota without reimbursement to the United States.section 241a of this title