Jurisdiction over ruins, archeological sites, historic and prehistoric monuments and structures, objects of antiquity, historic landmarks, and other objects of historic and scientific interest, shall be exercised under the act by the respective Departments as follows:
(a) By the Secretary of Agriculture over lands within the exterior limits of forest reserves;
(b) By the Secretary of the Army over lands within the exterior limits of military reservations;
(c) By the Secretary of the Interior over all other lands owned or controlled by the Government of the United States, Provided, The Secretaries of the Army and Agriculture may by agreement cooperate with the Secretary of the Interior in the supervision of such monuments and objects covered by the Act of June 8, 1906 (34 Stat. 225; 16 U.S.C. 431-433), as may be located on lands near or adjacent to forest reserves and military reservations, respectively.