Subject to valid rights and entries initiated under the public land laws, prior to June 7, 1924, any or all of the following described lands in Government ownership may be withdrawn from entry and disposition by proclamation of the President for the purpose of protecting and propagating antelope and other game animals and birds: National forest lands⁠—Township 18 north, range 7 east, Black Hills meridian, section 24, south half, and south half north half; section 25, all; township 18 north, range 8 east, sections 17 to 20, inclusive; section 21, west half; sections 29 to 32, inclusive. Public lands⁠—Township 18 north, range 7 east, sections 5 to 9, inclusive; sections 13 to 23, inclusive; section 24, north half north half; sections 26 to 36, inclusive; and those parts of sections 3, 4, 10, and 11 lying south and west of the Riva Road. The withdrawal of the lands herein authorized shall not affect withdrawals for national forest purposes made prior to June 7, 1924.