When title to lands and interests in lands in an amount sufficient to constitute an efficiently administerable 1

unit for the purposes of sections 459g to 459g–7 of this title is vested in the United States, the Secretary shall declare the establishment of the seashore by publication of notice thereof in the Federal Register. Such notice shall contain a refined description or map of the boundaries of the seashore as the Secretary may find desirable and such exterior boundaries shall encompass, as nearly as possible, the area generally described in