“ The United States is now, and has been at all times pertinent hereto, possessed of paramount rights in, and full dominion and power over, the lands, minerals and other things underlying the Gulf of Mexico, lying seaward of the ordinary low-water mark on the coast of Louisiana, and outside of the inland waters, extending seaward twenty-seven marine miles and bounded on the east and west, respectively, by the eastern and western boundaries of the State of Louisiana. ”