the third of four divisions (in ascending order) of Eocene (Eocene Epoch) rocks, representing all rocks deposited worldwide during the Bartonian Age (40.4 million to 37.2 million years ago) of the Paleogene Period (65.5 million to 23 million years ago). The name of the stage is derived from the Barton Beds found between Highcliffe and Milford-on-Sea in Hampshire, England. The Bartonian is underlain by the Lutetian Stage and overlain by the Priabonian Stage.