New data on the lower Tertiary of the Paris basin places the Vigny limestone in the Montian (Paleocene). The Thanetian-Sparnacian (lower-upper Paleocene) boundary is well-marked. The Ypresian (lower Eocene) in the basin includes the basal lagoonal Sparnacian and the Cuisian at the top. The upper section of the Lutetian includes the Biarritzian. The Ledian (upper Eocene) and probably the Wemmelian in Belgium, and the upper Bracklesham beds in Hampshire (England) should be correlated with the upper Lutetian. The Bartonian substage is extended to include the Auversian, Marinesian, and Ludian which are equivalent to the upper Eocene. The Eocene-Oligocene boundary is situated at the base of the Romainville green shale. The supragypsiferous marls, the lower Tongrian and the Bembridge beds are assigned to the upper Eocene. The Sannoisian is referred to the Stampian in the Paris basin, which corresponds to the upper Tongrian and Rupelian in Belgium and to the Hamstead beds in England. Charts correlating the stages in the Paris basin with the neighboring countries of Belgium and England are given for each stage.