{ _a._ Lower freshwater limestone and marl, or { gypseous series. { _b._ Sandstone and sands with marine shells (_Sables_ 2. Middle Eocene { _moyens_, or _gres de Beauchamp_). { _c._ Calcaire grossier, limestone with marine shells. { _d._ Calcaire siliceux, hard siliceous freshwater { limestone, for the most part contemporaneous { with _c_. { _a._ Lower sands with marine shelly beds (_Sables_ 3. Lower Eocene { _inferieurs et lits coquilliers_). { _b._ Lower sands, with lignite and plastic clay { (_Sables inferieurs et argiles plastiques_). Postponing to the next chapter the consideration of the Middle and Lower Eocene groups, I shall now speak of the Upper Eocene of Paris, and its foreign equivalents. The upper freshwater marls and limestone (1. _a_) seem to have been formed in a great number of marshes and shallow lakes, such as frequently overspread the newest parts of great deltas. It appears that many layers of marl, tufaceous limestone, and travertin, with beds of flint, continuous or in nodules, accumulated in these lakes. _Charae_, aquatic plants, already alluded to (see p. 32.) left their stems and seed-vessels imbedded both in the marl and flint, together with freshwater and land shells. Some of the siliceous rocks of this formation are used extensively for millstones. The flat summits or platforms of the hills round Paris, large areas in the forest of Fontainebleau, and the Plateau de la Beauce, between the Seine and the Loire, are chiefly composed of these upper freshwater strata.