194 UPFEK EOCENE STRATA OF FRANCE. [Cu. XV 



Between the Hempstead beds above deseribed and those next below them, thert 

 is no break, as before stated, p. IST. The freshwater, brackish, and marine 

 limestones and marls of the underlying or Bembridge group are in conformable 

 stratification, and contain Gyrena semistriata, fig. 171, Melania miiricata, Palu- 

 d'lna lenta, fig. 175, and several other shells belonging to the Hempstead beds. 

 Prof. Forbes therefore classes both of them in the same Upper Eocene division. 

 I have called the Bembridge beds Middle Eocene, for convenience sake, as 

 already explained (pp. 18B, 187.) 



UPPER EOCENE STRATA OF FRANCE. 



[Lower Miocene of many French authors) 



The Gres de Fontainebleau, or sandstone of tlie Forest of Fontainebleau, 

 has been frequently alluded to in tlie preceding pages, as corresponding 

 in age to the Liraburg or Hempstead beds. It is associated in the sub- 

 urbs of Paris with a set of strata, very varied in their composition, and 

 containing in their lower portion a green clay with abundance of small 

 oysters [Ostrea cyathula^ Lam.) which are spread over a wide area. The 

 marine sands and sandstone which overlie this clay include Cytherea in- 

 crassata and many other Limburg fossils, the finest collections of which 

 have been made at Etampes, south of Paris, where they occur in loose 

 sand. The Gres de Fontainebleau is sometimes called the " Upper marine 

 sands" to distinguish it from the " Middle sands" or Gres de Beauchamp, 

 a Middle Eocene group. 



Calcaire lacustre suj^erieur. — Above the Gres de Fontainebleau is seeji 

 the upper freshwater limestone and marl, sometimes called Calcaire de la 

 Beauce, which with its accompanying marls and siliceous beds seem to 

 have been formed in marshes and shallow lakes, such as frequently over- 

 spread the newest parts of great deltas. Beds of flint, continuous or in 

 nodules, accumulated in these lakes, and Chares, aquatic plants, already 

 alluded to, 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 sum- 

 mits 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. "When they 

 reach the valley of the Loire, they occasionally underlie and form the 

 boundary of the marine Miocene faluns, fragments of the older freshwater 

 limestone having been broken ofl" and rolled on the shores and in the bed 

 of the Miocene sea, as at Pontlevoy, on the Cher, where the perforating 

 marine shells of the Miocene period still remain in hollows drilled in the 

 blocks of Eocene limestone. 



Central France. — Lacustrine strata, belonging, for the most part, to 

 the same Upper Eocene series, are again met wdth in Auvergne, Cantal, 

 and Velay, the sites of which may be seen in the annexed map. They 

 appear to be the monuments of ancient lakes, which, like some of those 

 now existing in Switzerland, once occupied the depressions in a mountain- 

 ous region, and have been each fed by one or more rivers and torrents. 



