Ch. XVI.] 



EOCENE STRATA OF FRANCE. 



303 



Sables inoyens, divide the gypseous beds from the calcaire grossier 

 proper. These sands, in which a small nummnlite (JV. variolaria) is 

 very abundant, contain more than 300 species of marine shells, many 

 of them peculiar, but others common to the next division. 



Calcaire grossier, upper and middle (B. 1, p. 298). — The upper divis- 

 ion of this group consists in great part of beds of compact, fragile 

 limestone, with some intercalated green marls. The shells in some 

 parts are a mixture of Cerithium, Cyclostoma, and Corbula ; in others 

 Limnea, Cerithium, Paludina, &c. In the latter, the bones of reptiles 

 and mammalia, Paleotherium and Lophiodon, have been found. The 

 middle division, or calcaire grossier proper, consists of a coarse lime- 

 stone, often passing into sand. It contains the greater number of the 

 fossil shells which characterize the Paris basin. No less than 400 dis- 

 tinct species have been procured from a single spot near Grignon, 

 where they are embedded in a calcareous sand,- chiefly formed of com- 

 minuted shells, in which, nevertheless, individuals in a perfect state of 

 preservation, both of marine, terrestrial, and freshwater species, are 

 mingled together. Some of the marine shells may have lived on the 

 spot ; but the Cyclostoma and Limnea must have been brought thither 

 by rivers and currents, and the quantity of triturated shells implies 

 considerable movement in the waters. 



Nothing is more striking in this assemblage of fossil testacea 

 than the great proportion of species referable to the genus Cerithium 

 (see figures, p. 240). There occur no less than 137 species of this 

 genus in the Paris basin, and almost all of them in the calcaire gros- 

 sier. Most of the living Cerithia inhabit the sea near the mouths of 

 rivers, where the waters are brackish ; so that their abundance in -the 

 marine strata now under consideration is in harmony with the hy- 

 pothesis that the Paris basin formed a gulf into which several rivers 

 flowed. 



In some parts of the calcaire grossier round Paris, certain beds 

 occur of a stone used in building, and called by the French geologists 



EOCENE FORAMINIFERA. 

 Fig. 265. Fig. 266. 



Calcarina rarispina, Desh. Spirolina stenostoma, Desh. 



&. Natural size, a, c. Same magnified. B. Natural size. A, C, D. Same magnified. 



