Ch. XVL] 



CALCAIEE SILICEUX. 



225 



and zoophytes, met with in many ancient European rocks, had ceased to 

 be inhabitants of the earth, but the majority even of the educated classes 



Fi<*. 235. 



XipTwdon gracile, or Anoplotherium gracUe, Cavler. Kestored outline. 



continued to believe that the species of animals and plants now contem- 

 porary with man, were the same as those which had been called into 

 being when the planet itself was created. It was easy to throw discredit 

 upon the new doctrine by asking whether corals, shells, and other crea- 

 tures previously unknown, were not annually discovered ? and whether 

 living forms corresponding with the fossils might not yet be dredged up 

 from seas hitherto unexamined ? But from the era of the publication of 

 Cuvier's Ossements Fossiles, and still more his popular Treatise called 

 " A Theory of the Earth," sounder views began to prevail. It was clearly 

 demonstrated that most of the mammalia found in the gypsum of Mont- 

 martre differed even genefically from any now known to exist, and the 

 extreme improbability that any of them, especially the larger ones, would 

 ever be found surviving in continents yet unexplored, was made manifest. 

 Moreover, the non-admixture of a single living species in the midst of so 

 rich a fossil fauna was a striking proof that there had existed a state of 

 the earth's surface zoologically unconnected with the present state of 

 things. 



Calcaire siliceux, or Travertin inferieur, B. 2. — This compact siliceous 

 limestone extends over a wide area. It resembles a precipitate from 

 the waters of mineral springs, and is often traversed by small empty 

 sinuous cavities. It is, for the most part, devoid of organic remains, 

 but in some places contains freshwater and land species, and never any 

 marine fossils. The siliceous limestone and the calcaire grossier usually 

 occupy distinct parts of the Paris basin, the one attaining its fullest de- 

 velopment in those places where the other is of slight thickness. They 

 are described by some writers as alternating with each other towards 

 the centre of the basin, as at Sergy and Osny ; and M. Prevost con- 

 cludes, that while to the north, where the Bay was probably open to the 



15 



