302 FOSSIL FOOTPEINTS IN THE [Ch. XVI. 



The whole assemblage, says Desnoyers, indicate the shores of a lake, 

 or several small lakes communicating with each other, on the borders 

 of which many species of Pachyderms wandered, and beasts of 

 prey which occasionally devoured them. The toothmarks of these 

 last had been detected by palaeontologists long before on the bones and 

 skulls of Paleotheres entombed in the gypsum. 



These footmarks have revealed to us new and unexpected proofs 

 that the air-breathing fauna of the Upper Eocene period in Europe 

 far surpassed in the number and variety of its species the largest es- 

 timate which had previously been formed of it. We may now feel 

 sure that the mammalia, reptiles, and birds, which have left portions 

 of their skeletons as memorials of then' existence in the solid gypsum, 

 constituted but a part of the then living creation. Similar inferences 

 may be drawn from the study of the whole succession of geological 

 records. In each district the monuments of periods embracing thou- 

 sands, and probably in some instances millions of years, are totally 

 wanting. Even in the volumes which are extant the greater number of 

 the pages are missing in any given region, and where they are found 

 they contain but few and casual entries of the physical events or liv- 

 ing beings of the times to which they relate. It may also be re- 

 marked that the subordinate formations met with in two neighbor- 

 ing countries, such as France and England (the minor Tertiary groups 

 above enumerated), commonly classed as equivalents and referred to 

 corresponding periods, may nevertheless have been by no means 

 strictly coincident in date. Though called contemporaneous, it is 

 probable that they were often separated by intervals of hundreds of 

 thousands of years. We may compare them to double stars, which 

 appear single to the naked eye because seen from a vast distance in 

 space, and which really belong to one and the same stellar system 

 though occupying places in space extremely remote if estimated by 

 our ordinary standard of terrestrial measurements. 



Calcaire siliceux, or Travertin inferieur (A. 2, p. 297). — This com- 

 pact 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 calcaire siliceux and the 

 calcaire grossier usually occupy distinct parts of the Paris basin, the 

 one attaining its fullest development in those places where the other is 

 of slight thickness. They are described by some writers as alternat- 

 ing with each other toward the centre of the basin, as at Ser gy and 

 Osny. 



The gypsiun, with its associated marls before described, is in great- 

 est force toward the centre of the basin, where the calcaire grossier 

 and calcaire siliceux are less fully developed. 



Gres de Beauchamp, or Sables moyens (A. 3, p. 298). — In some parts 

 of the Paris basin, sands and marls, called the Gres de Beauchamo, or 



