102 FOSSIL MAMMALIA. 



dignified with the title of systems, and based it on the natural 

 and necessary relations which link together the various parts of 

 all organized bodies. 



These researches, also, led to geological conclusions of vast 

 importance. They proved that the sea had covered, for a long 

 period, all that country in the neighbourhood of the French 

 metropolis, and tranquilly deposited there a variety of different 

 kinds of strata : it then abandoned it to the fresh water, which 

 then expanded over the soil in vast lakes. In these lakes were 

 found the gypsum and the marly strata alternating with it, or 

 immediately covering it. The peculiar animals, with whose 

 bones this gypsum is replete, lived on the banks, or in the 

 islands of these lakes, swam in their waters, and fell in there 

 when they died. At a more recent era the sea re-occupied its 

 ancient domain^ and deposited sand and marl, filled with shells. 

 Finally, after its last retreat, the surface of the soil, as well in 

 its elevations as its vallies, was again, for a long period, covered 

 with ponds or marshes, which have left thick strata of stone, 

 abounding with shells of the fresh- water. 



This peculiar stone of fresh-water formation, neglected or 

 unknown by geologists, is one of the most remarkable results 

 of the Baron's labours. Its existence has since been ascertained 

 in almost every part of France, but its alternation with the 

 marine strata is no where so evident as in the neighbourhood of 

 Paris. 



When animals approximating to those of the Parisian envi- 

 rons are found elsewhere, they are invariably in a stratum of 

 fresh- water formation, but not always in the gypsum. The 

 calcareous depositions of Orleans and Buchsweiler, which con- 

 tain such remains, also contain abundance of lacustral shells ; 

 and those of Buchsweiler are covered, like the gypsum of 

 Paris, with marine coquillaceous strata. This parity of phe- 

 nomena proves the vast extent of the catastrophes which pro- 

 duced them. 



It may be as well, before we enter on any specific notice of 



