263 



fresh-water lakes might also have had the quality of depo- 

 siting stony beds, such as gypsum, fresh-water marbles, &c. 

 and of enveloping in them the animals and vegetables which 

 lived in these waters, or on their borders. But, whilst 

 forming these opinions, M. Brongniart found it necessary to 

 admit that the formation of gypsum might also have taken 

 place both in fresh and in salt water ; and was obliged to 

 allow, that in some places, as in the quarries of Beauchamp, 

 the river and the sea shells are really mixed together. 



These opinions, particularly as to the alternation of de- 

 position, have been strongly opposed by Messrs. de la 

 Metherie, Brard, and Faujas St. Fond. By the first of 

 these it is said, that as land shells are found in these 

 formations, they, as well as the bones of the land animals, 

 must have been carried in by currents ; and, therefore, it is 

 probable, that the fresh-water shells might also have been 

 carried into the sea in the same manner, and thus have 

 formed the present beds. M. Brard and Faujas St. Fond 

 are of opinion, that all shells, previous to these depositions, 

 existed in water of the same nature ; but that, in the pro- 

 cess of time, perhaps from the increase of the saltness of the 

 sea, a separation took place, the inhabitants of the shells 

 which are at present found in fresh v/ater, or on land, 

 having migrated to situations more congenial to their 

 nature.* M. Faujas St. Fond, too, having found ampul- 

 larice and melanicc^ with a shell much resembling those of 

 the genus planorhis^ in bituminous marl between beds of 

 coal, concluded that their presence here could only be 

 accounted for by supposing them to have been brought 

 by the torrents of an overwhelming sea; and takes the 

 opportunity of thus attacking Cuvier, who had pointed 

 out the errors he had committed whilst describing some 



* Annales du Mus. Tom. xiv. p. 314. 



