s;i i!i e r 



Extract of a Memoir on the possibility of causing 



fresh-water molusccB to live in salt-water, and 



marine molusccs in fresh-water, with geolo^ 



" gical applications. By M. Beudant. 



Annales des Mines, 1816. 

 Read at the Royal Academy of Sciences, May 13, 1816. 



THE rocks of the country round Paris are known to be 

 divided into marine and fresh-water formations ; this dis- 

 tinction has been made because the shells found in the for- 

 mer are only analogous with those that exist in the sea, 

 while the shells found in the latter are analogous with those 

 that live in fresh-water. 



M. Beudant had however discovered (in 1808), in the 

 sandstone of Beauchamp, near Pierrelaye, a mixture of ma- 

 rine and fresh-water sl-iells ; he has since observed the same 

 circumstance in a marl bed in the environs of Vaucluse, 

 There are, besides, many other shelly beds, about the origin 

 of which naturalists are divided, not being yet agreed with 

 respect to the analogy of a part of their fossil shells : such, 

 among others, is the shelly bed observable in the neigh- 

 bourhood of Mayence. 



These considerations, joined with that of the perfect pre- 

 servation of the shells, rendering it reasonable to believe 

 that they have not been transported, but that the animals 

 which inhabited them have lived in the same places where 

 their remains are now found, caused Mr. Beudant to con- 

 ceive it possible for raoluscae, naturally marine, to live in 



