FOSSIL INVERTEBRATED ANIMALS. 463 



to this hypothesis. Still, however, a conjecture of this kind 

 requires the support of a much greater number of facts before 

 it can receive the full assent of any cautious philosopher. 



There are certain genera, such as oysters, mussels, &c., 

 which are discovered in a fossil state in all countries, like the 

 ammonites. But we cannot pretend to deduce from this fact 

 the same consequences as from the universality of the ammo- 

 nites, inasmuch as oysters and mussels are found, in the living 

 state, in all the climates of the earth. 



Identical species, in localities different or much remote from 

 each other, are rare among the fossil shells — especially if, by 

 identical, we understand exactly similar. M. de France has 

 met with but one genuine example of such identity, which is 

 presented by 'the bulinius terebellatus, which is found at Gri- 

 gnon, altogether similar to that which has been collected from 

 the strata of the Placentine. It is with other species as with the 

 auricula ringens, which is found in the strata posterior to the 

 chalk in this country, and in the environs of Paris, in Touraine, 

 in the neighbourhood of Bourdeaux, and in Italy ; but in each 

 of its localities, this species is rather analogous than identical. 

 However, if we only take into consideration the general modi- 

 fication of all the species taken in different localities, we may 

 be justified in regarding them as identical ; and none of the 

 species, found in the strata posterior to the chalk, are to be 

 found below the coarse limestone. 



Above all the strata, whether marine or of fresh- water forma- 

 tion, which appear to have been deposited in waters more or 

 less tranquil, another is found which presents itself in the 

 neighbourhood of Paris, in the basins of the Seine, the Marne, 

 the Oise, and the Loire, and doubtless of many other rivers ; 

 and in which are found the debris of all the other strata, mixed 

 up with the bones of terrestrial mammiferous animals and 

 cetacea. 



This stratum, which shows itself immediately under the ordi- 

 nary soil, and even sometimes at its very surface, is not petri- 



