WORK IN PALEONTOLOGY 127 



sils are extinct species, and that the earth has passed 

 through a general catastrophe {un bouleversement uni- 

 versel) with the result that a multitude of species 

 of animals and plants were consequently absolutely 

 lost or destroyed, and remarks in the following telHng 

 and somewhat derisive language : 



/a universal catastrophe {bouleversement) which 

 necessarily regulates nothing, mixes up and disperses 

 everything, is a very convenient way to solve the 

 problem for those naturalists who wish to explain 

 everything, and who do not take the trouble to observe 

 and investigate the course followed by nature as re- 

 spects its production and everything which constitutes 

 its domain. I have already elsewhere said what should 

 be thought of this so-called universal overturning of 

 the globe ; I return to fossils. 



i^lt is very true that, of the great quantity of fossil 

 shells gathered in the different countries of the earth, 

 there are yet but a very small number of species whose 

 living or marine analogues are known. Nevertheless, 

 although this number may be very small, which no 

 one will deny, it is enough to suppress the universality 

 announced in the proposition cited above. 



/ It is well to remark that among the fossil shells 

 whose marine or living analogues are not known, there 

 are many which have a form closely allied to shells of 

 the same genera known to be now living in the sea. 

 However, they differ more or less, and cannot be lig- 

 orously regarded as the same species as those known 

 to be living, since they do not perfectly resemble 

 them. These are, it is said, extinct species. 



/ I am convinced that it is possible never to find, 

 among fresh or marine shells, any shells perfectly sim- 

 ilar to the fossil shells of which I have just spoken. I 

 believe I know the reason ; I proceed to succinctly 

 indicate, and I hope that it will then be seen, that al- 



