WORK IN PALEONTOLOGY 



125 



in general was published at the end of his Systime 

 des Animaux sans VcrUbres (pp. 401-41 1), in 1801, 

 a year before the publication of the HydrogMogie. 

 " I give the name fossils" he says, " to remains of 

 living beings, changed by their long sojourn in the 

 earth or under water, but whose forms and structure 

 are still recognizable. 



" From this point of view, the bones of vertebrate 

 animals and the remains of testaceous molluscs, of 

 certain Crustacea, of many echinoderms, coral polyps, 

 when after having been for a long time buried in the 

 earth or hidden under the sea, will have undergone 

 an alteration which, while changing their substance, 

 has nevertheless destroyed neither their forms, their ,1 

 figures, nor the special features of their structures." 



He goes on to say that the animal parts having been 

 destroyed, the shell remains, being composed of cal- 

 careous matter. This shell, then, has lost its lustre, 

 its colors, and often even its nacre, if it had any ; 

 and in this altered condition it is usually entirely 

 white. In some cases where the shells have remained 

 for a long period buried in a mud of some particular 

 color, the shell receives the same color. 



" In France, the fossil shells of Courtagnon near 

 Reims, Grignon near Versailles, of what was formerly 

 Touraine, etc., are almost all still in this calcareous 

 state, having more or less completely lost their animal 

 parts — namely, their lustre, their peculiar colors, and 

 their nacre. 



" Other fossils have undergone such an alteration 

 that not only have they lost their animal portion, but 

 their substance has been changed into a silicious 

 matter. I give to this second kind of fossil the name 



