446 FOSSIL INVERTEBRATED ANIMALS. 



point, of a clearer colour, appears to serve them as a centre^ 

 and in some of them two such points are distinguishable. In 

 some localities of the same countries, they are smaller than 

 the last, flatted, and some, which are of a larger size, exhibit 

 varieties of flatted forms. These oolites, in general of regular 

 forms, are met with in strata which, from the preservation of 

 the fossils which they contain, appear to have been tranquil, 

 and seem to differ essentially from those of other places, — ^for 

 example, of Nevers and Auxerres. These last are found in 

 white beds, of which they constitute the major part. They 

 are accompanied by debris of shells, of polyparia, and other 

 marine bodies. It appears that these depositions have been 

 exposed to considerable convulsions, for there remain only of 

 certain univalve shells, extremely thick, some very short and 

 mutilated portions. These we may recognize by their spathic 

 and shining brilliancy, and by their form, the remains of the 

 stems of Encrinites, some flatted fragments, and some which 

 appear to be debris of bivalve shells, though they have not the 

 contexture of the latter. Others, which are rounded, are 

 filled with crystals in their centre. The surplus of the mass 

 is composed of oolites of different sizes, from the bulk of a 

 poppy seed to that of a small pea. Some of the larger ones 

 seem to be formed by an agglomeration of the smaller. The 

 whole is cemented by a white and transparent crystallization. 



These oolites are white, and appear to have been formed by 

 the bruised matter of shells, and other marine bodies, muti- 

 lated debris of which are found along with them. Considering 

 the state of disorder in which they are found, we may be justi- 

 fied in attributing to them a different origin from that of the 

 others which we first mentioned. 



What we remark in certain marbles which contain marine 

 bodies, would lead us to the conclusion that they had under- 

 gone petrifaction at several successive times. The first petri- 

 faction which probably took place in the waters would have 

 formed the ordinary coloured stratum, which surrounds them 



