FOSSIL INVERTEBRATED ANIMALS. 447 



in all their parts. From some cause, with which we are not 

 acquainted, longitudinal fissures have taken place in this 

 stratum in all directions, breaking the shells and other marine 

 bodies thus fixed, and leaving a certain interval between the 

 broken parts. A second petrifaction or spathic infiltration of 

 a white colour, supervened to fill exactly not only all the 

 fissures, but also the concave mould of the shells which had 

 disappeared, as may be remarked in certain black marbles. 



A third sort of petrifaction seems to have taken place in the 

 breccie. — For, in the debris of which they are composed are 

 found fragments which appear to have been divided and then 

 rejoined by a spathic crystallization which has no analogy with 

 that which unites together all these fragments. Certain 

 marbles seem to have broken twice in the same places, since 

 the same clift is found filled with two parallel infiltrations, one 

 of which is white and the other yellow. 



M. de France mentions an orthoceratite in his possession, 

 found in the stratum of brown marble of Valognes. This 

 fossil is traversed, in different directions, by sinuous veins of 

 calcareous spath from half a line to two lines in breadth ; and, 

 what is singularly remarkable is, that one of these veins tra- 

 verses in their diameter some partitions, whose separated parts 

 do not correspond one before the other as before the separa- 

 tion. This fact seems to prove that the marine body, filled 

 with paste, must have been cleft after its petrifaction, and that 

 the calcareous spath then succeeded, and was crystallized in 

 the cleft. Still one can scarcely conceive, according to what is 

 seen to take place in our own days, how two clefts could have 

 taken place within half a line distant from each other. There 

 is nothing analogous to a fact of this kind, except the clefts 

 produced by humidity in a chalky stone, or dried potters' 

 earth. How, again, is it possible to explain certain spathic 

 veins nearly parallel, and sometimes very closely approximated 

 to each, which are found to traverse some of those shelly frag- 

 ments, and which, without destroying them, cut most exactly 



