85 



It is remarkable that the composition of these scales is very ana- 

 logous to that of the scales of the recent Lepisosteus, if we suppose 

 the perishable animal matter in the latter to be replaced by infiltra- 

 tion by the hydrated siliceous matter in the fossil scales. In those 

 of the recent Lepisosteus, Chevreul found — 



Phosphate of Lime, 

 Carbonate of Lime, 

 Gelatinous Animal matter 

 Phosphate of ilagnesia, 

 Fatty matter, . 

 Carbonate of Soda, . 



46-20 



1000 



4110 



2-2 



•10 



•10 



100- 



The result of the analysis of the bony rays of the Gyracanthus 

 may also be compared with the constitution of certain recent fish 

 bones. Those of the pike, as determined by Dumenil, consist of — 



Phosphate of Lime, 

 Carbonate of Lime, 

 Animal matter, 

 Traces of Soda, and loss. 



55-26 

 616 



37-36 

 1-32 



100- 



If we suppose the animal matter to be replaced partly by siliceous 

 matter and partly by carbonate of lime, the composition of the recent 

 and of the fossil bones becomes very similar. 



The ratio of the phosphate of lime to the carbonate of lime in the 

 Coprolites, according to the analysis formerly communicated to the 

 Society, does not differ much from the proportions in the above ana- 

 lysis of recent fish bones. The Coprolites may therefore be viewed 

 as aggregated masses of fish-bone earth, the animal matter having 

 decayed almost without any substitution, from fecal matter not pos- 

 sessing that structure and solidity which seem usually essential to 

 the proper process of mineralization by infiltration. Since his for- 

 mer communication, the author has found a trace of fluoride of cal- 

 cium in the Coprolites. 



It is remarkable that the limestone matrix itself contains a very 

 decided trace of animal matter, doubtless derived from the great 

 quantity of animal remains which have been entombed in it. 



