Organic Remains of Burdiehouse. 



293 



lime are unchanged in their nature, whilst the animal matter has 

 been converted into a hydrated siliceous substance. The miner- 

 alizing substance of the silicefied shells is often also a hydrated 

 silica or opal.* 



As we possess one or two analyses of recent fish bones, we are 

 also enabled to institute a comparison between the result of these 

 analyses and that of the fossil bony rays. The following are the 

 constituents found by Dumenil in the bones of the pike, and by 

 Chevreul in those of the cod.f 



Phosphate of Lime, 

 Carbonate of Lime, 

 Animal matter, 

 Traces of Soda, &c. and loss, 



Pike. 

 55.26 



6.16 

 37.36 



1.32 





100.00 





Cod. 



Phosphate of Lime, 



47.96 



Carbonate of Lime, 



5.50 



Animal Matter and Moisture, 



43.94 



Phosphate of Magnesia, 



2. 



Soda Salt, .... 



6. 



105. 



The first circumstance that here strikes us, is, that the pro- 

 portion of phosphate of lime is almost identical in the recent 

 bones of the pike, and in those of the ancient Gyracanthus of 

 Burdiehouse ; and it is very remarkable, that if we suppose the 

 animal matter in the fresh bones of the Gyracanthus to be re- 

 placed partly by siliceous and partly by calcareous matter, — a 

 supposition sufficiently legitimate, because both these matters are 

 present in the matrix, and both are soluble in water under favour- 



* In examining, however, the insoluble siliceous matter of the scales by the blow- 

 pipe, it appears not to be a quite pure hydrated silica, but probably to contain a 

 small quantity of lime. 



f Berzelius, Lehrb. iv. 448. 



