THE PRESERVATION OP EOZOON. 



103 



that when decalcified these are most beautifully repre- 

 sented by their casts, Dr. Hunt has proved the filling 

 mineral to be a silicate of alumina, iron, magnesia 

 and potash, intermediate between serpentine and 

 glauconite. We have, therefore, ample warrant for 

 adhering to Dr. Hunt's conclusion that the Lauren- 



FIG. 25. Joint of a Crinoid, having its pores injected with a 



Hydrous Silicate. 

 Upper Silurian Limestone, Pole Hill, New Brunswick. Magnified 25 diameters. 



tian serpentine was deposited under conditions similar 

 to those of the modern green-sand. Indeed, indepen- 

 dently of Eozoon, it is impossible that any geologist 

 who has studied the manner in which this mineral 

 is associated with the Laurentian limestones could 

 believe it to have been formed in any other way. Nor 



