52 



THE DAWN OP LIFE. 



become gradually finer as they recede from the pyroxene, and 

 occasionally occupy a total thickness of five or six inches. 

 These portions constitute the unbroken fossil, which may 

 sometimes spread over an area of about a square foot, or per- 

 haps more. Other parts, immediately on the outside of the 

 sheet of serpentine, are occupied with about the same thick- 

 ness of what appear to be the ruins of the fossil, broken up 

 into a more or less granular mixture of calc-spar and serpen- 

 tine, the former still showing minute structure ; and on the 

 outside of the whole a similar mixture appears to have been 

 swept by currents and eddies into rudely parallel and curving 

 layers ; the mixture becoming gradually more calcareous as it 

 recedes from the pyroxene. Sometimes beds of limestone of 

 several feet in thickness, with the green serpentine more or 

 less aggregated into layers, and studded with isolated lumps 

 of pyroxene, are irregularly interstratified in the mass of 

 rock ; and less frequently there are met with lenticular patches 

 of sandstone or granular quartzite, of a foot in thickness and 

 several yards in diameter, holding in abundance small dis- 

 seminated leaves of graphite. 



" The general character of the rock connected with the fossil 

 produces the impression that it is a great Foraminiferal reef, 

 in which the pyroxenic masses represent a more ancient por- 

 tion, which having died, and having become much broken up 

 and worn into cavities and deep recesses, afforded a seat for a 

 new growth of Foraminifera, represented by the calcareo-ser- 

 pentinous part. This in its turn became broken up, leaving 

 in some places uninjured portions of the general form. The 

 main difference between this Foraminiferal reef and more re- 

 cent coral-reefs seems to be that, while in the latter are usually 

 associated many shells and other organic remains, in the more 

 ancient one the only remains yet found are those of the animal 

 which built the reef." 



(B.) Note by Sir William E. Logan, on Additional 



Specimens of Eozoon. 



[Journal of Geological Society, August, 1867.] 



" Since the subject of Laurentian fossils was placed before 

 this Society in the papers of Dr. Dawson, Dr. Carpenter, Dr. 



