28 OUR COMMON BRITISH FOSSILS. 



organic remains thus identified are those small and 

 beautiful objects, the foraminifera. Microscopically 

 small though they are, it is questionable whether the 

 bulk of our limestones is not more due to them than 

 even to ancient coral-reefs ! 



The fossil foraminifera are usually represented 

 by small limy shells, or casts of them. The creatures 

 to which these belonged were of very low organiza- 

 tion, rising scarcely above the zoological rank of the 

 little amcebas of our ponds and ditches. These 

 minute shells are abundantly perforated, in one 

 division, for the passage of spider's-web-like threads 

 of protoplasm which proceed from the animal's body ; 

 in another division the shells are imperforate. Some- 

 times the soft bodies were protected by walls of 

 minute sand-grains. The oldest so-called, but much 

 debated organism yet recognized, is Eozoon Canadense, 

 and this is regarded as a foraminifer. We pass over 

 the Eozoon, however, because its organic nature is 

 still held to be doubtful. "Eozoonal structure," as 

 it is now termed, is not confined to the oldest Lauren- 

 tian rocks. Professor King has discovered it in the 

 Ophite, or metamorphosed Liassic rocks of the island 

 of Lewis. It is also abundant in the green crystal- 

 line marbles, of Lower Silurian age, in Connemara, 

 in Ireland ; and something approaching it has been 

 found in Sutherlandshire. Now, the distribution of 

 lowly organized forms can never be safely accepted 

 as indicating the age of a rock. Naturalists are well 



