OOLITIC ERA. 



131 



as numerical abundance, and indicates genial and continu- 

 ous geographical conditions so genial as to give rise in 



Palm, Screw-pine, Araucaria, Cycas, Tree-fern, &c. 



many areas (Europe, India, the Indian Islands, and North 

 America) to repeated and valuable deposits of coal. Indeed, 

 many coal-fields at one time attributed to the carboniferous 



