54 



MANUAL OF ZOOLOGY. 



IDEAL SECTION OF THE CRUST OF THE EARTH. 



rig. 5 ; 



)o Post-Tertiary and Recent. 

 |- Pliocene. 



Miocene. 

 Eocene. 



Cretaceous. 



Oolitic or Jurassic. 



Triassic. 



Permian. 



Carboniferous. 



Devonian, or Old Red Sandstone. 



Silurian. 



Cambrian. 

 Huronian. 



Laurentian. 



