42 PRINCIPLES OF PALEONTOLOGY. 



rarely find many of the primary formations following one 

 another consecutively and in their regular order. 



In no case, however, do we ever find the Devonian resting 

 upon the Carboniferous, or the Silurian rocks reposing on the 

 Devonian. We have therefore, by a comparison of many 

 different areas, an established order of succession of the strati- 

 fied formations, as shown in the subjoined ideal section of the 

 crust of the earth (fig. 1 7). 



The main subdivisions of the stratified rocks are known by 

 the following names : 



1. Laurentian. 



2. Cambrian (with Huronian ?). 



3. Silurian. 



4. Devonian or Old Red Sandstone. 



5. Carboniferous. 



8. Jurassic or Oolitic. 



9. Cretaceous. 



10. Eocene. 



11. Miocene. 



12. Pliocene. 



13. Post-tertiary. 



