FOSSILIFEROUS ROCKS. 



21 



solid compact rock by infiltrated carbonate of lime^ occur in 

 the north-east of Arran, which contain numerous stems, 

 branches, and fruits of carboniferous plants. These represent 

 the remains of successive forests which grew on this locality, 

 and were one after the other destroyed by the ash-showers 

 poured forth from a neighbouring volcano during its inter- 

 mittent periods of activity. 



Fossil remains are extremely rare in certain rocks, which, 

 from the changes they have undergone, have been deno- 

 minated Metamorphic. These include Gneiss and Mica-slate, 

 which are stratified rocks subsequently altered by heat and 

 other causes, and so completely metamorphosed that the 

 traces of organisms have been nearly obliterated. Never- 

 theless, recognisable traces of plant and animal remains have 

 been found in what were recently thought to be azoic rocks. 

 The absence of organic remains in rocks is therefore not 

 sufficient to enable us to state that these rocks were formed 

 before animals or vegetables existed. 



The stratified rocks which contain fossils have been 

 divided into three great groups — the Pala30zoic, the Second- 

 ary, and the Tertiaiy, or into Pala30zoic and Neozoic groups. 

 The formations included under these are exhibited in the 

 following table, taken from Lyell's Manual of Geology : — 



1. Recent. 



2. Post Pliocene. 



3. Newer Pliocene. 



4. Older Pliocene. 



5. Upper Miocene. 



6. Lower Miocene. 



7. Upper Eocene. 



8. Middle Eocene. 



9. Lower Eocene. 



10. Maestricht Beds. 



11. White Chalk. 



12. Chloritic Series. 



13. Gault. 



14. Neocomian. 



15. Wealden. 



> Post Tertiary. 



Pliocene. 

 Miocene. 



Eocene. 



Cretaceous. 



Eecent. 



Tertiary 

 or 

 ! Cainozoic. 



1 



Secondary 



or 

 Mesozoic. 



JSTeozoic. 



