DISTRIBUTION. 



45 



4. The series of aqueous rocks is capable of being divided 

 into a number of definite groups of strata, which are technically 

 called " formations." 



5. Each of these definite rock groups, or " formations," is 

 characterised by the occurrence of an assemblage of fossil 

 remains more or less peculiar and confined to itself. 



6. The majority of these fossil forms are " extinct" that is 

 to say, they do not admit of being referred to any species at 

 present existing. 



7. No fossil, however, is known, which cannot be referred 

 to one or other of the primary subdivisions of the Animal 

 Kingdom, which are represented at the present day. 



8. When a species has once died out, it never reappears. 



9. The older the formation, the greater is the divergence 

 between its fossils and the animals and plants now existing on 

 the globe. 



10. All the known formations are divided into three great 

 groups, termed respectively Palaeozoic or Primary, Mesozoic 

 or Secondary, and Kainozoic or Tertiary. 



The Palaeozoic or Ancient-life period is the oldest, and is 

 characterised by the marked divergence of the life of the period 

 from all existing forms. 



In the Mesozoic or Middle-life period, the general fades of 

 the fossils approaches more nearly to that of our existing fauna 

 and flora ; but with very few exceptions the characteristic 

 fossils are all specifically distinct from all existing forms. 



In the Kainozoic or New-life period, the approximation of 

 the fossil remains to existing living beings is still closer, and 

 some of the forms are now specifically identical with recent 

 species ; the number of these increasing rapidly as we ascend 

 from the lowest Kainozoic deposit to the Recent period. 



Subjoined is a table giving the more important subdivisions 

 of the three great geological periods, commencing with the 

 oldest rocks and ascending to the present day (Fig. i). 



