DISTRIBUTION IN TIME. 55 



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 ?nd ascending to the present day (fig. 5). 



I. PAL/EOZOIC OR PRIMARY ROCKS. 



1. Laurentian. (Lower .and Upper.) 



2. Cambrian. (Lower and Upper, with Huronian rocks?) 



3. Silurian. (Lower and Upper.) 



4. Devonian, or Old Red Sandstone. (Lower, Middle, and 

 Upper.) 



5. Carboniferous. (Mountain-limestone, Millstone-grit, and 

 Coal-measures.) 



6. Permian. ( = the lower portion of the New Red Sand- 

 stone.) 



11. MESOZOIC "OR SECONDARY ROCKS. 



7. Triassic Rocks. (Bunter Sandstein, or Lower Trias ; 

 Muschelkalk, or Middle Trias ; Keuper, or Upper Trias.) 



8. Jurassic Rocks. (Lias, Inferior Oolite, Great Oolite, 

 Oxford Clay, Coral Rag, Kimmeridge Clay, Portland Stone, 

 Purbeck beds.) 



9. Cretaceous Rocks. (Wealden, Lower Greensand, Gault, 

 Upper Greensand, White Chalk, Maestricht beds.) 



* III. KAINOZOIC OR TERTIARY ROCKS. \ , - ^ 



10. Eocene. (Lower, Middle, and Upper.) 

 TI. Miocene. (Lower and Upper.) ! 



12. Pliocene. (Older Pliocene and Newer Pliocene.) 



13. Post-tertiary. (Post-pliocene and Recent^) :: 



