38 MANUAL OP ZOOLOGY. 



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 Paleozoic or Primary, Mesozoic 

 or Secondary, and Kainozoic, or Tertiary. 



The Paleozoic, 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. 



I. PALEOZOIC 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.) 



11. Miocene. (Lower and Upper.) 



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



13. Post-tertiary. (Post-pliocene, and Recent.) 



