ON THE CLASSIFICATION OF THE TERTIAKY PEEIOD. 379 



29. The Classification of the Tertiary Period hy means of the Mam- 

 malia. By W. Boyd Dawkins, M.A., F.R.S., F.G.S., Professor 

 of Geology in Owens College. (Bead April 14, 1880.) 



Contents. 



1. Introduction. 



2. The Value of Invertebrates and Vertebrates in Classification. 



3. The Principle of Classification. 



4. The Eocene Mammalia of Britain and France. 



5. Characteristic Forms of the Three Eocene Divisions. 



6. The Miocene Mammalia. 



7. The Lower-Miocene Mammalia of France. 



8. The Characteristic Lower-iMiocene Forms. 



9. The Mid- Miocene Mammalia of France. 



10. The Characteristic Mid-Mioceue Forms. 



11. The Upper-Miocene Mammalia. 



12. The Charactei-istic Upper-Miocene Forms 



13. The Lower-Pliocene Mammalia of France. 



14. The Upper-Pliocene Mammalia of France and Italy. 



15. The Characteristic Upper-Pliocene Forms. 



16. The Development of Antlers in the Deer. 



17. The Pleistocene Mammalia. 



18. The Early Pleistocene Mammals of Britain. 



19. The Magnitude of the Break between the Plio- and Pleistocene Periods. 



20. The Mid-Pleistocene Mammalia of Britain. * ^- 



21. The Late Pleistocene Mammalia of Britain. 



22. The Prehistoric Mammalia of the British Isles. 



23. The Characteristic Forms. 



24. The Historic Mammalia of the British Isles. 



25. The Prehistoric and Historic Divisions belong to the Tertiary Period. 



26. General Conclusions. 



1. Introduction. 



The classification of the Tertiary, or the third of the great life- 

 periods, sketched in outline more than fifty years agO; and since then 

 altered in no important degree, seems to me not to be in harmony 

 with our present knowledge ; and the definitions of the series of 

 events which took place in it have been materially modified by 

 recent discoveries in various parts of the world. The terms 

 Eocene, Miocene, and Pliocene* no longer express the idea of per- 

 centages of living species on which they were based, and Qua- 

 ternary, Post-Tertiary, and Eecent are founded on an assumed great 

 break in the life-history between the present day and the Tertiary 

 period, comparable to that which separates the Secondary from the 

 Tertiary or the Primary periods, a break which has been disproved by 

 more recent inquiries. It has therefore seemed to me opportune to lay 

 before the Society the results of the investigations which I have 

 carried on for some years into these questions, and to propose a 

 classification of the Tertiary period of Europe by appealing to the 



* The "Miocene" and " Pliocene " of the text have been substituted for the 

 " Meiocene " and " Pleiocene " of the author, which appear to him to agree better 

 with their Greek roots, 



