CONTENTS 



PAOK 



Preface v 



CHAPTER I. INTRODUCTION 



I. Philosophy of the Structure of Mammals 1 



Rise of Palivontology .1 



Law of Correlation ........... 2 



Systematic Palaeontology 4 



Darwin's Influence 5 



Primitive and Progressive Stages 7 



Precise and Philosophical Research 7 



Influence of American Discovery ' . 9 



Primitive and Progressive Forms of Teeth .10 



Primitive and Progressive Foot Structure 13 



Primitive and Progressive Skull Structure 17 



II. Mammals and their Environment 18 



Origin and Migration . . .19 



The Law of Adaptive Radiation 22 



The Orders of Mammals 25 



Adaptive Radiation and Geography 29 



The Polyphyletic Law 30 



Adaptations to Alternations of Habitat ....... 31 



The Law of Analogous Evolution . 32 



The Law of Irreversibility of Evolution . 34 



III. Geographic or Space Distribution of Mammals . . . .35 



Zoogeography 35 



Migration Routes and Barriers 38 



IV. Geologic or Time Distribution of Mammals 39 



Time Divisions 39 



Preliminary Correlation .......... 41 



Importance of Time Correlation .42 



Time Value of Fossils . 44 



Geologic Formations and Life Zones .47 



Progressive Correlation . 50 



Geologic Formations as a Record of Environments ..... 53 



V. Duration of the Age of Mammals 58 



Mountain Births ............ 58 



Modes of Estimating Caenozoic Time 01 



Length of the Cienozoic Era 63 



VI. The World Supply of Mammals 64 



Mammals of the Northern Hemisphere, Holarctica 65 



Africa as a Center of Mammalian Evolution . . . " . . .68 



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