IV CONTENTS. 



PAOB 



faunas, 52. The middle Triassic faunas, 54. The later Trias- 

 sic faunas, 55. General nature of the fauna, 55. The 

 cephalopods again in leadership, 56. Old and new gastropod 

 types, 56. The transition and rise of the pelecypods, 56. 

 The change in the type of brachiopods, 57. The echinoids 

 become the leading echinoderms, 57. The corals, 57. Other 

 forms, 57. 



CHAPTER XIII. 

 THE JURASSIC PERIOD. 



Formations and Physical History 59 



The eastern part of the continent, 59. The western part 

 of the continent, 61. The Lower and Middle Jurassic of the 

 Pacific coast, 61. Lower and Middle Jura in the western in- 

 terior, 63. The Upper Jurassic, 64. Surface distribution and 

 position of beds, 67. Jurassic in Alaska, 67. 



Close of the Jurassic, in America 67 



Orogenic movements, 67. Changes in geography, 69. 



Foreign Jurassic 70 



Europe, 70. Lower Jura or Lias, 72. Middle Jura, 73. 

 The Upper Jura, 74. Extra-European Jurassic, 77. Arctic 

 lands, 77. Asia, 77. Africa, 77. Australia, 78. Central 

 and South America, 78. 



Coal 78 



Geography of the Jurassic Period 78 



Climate 79 



Close of the Jurassic, in Europe 79 



The Jurassic Life 80 



The Marine Life 80 



Marine reptiles, 86. The American marine faunas, 90. 

 The northern and more interior province, 92. 



The Land Life 94 



I. The Vegetation 94 



II. The Land Animals 95 



Classificatory difficulties, 95. The Jura-Comanchean 

 development of the land vertebrates, 97. The dominance 

 of the dinosaurs, 97. Other reptilians, 100. The advent 

 of aerial life; the pterosaurs, 101. The appearance of true 

 birds, 102. The non-placental mammals, 103. The in- 

 sects, 104. 



