CONTENTS. V 



CHAPTER XIV. 

 THE COMANCHEAN (LOWER CRETACEOUS) PERIOD. 



PAGE 



Formations and Physical History 106 



Introductory 106 



The Comanchean (Shastan, Lower Cretaceous) System 108 



The Atlantic and Gulf Border regions, 108. Constitution 

 and structure of the Potomac and Tuscaloosa series, 112. 

 Stratigraphic relations, 114. Thickness, 115. The Texas 

 region, 115. ' Westward and northward extension, 117. In 

 Mexico, 118. The Northern Interior, 119. The Pacific 

 Border, 122. In the United States, 122. North of the 

 United States, 123. Panama, 124. 



The Close of the Comanchean (Lower Cretaceous) Period 124 



The Lower Cretaceous in Other Continents 125 



In Europe, 128. Other continents, 129. Climate, 129. 



Close of the Period 130 



The Life of the Comanchean Period 130 



The terrestrial vegetation, 130. The introduction of 

 angiosperms, 130. The land animals, 133. The fresh-water 

 fauna, 134. The marine faunas, 134. 



CHAPTER XV. 



THE (LATER) CRETACEOUS PERIOD. 



Formations and Physical History 137 



The Atlantic Border Region 137 



Thickness, 140. Classification, 140. Changes in the beds 

 since deposition, 140. The Gulf border region east of the 

 Mississippi, 140. The western Gulf border region, 142. 



The Western Interior 144 



The Dakota formation, 144. The Colorado series, 148. 

 The origin of chalk, 149. The Montana series, 151. The 

 Laramie series, 152. Transition beds between Mesozoic and 

 Cenozoic, 154. Coal, 159. Thickness of the (Upper) Creta- 

 ceous system, 160. 



The Pacific Coast 160 



Climate 161 



