xii LIST OF ILLUSTRATIONS 



FIGURE PAGE 



94. Geologic structure section through one of the anthracite coal 



fields of eastern Pennsylvania 160 



95. Geologic (columnar) section in western Pennsylvania showing the 



vertical distribution of coal beds (heavy black bands) and their 

 relations to associated strata 162 



96. Paleogeographic map of North America during Pennsylvanian time 165 



97. Sketch map showing the relations of land and water in Europe 



during Pennsylvanian (Upper Carboniferous) time 167 



98. Lepidodendron bark (a) and Sigillarian bark (6), showing arrange- 



ment of leaf scars 170 



99. Fronds of a Pennsylvanian Fern, Mariopteris 171 



100. A Living Tree-fern 172 



101. A Permo-Carboniferous landscape, showing some of the most 



conspicuous plants of the great Coal Age 173 



102. A Cycadofilices or Seed-fern 174 



103. Cordaites restored 175 



104. A Pennsylvanian Goniatite 175 



105. Pennsylvanian Eucrustaceans 176 



106. Pennsylvanian Arachnids 176 



107. A Pennsylvanian Insect, Corydaloides scudderi (Brogniart) .... 177 



108. A Pennsylvanian Amphibian (Labyrinthodont), Eryops 178 



109. Transverse section of a Labyrinthodont tooth 179 



110. Late Permian or early Triassic "Red Beds" in Red Butte, eastern 



Wyoming 182 



111. Paleogeographic map of North America during latest Paleozoic 



(Permian) time 184 



112. Highly generalized structure sections across the Appalachian 



Mountains and adjoining districts to illustrate certain impor- 

 tant features in the history of the region 186 



113. Structure section through a portion of the Appalachian Moun- 



tains of western Virginia showing the typical deformation of 

 Paleozoic strata 187 



114. Sketch map showing the relations of land and water in Europe 



during later Permian time 189 



115. A Permian chambered Cephalopod, Waagenoceras cumminsi 



(White), showing highly folded suture (partition) lines .... 191 



116. A Permian Reptile, Pareiasaurus serrideus 192 



117. A Permian Reptile (Pelycosaurian), Naosaurus claviger 192 



118. Highly generalized paleogeographic map of North America during 



the Paleozoic era 196 



119. Map showing the surface distribution (areas of outcrops) of Triassic 



and Jurassic strata in North America 202 



120. Structure section across the Triassic basin of the Connecticut 



Valley near Northampton, Mass., showing the tilted and faulted 

 character of the rocks 203 



121. Tilted and faulted Triassic sandstone in the Connecticut Valley near 



Northampton, Mass 204 



122. Columnar (geologic) section showing ages, character and thickness 



of strata in northeastern Wyoming 205 



