IX 



JHAPTKR PAGE 



XV. THE CAMBRIAN PERIOD 



FORMATIONS AND PHYSICAL HISTORY 344 



LIFE OF THE CAMBRIAN 358 



XVI. THE ORDOVICIAN (LOWER SILURIAN) PERIOD 



FORMATIONS AND PHYSICAL HISTORY 367 



LIFE 376 



XVII. THE SILURIAN (UPPER SILURIAN) PERIOD 



FORMATIONS AND PHYSICAL HISTORY 388 



LIFE 394 



XV HI. THE DEVONIAN PERIOD 



FORMATIONS AND PHYSICAL HISTORY 402 



LIFE 413 



XIX. THE MISSISSIPPIAN (EARLY CARBONIFEROUS) PE- 

 RIOD 



FORMATIONS AND PHYSICAL HISTORY 426 



LIFE 432 



XX. THE PENNSYLVANIAN (UPPER CARBONIFEROUS) PE- 

 RIOD 



FORMATIONS AND PHYSICAL HISTORY 441 



LIFE 458 



XXI. THE PERMIAN PERIOD 



FORMATIONS AND PHYSICAL HISTORY 470 



LIFE 475 



PROBLEMS OF THE PERMIAN 482 



THE MESOZOIC ERA 



XXII. THE TRIASSIC PERIOD 



FORMATIONS AND PHYSICAL HISTORY 484 



LIKE 493 



XXIII. THE JURASSIC PERIOD 



FORMATIONS AND PHYSICAL HISTORY 502 



LIFE 1507 



XXIV. THE COMANCHEAN (LOWER CRETACEOUS) PERIOD 



FORMATIONS AND PHYSICAL HISTORY 523 



LIFE 528 



XXV. THE CRETACEOUS PERIOD 



FORMATIONS AND PHYSICAL HISTORY 532 



LIFE ...... 546 



