Xll CONTENTS. 



PART III —Historical Geology. 



PAGE ' 



General Divisions in the History 125 



I. AZOIC TIME or AGE 134 



Review of the Animal Kingdom 147 



Review of the Vegetable Kingdom 165 



II. PALAEOZOIC TIME 167 



I. Age of Mollusks, or Silurian Age 167 



A. Lower Silurian 171 



1. Potsdam or Primordial Period (Potsdam and 



Calciferous Epochs) 171 



[Review of the Order of Brachiopods 179 



2. Trenton Period (Chazy and Trenton Epochs) 205 



3. Hudson Period (Utica and Hudson River Epochs) 217 



4. General Observations on the Trenton and 



Hudson Periods 222 



Disturbances closing the Lower Silurian Era, and 



Geographical Results 226 



B. American Upper Silurian 229 



1. Niagara Period 229 



1. Oneida Epoch 230 



2. Medina Epoch 231 



3. Clinton Epoch 233 



4. Niagara Epoch 237 



General Observations on the Niagara Period... 243 



2. Salina Period (Leclaire and Saliferous Epochs).. 246 



3. Lower Helderberg Period 251 



Observations on the American Upper Silurian 256 



C. Foreign Upper Silurian 260 



II. Age op Fishes, or Devonian Age 265 



1. American Subdivisions 265 



1. Oriskany Period 266 



2. Corniferous Period (Cauda-Galli, Schoharie, and 



Upper Helderberg Epochs) 269 



[Review of the Class of Fishes 277 



3. Hamilton Period (Marcellus, Hamilton, and 



Genesee Epochs) 280 



4. Chemung Period (Portage and Chemung Epochs) 287 



5. Catskill Period 291 



2. Foreign Devonian 294 



3. General Observations on the Devonian Age 299 



4. Disturbances closing the Devonian Age 304 



