762 APPENDIX. 



General distribution of the rocks in America. — Kinds of rocks. — 176. Their 

 structural peculiarities. — 178. Kinds of plants. — 179. The Sub-kingdoms of ani- 

 mals represented. — The subdivisions of Protozoans represented. — Id. of Ra- 

 diates. — Id. of Mollusks, and the peculiarity in this respect of the Molluscan 

 Sub-kingdom. — 181. Id. of Articulates. — 182. The most abundant fossils. — 186. 

 Names of modern genera which began in the Potsdam Period. — 193. Relation 

 of Primordial life of Europe to that of America. — 195. Igneous ejections, and 

 copper mines of Keweenaw Point. — 196. Evidence as to North American 

 Geography in the Potsdam Period.— 197. Peculiarities in the thickness of the 

 deposits in the Appalachian region. — 199. Formation of the Lake Superior 

 sandstone and trap rocks. — 200. Origin of the material of the fragmental 

 rocks. — 201. Id. of limestones. — 202. Evidence as to the climate of the Period. 

 — Grades of life. — 203. Exterminations of life. — Reality of the Primordial 

 Period in America. 



IX. Lower Silurian, Concluded. — Page 205. The second Period in the Si- 

 lurian Age. — Its two Epochs. — Characteristics of the Period. — General distribu- 

 tion and thickness of the rocks. — 207. Resemblance of European to North 

 American. — Kinds of plants. — 208. The prevailing kinds of animal life in the 

 three Sub-kingdoms represented. — Two types wholly unfolded. — Absence of Ver- 

 tebrates. — Characteristics of Orthocerata. — Id. of Trilobites. — Id. of Bryozoans. 

 — 209. Importance of bivalve Crustaceans or Ostracoids. — 217. Third Period of 

 the Silurian Age. — Its two Epochs. — Kinds and general distribution of rocks. — 

 219. Kinds of plants. — Animal life. — 222. Evidence as to the Geography of 

 America in the Trenton and Hudson Periods. — 223. Subsidence in progress 

 during the formation of the deposits. — 224. Contrast between the Mississippi 

 basin and the Appalachian region. — Evidence as to climate. — 225. Explanation 

 of the exterminations of species. — 226. Recapitulation, as to fresh waters ; as to 

 life; as to the conditions of the continent. — Conditions of formation of the 

 deposits ; oscillations. — 227. Instances of unconformability, and what they prove. 

 — Evidence as to the time of origin of the Champlain valley. — 228. Increase 

 of dry land, and its effects. — 229. Disturbances in Europe. 



X. Upper Silurian. — Page 229. General characteristics of the Upper Silu- 

 rian. — Periods of the Upper Silurian. — Fourth Period of the Silurian, or first 

 of the Upper Silurian. — Epochs. — 230. First Epoch; general distribution of the 

 rocks. — Kinds of rock. — Life. — 231. Second Epoch ; general distribution of the 

 rocks, contrasting the Interior and Appalachian regions. — Kinds of rocks. — 

 232. Evidence from structural peculiarities. — Plants. — 233. Most common Mol- 

 lusks. — Third Epoch. — Distribution of rocks, comparing the Interior and Appa- 

 lachian regions. — Kinds of rocks. — 235. Plants. — Common kinds of animal life. 

 — The Sub-kingdoms represented. — 237. Fourth Epoch ; kinds of rocks and dis- 

 tribution. — 238. Thickness at the Falls of Niagara. — 239. General character of 

 the life. — 240, 241. The Sub-kingdoms represented. — 243. Geographical changes 

 in the Niagara Period. — 244. Review of the changes after the Trenton Period. — 

 245. Extent of changes or oscillations of level in the Appalachian and Interior 

 regions compared. — 246. Question as to the existence of land-plants. 



XI. — Upper Silurian, Concluded. — Page 246. Fifth Period of the Silurian, 

 or second of the Upper Silurian. — Kinds and distribution of rocks. — 248. Im- 

 portant minerals. — Mode of occurrence of the gypsum, and its origin. — Mode 



