Geological Epoch | Petrographic | Ascendant Form | Thickness Sub-Division | Formation | of Life | of of G. E. | | | Deposits | | | Paleozoic | | | | | | Laurentian | Archaic Igneous | Eozoon | | Rocks | Canadense | 30,000 ft. Cambrian or | | | L. Silurian | Potsdam Sandstone |} | | Magnesian Limestone |} Diatoms | 18,000 ft. | Trenton Limestone |} | | | | Upper Silurian| Niagara Limestone |} | | Medina Sandstone |} | | Saline Formations |} Lower Fishes | 22,000 ft. | Lower Helderberg |} | | Oriskany Sandstone |} | | | | Devonian | Corniferous or |} | | Upper Helderberg |} | | Limestone, |} Dipnoi | | Hamilton, |} | | Portage and Chemung|} | | Shales |} | | | | Carboniferous | Crinoidal Limestone |} | | Lower Coal Measures |} | | Mill Stone Grit |} Amphibia and | 42,000 ft. | Upper Coal Measures |} Sagillaria | | Permian Sandstone |} | | | | Mesozoic | | | | | | Triassic | Sandstones | Monotremes and | | | Gymnosperms | Jurassic | Wassatch Mountains | Marsupials | 15,000 ft. | | | Cretaceous | Sandstone and Chalk | Placentals | | | | Cenozoic | | | | | | Tertiary-- | | Lowest Primates | Eocene | | and Angiosperms| 3,000 ft. Miocene | | Simiæ | Pliocene | | Catarrhinæ |