The geologic ages are as follows: 1. The Archæan, including the time when was no life and the time of the earliest and simplest forms of life. 2. The age of Invertebrates, or the Silurian, when the life on the globe consisted distinctively of invertebrates. 3. The age of Fishes, or the Devonian, when fishes were the dominant race. 4. The age of Coal Plants, or Acrogens, or the Carboniferous age. 5. The Mesozoic or Secondary age, or age of Reptiles, when reptiles prevailed in great numbers and of vast size. 6. The Tertiary age, or age of Mammals, when the mammalia, or quadrupeds, abounded, and were the dominant race. 7. The Quaternary age, or age of Man, or the modern era. Dana.