Age of Amphibians PALÆOZOIC Permian. Age of Acrogens and Fishes. Carboniferous. and Gymnosperms. Erian, or Devonian. Age of Mollusks, Upper Silurian. Corals, and Lower Silurian, or Crustaceans. Siluro-Cambrian. Cambrian or Primordial. Age of Algæ. Age of Protozoa, EOZOIC Huronian. Beginning of Age and dawn of Upper Laurentian. of Algæ. Animal Life. Lower Laurentian. [Illustration: Plate II. MAP SHEWING THE DISTRIBUTION OF THE LAURENTIAN LIMESTONES HOLDING EOZOON IN THE COUNTIES OF OTTAWA & ARGENTEUIL. _Drawn by M. R. Barlow_ _Stanford's Geog. Estab^t. Charing Cross, London._ Reprinted with additions from the Report of the Geology of Canada, by Sir W. Logan, F.R.S., 1863.] CHAPTER II. THE LAURENTIAN ROCKS. As we descend in depth and time into the earth's crust, after passing through nearly all the vast series of strata constituting the monuments of geological history, we at length reach the Eozoic or Laurentian rocks, deepest and oldest of all the formations known to the geologist, and more thoroughly altered or metamorphosed by heat and heated moisture than any others. These rocks, at one time known as Azoic, being supposed destitute of all remains of living things, but now more properly Eozoic, are those in which the first bright streaks of the dawn of life make their appearance.[A] [Footnote A: Dana has recently proposed the term "_Archæan_," on the ground that some of these rocks are as yet unfossiliferous but as the oldest known part of them contains fossils, there seems no need for this new name.]