Leaving the Eozoic age, we find ourselves next in the Primordial or Cambrian, and here we discover the sea already tenanted by many kinds of crustaceans and shell-fishes, which have been collected and described by palæontologists in Bohemia, Scandinavia, Wales, and North America;[AI] curiously enough, however, the rocks of this age are not so rich in Foraminifera as those of some succeeding periods. Had this primitive type played out its part in the Eozoic and exhausted its energies, and did it remain in abeyance in the Primordial age to resume its activity in the succeeding times? It is not necessary to believe this. The geologist is familiar with the fact, that in one formation he may have before him chiefly oceanic and deep-sea deposits, and in another those of the shallower waters, and that alternations of these may, in the same age or immediately succeeding ages, present very different groups of fossils. Now the rocks and fossils of the Laurentian seem to be oceanic in character, while the Huronian and early Primordial rocks evidence great disturbances, and much coarse and muddy sediment, such as that found in shallows or near the land. They abound in coarse conglomerates, sandstones and thick beds of slate or shale, but are not rich in limestones, which do not in the parts of the world yet explored regain their importance till the succeeding Siluro-Cambrian age. No doubt there were, in the Primordial, deep-sea areas swarming with Foraminifera, the successors of Eozoon; but these are as yet unknown or little known, and our known Primordial fauna is chiefly that of the shallows. Enlarged knowledge may thus bridge over much of the apparent gap in the life of these two great periods. [Footnote AI: Barrande, Angelin, Hicks, Hall, Billings, etc.]