Just as Fishes prevailed in the primary epoch, _Reptiles_ predominated in the secondary epoch over all other vertebrate animals. It is true that during this period the first birds and mammals originated; at that time, also, there existed important amphibious animals, especially the gigantic Labyrinthodonts, in the sea the wonderful sea-dragons, or Halisaurii, swam about, and the first fish with bones were associated with the many primæval fishes (Sharks) and enamelled fish (Ganoids) of the earlier times; but the very variously developed kinds of reptiles formed the predominating and characteristic class of vertebrate animals of the secondary epoch. Besides those reptiles which were very nearly related to the present living lizards, crocodiles, and turtles, there were, during the mesolithic period, swarms of grotesquely shaped dragons. The remarkable flying lizards, or Pterosaurii, and the colossal land-dragons, or Dinosaurii, of the secondary epoch, are peculiar, as they occur neither in the preceding nor in the succeeding epochs. The secondary epoch may be called the era of _Reptiles_; but on the other hand, it may also be called the era of _Pine Forests_, or more accurately, of the _Gymnosperms_, that is, the epoch of _plants having naked seeds_. For this group of plants, especially as represented by the two important classes—the pines, or _Coniferæ_, and the palm-ferns, or _Cycadeæ_—during the secondary epoch constituted a predominant part of the forests. But towards the end of the epoch (in the Chalk period) the plants of the pine tribe gave place to the leaf-bearing forests which then developed for the first time. SURVEY _Of the Palæontological Periods, or of the Greater Divisions of the Organic History of the Earth._ I. _First Epoch_: ARCHILITHIC ERA. _Primordial Epoch._ (Era of Skull-less Animals and Forests of Tangles.) 1. Older Primordial Period or Laurentian Period. 2. Middle Primordial Period ” Cambrian Period. 3. Later Primordial Period ” Silurian Period. II. _Second Epoch_: PALÆOLITHIC ERA. _Primary Epoch._ (Era of Fish and Fern Forests.) 4. Older Primary Period or Devonian Period. 5. Mid Primary Period ” Coal Period. 6. Later Primary Period ” Permian Period. III. _Third Epoch_: MESOLITHIC ERA. _Secondary Epoch._ (Era of Reptiles and Pine Forests.) 7. Older Secondary Period or Trias Period. 8. Middle Secondary Period ” Jura Period. 9. Later Secondary Period ” Chalk Period. IV. _Fourth Epoch_: CÆNOLITHIC ERA. _Tertiary Epoch._ (Era of Mammals and Leaf Forests.) 10. Older Tertiary Period or Eocene Period. 11. Newer Tertiary Period ” Miocene Period. 12. Recent Tertiary Period ” Pliocene Period. V. _Fifth Epoch_: ANTHROPOLITHIC ERA. _Quaternary Epoch._ (Era of Man and Cultivated Forests.)