n
| | Invertebrates. |Species
| | |appear.
|Miocene. |Living Invertebrates more|
| | numerous. |
| | |
|Pliocene. |Living Invertebrates |
| | still more numerous. |
--------------------------------------------------------------------
V. |Post-Pliocene. |First living Mammals. |Existing
POST- | |Living Invertebrates |vegetation.
TERTIARY | | prevalent. |
OR | | |
MODERN |Post-Glacial |Man and living Mammals. |
PERIOD. |and Recent. | |
====================================================================

The oldest fossil remains known are the Protozoa of the Laurentian
rocks. In the succeeding Cambrian or Primordial rocks we find many
extinct species of zoophytes, shell-fish, and crustaceans, and the
algae or sea-weeds. In the Palaeozoic period as a whole, though numerous
Batrachian or Amphibian reptiles existed toward its close, the higher
orders of fishes seem to have been the dominant tribe of animals; and
vegetation was nearly limited to cryptogams and gymnosperms. In the
Mesozoic period, though small mammalia had been created, large
terrestrial and marine reptiles were the ruling race, and fishes
occupied a subordinate position; while, at the close, the higher
orders of plants took a prominent place. In the Tertiary and Modern
eras, the mammalia, with man, have assumed the highest or dominant
position in nature.

On this series of groups, and the succession of living beings, Sir. C.
Lyell remarks "It is not pretended that the principal sections called
Primary, Secondary, and Tertiary are of equivalent importance, or that
the subordinate groups comprise monuments relating to equal portions
of time or of the earth's history. But we can assert that they each
relate to successive periods, during which certain animals and plants,
for the most part peculiar to their respective eras, flourished, and
during which different kinds of sediment were deposited."

We have already, in previous chapters, noticed the parallelism of the
succession of life in the earth as revealed in Gen