Marine
reptiles, of a snake-like structure, ran to fifteen feet in
length. Crocodiles and alligators swarmed in the rivers of Europe
until the chilly Pliocene bade them depart to Africa.
In a word, it was the seven years of plenty for the whole living
world, and the expansive development gave birth to the modern
types, which were to be selected from the crowd in the subsequent
seven years of famine. We must be content to follow the evolution
of the higher types of organisms. I will therefore first describe
the advance of the Tertiary vegetation, the luxuriance of which
was the first condition of the great expansion of animal life;
then we will glance at the grand army of the insects which
followed the development of the flowers, and at the accompanying
expansion and ramification of the birds. The long and interesting
story of the mammals must be told in a separate chapter, and a
further chapter must be devoted to the appearance of the human
species.
We saw that the Angiosperms, or flowering plants, appeared at the
beginning of the Cretaceous period, and were richly developed
before the Tertiary Era opened. We saw also that their precise
origin is unknown.
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