along with their descendants of the Mesozoic.





CHAPTER XX

THE MESOZOIC


With the close of the Permian the world of animal and vegetable
life had so changed that the line is drawn here which marks the
end of the old order and the beginning of the new and separates
the Paleozoic from the succeeding era,--the Mesozoic, the Middle
Age of geological history. Although the Mesozoic era is shorter
than the Paleozoic, as measured by the thickness of their strata,
yet its duration must be reckoned in millions of years. Its
predominant life features are the culmination and the beginning of
the decline of reptiles, amphibians, cephalopod mollusks, and
cycads, and the advent of marsupial mammals, birds, teleost
fishes, and angiospermous plants. The leading events of the long
ages of the era we can sketch only in the most summary way.

The Mesozoic comprises three systems,--the TRIASSIC, named from
its threefold division in Germany; the JURASSIC, which is well
displayed in the Jura Mountains; and the CRETACEOUS, which
contains the extensive chalk (Latin, creta) deposits of Europe.

In eastern North America the Mesozoic rocks are much less