Thus we see what a great advance was made in life during this
period. The forms of life during the early stages of this age
were inferior in this, also, that they were all water
species.<11> But, before it closes, we have a rich and varied
terrestrial vegetation, and also air-breathing animals.
The class Mammalia, to which man belongs, had no representative
on the earth during the extended Paleozoic time.

We can easily see, from the foregoing, how appropriately this
period has been named that of old life forms. In imagination we
can recall a scene of this old age. The air is sultry and full
of vapors. The soil seems hot and steaming. This is a veritable
forest, but we see none of the beautiful flowers which we
associate with tropical vegetation to-day. In the branches of
the graceful tree-ferns, we will look in vain for birds.
They were yet far in the future. Neither were there any of the
higher orders of animals present. Not a single representative of
the great class of mammals enlivened the depths of the forest.
There were fishes in the waters, but not the fishes of to-day.
Some true reptiles and amphibians disported themselves in swampy
jungles, but they were unimportant. Almost the only sound to
break the stillness, was the hum of marsh-loving insects, the
whistling of the wind, and the roar of the tempests, which we
may well believe raged with the more than tropic severity of
the present.<12>

The time at last came for the dawning of a new era. Vast changes
had been taking place in the geography of both continents. The
region to the south-west of the Green Mountains was upturned.