represent a tooth and a spine from one of
the most characteristic groups, but I have not thought it worth while to
enumerate or to figure others here, for there are no perfect specimens,
and their structural differences consist chiefly in the various form and
appearance of the teeth, scales, and spines, and would be uninteresting
to most of my readers. I would refer the more scientific ones, who may
care to know something of these details, to my investigations on Fossil
Fishes, published many years since under the title of "Recherches sur
les Poissons Fossiles."

[Illustration]

[Illustration]

Although the Vertebrate division of the Animal Kingdom still waited for
its higher classes, yet it had received one important addition since
the Silurian and Devonian periods. The Carboniferous marshes were not
without their reptilian inhabitants; but they were Reptiles of the
lowest class, the so-called Amphibians, those which are hatched from the
egg in an immature condition, undergoing metamorphosis after birth. They
have no hard scales, and lay a large number of eggs. I am unable to
present any figure of one of these ancient Reptiles, as they are found
in so imperfect a state of preservation that no plates have been made
from them. I would add in connection with this subject that I believe
a large number of animals found in the Carboniferous deposits, and
referred to the class of Reptiles, to be Fishes allied to Saurians.

Before leaving the Carboniferous period, let us see what territory the
United States has conquered from the Ocean during that time. All
its central portion, from Canada to Alabama, and from Western Iowa,
Missouri, and Arkansas to Eastern Virginia, was raised above the water.
But as yet the Alleghanies and the Rocky Mountains did not exist; a
great gulf ran up to the mouth of the Ohio, for the Mississippi had not
yet accumulated the soil for the fertile valley through which it was to
take its southern course; the Coral-Builders had still their work to do
in constructing the peninsula of Florida; and, indeed, all the borders
of the continent of North America, as well as a large part of its
Western territory, were still to be added. But although its central
portion held its ground and was never submerged again, yet the continent
was slowly subsiding during the middle geological periods, so that,
instead of enlarging gradually by the increase of deposits, its limits
remained much the same.

This accounts