and their relationships with animals now living upon the earth;
but these points are held to occupy a subordinate place, and to
require nothing more than a comparatively general attention.

In a former work, the Author has endeavoured to furnish a summary
of the more important facts of Palæontology regarded in its strictly
scientific aspect, as a mere department of the great science of
Biology. The present work, on the other hand, is an attempt to
treat Palæontology more especially from its historical side, and
in its more intimate relations with Geology. In accordance with
this object, the introductory portion of the work is devoted to a
consideration of the general principles of Palæontology, and the
bearings of this science upon various geological problems--such
as the mode of formation of the sedimentary rocks, the reactions
of living beings upon the crust of the earth, and the sequence
in time of the fossiliferous formations. The second portion of
the work deals exclusively with Historical Palæontology, each
formation being considered separately, as regards its lithological
nature and subdivisions, its relations to other formations, its
geographical distribution, its mode of origin, and its characteristic
life-forms.

In the consideration of the characteristic fossils of each successive
period, a general account is given of their more important zoological
characters and their relations to living forms; but the technical
language of Zoology has been avoided, and the aid of illustrations
has been freely called into use. It may therefore be hoped that
the work may be found to be available for the purposes of both the
Geological and the Zoological student; since it is essentially an
outline of Historical Palæontology, and the student of either of