THE
ANCIENT LIFE-HISTORY
OF
THE EARTH

A COMPREHENSIVE OUTLINE OF THE PRINCIPLES AND LEADING FACTS OF PALÆONTOLOGICAL SCIENCE

BY
H. ALLEYNE NICHOLSON

M.D., D.SC., M.A., PH. D. (GÖTT), F.R.S.E, F.L.S.

PROFESSOR OF NATURAL HISTORY IN THE UNIVERSITY OF ST ANDREWS

PREFACE.

The study of Palæontology, or the science which is concerned with the living beings which flourished upon the globe during past periods of its history, may be pursued by two parallel but essentially distinct paths. By the one method of inquiry, we may study the anatomical characters and structure of the innumerable extinct forms of life which lie buried in the rocks simply as so many organisms, with but a slight and secondary reference to the time at which they lived. By the other method, fossil animals are regarded principally as so many landmarks in the ancient records of the world, and are studied historically and as regards their relations to the chronological succession of the strata in which they are entombed. In so doing, it is of course impossible to wholly ignore their structural characters, 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 the above-mentioned sciences must perforce possess some knowledge of the last. Whilst primarily intended for students, it may be added that the method of treatment adopted has been so far untechnical as not to render the work useless to the general reader who may desire to acquire some knowledge of a subject of such vast and universal interest.

In carrying out the object which he has held before him, the Author can hardly expect, from the nature of the materials with which he has had to deal, that he has kept himself absolutely clear of errors, both of omission and commission. The subject, however, is one to which he has devoted the labour of many years, both in studying the researches of others and in personal investigations of his own; and he can only trust that such errors as may exist will be found to belong chiefly to the former class, and to be neither serious nor numerous. It need only be added that the work is necessarily very limited in its scope, and that the necessity of not assuming a thorough previous acquaintance with Natural History in the reader has inexorably restricted its range still further. The Author does not, therefore, profess to have given more than a merely general outline of the subject; and those who desire to obtain a more minute and detailed knowledge of Palæontology, must have recourse to other and more elaborate treatises.

UNITED COLLEGE, ST ANDREWS.
    October 2, 1876.

CONTENTS.

PART I.

PRINCIPLES OF PALÆONTOLOGY.

INTRODUCTION.

The general objects or geological science—The older theories of catastrophistic and intermittent action—The more modern doctrines of continuous and uniform action—Bearing of these doctrines respectively on the origin or the existing terrestrial order—Elements or truth in Catastrophism—General truth of the doctrine of Continuity—Geological time.

CHAPTER I.

Definition of Palæontology—Nature of Fossils—Different processes of fossilisation.

CHAPTER II.

Aqueous and igneous rocks—General characters of the sedimentary rocks—Mode or formation of the sedimentary rocks—Definition of the term "formation"—Chief divisions of the aqueous rocks—Mechanically-formed rocks, their characters and mode of origin—Chemically and organically formed rocks—Calcareous rocks—Chalk, its microscopic structure and mode of formation—Limestone, varieties, structure, and origin—Phosphate of lime—Concretions—Sulphate of lime—Silica and siliceous deposits of various kinds—Greensands—Red clays—Carbon and carbonaceous deposits.

CHAPTER III.

Chronological succession of the fossiliferous rocks—Tests or age of strata—Value of Palæontological evidence in stratigraphical Geology—General sequence of the great formations.

CHAPTER IV.

The breaks in the palæontological and geological record—Use of the term "contemporaneous" as applied to groups of strata—General sequence of strata and of life-forms interfered with by more or less extensive gaps—Unconformability—Phenomena implied by this—Causes of the imperfection of the palæontological record.

CHAPTER V.

Conclusions to be drawn from fossils—Age of rocks—Mode of origin of any fossiliferous bed—Fluviatile, lacustrine, and marine deposits—Conclusions as to climate—Proofs of elevation and subsidence of portions of the earth's crust derived from fossils.

CHAPTER VI.

The biological relations of fossils—Extinction of life-forms—Geological range of different species—Persistent types of life—Modern origin of existing animals and plants—Reference of fossil forms to the existing primary divisions of the animal kingdom—Departure of the older types of life from those now in existence—Resemblance of the fossils of a given formation to those of the formation next above and next below—Introduction of new life-forms.

PART II.

HISTORICAL PALÆONTOLOGY.