THE
ANCIENT LIFE-HISTORY
OF
THE EARTH
A COMPREHENSIVE OUTLINE OF THE PRINCIPLES AND LEADING FACTS OFPALÆONTOLOGICAL 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
Page vPREFACE.
The study of Palæontology, or the science which is concernedwith the living beings which flourished upon the globe duringpast periods of its history, may be pursued by two parallel butessentially distinct paths. By the one method of inquiry, we maystudy the anatomical characters and structure of the innumerableextinct forms of life which lie buried in the rocks simply as somany organisms, with but a slight and secondary reference tothe time at which they lived. By the other method, fossilanimals are regarded principally as so many landmarks in theancient records of the world, and are studied historicallyand as regards their relations to the chronological successionof the strata in which they are entombed. In so doing, it is ofcourse 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 torequire nothing more than a comparatively general attention.
In a former work, the Author has endeavoured to furnish a summaryof the more important facts ofPage viPalæontology regarded in itsstrictly scientific aspect, as a mere department of the greatscience of Biology. The present work, on the other hand, is anattempt to treat Palæontology more especially from itshistorical side, and in its more intimate relations with Geology.In accordance with this object, the introductory portion of thework is devoted to a consideration of the general principles ofPalæontology, and the bearings of this science upon variousgeological problems—such as the mode of formation of thesedimentary rocks, the reactions of living beings upon the crustof the earth, and the sequence in time of the fossiliferousformations. The second portion of the work deals exclusively withHistorical Palæontology, each formation being consideredseparately, 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 successiveperiod, a general account is given of their more important zoologicalcharacters and their relations to living forms; but the technicallanguage of Zoology has been avoided, and the aid of illustrationshas been freely called into use. It may therefore be hoped thatthe work may be found to be available for the purposes of both theGeological and the Zoological student; since it is essentially anoutline of Historical Palæontology, and the student of eitherof the above-mentioned sciences must perforce possess some knowledgeof the last. Whilst primarily intended for students, it may be addedthat the method of treatment adopted has been so far untechnical asnot to render the work useless to the general reader who may desirePage viito acquire some knowledge of a subject of such vast and universalinterest.
In carrying out the object which he has held before him, theAuthor can hardly expect, from the nature of the materials withwhich he has had to deal, that he has kept himself abs