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 |