It is obvious that any great cosmical change, affecting to a wide extent any of the regions, might determine a destruction of specific existence; and this on a large scale, in comparison with the change which is always progressing in a smaller degree in the different and isolated divisions. The brief remarks which I have made on this subject are intended to suggest, rather than to demonstrate--which could only be done by a lengthy series of examples--the causes influencing specific existence and its in many cases extreme frailty of tenure. And I shall now conclude by citing from the works of Lyell and Wallace a short list of notable species, now extinct, whose remains have been collected from late Tertiary, and Post Tertiary deposits--that is to say, at a time subsequent to the appearance of man. From other authors I have extracted an enumeration of species which have become locally or entirely extinct within the historic period. These instances will, I think, be sufficient to show that, as similar destructive causes must have been in action during pre-historic times, it is probable that, besides those remarkable animals of which remains have been discovered, many others which then existed may have perished without leaving any trace of their existence. There is, consequently, a possibility that some at least of the so-called _myths_ respecting extraordinary creatures, hitherto considered fabulous, may merely be distorted accounts--_traditions_--of species as yet unrecognised by Science, which have actually existed, and that not remotely, as man's congener. _Extinct Post Tertiary Mammalia._ THE MAMMOTH.--Among other remarkable forms whose remains have been discovered in those later deposits, in which geologists are generally agreed that remains of man or traces of his handicraft have also been recognised, there is one which stands out prominently both for its magnitude and extensive range in time and space. Although the animal itself is now entirely extinct, delineations by the hand of Palæolithic man have been preserved, and even frozen carcases, with the flesh uncorrupted and fit for food, have been occasionally discovered. [Illustration: FIG. 9.--THE MAMMOTH. (_After Jukes._)]