The geographical distribution of animals, with a study of the relations ...

chap, vii.] MAMMALIA OF THE NEW WORLD. 149and New Worlds.—Leaving the more special applications ofpalseontological evidence to be made after discussing the relationsof the existing fauna of the several regions, we propose here toindicate briefly, some of the more general deductions from theevidence which has now been laid before our readers.The first, and perhaps the most startling fact brought out byour systematic review, is the very recent and almost universalchange that has taken place in the character of the fauna,all the areas we have been considering ;overa change which seemsto be altogether unprecedented in the past history of the samecountries as revealed by the geological record. In Europe, inNorth America, and in South America, we have evidence that avery similar change occurred about the same time. In all threewe find, in the most recent deposits—cave-earths, peat-bogs, andgravels—the remains of a whole series of large animals, whichhave since become wholly extinct or only survive in far-distantlands. In Europe, the great Irish elk, the Machairodus andcave-lion, the rhinoceros, hippopotamus, and elephant ;—in NorthAmerica, equally large felines, horses and tapirs larger than anynow living, a llama as large as a camel, great mastodons andelephants, and abimdance of huge megatheroid animals of almostequal size ;—in South America these same megatheroids in greatervariety, numerous huge armadillos, a mastodon, large horses andtapirs, large porcupines, two forms of antelope, numerous bears andfelines, including a Machairodus, and a large monkey,—have all becomeextinct since the deposition of the most recent of the fossilbearingstrata. This is certainly not a great while ago, geologically; and it is almost certain that this great organic revolution,implying physical changes of such vast proportions that theymust have been due to causes of adequate intensity and proportionaterange, has taken place since man lived on the earth.This is proved to have been the case in Europe, and is supportedby much evidence both as regards North and South America.It is clear that so complete and sudden a change in the higherforms of life, does not represent the normal state of things.Species and genera have not, at all times, become so rapidlyextinctThe time occupied by the " Eecent period," that is the