478 
VERTEBRATA. 
in South America. To these facts we may add, in the words of the intelligent English traveler 
Darwin, that " the Pampas may be regarded as one great sepulcher of lost quadrupeds." From 
an examination of the soil, it appears that this immense prairie — now exhibiting a sea of waving 
grass for eight hundred miles- — occupies the site of what was once an immense bay or arm of the 
sea. In the countless ages of the past this has gradually been filled by soil, and in this are em- 
bedded the relics of these various races which have passed away. ISTot only are here found the 
relics we have described, but many others, including those of the Toxodon^ strangely blending in 
its structure some of the organic features of the rodentia, ruminantia, and cetacea, — those of 
the Macraxichenia^ which alike resembled the tapir, the camel, and the giraffe; and many others 
equally strange and wonderful. 
In listening to these and similar accounts, especially those which relate to the Mastodon^ the 
Mammoth^ the Megalonix^ the Iguanodon^ and other giants of the geological ages, it is natural to 
ask by what means did these creatures, the seeming masters as well as monsters of the world, 
cease to exist? The answer is for the most part supplied by well known facts. In some 
cases the earth has been submerged by convulsions of nature, sudden or slow, and its tenants 
have been swallowed up in the sea ; in others, there have been great changes of climate, render- 
ing whole regions unfit, alike by their temperature and their productions, to sustain the animals 
which before inhabited them. And, finally, it may be stated that all very large animals seem 
destined, by a sort of necessity, to pass away. These enormous creatures were few in number, 
for the earth could not sustain many, and multitudes of smaller animals combined for the de- 
struction of such as did exist, as they do now. It is true that in the eras to which we refer, Man, 
THE GLXPTODON ACCOEDING TO THE DESIGNS OF W. HAWKINS. 
the great destroyer, was not there, but there were lions, tigers, hyenas, and bears, to devour the 
young, to attack and destroy the sick and disabled. There were myriads of animals to penetrate 
the bowels and perforate the skin, to inflict disease and occasion death. With combinations of 
these and other creatures lay the strength of the world, and to them its dominion gradually 
tends. In short, these enormous animals were not adapted to the earth, in its actual state, 
and so, by the laws of nature, some in one way and some in another,— they ceased to exist, leav- 
ing: no record bat their bones. 
