in iliv o b a b lo th a t a n o th e i- largo a n im a l h a s likowiso a s im ila r
atVuiitv.
'I’ho to o th o f th o r o d o n t n o a rly o iiiia llin g in s iz e th o s o o f
th o C a p v h a ra , w h io h woro d iso o v o ro d n o a r B ah ia B la n c a ,
m u s t a lso ho rom om h o ro d .
Tho law of tho suooossiou of typos, aUhongli suhjoct to
some remarkablo oxooptions, must possess tho liighost.
interest to ovory pliilosophioal naturalist, and was first clearly
observed in regard to Australia, whore fossil remains of a
largo and extinct species of Kangaroo and other marsupial
animals wore discovered buried in a cave. In America the
most marked change among tlic mammalia has been the
loss of several speeics of Mastodon, of an eleiihant, and of
the horse. These Pachydermata appear formerly to have
had a range over the world, hke that which deer and antelopes
now hold. If Buftbn had known of these gigantic
armadilloes, llamas, great rodents, and lost pachydermata,
he would have said with a greater semblance of truth, that
the creative force in America had lost its vigour, rather than
tliat it had never possessed such powers.
It is impossible to reflect without the deepest astonishment,
on the changed state of this continent. Formerly it
must have swarmed with great monsters, like the southern
parts of Africa, but now we find only the tapir, guanaco, arma-
diUo, and capybara; mere pigmies compared to the antecedent
races. The greater number, if not all, of these extinct
quadrupeds lived at a very recent period ; and many of them
were contemporaries of the existing moUuscs. Since their
loss, no very great physical changes can have taken place in
the nature of the countrix What then has exterminated so
many hving creatures? In the Pampas, the great sepulchre
of such remains, there are no signs of violence, but on
the contrar}-, of the most quiet and scarcely sensible changes.
At Bahia Blanca I endeavoured to show the probability that
the ancient Edentata, hke the present species, lived in a dry
and sterile countrv-, such as now is found in that neighbourhood.
With respect to the camel-like llama of Patagonia,
tlic same grounds which, liefore Icnowing more tlian the size
of the remains, periilcxcd me, liy not allowing any great
cluuigc of climate, now that we can guess tlic iiabits of the
animlil, arc strangely confirmed. What shall wc say of tlie
death of the fossil horse ? Did those plains fail in pasture,
which afterwards were overrun by tliousands and tens of
thousands of the successors of tlie frcsii stock introduced
with the Spanish colonist? In some countries, we may
believe, that a number of species subsequently introduced,
by consuming the food of the antecedent races, may have
caused their extermination; but we can scarcely credit that
the armadillo has devoured the food of the immense Megatherium,
the capyliara of the Toxodon, or the guanaco of
the camel-like kind. But granting that all such changes
have been small, yet we are so profoundly ignorant concerning
the physiological relations, on which the life, and even
liealtli (as shown by epidemics) of any existing species
depends, that we argue with still less safety about either the
life or death of any extinct kind.
One is tempted to believe in such simple relations, as
variation of climate and food, or introduction of enemies, or
the increased numbers of other species, as the cause of the
succession of races. But it may be asked whether it is probable
than any such cause should have been in action during
the same epoch over the whole northern hemisphere, so as
to destroy the Elephas primigenus, on the shores of Spain,
on the plains of Siberia, and hi Northern America; and in
a like manner, the Bos w a s , over a range of scarcely less
extent? Did such changes put a period to the life of
Mastodon angustidens, and of the fossil horse, both in
Europe and on the Eastern slope of the Cordillera in
Southern America? If they did, they must have been
changes common to the whole world; such as gradual
refrigeration, whether from modifications of physical geography,
or from central cooling. But on this assumption,
we have to struggle with the difficulty that these supposed
changes, although scarcely sufficient to affect molluscous
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