Ctenomys; the species being different from the Tucutuco, but with a
close general resemblance. The red earth, like that of the Pampas, in
which these remains were embedded, contains, according to Professor
Ehrenberg, eight fresh-water and one salt-water infusorial animalcule;
therefore, probably, it was an estuary deposit.
The remains at Punta Alta were embedded in stratified gravel and
reddish mud, just such as the sea might now wash up on a shallow bank.
They were associated with twenty-three species of shells, of which
thirteen are recent and four others very closely related to recent
forms. [1] From the bones of the Scelidotherium, including even the
knee-cap, being intombed in their proper relative positions, and from
the osseous armour of the great armadillo-like animal being so well
preserved, together with the bones of one of its legs, we may feel
assured that these remains were fresh and united by their ligaments,
when deposited in the gravel together with the shells. [2] Hence we
have good evidence that the above enumerated gigantic quadrupeds, more
different from those of the present day than the oldest of the tertiary
quadrupeds of Europe, lived whilst the sea was peopled with most of its
present inhabitants; and we have confirmed that remarkable law so often
insisted on by Mr. Lyell, namely, that the "longevity of the species in
the mammalia is upon the whole inferior to that of the testacea." [3]
The great size of the bones of the Megatheroid animals, including the
Megatherium, Megalonyx, Scelidotherium, and Mylodon, is truly
wonderful. The habits of life of these animals were a complete puzzle
to naturalists, until Professor Owen [4] solved the problem with
remarkable ingenuity. The teeth indicate, by their simple structure,
that these Megatheroid animals lived on vegetable food, and probably on
the leaves and small twigs of trees; their ponderous forms and great
strong curved claws seem so little adapted for locomotion, that some
eminent naturalists have actually believed, that, like the sloths, to
which they are intimately related, they subsisted by climbing back
downwards on trees, and feeding on the leaves. It was a bold, not to
say preposterous, idea to conceive even antediluvian trees, with
branches strong enough to bear animals as large as elephants. Professor
Owen, with far more probability, believes that, instead of climbing on
the trees, they pulled the branches down to them, and tore up the
smaller ones by the roots, and so fed on the leaves. The colossal
breadth and weight of their hinder quarters, which can hardly be
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