part of a reddish clay, and in part of a highly calcareous
marly rock. Nearer the coast there are some plains formed
from the wreck of the upper plain, and from mud, gravel,
and sand thrown up by the sea during the slow elevation of
the land, of which elevation we have evidence in upraised
beds of recent shells, and in rounded pebbles of pumice
scattered over the country. At Punta Alta we have a section of
one of these later-formed little plains, which is highly
interesting from the number and extraordinary character of the
remains of gigantic land-animals embedded in it. These have
been fully described by Professor Owen, in the Zoology of the
voyage of the Beagle, and are deposited in the College of
Surgeons. I will here give only a brief outline of their nature.

First, parts of three heads and other bones of the Megatherium,
the huge dimensions of which are expressed by its
name. Secondly, the Megalonyx, a great allied animal.
Thirdly, the Scelidotherium, also an allied animal, of which
I obtained a nearly perfect skeleton. It must have been as
large as a rhinoceros: in the structure of its head it comes
according to Mr. Owen, nearest to the Cape Anteater, but
in some other respects it approaches to the armadilloes.
Fourthly, the Mylodon Darwinii, a closely related genus of
little inferior size. Fifthly, another gigantic edental quadruped.
Sixthly, a large animal, with an osseous coat in compartments,
very like that of an armadillo. Seventhly, an
extinct kind of horse, to which I shall have again to refer.
Eighthly, a tooth of a Pachydermatous animal, probably the
same with the Macrauchenia, a huge beast with a long neck
like a camel, which I shall also refer to again. Lastly, the