harbour.

The plain, at the distance of a few miles from the coast, belongs
to the great Pampean formation, which consists in 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
Ant-eater, 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 Toxodon, perhaps one of the
strangest animals ever discovered: in size it equalled an elephant
or megatherium, but the structure of its teeth, as Mr. Owen states,
proves indisputably that it was intimately related to the Gnawers,
the order which, at the present day, includes most of the smallest
quadrupeds: in many details it is allied to the Pachydermata:
judging from the position of its eyes, ears, and nostrils, it was
probably aquatic, like the Dugong and Manatee, to which it is also
allied. How wonderfully are the different Orders, at the present
time so well separated, blended together in different poin