33 ^ 
Glacial Period in the 
[July. 
formation are its vast extent and the great number of the 
remains of large extindt mammals imbedded in it. Mr. 
Darwin says that he is firmly convinced that it would be 
impossible to cut a deep trench in any line across the 
Pampas without meeting with the remains of some quadru- 
ped. Wherever sedtions are exposed skeletons or detached 
bones are found, so that “ the whole area of the Pampas is 
one wide sepulchre of these extindt gigantic quadrupeds.”* 
At Punta Alta, within an area of about 200 yards square, 
were found the remains of no less than nine species of 
gigantic extinct mammals, including three Megatheriums, a 
Megalonyx, a Mylodon, and an extindt horse. Some of the 
skeletons were nearly perfedt, besides which there were 
many detached bones. On the banks of the Parana two 
entire skeletons of the Mastodon were found near the base 
of the Pampean mud. 
The Pampas extend southwards to the Rio Colorado. 
There, beds of gravel begin to take the place of the Pam- 
pean mud. These are at first thin, and composed of small 
pebbles. Farther south the gravel-beds are composed of 
coarser pebbles, with sometimes large boulders. This de- 
posit of shingle extends for 800 miles up to the Straits of 
Magellan. In some parts the plains of gravel rise in step- 
formed terraces to a height of 1200 feet above the sea. 
Marine shells are scattered over the surface of the plains, 
but are not found in the beds of gravel, which, like the 
Pampean mud, contain in some parts numerous remains 
of the great extindt quadrupeds. 
Darwin mentions that the Mammalian remains have not 
anywhere been found in existing marshes or peat-beds : all 
are entombed in the body of the deposit of which the plains 
are composed. 
In the Pampas, in the caves of Brazil, and in deposits of 
similar age in other parts of South America, more than one 
hundred extindt species of quadrupeds, many of great size, 
have been found. There are representatives of the sloths 
and armadillos as large as existing elephants. There are 
also representatives of genera that do not now exist in 
South America, but still live in other parts of the world — 
such as leopards and antelopes. The remains of the horse 
are abundant, though when the Spaniards discovered America 
it was extindt there. 
Mr. Wallace, in his great work on the distribution of 
* Darwin, Naturalist’s Voyage, p. 155. The whole of my information 
respecting the Pampas is derived from this work and from The Geological 
Observations on South America by the same author. 
