130 ST. FE. [cHAP. VII. 
‘Ehrenberg has had the kindness to examine for me a little of the 
red earth, taken from low down in the deposit, close to the 
skeletons of the mastodon, and he finds in it many infusoria, 
partly salt-water and partly fresh-water forms, with the latter 
rather preponderating ; and therefore, as he remarks, the water 
must have been brackish. M. A. d’Orbigny found on the banks 
of the Parana, at the height of a hundred feet, great beds of an 
estuary shell, now living a hundred miles lower down nearer the 
sea; and I found similar shells at a less height on the banks of 
the Uruguay: this shows that just before the Pampas was slowly 
elevated into dry land, the water covering it was brackish. 
Below Buenos Ayres there are upraised beds of sea-shells of 
existing species, which also proves that the period of elevation 
of the Pampas was within the recent period. 
In the Pampeean deposit at the Bajada I found the osseous armour 
of a gigantic armadillo-like animal, the inside of which, when the 
earth was removed, was like a great cauldron ; I found also teeth of 
the Toxodon and Mastodon, and one tooth of a Horse, in the same 
stained and decayed state. This latter tooth greatly interested 
me,* and I took scrupulous care in ascertaining that it had been 
embedded contemporaneously with the other remains; for I was 
not then aware that amongst the fossils from Bahia Blanca there 
was a horse’s tooth hidden in the matrix: nor was it then known 
with certainty that the remains of horses are common in North 
America. Mr. Lyell has lately brought from the United States 
a tooth ofa horse; and it is an interesting fact, that Professor 
Owen could find in no species, either fossil or recent, a slight 
but peculiar curvature characterizing it, until he thought of com- 
paring it with my specimen found here: he has named this ” 
American horse Equus curvidens. Certainly it is a marvellous 
fact in the history of the Mammalia, that in South America a 
native horse should have Kved and disappeared, to be succeeded 
in after ages by the countless herds descended from the few 
introduced with the Spanish colonists ! 
The existence in South America of a fossil horse, of the 
mastodon, possibly of an elephant, and of a hollow-horned 
* I need hardly state here that there is good evidence against any horse 
living in America at the time of Columbus. 
t Guvies, Ossemens Fossiles, tom. i. p. 158. 
