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 Pampsean 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 Plorse, 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 certaintv that the remains of horses are common in North 

 America. Mr. Lyell has lately brought from the United States 

 a tooth of a 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 historv of the Mammalia, that in South America a 

 native horse should have lived 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, 

 f Cuvier, Ossemens Fossiles, torn. i. p. 158. 



