74 MOSTLY MAMMALS 
there is not a vestige of rock or stone to be seen, unless 
it be in the few places where the aforesaid “tosca” has 
been brought to the surface. In spite of its fresh-water 
origin, there is, however, evidence that portions of the 
Pampean formation have been submerged beneath the sea. 
For instance, in the neighbourhood of the city of La Plata 
there occurs a bed of marine shells overlying the alluvial 
mud, all the species of molluscs being now found living 
in the Bay of Monte Video. I have also observed a 
similar bed at Santa Lucia, in the Banda Oriental, at an 
elevation of about one hundred feet above the sea, which 
was overlain by a considerable thickness of sands; and 
the same deposit occurs far inland, at the town of Parana. 
From these data it may be inferred that after the temporary 
subsidence of the Pampas, during which the marine beds 
were deposited, there has been a considerable elevation 
(which is probably still going on) of the whole country; 
and that these movements have taken place at a very recent 
epoch indeed. 
At the present day the Argentine Pampas, with the 
exception of a few willows along the river courses, is 
practically destitute of trees (save where they have of late 
years been planted around the various settlements), and 
forms a boundless sea of grass, relieved here and there by 
tussocks of the tall Pampas-grass, or giant thistles, and 
adorned in spring with scarlet verbena and other bright- 
hued flowers. Till the introduction of the countless herds 
of horses, cattle, and sheep, which now roam over its 
extent, this vast tract of country was tenanted by the 
guanaco, the Pampas-deer, the viscacha, and the rhea, 
which, with the exception of certain carnivores, were 
almost the only animals of any size to be found throughout 
its length and breadth. 
“4 
