70 KiO COLORADO. [cHaP. Iv. 
that genus in many essential respects ; for instance, it has only 
three toes behind. It is also nearly twice the size, weighing 
from twenty to twenty-five pounds. The Agouti is a true friend 
of the desert ; it is a common feature in the landscape to see two 
or three hopping quickly one after the other in a straight line 
atross these wild plains. They are found as far north as the 
Sierra Tapalguen (lat. 37° 30’), where the plain rather suddenly 
becomes greener and more humid; and their southern limit is 
between Port Desire and St. Julian, where there is no change in 
the nature of the country. It is a singular fact,|that although 
the Agouti is not now found as far south as Port St. Julian, yet 
that Captain Wood, in his voyage in 1670, talks of them as 
being numerous there. What cause can have altered, in a wide, 
uninhabited, and rarely-visited country, the range of an animal 
like this? It appears also from the number shot by Captain 
Wood in one day at Port Desire, that they must have been 
considerably more abundant there formerly than at present. 
Where the Bizcacha lives and makes its burrows, the Agouti 
‘uses them; but where, as at Bahia Blanca, the Bizcacha is 
not found, the Agouti burrows for itself. The same thing 
occurs with the little owl of the Pampas (Athene cunicularia), 
which has so often been described as standing like a sentinel 
at the mouth of the burrows; for in Banda Oriental, owing to 
the absence of tne Bizcacha, it is obliged to hollow out its own 
habitation. 
The next morning, as we approached the Rio Colorado, the 
appearance of the country changed; we soon came on a plain 
covered with turf, which, from its flowers, tall clover, and little 
owls, resembled the Pampas. We passed also a muddy swamp 
of considerable extent, which in summer dries, and becomes in- 
crusted with various salts; and hence is called a salitral. It was 
covered by low succulent plants, of the same kind with those 
growing on the sea-shore. The Colorado, at the pass where we 
crossed it, is only about sixty yards wide; generally it must be 
nearly double that width. Its course is very tortuous, being 
marked by willow-trees and beds of reeds: in a direct line the 
distance to the mouth of the river is said to be nine leagues, but 
by water twenty-five. We were delayed crossing in the canoe 
by some immense troops of mares. which were swimming the 
