294 The Naturalist in La Plata. 
up, but cleans it away so far in a straight line from 
the entrance, and scratches so much on this line 
(apparently to make the slope gentler), that he 
soon forms a trench a foot or more in depth, and 
often three or four feet in length. Its use is, as I 
have inferred, to facilitate the conveying of the 
loose earth as far as possible from the entrance of 
the burrow. But after a while the animal is un- 
willing that it should accumulate even at the end of 
this long passage; he therefore proceeds to form 
two additional trenches, that form an acute, some- 
times a right angle, converging into the first, so 
that when the whole is completed it takes the form 
of a capital Y. 
These trenches are continually deepened and 
lengthened as the burrow progresses, the angular 
segment of earth between them scratched away, 
until by degrees it has been entirely conveyed off, 
and in its place is the one deep great unsymmetrical 
mouth | have already described. ‘There are soils 
that will not admit of the animals working in this 
manner. Where there are large cakes of “ tosca”’ 
near the surface, as in many localities on the 
southern pampas, the vizcacha makes its burrow as 
best he can, and without the regular trenches. In 
earths that crumble much, sand or gravel, he also 
works under great disadvantages. 
The burrows are made best in the black and 
red moulds of the pampas; but even in such soils 
the entrances of many burrows are made differently. 
In some the central trench is wanting, or is so short 
that there appear but two passages converging 
directly into the burrow; or these two trenches 
