294 The Naturalist m La Plata. 



up, but cleans it away so far in a straight line from 

 tlie entrance, and scratch.es so mucli 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 f onr 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 make 

 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 I 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 tbe 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 



