Biography of the Viscacha, 295 
may be so curved inwards as to form the segment 
of a circle. Many other forms may also be noticed, 
but usually they appear to be only modifications of 
the most common Y-shaped system. 
As I have remarked that its manner of burrowing 
has peculiarly adapted the vizcacha to the pampas, 
it may be asked what particular advantage a species 
that* makes a wide-mouthed burrow possesses over 
those that excavate in the usual way. On a 
declivity, or at the base of rocks or trees, there 
would be none; but on the perfectly level and 
shelterless pampas, the durability of the burrow, a 
circumstance favourable to the animahs preserva- 
tion, is owing altogether to its being made in this 
way, and to several burrows being made together. 
The two outer trenches diverge so widely from the 
mouth that half the earth brought out is cast 
behind instead of before it, thus creating a mound 
of equal height about the entrance, by which it is 
secured from water during great rainfalls, while 
the cattle avoid treading over the great pit-like 
entrances. But the burrows of the dolichotis, 
armadillo, and other species, when made on perfectly 
level ground, are soon trod on and broken in by 
cattle; in ^ summer they are choked up with dust 
and rubbish ; and, the loose earth having all been 
thrown up together in a heap on one side, there is 
no barrier to the water which in every great rain- 
fall flows in and obliterates the kennel, drowming 
or driving out the tenant. 
I have been minute in describing the habitations 
of the vizcacha, as I esteem the subject of prime 
importance in considering the zoology of this 
