292 The Naturalist in La Plata. 
open pampas. Other burrowing species seem 
always to fix upon some spot where there is a bank 
or a sudden depression in the soil, or where there 
is rank herbage, or a bush or tree, about the roots 
of which to begin their kennel. ‘They are averse 
to commence digging on a clear level surface, 
either because it 1s not easy for them where they 
have nothing to rest their foreheads against while 
scratching, or because they possess a wary instinct 
that impels them to place the body in concealment 
whilst working on the surface, thus securing the 
concealment of the burrow after it is made. 
Certain it is that where large hedges have been 
planted on the pampas, multitudes of opossums, 
weasels, skunks, armadillos, &c., come and make 
their burrows beneath them ; and where there are 
no hedges or trees, all these species make their 
kennels under bushes of the perennial thistle, or 
where there is a shelter of some kind. The vizcacha, 
on the contrary, chooses an open level spot, the 
cleanest he can find to burrow on. The first thing 
that strikes the observer when viewing the vizca- 
chera closely is the enormous size of the entrance 
of the burrows, or, at least, of several of the central 
ones in the mound; for there are usually several 
smaller outside burrows. The pit-like opening to 
some of these principal burrows is often four to six 
feet across the mouth, and sometimes deep enough 
for a tall man to stand up waist-deep in. How 
these large entrances can be made on a level surface 
may be seen when the first burrow or burrows of 
an incipient vizcachera are formed. It is not 
possible to tell what induces a vizeacha to be the 
