18 The Naturalist in La Plata. 
Didelphys crassicaudata—has a long slender, wedge- 
shaped head and body, admirably adapted for push- 
ing through the thick grass and rushes; for it is 
both terrestrial and aquatic, therefore well suited 
to inhabit low, level plains liable to be flooded. On 
dry land its habits are similar to those of a weasel ; 
in lagoons, where it dives and swims with great 
ease, it constructs a globular nest suspended from 
the rushes. The fur is soft, of a rich yellow, reddish 
above, and on the sides and under surfaces varying 
in some parts to orange, in others exhibiting beau- 
tiful copper and terra-cotta tints. These lovely 
tints and the metallic lustre soon fade from the fur, 
otherwise this animal would be much sought after 
in the interests of those who love to decorate them- 
selves with the spoils of beautiful dead animals— 
beast and bird. The other opossum is the black 
and white Didelphys azare; and it is indeed 
strange to find this animal on the pampas, although 
its presence there is not so mysterious as that of 
the tuco-tuco. It shuffles along slowly and awk- 
wardly on the ground, but is a great traveller 
nevertheless. ‘Tschudi met it mountaineering on 
the Andes at an enormous altitude, and, true to its 
lawless nature, it confronted me in Patagonia, where 
the books say no marsupial dwells. In every way 
it is adapted to an arboreal life, yet it is everywhere 
found on the level country, far removed from the 
conditions which one would imagine to be necessary 
to its existence. For how many thousands of years 
has this marsupial been a dweller on the plain, all 
its best faculties unexercised, its beautiful grasping 
hands pressed to the ground, and its prehensile tail 
