OPOSSUMS. 307 
Stirling, by whom the marsupial mole was first made known to science, states that 
most of the specimens he obtained were “captured by the aboriginals, who, with their 
phenomenal powers of tracking, follow up their traces until they are caught. For 
this reason they can only be found with certainty after rain, which sets the surface 
of the sand and enables it to retain 
tracks that would be immediately 
obliterated where it is dry and loose. 
Nor are they found except during 
warm weather, so that the short period 
of semitropical summer rains appears | 
to be the favourable time for their 
capture.” Perpetual burrowing seems 
to be the characteristic trait of this 
animal. On “emerging from the sand, 
it travels on the surface for a few 
feet, at a slowish pace, with a peculiar 
sinuous motion, the belly much. flat- 
tened against the ground, while it 
rests on the outsides of its fore-paws, 
which are thus doubled in under it. 
It leaves behind it a peculiar sinuous SKULL (1 and 2) AND SKELETON OF THE HIND (3) AND 
¢ : : FORE (4) FEET OF THE POUCHED-MOLE (about 3 nat. 
triple track, the outer impressions, size). —After Stirling. 
more or less interrupted, being caused 
by the feet, and the central continuous line by the tail, which seems to be pressed 
down in the rear. It enters the sand obliquely, and travels underground either for 
a few feet or for many yards, not apparently reaching a depth of more than 
two or three inches, for whilst underground its progress can often be detected by 
a slight cracking or moving of the surface over its position.” 
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THE OPOSSUMS. 
Family DIDELPHYIDZ. 
The last family of the existing Marsupials is constituted by the well-known 
opossums, which are now confined to America, although during the early portion 
of the Tertiary period they also ranged over Europe. Closely allied to the 
Australian Dasywride, the opossums are mainly distinguished by the hind-foot 
having a well-developed inner toe, which, although nailless, is capable of being 
opposed to the other digits. They are further distinguished by the number of their 
incisor teeth, of which there are five pairs in the upper and three in the lower jaw. 
The tail is generally of considerable length, partially naked and prehensile at the 
extremity; and the feet are likewise devoid cf any hairy covering. Although com- 
plete in a few of the species, the pouch is generally either wanting altogether, or 
represented merely by a couple of longitudinal folds in the skin of the abdomen, which 
partially conceal the numerous teats. As a rule, opossums may be compared in 
general outward appearance to rats, although they have longer snouts terminating 
