OPOSSUMS. 



277 



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. 



Xor 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. 



SKULL (1 and 2) AND SKELETON OF THE HIND (3) AND 



FORE (4) FEET OF THE POUCHED -MOLE (about nat. 



size). After Stirling. 



It leaves behind it a peculiar sinuous 

 triple track, the outer impressions, 

 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. 5 ' 



THE OPOSSUMS. 

 Family DlDELPHYID^. 



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 Ddsyuridce, 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 of 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 



