THE OPOSSUMS 



1449 



MOLE. 



(About two-thirds natural size.) 

 (After Stirling.) 



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 sur- 

 face 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 favorable 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 flattened 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 pe- 

 culiar sinuous triple track, the outer SKULL (i and 2) AND SKELETON OF THE HIND 



(3) AND FORE (4) FEET OF THE POUCHED 



impressions, more or less interrupted, 

 being caused by the feet, and the cen- 

 tral 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 while underground its progress can often be 

 detected by a slight cracking or moving of the surface over its position." 



THE OPOSSUMS 

 Family DlDELPHTIDsE 



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 

 Dasyuridce, 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 complete 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 par- 

 tially conceal the numerous teats. As a rule, opossums may be compared in gen- 

 eral outward appearance to rats, although they have longer snouts terminating in a 

 perfectly-naked muzzle; while in the larger species the body becomes proportion- 

 ately stouter. 



