40 THE NOTOG^IC REALM. [CHAP. 



with the aberrant banded anteater (Myrmecobius), which although 

 generally included in the Dasyuridce, should perhaps form the 

 type of a family by itself; this animal differing from all the fore- 

 going in the number, and also in the structure of the cheek-teeth, 

 and thereby making a marked approximation to certain Marsupials 

 of the Jurassic epoch noticed in the sequel. 



Before leaving this family, it should be mentioned that certain 

 extinct Marsupials from the Tertiaries of Patagonia, referred to in 

 the next chapter, seem to be inseparable from it, while there are 

 strong reasons for regarding one of them (Prothylacinus) as very 

 nearly allied to the existing genus Thylacinus. 



The last of the Australian families {Notary ctidce] of the sub- 

 order is represented solely by the marsupial mole (Notoryctes), 

 from the sandy deserts of central South Australia ; this being the 

 only member of the order which has taken to a subterranean mode 

 of life. There are no extinct Australian genera of the sub-order. 



Exclusive of the bats, the only other order of mammals well 

 represented in the Australian region is that of the 

 Rodentia, or Gnawing Mammals, which bear, how- 

 ever, a small proportion to the marsupials, and all of which belong 

 to the mouse-family (Murtdce). And it is noteworthy that although 

 several of these belong to generic types unknown elsewhere, the 

 whole of them are animals of comparatively small size, so that it 

 is possible that their ancestors may have been introduced without 

 a direct land-connection with any other part of the world. A 

 curious feature in connection with this group is that two of the 

 Australian species, namely Hydromys chrysogaster and Musfuscipes, 

 are aquatic in their habits ; whereas, as we have seen, none of the 

 Australian marsupials are natatorial, although the duckbill is 

 eminently so. The Australian water-rat (Hydromys), which is 

 common to Australia and New Guinea, belongs to a sub-family 

 typically distinguished from all other Murtdce by the reduction of 

 the molar teeth to two pairs in each jaw. While this animal has 

 partially webbed toes, and is strictly aquatic in its habits, the 

 allied Xeromys from Queensland is terrestrial, and approximates 

 to the more typical members of the family, although to which 

 group is still uncertain. The only other representatives of the 

 sub-family Hydromyina are met with in the mountains of Luzon, 



