QUADRUPEDS. 



333 



number of terrestrial Mammalia known may amount to 

 about 1700 species, of which 137 are Marsupialia. The 

 facts will be better seen it placed in juxtaposition, thus : — 



The Australian region contains 120 terrestr. Mammalia. 



,, „ 100 Marsupialia. 



The whole world besides contains ... 1580 terrestr. Mammalia. 



,, ,, . 37 Marsupialia 



Thus we find the Marsupial Mammalia almost confined 

 to Australia, and Australia almost confined to them. 



The most obvious peculiarities which distinguish these 

 animals, and which have conferred upon them their 

 scientific designation, are the immature condition of the 

 young at the time of birth, and its reception into a pouch 

 (marsupium) or fold of the skin on the abdomen of the 

 female, in which it is protected from exposure to the air 

 and injury; while suspended from the teat, to which it 

 is very early attached, it gradually assumes the form of its 

 adult condition, and acquires the powers necessary for its 

 independent existence. For some time, however, after it 

 is able to procure its own living, and to run and play 

 by the side of its mother, the young Marsupial instinc- 

 tively flees to the maternal pouch for protection on the 

 approach of danger. 



But besides these more obvious peculiarities, there are 

 others scarcely less important, which are recognised by the 

 comparative anatomist. Diversities in the reproductive 

 organs, in the arterial system, and in the structure of the 

 brain ; the open condition of the skull, the bones of which 

 remain permanently separate ; the tendency to a multipli- 

 cation of the teeth ; the presence of marsupial bones in the 

 skeleton, even where the marsupium itself is not developed ; 

 and the absence of a true voice, — all manifest a departure 



