QUADRUPEDS. 
333 
number of terrestrial Mammalia known may amount to 
about 1700 species, of which 137 are Marsupialia. The 
facts will he better seen if placed in juxtaposition, thus : 
The Australian region contains 120 terrostr. Mammalia. 
100 Marsupialia. 
The whole world besides contains ... 15S0 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 repiod active 
organs, in the arterial system, and in the structure of the 
b r ain : 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 m the 
skeleton even where the marsupmm itself is not developed ; 
and the absence of a true voice,— all manifest a departure 
