596 GEOGRAPHICAL DISTRIBUTION 
line called Wadlace’s line dividing the two realms passes 
northwards between Bali and Lombok, between Borneo and 
Celebes and eastwards of the Philippines. Celebes has, 
however, some claims to be regarded as belonging to 
Arctogeoea. 
We may naturally ask—What is the meaning of this 
faunistic character of the realm Notogcea? How has this 
realm come to be a sort of “preserve” for the two archaic 
sub-classes to the almost entire exclusion of the third and 
more highly organised sub-class? The past history of 
Notogcea does not help us much, for its geological strata 
have not been sufficiently investigated. Remains of the 
modern Monotremes are found in the Pleistocene of 
Australia. The same is true of the Ae¢atheria, including 
the large extinct forms of Dzprotodon and Thylacoleo. 
Further back than the Pleistocene, or at least the Pliocene, 
we know nothing of the fossils of Notogcea. On the other 
hand, we find that remains of Mefatheria occur in Europe 
and North America from the Triassic through Jurassic 
to Cretaceous. Indeed, Europe and North America, 
and possibly Asia by inference, were largely peopled by 
Metatheria during the secondary period; but, we have as 
yet no evidence of Eutherian mammals during this 
period. Hence in these important respects the fauna of 
Notogcea at the present day resembles that of Eurasia in 
the secondary period. The inference is that at that period 
Notogoea (Australia and New Guinea) was connected by 
land with the Eurasian continent, and further, that this land 
connection was broken at the dawn of the Tertiary epoch 
before the Eutherian mammals were evolved. ‘The connec- 
tion having never since been restored, the Afe¢atheria in 
Notogcea have been free to become modified and adapted 
into their numerous types now existing. The few Eutheria 
now existing in Notogcea have on this assumption effected a 
crossing either in canoes (man and probably the native 
dingo), or timber (the M/uride), or by flight (the bats). Man 
has more lately introduced the Eutherian rabbit and sheep, 
besides other types, and the rabbit at least appears to be 
making up rapidly for the time lost since the early Tertiary, 
during which it has been excluded from the district. If 
we may regard the AMotheria as true Prototheria, we may 
