POUCHED MAMMALS, OR MARSUPIALS. 175 



firmed by the structure of their brain, and many othei 

 parts of the body. 



As already observed, the Marsupials are mainly con- 

 fined to the Australian region, the only exception being 

 the Opossums of America ; and not only are they mainly 

 confined to that region, but they and the Monotremes 

 are the only Mammals found there, with the exception 

 of a few Bats, two or three rat-like Rodents, and the 

 remarkable native Dog, or Dingo, the latter having not 

 improbably been introduced by human agency. This 

 remarkably circumscribed area of distribution would 

 of itself lead us to conclude that the existing Mar- 

 supials are survivors of an old and therefore lowly 

 type of Mammalian life, since so many of the products 

 of Australia and New Zealand are so utterly unlike 

 those of other parts of the globe, and present affinities 

 to types long extinct elsewhere. Thus, in Queensland 

 alone, we have the peculiar fish known as the Bara- 

 munda (see page 6), which is the direct survivor of 

 fossil fishes found in the oldest Secondary rocks of 

 Europe; while in New Zealand the scarce Tuatara 

 Lizard is almost equally closely related to fossil Lizards 

 of the same European rocks. These primd facie con- 

 clusions as to the antiquity of the Marsupial type are 

 fully borne out by actual facts, since the Secondary rocks 

 of England, such as the well-known Stonesfield slate 

 of Oxfordshire, and the Purbeck beds of Dorsetshire, 

 as well as many of the equivalent rocks in the United 

 States, have yielded jaws of a number of small fossil 

 Mammals, many of which were evidently very closely 



