92 THE MAMMALIA. 



becoming established. On the other hand, to 

 t:ikc a very obvious case, when competent au- 

 thorities emphasize the possibility that birds of 

 the ostrich species (the Ratitae) are of a different 

 reptile origin to the other birds e.g. those with 

 a keel-shaped breast-bone the supposition of a 

 convergence would, in fact, be established ; for bird- 

 like peculiarities are met with in the skeleton of 

 several fossil groups of reptiles, hence the trans- 

 formation to the real bird would in various respects 

 be absolutely no wonder at all. 



The geographical distribution of the Monotrema 

 is confined to South Australia and Tasmania. But 

 a few years ago a new species of Ornithoryncha 

 was described from a perfect skull found in New 

 Guinea. This does not really make the range of 

 tlu-ir distribution any larger, as New Guinea was 

 clearly at one time connected with the continent of 

 Australia, and consequently belonged to the same 

 zoological province. Not a trace of any fossil 

 discovery leads us from the present living Mono- 

 trema hack to the primeval world, to which never- 

 theless they stand in such palpable relation. Tlu-y 

 are, moreover, widely different from the other 

 groups of living Mammals. Even admitting the 

 debatable supposition that they were directly allied 



