GEOGRAPHICAL SUCCESSION OF ORGANIC FORMS. 561 



existing species " (Lyell). In other words, though the extinct 

 Mammals of the later geological deposits of any given country 

 differ specifically from those now existing in the same country, 

 they are nevertheless referable to the same orders, and are in 

 every respect more closely allied to the present Mammalian 

 fauna than to that of any other country. A few examples will 

 render this perfectly clear. 



Australia at the present day is an altogether peculiar zoolo- 

 gical province, characterised by the abundance and variety of 

 Marsupials which inhabit it. In the Post-tertiary deposits of 

 Australia, however, we are presented with proofs that Marsu- 

 pials were just as characteristic of Australia during late geolo- 

 gical epochs as they are now. In the Post-pliocene period 

 we know that Australia was occupied by Kangaroos, Kan- 

 garoo-rats, Wombats. Phalangers, and Carnivorous Marsupials, 

 in every way representing the living Marsupials in zoological 

 value, but specifically distinct, and generally of gigantic size. 



In the same way, South America at the present day is espe- 

 cially characterised by a Mammalian fauna containing many 

 peculiar forms, the Edentata being especially conspicuous, and 

 having a larger representation than in any other region. 

 Similar but distinct forms, however, are found to have existed 

 in South America anterior to the creation of any existing 

 species. Thus, the modern Sloths of South America are re- 

 presented by the colossal Mylodon, Megalonyx, Scelidotherium, 

 and Megatherium. The little armour-plated Armadillos are 

 represented by the equally colossal Glyptodon. The Llamas 

 representing in South America the Camels of the Old World 

 are represented by the curious extinct genus Macrauchenia. 

 The Platyrhine Monkeys have their extinct representatives. 

 Fossil Tapirs take the place of the two existing species ; and 

 the Peccaries are represented by at least five extinct species 

 of Dicotyles. The bone-caves of Brazil have also yielded re- 

 mains of Sloths, Coatis, Kinkajous, Armadillos, Guinea-pigs, 

 Agoutis, Capybaras, Pacas, Coypus, Vampire Bats, and Cerco- 

 labes, allied to, yet distinct from, the species now inhabiting 

 South America. 



Similarly, India is at present the only country in which 

 four-horned Antelopes occur; and it is in the Siwalik Hills 

 that there have been found the two gigantic four-horned An- 

 telopes, which constitute the genera Sivatherium and Brama- 

 therium. 



In Europe, again, the Mammalian fauna of the later Ter- 

 tiary periods is much more closely allied to that now charac- 

 terising the Old World, than to that of the New. We have 



2 N 



