OF MAMMALIA. 599 



But one of the most extraordinary discoveries with regard to this 

 reahn is the fact that it has had a great past history. The fossils teach 

 us, firstly, that the Xenarthra at one time were so numerous and attained 

 such large dimensions as to form quite the leading feature of the realm. 

 The giant ground-sloth or Megatherium and its near ally the Mylodon 

 are found in the Pleistocene and Recent, whilst the equally ponderous 

 Glyptodons or giant armadillos occurred at about the same period. 

 These Edentata as a group appear to have extended back at least as far 

 as the Miocene, if not the Oligocene, and at present we have no good 

 evidence that Edentata have ever occurred in other parts of the world, 

 with the reservation that one or two types appear to have made their 

 way into North America during the Miocene epoch, just as some arma- 

 dillos have done at the present time. 



The second lesson learnt from the fossil beds is that the peccaries, 

 vicunas, guanacos, deer and tapirs which now form the very sparse 

 representatives of the great order Ungtilata, and the Carnivora are all 

 comparatively recent immigrants from the North, no trace of any of 

 them occurring below the Pliocene of Neogoea, though abundant remains 

 are found in North America. On the other hand, there appears to have 

 been a very rich ungulate fauna during the past, though they in their 

 turn may have originated in the North and migrated southwards. How- 

 ever that may be, the horse flourished here in Pleistocene times, as also 

 the Mastodon, both probably northern immigrants. In addition, there 

 were from the Miocene onwards an enormous number of strange ungu- 

 lates, some like rhinoceroses in size and other features. At least four 

 entirely peculiar sub-orders of the Ungiilata have to be instituted to 

 hold these extinct forms. 



The Carnivora, for the same reasons as stated above, appear to 

 have been comparatively recent immigrants from the North, like the 

 peccaries and others. We therefore have a considerable light thrown 

 upon the past history of Neogoea which enables us, at any rate to some 

 extent, to explain its peculiarities at the present day. Put succinctly 

 the history of events appears to have been as follows : — The land-union 

 between North and South America appears to have been of recent date, 

 and from some unknown time up to at least the close of the Miocene 

 epoch, the two continents were separated by the sea. South America 

 then had its peculiar fauna of abundant Edentata and UngiUata, 

 differing from any other part of the world, but upon the establishment 

 of the land connection between the two continents the Neogoean 

 realm was flooded with up-to-date immigrants from the north. Vicunas 

 and guanacos, "cats" and "dogs" {Felidce and Cafiidce), raccoons and 

 skunks, deer, horses, peccaries and mastodons, opossums and many 

 rodents rapidly spread over the land and may have contributed consider- 

 ably to the extermination of many of the indigenous types. Through 

 the Pliocene and Pleistocene this hybrid fauna flourished until all the 

 larger types were for some unknown reason exterminated and the present 

 fauna remained. 



But we still have the indigenous fauna of Neogoea and cannot help 

 attempting to trace its origin. Whence arose all the primitive Ungulates, 

 the Edentates, hystricomorphous rodents, the monkeys and the mar- 

 supials other than opossums (opossum-rats and fossil allies in the 



