THE BEAK OF SOUTH AMERICA 351 



is confined to the Andes between Colombia and Chile, that is 

 to say, altogether to western South America. This range sug- 

 gests that the bears are not originally a South American family, 

 otherwise we might expect their having a wider distribution. 

 The only alternative is that they migrated from some other 

 part of the world to the part of South America where they 

 still maintain themselves. Dr. von Ihering * argued that the 

 ancestors of the South American bear originally came from 

 Asia, and that they wandered across on a Miocene land con- 

 nection which united eastern Asia with Central America with- 

 out touching North America. In that case they would be older 

 than the North American bears which, according to Professor 

 Osborn,! belong to the much later Pleistocene Eurasiatic inva- 

 sion. As a matter of fact, the geological history of the bears in 

 America has never received the careful attention it deserves. 

 Bears, it is well known, are entirely absent from Africa south 

 of the Sahara, that is to say, from what is known as the 

 Ethiopian Region, and no fossil remains of any members of 

 the family have ever been discovered there. Hence it is un- 

 likely that Africa was the source of the Ursidae or that they 

 invaded South America by means of a direct land bridge from 

 that continent as suggested by Dr. Ameghino. J The absence 

 of bears from the whole of eastern South America indicates, 

 moreover,, that bears have made their; entry from the west. Thte 

 bears of South and North America are not closely related. 

 They appertain to different genera. A fossil bear (Arcto- 

 therium vetustus), belonging to a genus closely related to or 

 identical with Tremarctos, has been recorded by Dr. Ameghino 

 from the Entrerios deposits of Argentina which are of Mio- 

 cene age. It would appear on that account as if Dr. von 

 Ihering's suggestion that the South American bears were older 

 than the North American ones, and had quite an independent 

 Asiatic origin, was borne out by palaeontological evidence. 

 Since Arctotherium also occurs fossil in some Pleistocene 

 beds of North America it must have spread northward in 

 recent times and subsequently have become extinct there. 



* Ihering, H. von, " Greschichte der Siidamer. Raubtiere," p. 1*79. 



t Osborn, H. F., "Age of Mammals," p. 438. 



J Ameghino, Fl., " Tetraprothomo argentinus," p. 230. 



