THE LLAMA AND ITS PAST HISTORY 407 
or llamas could have originated. And that is precisely what 
happened, as already mentioned (p. 86). Towards the 
latter end of the Eocene Period there appeared four genera 
in western North America, all of which exhibit decidedly 
camel-like characters, and Professor Osborn * believes that 
one of these, the diminutive Protylopus, may possibly repre¬ 
sent. the most remote ancestor of the grand American phylum 
of camels. Other genera occur in Oligocene and Miocene beds 
of North America. During the latter period camels had ap¬ 
parently spread in great herds over the continent. It is 
thus probable that they then extended their range to other 
parts of the world. Some of them, like Pliauchenia, had 
assumed llama-like characters, and as the western Pacific land- 
belt was then in communication with California the ances¬ 
tors of the South American llamas were able to pass south¬ 
ward. According to Professor Osborn llamas survived in 
North America until Pleistocene times. They were then 
becoming extinct in the eastern States, lingering on in Cali¬ 
fornia where the great sabre-tooth tiger no doubpstalked tfiem. 
In the Siwalik beds of northern India camels first appear in 
the Pliocene, as in South America, and it is generally assumed 
that the ancestors of the Old World camels crossed over to 
Asia by the Bering Strait land bridge. But as it was probably 
in Miocene times that these early camels wandered westward 
from North America, the Bering Strait land bridge had not 
yet come into existence. They must have utilised the more 
southern bridge, which I think replaced it in earlier Tertiary 
times (Fig. 16). 
Recently we have received clear proof of a migration of 
mammals from Asia to North America, which I think must 
have taken place across the same Pacific land bridge. One 
of the most remarkable discoveries among the many note¬ 
worthy ones in North American palaeontology is that by Dr. 
Matthew and Mr. Cookf of Asiatic antelope remains in 
western Nebraska. The American invasion by true Asiatic 
antelopes was brilliantly and amply confirmed, according to 
Professor Osborn, by Mr. Merriam’s discovery in Nevada. 
* Osborn, H. F., “Age of Mammals,” p. 170. 
f Matthew, W. D., and H. J. Cook, “Pliocene Fauna from Nebraska.” 
