Skull of young Camel. 



middle Oligocene called Proebrotherium, which in turn was preceeded 

 in the lower or Unita Oligocene by a representative called Lepto 

 tragulus, which itself may have sprung from a still earlier form, the 

 Homacodon of the Bridger (earlier Eocene) beds. 



It is quite evident that the camels of today came in rather direct 

 line from more generalized forms and were originally a North Ameri- 

 can group. Hence when the camel lay down and died in the Brea 

 Beds, it was buried in its native country. From this favored spot 

 the earliest forms began their long process of differentiation and 

 migration of the earth. That the molar dentition of the Siwalik 

 camels is very similar to that of the vicunas and guanacos of South 

 America is remarkable, and a common branch must appear somewhere 

 in the genetic tree. Why this species (having peculiar molar teeth) 

 should become extinct in India, but develop and survive in South 

 America, is likewise a problem. What native tendency or habit or 

 climatic conditions or character of food should, in two such widely 

 separated regions, give rise to the dentition, and in the one fade 

 away, and in the other survive, are queries that remain unanswered. 

 In fact, the disappearance of the camels from North America is very 

 strange indeed, yet not more singular and perplexing than the 

 disappearance of this whole great group of other large animals repre- 

 sented in the Brea Beds. 



On the whole then, we have here a very remarkable illustration 

 of world-wide migration, beginning in the United States in the lower 

 Eocene (Fintocene Oligocene) beds. From here the distribution was 

 rapid over the Mississippi valley with one branch, (llamas) turning 

 southward, and probably by the way of tne Isthmus of Panama, 

 entered the South American continent in the Post-pleistocene times, 

 to be spread over the whole region and subsequently to survive in 

 the sheltering Andes. The other branch (Cameius) pushed to the 



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