THE STORY OF THE HORSE 



223 



and steadily advanced. Side lines developed which 

 finally disappeared, but the main line kept on, and 

 when the Quaternary came the horse arrived with it. 

 Many of the skeletons in this series were known be- 

 fore it was realized what they were. As time went 

 on and intermediate forms were found, it became pos- 

 sible to recognize these as ancestors of the horse and 

 to assign them their proper position in the family tree. 



Wrist' 



After H. F. Osborne and Charles R. Knight. By permission of the American Museum of 

 Natural History. 



THE EVOLUTION OF THE HORSE'S FOOT 



The earliest of the forerunners of the horse with 

 which we are acquainted would certainly not be recog- 

 nized as such by any but the most careful student of 



