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Fig. 1. — Evolution of the horse. Stages passed through from the 

 earhest four-toed Eo hip pus (upper left) to the three-toed Meso- 

 h'tppus (upper middle) to a form with the side toes reduced 

 (Merychippus, upper right) to the small, clumsy, one-toed Equus 

 scotti (lower left) to the modern horse (lower right) . 



Reproduced from photographs hy W. E. Corbin of fos§ils found in 

 successive layers of rocks and now preserved in the Museum at Amherst 

 College. 



