INTRODUCTORY. 



nearest to the Tapirs, which are the most lowly differen- 

 tiated of existing Perissodactyles. 



The Lophodon is hence regarded as the ancestral form of 

 the modern Tapiridse. 



The Acerotherium is the earliest representative of the 

 Khinoceros, and is met with in the Miocene strata of 

 the Old World. 



The Palaeotheres first occur in the Eocene strata of 

 Europe and North America. They varied in size from 

 that of a Eoedeer to that of a Tapir, and their molar teeth 

 resembled, in the pattern of the grinding surface, those of 

 the Rhinoceros. 



They are allied on the one hand with the Horse and 

 Ehinoceros, and through the Macraucheniada? on the other 

 with the Camels and Tapirs. 



Palseotherium Magnum was of the same size as a Horse, 

 and Paleeotherium Medium of the same size as a Pig. 



In the Eocene strata of the Utah Territory of North 

 America is found the Eohippus. This extinct animal is the 

 earliest ancestral form of the Horse. It was of about the 

 same size as a Fox, and its feet have three toes behind and 

 three in front. 



In the early Miocene and late Eocene the Anchitherium 

 appears. It was of the size of a sheep. 



In the early Pleiocene and late Miocene the Hipparion, 

 Protohippus and Pleiohippus appear. These extinct forms 

 were about the size of an Ass. 



The Hipparion was a small graceful animal, having three 

 well developed toes, each bearing a hoof. The middle toe 

 was strong and large, while the lateral toes were so small 

 as not to reach beyond the fetlock. 



It is noteworthy that cases are recorded where Horses 

 have been born with a tridactyle foot in every respect 

 similar to that of Hipparion. 



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