358 PALAEONTOLOGY AND EVOLUTION xi 



The Hipparion has large depressions on the 

 face in front of the orbits, like those for the 

 " larmiers " of many ruminants ; but traces of these 

 are to be seen in some of the fossil horses from 

 the Sewalik Hills; and, as Leidy's recent re- 

 searches show, they are preserved in Anchi- 

 therium. 



When we consider these facts, and the further 

 circumstance that the Hipparions, the remains of 

 which have been collected in immense numbers, 

 were subject, as M. Gaudry and others have 

 pointed out, to a great range of variation, it 

 appears to me impossible to resist the conclusion 

 that the types of the Anckitherium, of the 

 Hipparion, and of the ancient Horses consti- 

 tute the lineage of the modern Horses, the Hip- 

 parion being the intermediate stage between the 

 other two, and answering to B in my former 

 illustration. 



The process by which the Anchitherium has 

 been converted into Equus is one of specialisation, 

 or of more and more complete deviation from what 

 might be called the average form of an ungulate 

 mammal. In the Horses, the reduction of some 

 parts of the limbs, together with the special modi- 

 fication of those which are left, is carried to a 

 greater extent than in any other hoofed mammals. 

 The reduction is less and the specialisation is less 

 in the Hipparion, and still less in the Anchi- 

 therium ; but yet, as compared with other mam- 



