ITS ANCESTORS AND RELATIONS 27 



mens of identical or similar forms were subsequently 

 found in Eocene formations in England and other parts 

 of Europe, and others referred to the same genus far 

 more abundantly and in a far more perfect state of pre- 

 servation in beds of corresponding age in North America. 

 To a closely allied form the name of Pachynolophus has 

 been given, while Pliolophus and Orohippus are probably 

 identical, and they are all so nearly related to a previ- 

 ously known but larger animal, called by Cuvier Lo- 

 plbiodon, that they are commonly associated to form a 

 family Lophiodontidce. Some of these animals 1 present 

 a very distinct advance in evolution upon Phenacodus, an 

 advance in some respects so great as to move them, 

 according to Cope, into a distinct ordinal division of the 

 Mammalia. This consists mainly in a modification of 

 the form and relations of the bones of the carpus and the 

 tarsus from their primitive condition, which modification 

 persists in all the more recent forms of true ungulates, 



hitherto-discovered extinct forms of life. They form the order 

 Hyracoidea of Huxley, but may be included in the Ungulata, using 

 that term in the very widest sense. They are the animals whose 

 Hebrew name is translated in the English Bible into 1 coney ' or 

 rabbit, to which in size, colour, and habit they bear a considerable 

 general resemblance. 



1 Madame Marie Pavlow has shown that under the name of Hyra- 

 cotherium some very different forms have been confounded, the type 

 species of Owen being the most primitive, and perhaps identical with 

 Cope's Phenacodus, while the American R. ve?iticolum, of which the 

 whole skeleton is known, and to which the description in the text 

 chiefly applies, is a much more advanced form. 



