ITS ANCESTORS AND RELATIONS 



10 



are nearly, if not quite, the oldest of the Eocene forma- 

 tions of North America. 



Although this most interesting animal was known 

 and named by Cope as long ago as 1873 from teeth 

 alone, it was not until the more recent discoveries by 

 Wortman of complete skeletons of more than one indi- 

 vidual with all their bones in connection that we were 

 put in possession of almost as perfect a knowledge of 

 its osteological characters as of any animal now exist- 

 ing. The figure, and descriptions published by Pro- 

 fessor Cope, 1 and the excellent casts sent to this country 

 of one of the skeletons, have made this knowledge widely 

 accessible. Although this creature was of an extremely 

 generalised form, it was obviously so far separated from 

 the primitive mammalian type, whatever that may have 

 been, as to come within the definition of the ungulate 

 group, using this term in its widest sense. The 

 terminal bones of the toes were of such a form as to 

 show that they were encased in hoofs, instead of carry- 

 ing claws, and it had no clavicles. The teeth also 

 were adapted for a herbivorous or omnivorous diet. 



Phenacodus, however, does not stand alone, even in 

 our present state of knowledge ; it belongs to a family 

 of which several generic modifications are already de- 

 scribed, and remains of still more generalised forms, the 



1 Report of the United States Surrey of the Territories, vol. iii. 

 1884. 



