ITS ANCESTORS AND RELATIONS. 33 



skeletons have been discovered and fully described 

 by Leidy, so that its osteology is now completely 

 known. A few further stages of modification lead 

 to the Palceotherium of the Paris basin (late Eocene), 

 an interesting form from its association with the 

 illustrious Cuvier, who in 1804 established its exist- 

 ence, and by comparison of its bones with those of 

 all known recent species of animals, demonstrated 

 for the first time to the satisfaction of the scientific 

 world that animals had inhabited the earth other than 

 those now found upon its surface. By this dem- 

 onstration he laid the foundation of the study of 

 palaeontology of vertebrated animals — a study which 

 has developed in this comparatively short period of 

 time to such a marvelous extent, and which has still 

 before it a future of unbounded promise. 



By the time that the Palaaotherium appeared, the 

 group of Perissodactyles was already breaking up 

 into different families by the gradual change in vari- 

 ous directions from the primitive Lophiodont type. 

 Some were passing step by step into tapirs, which 

 still exist and retain much more of the original char- 

 acters of the primitive ungulates of the Eocene 

 period than any of the others now remaining on 

 the earth, having indeed continued practically un- 

 changed since the Miocene times; while almost all 

 other mammalian forms which existed then have 



