ITS PLACE IN NATURE 



9 



longest lived as species, while such very strangely modi- 

 fied forms as Uintatherium^ Ma chair odus, 2 and Thyla- 

 coleo* passed rapidly over the stage and then vanished 

 from sight. 



It is proposed in this little work to treat of the 

 horse, not as an isolated form, but as one link in a great 

 chain, one term in a vast series, one twig of a mighty 

 tree ; and to endeavour to trace, as far as our present 

 knowledge permits, what its relations are to the rest, 

 and by what steps of modification in its various parts it 

 has come to be the very singular and highly specialised 

 animal we have now before us, so distinct from all 

 existing forms of life that in most of the older 

 zoological systems it was (at least associated only with 

 some very immediate allies, structurally almost identical) 

 placed in an order apart from all other mammals, under 

 the name of Solidungnla, Solipedia, or Monodadyla, the 

 animal with the solid foot, or rather with a single toe 

 on each extremity. 



1 A huge beast from the Eocene of North America, with limbs 

 resembling those of an elephant, and a rhinoceros-like skull, but 

 with great descending flattened tusks in the upper jaw, and three 

 pairs of bony prominences, like horns, on the top of the head. 



2 An animal allied to the tiger, with enormous sabre-like upper 

 canines, found in the later Tertiaries of both Europe and America. 



3 A marsupial of the late Tertiary period of Australia, as large as 

 a sheep, allied to the phalangers and kangaroos, but with one huge 

 cutting cheek-tooth (premolar), and one great incisor on each ^ide 

 of each jaw, all the other teeth being extremely reduced in size and 

 almost functionless. 



