TEETH uxea:.t:izd J 



iT ORESTOX, ENG. lOT 



biiobed posterior termination of tlie grinding surface 

 of tiie last upper molar, more closely approximates to 

 the extinct horse of the Miocene period, winch Herr 

 von Meyer has characterized under t!ie name of Eqmis 

 cctbaUus primigenius. The Oreston fossil teeth differ, 

 however, from tliis in the form of the tifth or internal 

 prism of dentine in the upper molars, and in its con- 

 tinuation with the anterior lobe of the teeth, the fifth 

 prism being oval and insulated in the Equus inimi- 

 (/cyz/^/s of Von Meyer. 



'•The Oreston fossil teeth, which in their principal 

 characters manifest so close a relatiouship with the 

 Miocene Equus primigenius, ^\'^^^^. like the later drift 

 species 'yE^i. fossilis), from the recent horse in a greater 

 proportional antero-posterior diameter of the crown, 

 and also in a less produced anterior angle of the first 

 premolar. I have named this British fossil horse 

 Equus plicidens. The fossil horse {Eq. cnrvidens) of 

 South America, which coexisted with the megathe- 

 rium,! and, like it, became extinct apparently before 



the more ancient primigenial species (Hippotlieria) of the conti- 

 nental Miocene deposits, without being reminded of the peculiar 

 character of the enamel of the molars of the Elasmotherium, in 

 which it is folded in elegant festoons. This extinct pachyderm, 

 which surpassed the rhinoceros in size, resembled that genus 

 very closely in the general disposition of the folds of enamel in 

 the grinding teeth, but agreed with the modern horse in the 

 deep implantation of those teeth by an undivided base. The 

 EUismothere appears, therefore, to have formed one of the links, 

 now lost, which connected the horse with the rhinoceros ; and 

 it is interesting lo observe that some of the extinct species of 

 horse, in the analogous complexity of the enamel folds, more 

 closely resembled the Elasmothere than do the present species." 

 f " The teeth of this most gigantic of the extinct quadrupeds 

 of the sloth tribe are small in proportion to the size of the ani- 



