108 FOSSIL HORSES' TEETH. 



the introduction of the human race, differs from the 

 existing horse by the greater degree of curvature of 

 the upper molars." 



The following account of two fossil molar teeth of an 

 extinct species of horse, discovered in South America, 

 may be found in Prof. Owen's "Fossil Mammalia and 

 Mammalia," (pp. 108-9) : 



"Notice of the remains of a species of Equus, found 

 associated witli the extinct Edentals and Toxodon at 

 Punta Alta, in Bahia Blanca, and with the Mastodon 

 and Toxodon at Santa Fe, in Entre Rios. The first of 

 these remains is a superior molar tooth of the right 

 side. It was imbedded in the quartz shingle, formed 

 of pebbles strongly cemented together with calcareous 

 matter, which adhered as closely to it as the corre- 

 sponding matrix did to the associated fossil remains. 

 The tooth was as completely fossilized as the remains 

 of the mylodon, megatherium, and scelidothere, and 

 was so far decomposed that in the attempt to detach 

 the adherent matrix it became partially resolved into 

 its component curved lamellae. Every point of com- 

 parison that could be established proved it to differ 

 from the tooth of the common Equus caballus only in 

 a slight inferiority of size. 



"The second evidence of the coexistence of the 

 horse with the extinct mammals of the tertiary epoch 

 of South America reposes on a more perfect tooth, 

 likewise of the upper jaw, from the red argillaceous 



mal. They are five in number on each side of the upper jaw, 

 and, probably, four on each side of the lower. They present a 

 more or less tetragonal figure, and have the grinding surface 

 traversed by two transverse angular ridges." Owen. 



