108 FOoSIL IIOIISES' TEETH. 



the iutroduction 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 Mammaha and 

 Mammaha /' (pp. 108-9) : 



''Notice of the remains of a impedes of Equus, found 

 associated with the extinct Edentcds and Toxodon at 

 Punta Attay in Bahia Blanca, and loith the Mastodon 

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

 these remains is a su}:>erior 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 tliat could be established proved it to differ 

 from the tooth of the common Equiis cdballus only in 

 a slight inferiority of size. 



"The second evidence of the coexistence of i\\^ 

 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 loss tetragonal tigure, and have the grinding surface 

 traversed by two transverse angular ridges." — Owen. 



