26 



EVOLUTION OF MAMMALIAN MOLAR TEETH 



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FIG. 12. Superior molars of Ptralcstts Owen. Upper Jurassic, England. Right side. 

 External, oblique and crown views. These upper molars were probably associated with lower 

 molars of the type seen in Spalae^Hn.riiim (Fig. 11). /(*, nietastyle; pr, pr, pr, main internal 

 cusps believed to be protocones ; ?pa, ?iw., smaller external cusps believed to be para- and meta- 

 cones. 



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FIG. 13. a, Kurtodon. Superior molar series of the left maxilla, viewed upon the wearing 

 surface, b, Amblotheriuni soriciwiui, inferior molar series, viewed from above. It 1 A. (Peraspalax) 

 talpoides. A lower molar viewed upon the internal face. c. The same. A lower molar viewed 

 from above, d, Ac/iyrodon nanus. A lower molar viewed from above. Much enlarged. 



