EVOLUTION OF THE SKULL AND TEETH OF EOCENE TITANOTHERES 



287 



Measurements of type of Lambdoiherium progressum {Am. 

 Mus. 14917) 



Millimeters 



P2-P1 26 



P2, anteroposterior 8 



P2, transverse (trigonid) 4. 8 



P3, anteroposterior 9 



This Wind River type is distinguished by ps, which 

 has a strong metaconid — that is, it is submolariform. 

 A series of molar teeth, p^-m^ (fig. 242), from the 

 highest level of the lower Huerfano, is referred to L. 

 progressum on the following grounds: (1) The upper 

 teeth fit pretty well those of the type of L. progressum 



L. macjnum type 

 Figure 240. — Jaws and teeth of Lambdoiherium 



Am. Mus. 17526, lower jaw of L. priscum, referred specimen from Huerfano A, outside and crown views. Am. Mus. 

 17527, outer view of type jaw of L. magnum, Huerfano A. Am. Mus. 15000, first and second upper molars of L. 

 magnum, referred specimen from the Wind River horizon of the Big Horn Basin, Wyo. Natural size. After 

 Osborn, 1919. 



P3, transverse 6 



P4, anteroposterior 9. 3 



P4, transverse 7. 3 



Ml, anteroposterior 11. 5 



Ml, transverse . 8. 5 



M2, anteroposterior 12. 5 



Mj, transverse 9. 5 



from the Wind River; (2) the parastyle is especially 

 prominent at the antero-external angle of m^, m'; (3) 

 m^ has prominent hypocone and cingular hypostyle; 

 (4) the outer cusps of the premolars are approximated, 

 conules prominent; (5) the cingulum is strong on p^ 

 and m'. 



