PANTODONTA. 519 



no external nor internal cingula. The surface of the enamel is strongly and 

 closely rugose where not worn. 



The posterior inferior molar exhibits a transverse posterior crest, with- 

 out any tubercle or ridge in the mouth of the posterior V-shaped valley. 

 There is a strong posterior cingulum, amounting to a narrow heel. As in 

 the case of the superior molar, the enamel where not worn is closely and 

 strongly wrinkled. The first superior premolar is characterized by the vexy 

 small development of its internal lobe, which is only a strong basal cingu- 

 lum. The crown proper has a sub-triangular outline, and the external face 

 is flat and not concave. No external cingulum; enamel wrinkled. An 

 external incisor has a large transversely extended crown, without cingula. 

 A low rib on the median line of the inner side. Enamel wrinkled. In 

 this and in another incisor the base of the crown is considerably expanded 

 laterally. 



Measurements. 



M. 



I anteroposterior 035 



Diameters of crown M. iii, sup. < transverse 041 



( vertical : 020 



Width of M. iii inferior, posteriorly 022 



Diameters of Pm.i, sup. 5 '*"*^'^°P"^*«"°'"- — "^^ 



( transverse 014 



Diameter base crown I, ii 024 



Length crown i, ii 019 



Width base crown i, iii 026 



The crowns of the molars of this species are about as large as those of 

 an ox. From the basin of the Big Horn, Northern Wyoming. 



ECTACODON Cope. 



American Naturalist, 1882, 73 (Dee. 30, 1881). Proceed. Amer. Philos. Soc, 1881, Dec, p. 167, Feb. 1882. 



In Ectacodon the last superior molar has more of the elements of a 

 posterior external V than in Coryphodon, but not so much as in Manteodon. 

 The posterior transverse crest, it is true, has no oblique posterior ridge 

 joining it, to form with it more or less of a V. But the external posterior 

 angle of the crown supports a cusp homologous with the vertical rib found 

 at the basal or external angles of the Vs in Palceosyops and allied genera, 



