MORRISON MAMMALS: PANTOTHERIA 7J 



Referred Specimen. — Y.P.M. 13748. Part of right maxilla with M*"'. 

 Horizon anh Locality. — Morrison formation, Quarry 9, Como Bluff, Wyoming. 

 Diagnosis. — Centroexternal cusp a triangular pyramid, posterointernal face con- 

 cave. Outer borders of molars straight. (Several lesser differences, see below.) 



Dentition 

 This species is much like the foregoing but differs in a number of details of molar 

 construction. The external border is straight, rather than concave, the anteroexternal 

 and posteroexternal cusps being less external relative to the centroexternal cusp. The 

 latter is slightly smaller relative to the internal cusp and is markedly triangular in 

 horizontal section. The posterior crest from its summit is sharper and runs posteroin- 

 ternally. The posterointernal face is concave rather than convex. The anterior crest 

 from the internal cusp stops at the base of the centroexternal cusp, but a strong angula- 

 tion runs from the apex of the latter anteriorly toward but not to the anteroexternal 

 cusp. The more posterointernal of the two cusps at the posteroexternal corner of the 

 crown is relatively smaller. 



Melanodon cf. goodrichi Simpson 



Material.— Y.P.M. No. i3749- Right maxilla with M*"*. 



Horizon and Locality.— Morrison formation. Quarry 9, Como Bluff, Wyoming. 



The teeth of this specimen are smaller than in the type and differ in a few details. 

 The anterior crest from the internal cusp does run to the apex of the centroexternal 

 cusp, so that two distinct angulations, very close to each other, run down the anterior 

 slope of this cusp. The posterior crest from this cusp runs somewhat more externally 

 than in the type of M. goodrichi. More material might show this to be a distinct species, 

 but at present it is preferred to impute its peculiarities to individual variation. The 

 molar widths follow : 



M* M- M» M* 

 1.4 1.7 1.9 2.0 



Herpetatrus or Melanodon, spp. indet. 

 1880. DryoUstesobtusus, Marsh, Amer. Jour. Sci. (3) XX, 237. 



Material.— Y.P.M. No. 11819A. Left maxilla with P' and M^'. Tj^pe of Dryo- 

 Ustesobtusus Marsh. Fig'd {TisDryolestes), Osborn 1904. PI. XXI, fig. ia; 1907, fig. 

 14A. 



