UPPER CRETACEOUS MULTITUBERCULATA 103 



Horizon and Locality. — Lance formation, Niobrara County " Wyoming. 



Diagnosis. — Ma cusp formula 4:2, length ^.^ mm., width 5.2 mm. M^ (referred, 

 type of "Tr'ipr'wdou coelatus"), cusp formula 3 : 3 : 4 or 3 : 4 : 4, length 6.6 mm., width 

 6.4 mm. Species used in a broad sense for all Metiiscocssus from the Niobrara County 

 Lance. 



Included Species 



1889. Dipriodon lunatus, Marsh, Amer. Jour. Sci. (3) XXXVIII, 85. Type: Y.P.M. No. 



1 1825, isolated Mj. Fig'd, Marsh 1889A, PI. II, figs. 16-18. 

 1889. Tripriodon coelatus, Marsh, Amer. Jour. Sci. (3) XXXVIII, 86. Type: Y.P.M. No. 



1 1853, isolated M*. Fig'd, Marsh 1889A, PI. II, figs. 19-21. 

 1889. Tripriodon caperatus. Marsh. Amer. Jour. Sci. (3) XXXVIII, 86. Type: Y.P.M. No. 



1 1852, isolated lower incisor. Fig'd, Marsh 1889A, PI. Ill, figs. 18-20. 

 1889. Selenacodon fragilis, Marsh, Amer. Jour. Sci. (3) XXXVIII, 86. Type: Y.P.M. No. 



1 1897, fragment of isolated M^ Fig'd, Marsh 1889A, PI. II, figs. 22-24. 

 1889. Selenacodon drevis, Marsh, Amer. Jour. Sci. (3) XXXVIII, 177. Type: Y.P.M. No. 



1 1876, isolated M^. Fig'd, Marsh 1889B, PI. VII, figs. 9-12. 

 1889. Halodon sculptus, Marsh, Amer. Jour. Sci. (3) XXXVIII, 87. Type: Y.P.M. No. 11810. 



isolated P4. Fig'd, Marsh 1889A, PI. Ill, figs. 11-13. 

 1889. Oracodon anceps, Marsh, Amer. Jour. Sci. (3) XXXVIII, 178. Type: Y.P.M. No. 11862, 



isolated last upper premolar. Fig'd, Marsh 1889B, PI. VIII, figs. 13-16. Doubtfully in- 

 cluded. 

 1892. Oracodon conulus. Marsh, Amer. Jour. Sci. (3) XLIII, 256. Type: U.S.N.M. No. 2141. 



isolated last upper premolar. Fig'd, Marsh 1892A, PI. VII, fig. 8. Doubtfully included. 



For convenience a list is given of Marsh's figures of specimens now included in 

 this broad species : 



Marsh 1889A, PI. II : Figs. 13-24. 



PI. Ill : Figs. 1-22. 

 1889B, PI. VII: Figs. 5-12. 



PI. VIII: Figs. 1-3,13-16. 

 1892A, PI. V: Figs. 1-7. 



PI. VI : Figs. I, 5. 



PI. VII: Figs. 6-8. 



Apparently two, possibly more, species are present, but they are clearly closely 

 related. Marsh's generic types are principally based on different parts of the dentition. 

 Only close comparison with the better known Ptilodus makes their association in one 

 genus possible. 



Dentition 



Lower Incisors. — Y.P.M. No. 11852 {Tripriodon caperatus) is typical of the 



==« "Laramie of Converse County" — the formation is now known as Lance (a restricted part of the 

 old Laramie) and the localities are in what is now Niobrara County. For exact localities of all these 

 forms see Lull, 191 5a. 



