138 AMERICAN MESOZOIC MAMMALIA 



Gypsonictops hypoconus Simpson 1927 

 1927. G. hypoconus, Simpson, Amer. Mus. Novitates, No. 267, p. 6. 



Type. — Y.P.M. No. 13662. Isolated upper molar. 



Horizon and Locality. — Lance formation, Niobrara County, Wyoming. Re- 

 ferred specimens from Hell Creek beds of Montana. 

 Diagnosis. — Sole known species of the genus. 



T elacodonlAiiX^ 1892 

 1892. Telacodon, Marsh, Amer. Jour. Set. (3) XLIII, 258. 



Definition. — Four premolars, simple, trench- 

 ant, the last much the largest. Canine present but 

 small. A much enlarged incisor, procumbent, with 

 root extending back beneath the canine. 

 % ti> ., '" ^^ Type. — T. laevis Marsh. 



Distribution. — Lance, Wyoming. 



Fig. 54. Telacodon laevis. Part of right jt jg uncertain whether T. fraestans Marsh, 



lower jaw with last three premolars ex- ^^ ^ ^^ ^ previous page, can be referred to this 

 ternal view, type. Ten times natural r r o ' 



size. genus. 



Telacodon laevis Marsh 1 892 

 1892. T. laevis. Marsh, Amer. Jour. Sci. (3) XLIII, 258. 



Type. — Y.P.M. No. 11 780. Anterior part of lower jaw with P2-4. Fig'd, Marsh 

 1892A, PI. IX,fig.3. 



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

 Diagnosis. — Sole species in which the parts shown by the type are known. 



Marsh believed that the alveoli anterior to the teeth preserved were for two more 

 premolars, making five in all, and a large procumbent canine. This interpretation does 

 not appear to be sustained by the present study. Anterior to the preserved teeth is an 

 alveolus for another premolar, the first, a very small tooth with a larger anterior and 

 shorter posterior root, very close together. The alveolus anterior to this one is wider 

 than any which follow and is quite undivided. It apparently lodged a small canine. 

 The large anterior alveolus, extending back beneath the canine, must have been for 

 an enlarged, procumbent incisor. 



Batodon Marsh 1892 

 1892. Batodon, Marsh, Amer. Jour. Sci. (3) XLIII, 258. 



Definition. — Premolars simple, trenchant, three or, more probably, four in num- 

 ber. Three teeth preserved in genoholotype preceded by a small alveolus, for Pi or a 



