ART. 1. PKIMATES OF THE FORT UNION GIDLEY. 11 



front in the series. In the general evolutionary stage of the lower 

 cheek teeth of Elphidotarsius they differ from those of the Eocene 

 members of the group in having the last molar unreduced, while the 

 fourth premolar is well advanced in specialization. 



This genus and species are known only from the type specimen, 

 hence its present reference is provisional on what the anterior lower 

 teeth and upper cheek teeth may show when discovered. From the 

 characters presented in the type, the genus would seem to fit best 

 into Division "V" of Matthew's key to the Tarsiidae, under a new 

 subdivision as follows: 



3. M3 unreduced, paraconida quite distinct; metaconids posterior to protoconids; 

 P4 with rather high, laterally compressed summit composed of three cusps, the 

 protoconid, paraconid, and metaconid, all of subequal size and height. 



Elphidotarsius . 



TETONIUS KEX, new species. 



Plate 3, Figure 4. 



Type.— A second left lower molar. (Cat. No. 9828, U.S.N.M. 

 Coll.) CoUected by A. C. Silberling. 



Locality and Jionzon.—"^o. 12," sec. 22, R. 14, E. T. 5 N, Sweet 

 Grass County, Montana. Fort Union ''No. 3." In upper part of 

 geologic section. 



Specific characters. — Antero-posterior diameter 3.8 mm.; transverse 

 diameter of heel portion 3.5 mm. Lower molars of the broad, low- 

 crowned Absarokius-Tetonius type but larger than any described spe- 

 cies of these genera. 



This species is represented in the collection by the single tooth 

 constituting the type. It merits this distinction only because of the 

 scarcity of material coming from this particular horizon which is 

 nearly 4,000 feet higher in the beds than in the " Gidley Quarry " 

 and " Silberling Quarry " levels, and is therefore here recorded. 



Family PLESIADAPIDAE. 



As Matthew has defined this f amily,« it includes the "Apatemyidae " 

 on the ground of the apparently close relationship of the American 

 genus Nothodectes to the European genus Plesiadapis. The Notho- 

 dectes section of the American group is represented in the Fort Union 

 material by several well-preserved lower jaw portions, a portion of an 

 upper jaw carrying a series of four cheek teeth, and a few character- 

 istic upper incisors. These indicate a new genus closely related to 

 Nothodectes of the Tiffany beds. 



•Bull. Amer. Mus. Nat. Hist., vol. 37, 1917, p. 8-33. 



