A'o. 8.1 COPE ON EOCENE VERTEBRATA OF WIND RIVER. 191 



elevated than in J), protenus. Diameters of latter tooth : Length antero- 

 posteriorly, .015; length of heel, .006; elevation of external side of 

 crown anteriorly, .015 ; width at same point, .009. Length of crown of 

 tuberular, .009 ; width of same, .006 ; elevation anteriorly, .005. 



25. DlDYMICTIS LEPTOMYLUS CopC. 



American Naturalist, 1880, Dec. p. 90rt. 

 Eepresented by the posterior three inferior molars. These indicate a 

 species of smaller size than the D. protenus, with the tubercular molar 

 relatively narrower, and perhaps longer. The anterior pa.rt of the latter 

 has the three cusps well defined and close together, and behind them is 

 an oblique longitudinal cutting edge. The middle of the posterior 

 margin rises into a tubercle. The anterior cusps of the tubercular sec- 

 torial are elevated ; the heel has a strong external cutting edge and 

 internal ledge. Length of tubercular sectorial, .009 ; width of same, 

 .005 ; length of tubercular, .007 ; width of same in front, 



26. DlDYMICTIS DAWKINSIANUS Sp. nOV. 



This flesh-eater is represented by more or less imperfect mandibular 

 rami of three individuals. The most complete of these lacks only the 

 portions posterior to the coronoid process, and those anterior to the 

 first premolar, and supports all the teeth excepting the first and second 

 premolars. The premolars are all two-rooted excepting the first. The 

 base of the fourth premolar is considerably longer than that of the 

 third. Both of these teeth have a short posterior heel, and above it a 

 cutting lobe. The fourth has a well-marked anterior basal tubercle. 

 The heel of the sectorial is relatively short, and the anterior portion of 

 the tooth elevated. The anterior and inner cusps are high, and about 

 equal, but the external cusp is much higher. The external border of the 

 heel is more elevated than the inner. The tubercular molar is elongate, 

 and has a small triangular anterior portion somewhat elevated, in slight 

 resemblance to the sectorial tooth. This portion consists of two opposite 

 cusps and a lower one in front of the anterior inner, which connects 

 with the external by an anterior ledge. The posterior portion has a 

 tubercle on the external side, besides a posterior elevation. The ramus 

 is rather slender, and the masseteric fossa is bounded by a prominent 

 ridge in front, but fades out below. 



The measurements show this to be the smallest species of the genus, 

 being much less than the D. leptomylus. 



Measurements. 



SI. 



Length of dental series, including first premolar 0265 



Length of premolar series 0168 



Length of hase of fourth premolar 0055 



Length of base of sectorial 0053 



Width of base of sectorial at middle .0035 



Elevation of sectorial 0055 



