21 



lacks the canine and incisors, and its inferior border anterior to the first premolar. From 

 the last circumstance it results that the presence or character of the mandibular tuber- 

 osities cannot be ascertained. Some separate molar teeth of the same species I have 

 recorded as above as the E. mortonii, to which the E. arclatum is nearly allied. 



The present species is a little inferior in dimensions to the E. mortonii and E. magnum, 

 and it differs from the former in the absence of diastemata between the premolar teeth, 

 except a very short one between the third and fourth. The latter is separated by a very 

 short space from the canine. The second premolar is larger than the first, and the third 

 and fourth are abruptly smaller than either. The latter has but one, a compressed, later- 

 ally-grooved root. The crowns of all the premolars are compressed, and have fore and 

 aft cutting edges. The true molars are peculiar in the elevation of the anterior part of 

 the crown of two tubercles, above the posterior part. The latter consists of three tubercles, 

 the third or posterior median tubercle being better developed than in the E. mortonii, 

 especially on the last molar. As the jaw is adherent to a block of conglomerate rock, 

 only the internal sides of the teeth are visible. These are without cingula, and the 

 enamel of the molars is smooth, while that of the premolars is wrinkled. 



A wide space separates the last molar from the base of the coronoid process, which is 

 low. The condyle is in line with the crowns of the molars. The ramus is compressed 



and not very deep. 



Measurements. 



Mm. 



Length from condyle to edge of canine alveolus 295 



" " last molar 125 



" of true molar series 67 



f Longitudinal 23 



Diameters of m. iii J. 



{ Transverse 13 



( Longitudinal 22 



Diameters of M. i J. 



(. Transverse 13 



(Vertical 20 



Diameters of P. m. i ... -J 



( Longitudinal at base - 2S 



(Vertical 21 



Diameters of P. m. ii. . . -J 



(. Longitudinal at base 2S 



( Vertical • ■ 13 



Diameters of P. m. iv. -j 



{_ Longitudinal at base 13 



Elevation of coronoid above border 57 



Depth of ramus at m. i 55 



This species is interesting as presenting a more primitive character than the Amer- 

 ican species so far known, in the closely-placed premolar teeth. The form of the true 

 molars is also more primitive in the elevation of the anterior pair of cusps, almost resem- 

 bling some species of Mioclaenus in this respect. The large fifth tubercle has a similar 

 significance. The type specimen was found by Mr. T. C. Weston near the head of the 

 Swift Current Creek in August, 1889. 



? OREO-DON, Leidy. 



The scarcity of Oreodontidse in the collections from the Cypress Hills is a matter of 

 surprise. An inferior fourth (first) premolar is the only indication of their presence. 

 The genus is not determinable. 



