Mbrycoidodon culbektsoni, Leidy. 

 Plate II, figs. 18-26. 



A second genus of Agriochosridce (Oreodontidce) is represented by separate teeth from 

 the Cypress hills, included in the collections of 1884, 1889 and 1904. They are referred to 

 Merycoidodon culbertsoni, Leidy, of the Oligocene of South Dakota, and consist of the 

 following specimens : — The left lower caniniform premolar, mentioned by Cope in part I of 

 this volume, but not assigned by him to any species (Weston, 1884), a left upper canine 

 (Lambe, 1904) and a right lower second molar (Lambe, 1904). 



The premolar, plate II, figs 18 and 19, agrees closely in size and' form with the corre- 

 sponding tooth of the female skull of M. culbertsoni, described and figured by Leidy iu " The 

 Ancient Fauna of Nebraska." This premolar shows signs of wear, in front on the outer side, 

 and behind on the inner side, where it closed against the upper canine and the upper first 

 premolar. 



Measurements of lower first premolar. 



MM. 



Exterior height of crown (worn) , 13 



Antero-posterior diameter of crown at base , 13 



Transverse diameter of crown at base , 7 ■ 5 



The left upper canine, figs. 20-23, is long, curved, and subtriangular in transverse section 

 throughout its length. The, posterior surface, fig. . 21, is flattened, and the exterior and 

 interior surfaces are nearly flat, the former being slightly more convex than the latter, fig. 

 20, in which a low, longitudinal median ridge is developed in the fang above the crown. In 

 the exterior surface a shallow groove is noticed in a corresponding position. The forwaijd 

 angulation is evenly rounded. The crown of the tooth is worn flat posteriorly, where it came 

 in contact with the lower first premolar, and its side angles are sharp. The immediate 

 extremity of the cr&wn is broken ofifbut it seems to have been bluntly pointed. The enamel 

 of the crown extended upward from the point, about 20 mm., measured along the forward 

 angulation. The antero-posterior diameter of the tooth throughout its entire length exceeds 

 the breadth of the posterior flattened surface (max. transverse diameter), otherwise the 

 resemblance of the Cypress Hills tooth to that of M. culbertsoni is strong. In describing the 

 upper canine of this species, Leidy, in his above mentioned memoir (p. 42), states that the 

 posterior side " is a little larger than the other sides," that is the transverse diameter 

 exceeded the antero-posterior diameter. 



Measurements of upper canine. 



MM. 



Total length of specimen along anterior curve , 58 



Max. transverse diameter at base of crown 9 



Antero-posterior diameter at base of crown 10-5 



Antero-p6sterior diameter near upper end of fang, 12 



Transverse diameter " " ' " 10 



The remaining tooth, referred to M. culbertsoni, is a lower right second molar, figs. 24, 

 25 and 26. Comparing the specimen with Leidy's figure of the corresponding tooth (op. cit. 

 pi. Ill, fig. 4) no difference is noticed, except that the Cypress Hills molar is a little the 

 larger of the two. 



