VERTEBRATE FAUNA OF THE LOUP FORK BEDS. 19 



1 refei' to this species with much reserve a last inferior molar, which 

 is for" the most part in excellent preservation. It resembles the inter- 

 nlediate molar on which the species was establislied in most respects, but 

 presents some important differences, among which is a relatively infe- 

 rior size. The fact that the last molar exceeds ver}^ little in length the 

 typical intermediate molar, renders the identification doubtful, unless it 

 indicates a small race of the same species. I provisionally adopt the 

 latter view. 



The molar referred to supports only tliree crests and a well developed 

 heel. These crests are elevated, with their apices contracted both longi- 

 tudinally and transversely. The usual median fissure divides each crest 

 into an internal and an external half, of which the former is obtusely 

 serrate or tubercular, and the external expands anteroposteriorly toward 

 the base, were it supports one or more small tubercles which obstruct the 

 transverse valleys. There is an external, but no internal cingulum. The 

 former extends round the external half of the anterior base, where it is 

 coarsely crenate. The robust external anterior cusp, in place of an an- 

 terior basal tubercle, sends downward and inward a wide ledge, which 

 passes cingulura-like round the base of the internal cusp to the inner side 

 of the crown. In the characters so far enumerated this tooth resembles 

 the typical specimen. The differences are as follows: In the new tooth 

 the internal half of the middle cross-crest has three tubercles; in the type 

 there are four (one smaller). On the external half of this crest there is 

 no tubercle besides the main cusp; in the type there is one, in line with 

 four of the other half. The new tooth shows a single tubercle behind 

 the main external cusp; in the type there are two. The posterior crest 

 has in both teeth three tubercles on the external half; on the internal half 

 there are three, besides the principal in the type, and but one in the new 

 tooth. 



In both teeth the internal part of the first cross-crest is not serrate. 

 In the new tooth the heel consists of three obtuse tubercles, of which the 

 external is the largest. The valley separating it from the crest in front 

 is not blocked by a tubercle. Enamel smooth. 



Measurements . 



Mm. 



Total length of crown 140 



Width of crown at first crest 80 



Width of crown at second crest 76 



Width of crown at third crest 68 



Width of apex of first crest 49 



Width of apex of third crest 36 



Elevation of first crest from cingnkim 46 



Elevation of third crest from cingulum 43 



As already remarked, this tooth is relatively smaller than the corre- 



