506 THE EOCENE PERIOD. 



features. The first is its superior size. The second is the flattened form 

 of the external faces of the true molars and the absence of the convexity 

 of the external bases of the crown. 



There is some variation in size. A few specimens apparently belong 

 to a smaller race, whose last four superior molars measure M. .032. 



All the specimens of this species in my possession were obtained by 

 D. Baldwin in the Wasatch beds of New Mexico. 



Meniscotherium tapiacitis Cope. 



Proceed. Amtr. Pbilos. Soc, 1882, p. 470. 

 Plate XXV/, fig. 15. 



The species now to be described is a good deal smaller than the 31. 

 chamense, and a fortiori than the M. terrcerubrce. It is known to me from 

 the nearly entire rami of a single mandible. These support the last five 

 molars of one side or the other, and alveoli of two others and of the canine 

 tooth. 



Two characters besides the small size are observable in this jaw. First, 

 the symphysis has not the shallow convex inferior outline in transverse sec- 

 tion, but is on the contrary angular, having subvertical sides separated from 

 a convex middle by a rounded angle. The symphysis is thus deeper than 

 in M. terrcerubrce. Second, the crown of the third inferior molar tooth has 

 the form of that of the second of the 31. terrcerubrce. It is anteroposteri- 

 orly short, and has no keel nor anterior basal lobe ; its section is lenticular, 

 and profile subconic. In 31. terrcerubrce this tooth is elongate; with well 

 developed keel and anterior lobe. The alveolus of the canine is relatively 

 larger than that of the 31. terrcerubrce. The coronoid process does not rise 

 so close to the last molar tooth, nor so steeply, as in the latter species. The 

 posterior recurvature of the internal extremity of the anterior limb of the 

 posterior V of the true molars is but little marked. 



Measiirements. 



M. 



Length of true molars ou base 018 



Diameters M. ;; 5 ant'^«PO«terior 006 



transverse 0038 



transverse 0044 



_.. , „ ...anteroposterior 0065 



Diameters M. "> ^ '■ 



