69 



The crown is long, compressed and recurved ; the posterior 

 margin is sliarp, and exhibits some indications of a slight ser- 

 ration. 



Premolars. — The first premolar is not preserved in our 

 specimen. The second and third are subequal, and of about 

 the same conformation. They are implanted by three fangs, 

 one internal and two external. The crown is subcircular at 

 the base. The basal ridge is large, and completely surrounds 

 the crown ; above this the crown becomes somewhat trihedral : 

 and is composed of two pyramidal lobes, which meet inter- 

 nally and externally, and are divided bv a valley. The 

 summits of the lobes form transverse grinding ridges ; the 

 anterior one is the lower, and is crescent-shaped, while the 

 posterior is straight ; the anterior ridges throughout the 

 series are much the most worn. The basal ridge is not 

 indented on the outer side at the opening of the valley as in 

 Dinoccras. 



Molars. — The true molars increase in size regularly back- 

 wards. The first molar is larger than the last premolar; 

 it is worn down nearly to the basal ridge, but shows a small 

 internal accessory tubercle on the back part of the posterior 

 lobe. The extremities of the lobes rise into points, and their 

 summits are transversely concave. The number and arrange- 

 ment of the fangs in the first and second molars is the same 

 as that of the premolars; in the last molar there are but two, 

 which are long and wide, and extend the whole breadth 

 of the crown. This tooth is b}' far the largest of the molar 

 series ; it is ovoidal in shape, with the apex at the outer point 

 of the forward lobe ; it is proportionally broader than in Uin- 

 tatJicriuui rolnistuui. The basal ridare is strong-, and extends 

 around the entire tooth, with some irregularities of outline at 

 the sides. This tooth, like the others, consists of two pyra- 

 midal lobes separated by a valley, which in this case is wide 

 and deep. The summit of the anterior lobe is the longer, and 

 extends obliquelv across the crown, while the posterior is 

 nearly straight. The free ends and junction of the lobes are 

 prolonged into points, which give a tripodal character to the 

 crown. The outer point of the anterior lobe is the longest 

 of the three, but the difference is not nearly so marked as in 

 U. robusttim ; the other two are of about the same height ; 



