64 



The inferior canine teeth are quite like those of the tapir in appearance. 

 They curve upward and forward, with a slight inclination outward. The 

 crown is laterally compressed conical, subacute in front and behind, but worn 

 in both these positions in the specimen under examination. 



The upper canines are unknown, unless the specimen represented in Fig. 

 17, Plate IV, is one. This was found at Grizzly Buttes by Dr. Corson, in 

 association with some upper premolars of Hyrachyus ; all of which look as if 

 they had belonged to the same individual. The crown of this specimen of 

 an upper canine is short, and worn off to a considerable extent at its fore 

 part. It is compressed conical, and has the inner and outer surfaces defined 

 by an acute ridge posteriorly. The fang is double the length of the crown, 

 and is laterally compressed. 



The incisor tooth, represented in Fig. 18, appears to be the second of 

 the series of the lower jaw. It resembles the corresponding tooth of the 

 tapir. Its chisel-like crown is worn off at the cutting edge. 



No characteristic portions of the upper jaw of Hyrachyus have come under 

 our notice. In one specimen the infra-orbital foramen is observed to occupy 

 a position above the third premolar. 



The lower jaw resembles, in its form and proportions, that of the Hyraco- 

 don and the tapir. The anterior extremity, in the construction of the chin, 

 the contraction between the position of the canines and molar series, and ' 

 other features, repeats the condition observed in the tapir. A similar wide 

 hiatus separates the canines from the molar teeth. The free border of the 

 hiatus, upward of an inch in length, is concave fore and aft, and acute. 



The body of the lower jaw is less robust or thick, in relation with its 

 depth, than in the tapir.- It is also less convex externally, and at the 

 base fore and aft. The outer surface, in comparison, appears quite 

 vertical. 



The ascending portion of the ramus rises vertically at its fore border, and 

 is deeply impressed on the outer surface just back of the latter. 



The condyle projects less externally and more posteriorly -than in the tapir. 

 Its articular surface is more flat, and in a less degree inclined inwardly. 



In the specimen represented in Fig. 13, Plate IV, five small mental 

 foramina are observed, in a row extending from the position of the third pre- 

 molar to that of the canine tooth. In the specimen represented in Fig. 25, Plate 

 XX, a large mental foramen is situated below the interval of the third and 



