39 



apjiearance as those of Palaeotheriuin and Anchitheriiiin at the same stages <>( 

 attrition. 



Tlie space occupied 1)}' the entire molar series is estimated at al»oiit G.^ 

 inches, of whicli the true molars occupy ratlier less tlian 4 inches. 



The measurements of the molar teeth contained in the lower jaw are as 

 follows : 



Antero- 

 posterior. 



Transverse. 



Diameter of tbird premolar . 

 Diameter of fourth premolar 



Diameter of first molar 



Diameter of second molar. . . 

 Diameter of last molar 



Lines. 

 8i 

 9 



15 

 19 



Lines. 



8 

 10 



The premolars are inserted by a pair of fangs, except the first, whicli has 

 but a single fang. 



The lower jaw of Palceosyops, as seen in Fig. 11, Plate V, appro.ximates in 

 form that of the tapir and hog, though presenting important differences. 

 The dentary portion of the ramus is proportionately shorter and deeper than 

 in either of those animals, and the alveolar border is more ascending poste- 

 riorly. The base is more convex fore and aft than in the hog but less than 

 in tiie tapii', and is more obtuse than in either. The outer surface is vertical, 

 with a slight outward slope at the fore part. 



The back part of the jaw is of more uniform breadth than in the tapir, and 

 is more like that in the hog. Toward the angle the outer surface is a verti- 

 cal plane, with the lower border or base more directed downwardly timn in 

 the hog. The upper or ascending portion presents a masseteric fossa about 

 as deep as in the tapir but of considerably greater width. 



The condyle is large and thick, and much like that in the tapir, but is less 

 inclined inwardly. It has about the same proportionate elevation above the 

 level of the base of the jaw, but less above the level of the teeth. 



The border of the jaw below the condyle behind is at first slightly concave 

 and then convex, as in the hog, but to a less degree. The coronoid process 

 is about as long as that of the tapir, but the fore part curves upward and 

 l)ack\vard without any inclination forward. The notch behind hardly descends 

 below the level of the condyle. 



