No. 2.] THE RELATIONS OF PROTOCERAS. 319 



premolar series and their very brachyodont condition. In 

 front oip~2 the thin edentulous upper border descends quite 

 abruptly, rising again slightly to form the alveolus of pi. The 

 incisive alveolar border is slightly widened and somewhat spatu- 

 late in form, though retaining a greater vertical depth than is 

 usual in the Pecora ; the widening is very limited, as would be 

 inferred from the extreme slenderness of the upper jaw in this 

 region. The symphysis is quite long and rather oblique, and 

 in some aged individuals the two rami of the jaw appear to be 

 coossified. Two rather large mental foramina occur in the 

 symphyseal region, the first underneath and the second slightly 

 behind p~i. The horizontal ramus has the undulating lower 

 margin and anterior taper found in existing ruminants, but is 

 rather stouter than is common in that group and is quite un- 

 like the straight, slender ramus of Leptomeryx. The ascend- 

 ing ramus is rather wider than in the most of the Pecora and 

 does not rise so high as in the cavicorns, which is due to the 

 fact that the glenoid cavity and base of the cranium are not so 

 much elevated above the level of the molars as in those forms. 

 The angle is thin and entirely inconspicuous, not projecting 

 behind the line of the condyle, being shaped very much as in 

 MoscJms, which is a striking difference from Leptomeryx. In 

 the latter the angle projects very far back of the condyle, in a 

 way which recalls that of the ancestral Tylopoda. The mas- 

 seteric fossa is less profoundly marked than in Leptomeryx and 

 extends farther downward and forward ; it is somewhat more 

 distinctly imprinted upon the jaw than in the musk-deer, but 

 has much the same shape and extension. The coronoid is very 

 low and tapers abruptly to a blunt point. This is the only 

 character in which the mandible of Protoceras resembles that 

 of the oreodonts ; the sigmoid notch is much narrower than in 

 Leptomeryx. The condyle is like that of the Pecora, but in 

 correlation with the better development of the postglenoid 

 process, the articular surface is more reflected upon the pos- 

 terior face of the condyle. While in the Pecora the latter is 

 slightly concave transversely, convex antero-posteriorly and thus 

 saddle-shaped, in Protoceras, on the other hand, it is plane trans- 

 versely and more strongly convex in the fore and aft direction. 



