No. 2.] THE RELATIONS OF PROTOCERAS. 305 



is quite strongly everted laterally. As in the oreodonts, the 

 canine is abraded upon the posterior face, which renders it 

 probable that in the male the first lower premolar had taken 

 on the form and function of a canine. The first premolar is 

 much the smallest of the series and has a simple compressed 

 and trenchant crown, implanted by two quite widely diverging 

 fangs, and consisting only of the protocone without additions. 

 The tooth stands by itself, being isolated by considerable dia- 

 stemata both from the canine and from Pj^. The second pre- 

 molar is remarkably elongate in the antero-posterior direction, 

 resembling in this respect the corresponding tooth of XipJiodon 

 and in a less degree that of Leptonieryx. The crown is very 

 low, compressed and trenchant ; obscurely marked anterior and 

 posterior basal cusps are separated by shallow grooves from the 

 protocone. There is a strong internal cingulum running the 

 whole length of the crown, thickened and elevated at the 

 median point to form an incipient deuterocone, which is sup- 

 ported on a third fang. In some specimens the deuterocone 

 can hardly be said to exist and the cingulum is feebly marked, 

 and then the crown is carried on two fangs only. Seen from 

 the outer side this tooth much resembles /£ in Leptovieryx, 

 except for its greater elongation, but in the latter the deutero- 

 cone is much larger and the cingulum absent. The third 

 premolar is very much like the second, but with some modifi- 

 cations ; thus the antero-posterior length is somewhat less, 

 while the transverse width is somewhat greater, an increase 

 which is chiefly due to the greater thickness of the protocone, 

 though the deuterocone is also better developed. This tooth 

 differs from A? in Leptonieryx in the much smaller deuterocone 

 and in the presence of a complete internal cingulum. The 

 fourth premolar is of the usual ruminant pattern, consisting of 

 a single pair of crescents. A fairly developed cingulum is 

 present in the inner crescent, which is very faint on the an- 

 terior side, but distinctly marked on the posterior. This 

 cingulum is of course not homologous with that on Pj^ and P3_. 

 A comparison at once shows that the cingulum of P3_ is repre- 

 sented by the horns of the inner crescent on p_4 and that the 

 inner cingulum of the latter is something superadded. 



