No. 2.] THE RELATIONS OF PROTOCERAS. 32 I 



as two ungulates well can be, since they have no common an- 

 cestor later than the most ancient Condylarthra. 



The most obvious difference in skull structure between the 

 two sexes lies in the great development of osseous protuberances 

 from various parts of the head in the male, all of which are, 

 however, faintly indicated in the female. The latter is far less 

 bizarre in appearance, and aside from the shortened nasals (a 

 character which is found still more strongly marked in the saiga 

 antelope and to a less degree in A Ices), does not depart in 

 any radical way from the modern hornless Pecora. Indeed, 

 most of its deviations from the skull-structure of those animals 

 is in the direction of the higher members of the same group. 

 Besides the protuberances, the various ridges and processes 

 for muscular attachments are naturally much stronger in the 

 male, as is to be seen in the greater prominence, thickness, 

 and rugosity of the lambdoidal, sagittal, temporal, and masse- 

 teric crests. From the temporal crests of the parietals arise a 

 pair of horn-like protuberances, which in the female are mere 

 roughenings of the crests. These processes are laterally com- 

 pressed, of elongate oval section, and with their long axes 

 running in the direction of the temporal ridges and oblique to 

 the sagittal suture ; their free ends are rounded and rough- 

 ened. The second pair of protuberances are formed by the 

 great development of the supraorbital borders of the frontals, 

 which are drawn out into a pair of large, depressed, wing-like 

 bodies, completely overhanging the orbits. These processes 

 are relatively better developed in the female than any others 

 of the paired protuberances. The posterior median eleva- 

 tion of the frontals is not much more conspicuous in the 

 males than in some females. A third pair of conical, horn- 

 shaped processes arise from the antero-external angle of the 

 frontals, where they unite with the nasals and lachrymals. 

 Feebly-marked indications of these processes are to be seen in 

 the female, more decidedly in some individuals than in others. 

 A fourth pair of protuberances are formed by the short, thick, 

 conical processes which are given off from the anterior ends of 

 the masseteric ridges of the maxillaries. These are likewise 

 to be found in the female, though very much less strongly 



