R. 8. Lull — Neiv Tertiary Artio dactyls. 



89 



Horns. — The most striking feature of the skull, when 

 preserved, is the horns, differing decidedly in the two 

 sexes as in the prongbuck, Antilocapra. These horns 

 arise over the posterior portion of the orbit as in Anti- 

 locapra and Bromomeryx, but differ from those of the 

 former in being triangular in cross-section at their base, 

 the forward angle continuous with the upper, the after 

 one with the hinder rim of the orbit, which is completely 

 surrounded by bone. The outer face of the horn is flush 



mae 



Fig. 2. Skull of Aletomeryx, adult male. Left lateral aspect. One- 

 third natural size, bo, auditory bulla; c, canine tooth; fon, fontanelle; fr, 

 frontal; h, male horn; j, jugal; I, lachrymal; m, mandible; mae, external 

 auditory meatus; mx, maxillary; n, nasal; o, orbit; oc, occipital condyle; pa, 

 parietal; pm, paramastoid (paroccipital) process; pmx, premaxillary ; t, tem- 

 poral. 



Fig. 3. Skull of Antilocapra, with milk dentition. Left lateral aspect. 

 One-third natural size. Lettering as in fig. 2. 



With the rim of the orbit ; in Antilocapra the rim extends 

 beyond the horn level. The inner angle is prolonged in- 

 ward as the supratemporal ridge over the top of the 

 cranium, curving backward to meet its fellow and form 

 the parietal crest, which is a thin but low ridge. 

 In Antilocapra, on the other hand, there is no crest, as 

 the limitations of the temporal fossae are wide apart and 

 the rounded hinder edge of the laterally compressed horn 



