166 R. S. Lull — Fauna of the Dallas Sand Pits. 



Cranium. — Almost the entire area of the two frontals 

 is preserved. All sign of the sutures, however, is oblit- 

 erated as in Antilocapra No. 0180, which was individ- 

 ually slightly younger than was the fossil spcimen at the 

 time of death. The skull contour is quite similar except 

 that its dorsal surface bears two pronounced ridges 

 which run forward toward the nasals and are separated 

 by a deep median depression which in turn bears a longi- 

 tudinal ridge in the wake of the interfrontal suture. The 

 orbits, in so far as they are preserved, are approximately 

 equal in the two genera, and the paired lacrymal ducts are 

 in the same position. The supra-orbital foramina show 

 no antero-posterior extension in the fossil, but the facial 

 groove leading forward is wider and more pronounced. 



Horns. — The anterior pair of horn-cores agree in form 

 and position with those of Antilocapra, differing in small 

 details such as a more rounded cross-section, especially 

 at their base. They lie nearer together at their base 

 than in Antilocapra, and their angulation outward agrees 

 with that of a young male (RSL, male)^ and is materially 

 less than in No. 01518 Y. P. M. In the prongbuck the 

 horns are connected by a transverse ridge across the 

 skull; in Tetrameryx this lies between the posterior 

 horns. The latter are much the longer and relatively 

 slenderer and less rapidly tapering. Externally they 

 bear a groove which passes around on to the anterior 

 surface to become external again as the summit of the 

 horn is reached. A similar, although less pronounced 

 sulcus, is seen on the external face of the anterior horn in 

 the fossil as well as in the recent form. There is little 

 question of the homology of the anterior horn-cores of 

 Tetrameryx with those of the prongbuck. Yale specimen 

 01515 bears, on the posterior side of the base of the 

 horns, a slight prominence which by marked hypertrophy 

 might conceivably give rise to posterior horns similar to 

 those in the new form. In the young buck (ESL, male) 

 these prominences are hardly discernible. The inference 

 is that, as in the prongbuck, these horn-cores were 

 sheathed with horns which were also probably deciduous. 

 Because of the smoothly rounded anterior outline of the 

 fossil horn-cores the presence of an anterior prong on the 

 horn sheaths is doubtful. 



^See this Journal (4), 50, fig. 3, p. 89, 1920. 



