96 . R. S. Lull — New Tertiary Artiodactyls. 



The jugal below the orbit is expanded transversely and 

 concave interiorly, as in Antilocapra and Dromomeryx; 

 in the former, however, it is the postorbital portion of 

 the frontal over which the widest measurement of the 

 skull is taken, in Aletomeryx it is the lower margin of 

 the orbit, in Dromomeryx it is over the wing-like pro- 

 cesses at the base of the horns. 



Basicranial portion of the skull. — As compared with 

 Antilocapra, the proportions of this area of the skull 

 differ markedly, as the entire after portion is relatively 

 much longer in proportion to the width in Aletomeryx. 

 Aside from this, the differences are largely those of detail. 

 The occipital condyles are relatively somewhat broader 

 in Aletomeryx, although their proportions vary slightly 

 in the several available crania, which is also true of 

 Antilocapra. The condyloid fossa is deep and the con- 

 dyloid or hypoglossal foramina are apparently single, 

 not double as in Antilocapra. In Dromomeryx antilo- 

 pinus, Scott describes the condyloid fossa as being much 

 larger and more deeply impressed than in Antilocapra. 

 This is not true of Aletomeryx. In both Dromomeryx 

 and Aletomeryx, however, the paroccipital process is fur- 

 ther in advance of the posterior limit of the condyles than 

 in the prongbuck. 



The auditory structure is much as in Antilocapra, the 

 wedge-shaped paramastoid process being laterally com- 

 pressed and pointing somewhat backward as in D. anti- 

 lopinus, not forward as in the prongbuck and in Douglass' 

 figure of D. borealis. 



The relations of the mastoid agree, apparently, in 

 Dromomeryx and Aletomeryx. Tympanic bullae are rela- 

 tively much the same as in Antilocapra; the deep groove 

 for the attachment of the stylohyoids of which Scott 

 speaks and which forms a deep pit in the Antilocapra 

 skull before me is hardly in evidence in skull No. 10735, 

 but is better developed in No. 10749 and No. 10750. The 

 shape and degree of inflation of the bullae differ quite 

 markedly in these three skulls. As in Dromomeryx, the 

 external auditory meatus is a long tube which is directed 

 more posteriorly than in Antilocapra, forming an angle 

 with the axis of the skull of about 60 degrees in Aleto- 

 meryx to 70 degrees in Antilocapra. 



The glenoid cavity is comparable to that of Antilo- 

 capra, except that the anteroposterior diameter is 

 greater and the pterygoid crest is much more developed. 

 The postglenoid process is much more prominent than 



