104 i?. 8. Lull — New Tertiary Artiodactyls. 



also speaks of the progressive increase in size of the 

 internal pillar of upper molars 1-3 in D. antilopinus and 

 of its being very small or absent on M 3 and larger on 

 M 1 ' 2 in D. borealis. These are variations within the 

 species of Aletomeryx, and are probably not of diagnostic 

 value in Dromomeryx. Scott also speaks of the relative 

 shortness of the hinder horn of the antero-internal cres- 

 cent and the curious crenulations of the adjacent horns, 

 which is also true of Aletomeryx, although in M 1 as a 

 rule the crenulations are most pronounced, while they 

 may be absent in M 3 . In D. borealis this crenulation is 

 apparently absent. The chief tooth distinctions there- 

 fore between Aletomeryx and D. antilopinus are the much 

 greater size of the entire series, the relatively greater size 

 of P 3 , and the decidedly brachyodont character of the 

 teeth of the latter. From D. borealis, the size and brachy- 

 odont distinction also holds, together with the distinction 

 of P 2 already mentioned, and the simplicity of the adja- 

 cent horns of the inner crescents, although in one speci- 

 men referred by Douglass 9 to this species this last 

 distinction does not hold. Cingula are mentioned by 

 Douglass on the anterior face of the antero-interior cusps 

 ( ^crescents). None are discernible in Aletomeryx. He 

 also states that the valleys between the inner and outer 

 crescents are not deep. In Aletomeryx they are very 

 deep in the unworn tooth. 



Lower dentition (fig. 8). — The premolars increase in 

 size and complexity from P 2 to P 4 ; their chief distinctions 

 from those of D. borealis and D. americanus lie not only in 

 the lesser actual size of the teeth, but in the greater sim- 

 plicity of P 3 . The molar teeth in Aletomeryx all lack the 

 " PalcBomeryx fold" on the posterior face of the antero- 

 external crescent; otherwise they also are generally 

 similar. 



The lower dentition in D. antilopinus is apparently un- 

 known. The degree of hypsodonty in the lower teeth of 

 D. americanus, I), borealis and D. madisonius is in ap- 

 proximate agreement with Aletomeryx. The enamel 

 wrinkling of the outer surface of the teeth is much the 

 same. There is here a slight individual variation in 

 Aletomeryx, depending in part on the degree of wear. 



The tooth measurements are (see also table of mandib- 

 ular measurements) : 



9 Op. eit., pi. LXIII, fig. 1. 



