Vol. 4] Sinclair. — John Day Rodents and Ungulates. 



131 



Dentition. — The teeth are short hypsodont and are well worn, 

 indicating the fully adult and somewhat aged condition of the 

 animal. Only the posterior root of P 2 is represented. P 3 is sup- 

 ported by three roots, but the crown is too poorly preserved to 

 permit description. P 4 is composed of two crescents, an outer 

 and an inner. The molars are without mesostyle, with the ex- 

 ternal ribs prominent and about equally developed. In M 3 the 

 metastyle has considerable posterior prolongation extending 

 above the alveolar border as a lamina of the postero-external root. 



Affinities. — The new genus finds its closest affinities among 

 the Hypertragulidae, in which family it may be placed. The 

 skull is larger than in Hypisodus and of a different shape. The 

 bullae are much smaller, approximating in size those of Lep- 

 tomeryx. It may be distinguished from Leptomeryx by the com- 

 plete closure of the orbit, the flatness of the top of the skull 

 and the projecton of the petrosal between the bullae and the 

 basioccipital. In Leptomeryx, the bulla is "separated, as in the 

 deer, from the basioccipital by a large reniform foramen within 

 which a portion of the petrosal is visible." *A mesostyle is pres- 

 ent on the molars of Leptomeryx, and there is no posterior ex- 

 tension of the metastyle on M 3 comparable to the structure devel- 

 oped in Allomeryx. 



Hypertragulus agrees with the new genus in the absence of 

 mesostyle, but the orbit is incompletely closed and jugal pro- 

 cesses are wanting, f The brain case is not as long as in Allo- 

 meryx^ and there is no extension of the petrosal on the inner 

 side of the bulla. In Allomeryx the interorbital tract and the 

 superior border of the sagittal crest lie in the same plane. This 

 is not true for the other members of the Hypertragulidae. The 

 palatine region also differs from both Leptomeryx and Hyper- 

 tragulus. In neither of these genera does the palatal border of 

 the nares extend anteriorly between the posterior molars as in 

 Allomeryx. 



* J. Leidy, Ext. Mamm. Fauna of Dakota and Nebraska, p. 168 and PI. 

 XIV, fig. 4. 



t W. B. Scott, Trans. Wagner Free Inst. Sci., Vol. VI, p. 18, 1899. 

 X Compare PI. 14, fig. 2, with Scott, op. tit., PI. 1, fig. 4. 



