0. C. Marsh — Description of Tertiary Artiodactyles. 261 



Parahyus aberrans, sp. no v. 



In figure 2 below, a last upper molar tooth is represented 

 natural size, which may be referred to the present genus, 

 described in 1876.* There -can be little doubt that the type 

 species, as well as the present tooth, belonged to suilline mam- 

 mals, although they indicate animals much larger than would be 

 expected from so low a horizon. Moreover the type had but 

 three lower premolars, and thus was more specialized than 

 most of the ungulates from the same horizon. 



The present specimen resembles somewhat the last upper 

 molar of Homacodon, but shows distinct indications of a third 

 posterior cone on its inner margin. This specimen was found 

 in the Coryphodon beds of Wyoming, near the locality where 

 the type of Parahyus vagus was discovered. It represents an 

 animal about half as large as the type of the genus. 



Figure 1.— Last upper molar of Eohyus distans, Marsh ; seen from below. 



Figure 2.— The same tooth of Parahijus aberrans, Marsh; seen from below. 



Figure 3. — Astragalus of Homacodon priscus, Marsh ; front view. All three 

 figures are natural size. 



Figure 4. — Astragalus of Homacodon pwAllus, Marsh ; front view. Twice 

 natural size. 



Homacodon priscus, sp. nov. 



Among the undoubted Artiodactyles of the lower Eocene 

 are two species which cannot at present be separated from the 

 genus Homacodon. The astragalus of one of these is repre- 

 sented above in figure 3, and a second smaller species, 

 H.pucillus, in figure 4. The other known remains of these two 

 species are not distinctive, but indicate true Artiodactyles of 

 the bunodont type, and are interesting mainly from proving 

 the existence of such forms in the lower Eocene. They occur 

 in the Coryphodon beds of Wyoming and New Mexico. 



Teeth resembling those of Helohyus are likewise found in 

 this horizon, but it is not certain that they pertain to true 

 Artiodactyles. Some have been referred to the Perissodactyles. 

 Others may belong to the Mesodactyla. 



*This Journal, vol. xii, p. 402, November, 1876. 



