126 ON THE EXTINCT MAMMALIA OF 



foramina occupy a position about half way between ilie median line and the post- 

 orbital process. The frontals are separate, as in Oreodon. 



Large vacuities or unossified spaces encroach deeply on each side of the forehead, 

 extending about half the width of the orbit, posterior to the ant-oibital margin. The 

 vacuities are separated by a prolongation of the frontals, about half an inch in length 

 and five lines wide, extending forward to articulate with the nasals, which are lost in 

 the specimen. Laterally the vacuities are bounded by the ant-orbital process, 

 articulating with the upper angle of the facial plate of the lachrymal. In advance of 

 the process just mentioned, the vacuities are narrowed, and extend forward above 

 and then in advance of the lachrymals. The facial plate of the latter is large, nearly 

 square and deeply impressed with an ant-orbital fossa. 



A prominent ridge appears to extend across the face, extending from the infra- 

 orbital arch, below the lachrymal fossa, to the fore-part of the maxilla where it 

 articulated with the nasal. 



The infra-orbital foramen, as in the upper jaw fragment previously described, is 

 situated above the third premolar tooth. 



The hard palate is constructed like that of Oreodon. The auditory bullaj are of 

 enormous proportions. They abut posteriorly against broad and sfrong paroccipitals. 

 They are antero-posteriorly oval and measure in this direction about an inch, and are 

 about eight lines in depth and seven in width. 



The lower jaw is like that of Oreodon and Merijchyus, as represented in figure 2, 

 plate XII. Below the position of the molars it is more convex, both externally and 

 at the base, than in the specimens of Merychyus elegans. The mental foramen is 

 situated below the interval of the first and second premolars, as in the latter and 

 Oreodon. 



The lower jaw, figure 2, contains a full series of teeth, consisting of six molars, a 

 canine, and four incisors, as in Oreodon and Meryclryus. In the upper jaw the teeth 

 are all broken, but sufficient of them remains to determine that the formula is the 

 same as in the two genera just named. 



The inferior true molars, figures 2, 3, as observed in the lower jaw just mentioned, 

 and in some fragments of others, closely resemble in character those of Merychym 

 elegans, except that in the case of the first and second of the series the inner constitu- 

 ent lobes of tlie crown are well defined internally by a well-marked fold or narrow 

 buttress, which is obsolete in Merychyus. In a corresponding position of the last 

 molar the buttress is not so well developed as in those in advance. 



In all the specimens under investigation the crowns of the lower true molars appear 

 as if made up of simple trilateral prisms, laid side by side. The triturating surfaces 

 exhibit triangular dentinal depressions bordered by enamel, without any trace of the 

 separation originally existing between the outer and inner constituent lobes. 



