G. T. BJSTTANT ON THE GENUS MERYCOCHCERU9. 26'3 



assigned to Merychyus elegans and medius (Extinct Mammalian 

 Fauna, pp. 118-121) appear to belong to Oreodon, while the teeth 

 figured under the name of Merycliyus major are referable on equally 

 good grounds to Meryeochcerus. 



In the third of his great works above referred to (' Contributions,' 

 p. 201), Prof. Leidy says "Merycliyus would appear to be the same 

 as Meryeochcerus, and the fossils which had been referred to it 

 belong to the same geological horizon." 



The following are to be added to the characters of Meryeochcerus'. — 



1. The side of the face is very nearly oblong (that of Oreodon 

 being a triangle truncated in front) ; and the whole upper surface 

 of the skull slants downward much less from behind forward than 

 that of Oreodon. 



2. The temporal fossa is much wider and deeper than in Oreodon. 



3. The outward curvature of the temporal ridges from the sagit- 

 tal crest is much more gentle and prolonged than in Oreodon. 



4. The whole squamous portion of the temporal bone is very 

 large. The length, breadth, height, and outward curvature of the 

 zygoma are much greater than in Oreodon. The form of the zygo- 

 matic crest diners very considerably, being greatly extended trans- 

 versely, and looking principally forwards and backwards, while its 

 aspect in Oreodon is principally inwards and outwards. 



5. The postglenoid processes are large and transversely extended. 



6. The suborbital arch is unusually deep and strong. 



7. The occipital foramen approaches nearly to a circular shape (it 

 is transversely oval in Oreodon). 



8. The posterior part of the basicranial axis is set at a much 

 greater angle with the longitudinal axis of the palate than in 

 Oreodon ; and its shape is that of a continuous curve of compara- 

 tively small radius. In M. temporalis the posterior extremity of the 

 basioccipital axis descends even below the plane of the palatal 

 surface. 



9. The palate extends considerably behind the last molar tooth, 

 viz. to one third of the distance between the latter and the auditory 

 bullae. In Oreodon the palate only extends to about the level of 

 the last molar tooth. 



I now proceed to a detailed description of this remarkable skull. 



The skull in Meryeochcerus is elongated, high, and massive. Its 

 median longitudinal section would be an oblong with the length 

 between three and four times as great as the height. Yiewed from 

 above, a high and strong sagittal crest is seen proceeding forwards 

 from a small transverse occipital crest. The sagittal crest is flanked 

 on each side by the convex wall of the cranial cavity, by a wide 

 temporal fossa, and a strongly arched zygoma, reaching out much 

 beyond the glenoid cavity. The sagittal crest bifurcates into two 

 gently and very symmetrically curved temporal ridges, which extend 

 to the posterior border of the orbit and then become lost on the 

 malar bone. The frontal surface of the skull is of considerable size, 

 and very nearly lozenge-shaped, the posterior angle being situated 

 between the two temporal ridges, the lateral angles corresponding 



