1884. ] 523 [Cope, 
characters, which appear most tangible among those mentioned by Mr. 
Bettany, the shortness of the occipital region, as measured by the angle 
made by a line drawn through the postglenoid and paroccipital processes, 
with the middle line, and second, the grooved character of the sub- 
orbital part of the malar bone, are not found in any of my specimens of . 
M. superbus. The anterior extremity of the squamosal process of the 
zygoma is protuberant in one of them, as in the I leidyi. Another char- 
acter is suggested by Mr. Bettany’s figure, but is not mentioned in the 
text. The angular border of the mandibular ramus extends obliquely 
forwards instead of being prominently convex as in the best preserved 
entire mandible of the M. superbus in my possession. Nevertheless in 
another specimen, where a good deal of the posterior border is preserved, 
the outline is nearly as oblique as in the M. leidyi. The species, however, 
is distinct so far as now known. ‘ 
John Day epoch, Oregon, C. H. Sternberg and J. L. Wortman. Local- 
ities, John Day river, Bridge creek, and Camp creek of Crooked river. 
Merycocheoerus leidyi Bettany. 
Quarterly Journal of the Geological Society of London, xxxi, 1875, 
p. 270; Plate XVIII. 
Defined and discussed under the preceding species. 
John Day epoch, Oregon ; Lord Walsingham. John Day river. 
Merycocheoerus chelydra, sp. nov. 
This species is known to me by a skull without mandible, which is 
entire, except that the extremity of the nasals and the border of the pre- 
maxillary bones are broken off. It is unfortunate that I have no second 
skull to confirm its characters, but my numerous specimens of the M 
superbus, to which it is most nearly allied, do not present any approxima: 
tions which suggest transitions between the two. 
The striking character of this cranium is its great breadth at the tem- 
poral region, as compared with its length and other dimensions. The 
forms of the otic bulla difter from those of the I. superbus: One method 
of expressing the width of the skull is as follows. The point of the frontal 
bone which is equidistant from the supraoccipital notch and the external 
edge of the zygomatic arch, measured in a horizontal plane, is directly 
above the posterior or nareal palatal border, when the skull rests on the 
teeth. In the MZ. superbus, in the most robust examples, this point is above 
& point which is a good deal nearer to the line of the anterior edge of the 
glenoid surfaces than to the palatal border, and at least 30mm. posterior 
to the latter. That this relative shortness of the basicranial axis is not 
due to a shortening posterior to the gleroid surfaces, as is the case in J 
letdyt Bett., is proven by the fact that a line drawn through the postglenoid 
and paroccipital process makes an angle of 90° with the middle line, as 
in M. superbus. 
The muzzle is compressed and its superior surface is regularly rounded 
