1884.] 531 [Cope. 



Measurements. \, M. 



Diameters inferior m. iii \ anteroposterior 044 



f. (transverse. 018 



. This fine species is from the John Day epoch of the Miocene. The 

 typical specimen was found by my assistant, Charles H. Sternberg, on 

 Bridge creek, Oregon. Much credit is due Mr. Sternberg for his unwearied 

 exertions in the cause of science, which have been continued through 

 many occasions of risk and discomfort. 



Merycoclioerus montanus, sp. nov. 



This large animal is represented in my collection by a nearly entire 

 skull with parts of both mandibular rami complete. Rami of another in- 

 dividual give the entire dentition of the lower jaw except the incisors. 

 A third individual is represented by a symphysis with premolars, ca- 

 nines and incisors, and by various parts of the skeleton, including feet. 

 Of the cranium mentioned, the muzzle to the preorbital fossa and the 

 palate to the first true molar are wanting. The region of the larmier is 

 lost, but the general resemblance of the species to the M. macrostegus in 

 other respects, leads me to suspect that it is absent, and that the M. mon- 

 tanus, is rightly referred to the genus Merycochcerus. This course is indi- 

 cated by the structure of the superior molar teeth, which have the character 

 of those of this genus, rather than that found in Merychyus. That is, the 

 posterior internal crescent sends its anterior horn to the external wall of 

 the crown, thus cutting off the posterior horn of the anterior crescent. 

 Dr. Leidy has shown that the reverse is the case in the Merychyus major ; 

 that is that the posterior horn of the anterior crescent reaches the external 

 wall of the crown, cutting off the anterior horn of the posterior crescent. 

 I have observed that this is also the case in the other species of Merychyus 

 which have come under my notice. 



. The posterior position of the infraorbital foramen and the greatly pro- 

 duced palate distinguish this species Irom those of the John Day epoch, 

 excepting the M. macrostegus, while in the M. rusticus and M. proprius, 

 the infraorbital foramen is still further posterior. The palate of these 

 species is unfortunately unknown. 



The part of the maxillary bone posterior to the infraorbital foramen is 

 nearly flat, and the proximal part of the malar bone is also flat. The in- 

 ferior edge of the latter is narrow and is marked by a groove which ter- 

 minates anteriorly in a shallow fossa. The ridge continuous with this edge 

 terminates above the anterior lobe of the second true molar. The zygoma 

 as far as the anterior border of the glenoid cavity is slender, and not con- 

 vex, but flat in every direction, nor is it decurved as in M. superbus. The 

 zygomatic foramen is relatively much smaller than in that species. Its 

 posterior or preglenoid boundary is not at right angles to the sagittal crest 

 as in that species, but is oblique outwards and forwards at an open angle. 

 The obtuse median edge of the zygoma looks upwards, not outwards as it 

 does in M. superbus and M. macrostegus, and the superior expansion is 



