Cope.J 54 2t [Jan. 18, 



Measurements. M. 



No. 1. 



Diameters in. iii { anteroposterior 019 



I- transverse 015 



Length of inferior dental series (axial) 098 



" " premolar series (axial) 038 



Long diameter of crown of canine 007 



" P-m. i 0086 



". P-m. ii 0084 



Diameters P-m. iv { anteroposterior 012 



<- transverse 009 



Diameters m. ii { anteroposterior 0147 



C transverse 010 



Diameters m. iii { anteroposterior 0223 



<- transverse .010 



The specimens all came from the Ticholeptus beds near Laramie Peak, 

 Wyoming, and were discovered by my assistant, J. C. Isaac. 



Merychyus pariogoims, sp. nov. 



The generic position of this species is uncertain, and it may belong to 

 Merycochcerus or even to Eucrotaphus, as its otic bullae are inflated. The 

 doubt as to its position is due to the fact that the anterior part of the skull 

 of the typical specimen is lost as far back as the anterior border of the 

 orbit, and the second molar tooth. I place it here provisionally because 

 the internal crescents of the superior molars are arranged as in M. major 

 and M. arenarum, i. e., with the anterior crescent excluding the posterior 

 at the point of junction of the two. 



The Merychyus pariogonus is about the size of the Oreodon culbertsoni. 

 The braincase is full, so that the internal side of the temporal fossa is 

 strongly convex, but without very prominent ridge along the parieto- 

 squamosal suture. The anterior temporal ridges unite at an acute angle, 

 but the sagittal crest is obsolete as far as a point above the posttympanic 

 process, where it gradually rises. The posterior temporal ridge is promi- 

 nent superiorly, but is not produced beyond the line of the occipital 

 condyles. It is discontinued in the direction of the supraauricular ridge, 

 but continues downwards as an obtuse ridge on each side towards the 

 foramen magnum. Between this and the squamoso-occipital angle is 

 a large open fossa which is present in the species of this genus, of Mery- 

 cochcerus and of Eucrotaphus, but is wanting in Oreodon culbertsoni. In 

 the obsolescence of the posterior temporal crest it agrees with the last 

 named species, and with some of those of Merycochcerus, but differs from 

 Eucrotaphus jacksoni where it is low, and from Merychyus leptorhynchus, 

 where it is well developed. In the size of the lateral occipital fossae this 

 species exceeds any of the others of this family. Below the depression, 

 the posterior tempdral crest rises abruptly, forming a convex edge which 

 continues downwards nearly obsolete, on the suture between the post- 





