Cope. J SwG [Jan. 18, 



Measurements. M. 



Elevation of oceiput from foramen 084 



Width of occipital condyles. 063 



Width of occiput at condyles 095 



Depth of skull at right angles to profile at glenoid face. .095 



orbit 087 



" . " " " P-m 1 075 



Length of superior dental series with canine 159 



' ' " premolar series 061 



" " true molar series ; 065 



Diameters M. i { anteroposterior 0180 



t. transverse 0185 



Diameters of canine { anteroposterior 016 



<- transverse 020 



Diameters P-m. ii \ anteroposterior 0155 



c transverse 090 



Width of palate at m. i 044 



" • P-m.i 057 



The typical specimen was found on the John Day river, Oregon, by 

 Mr. J. L. Wortman. 



Merycochcerus macrostegus, sp. nov. 



I have been able to discover in my collection as yet, but one cranium 

 with entire mandible of this species. The very marked characters of this 

 skull are such that no farther evidence of its reference to a peculiar species 

 is needed. Its affinities, as expressed in the analytical key which accom- 

 panies the general discussion of this genus, are with the M. montanus. 

 This is shown in the posterior positions of the infraorbital foramen, and 

 of the posterior nares. As peculiar characters may be added the form of 

 the frontal plane and of the otic bulla ; also the prolongation of both the 

 premaxillary and supraoccipital regions, and the forms of the zygoma, the 

 angle of the mandible, and the first inferior premolar tooth. The skull 

 reaches a greater length than that of any species, excepting the M. mon- 

 tanus, but is not nearly so robust as in the M. chelydra, resembling in 

 this respect rather the M. superbus. 



The muzzle is compressed, and there is a decided concavity just above 

 the second premolar, above which the surface is a little convex. Above 

 the infraorbital foramen, the face is abruptly convex, the convexity slop- 

 ing upwards to the base of the median ridge formed by the convex nasal 

 bones. Behind this the side of the face is a plane which slopes outwards 

 as it descends, which is only interrupted by the rather small, but well de- 

 fined, preorbital fossa. The fossa is better defined in front than in the other 

 species, but I do not know whether the character is constant. The front 

 is a transverse diamond-shaped area, bounded posteriorly by the anterior 

 temporal ridges, and anteriorly by the lines of the supraorbital borders 



