Cope.] 5bb |- Jan 18j 



Measurements. M. 



Width of skull between last upper molars, inclusive... .070 



Depth of occiput to foramen magnum 043 



" " " " basioccipital bone 058 



" " skull at last superior molar, exclusive 058 



" " " " first premolar, exclusive 055 



" " ramus mandibuli at front of M. iii 035 



" " '• " " " " P-m. iv 027 



" " zygomatic arch above glenoid facet 027 



Diameters of base of crown ( anteroposterior 009 



of superior canine t transverse 0085 



Length of superior diastema 022 



" " premolar series 039 



" " true molar series 043 



Width of premaxillary bones together 043 



Diameters of base crown inferior P-m. i ; anteropos- 

 terior 0085 



Length inferior diastema 015 



" " last three premolars 031 



" " true molars 046 



" " last true molar 021 



" " third premolar 009 



" fourth 012 



Horizontal diameters of otic bulla \ anteroposterior. . . .019 



( transverse 017 



The specimens of this species which I have seen, are from the John Day 

 river, and were obtained by Messrs. Sternberg, Wortman and Davis. The 

 skull from which the above description was taken is the most perfect one 

 of the genus Agriochcer us which has yet been found. 



Agrioclieerus ryderanus Cope. 



Coloreodon ryderanus Cope, Bulletin U. S. Geological Survey Territo- 

 ries, vi, p. 173. 



This species is represented in my collection by three nearly complete 

 skulls without mandibular rami. While of the general size of the A. guyo- 

 tianus, this species displays various well marked peculiarities. The most 

 important of these are (1) the shape of the otic bulla, in which it differs 

 from all other known Oreodontidse ; (2), the position of the infraorbital 

 foramen, in which it resembles in this genus only the A. trifrons ; (3), in 

 the form of the nasal bones posteriorly, in which it differs from the species 

 where this part is known ; (4), in the form of the palatonareal border; 

 (5), in the form of the postglenoid process ; (6), in the outline of the sec- 

 tion of the frontal bone. 



Agriochozrus ryderanus has the muzzle compressed laterally and flattened 

 on top, as seen in the A. guyotianus and A. trifrons, and the side of the 



