Vol. 4] Sinclair. — John Day Rodents and Ungulates. 



127 



supraorbital border. It presents, on the contrary, a subacute 

 superior edge, flush with the inferior part of the same border. 

 These edges leave the orbital border posteriorly, and converge in 

 straight lines to an acute angle, forming two temporal ridges." 

 * E. minor is much smaller than E. sperryi and the other species 

 of the genus and like E. planifrons is "characterized by the per- 

 fectly flat interorbital region and the absence of temporal 

 ridges." fin E. cavifroois, the superciliary margins "do not 

 meet nor converge to form a sagittal crest. They are thickened, 

 forming two subparallel ridges which are separated by a shallow 

 concavity of the frontal bone." t In E. crassiramis the "inter- 

 nal orbital walls are rolled inward at the supraorbital region so 

 as to meet at a point opposite the posterior border of the orbital 

 space. Opposite the anterior part of the orbit, the ridges are more 

 widely separated, so that the interspace is a narrow wedge- 

 shaped fossa, opening forwards." § Temporal ridges are wanting 

 and the sagittal crest is weak. The mandible differs from E. 

 sperryi in the absence of the long horizontal symphysial border 

 characteristic of that species. In E. crassiramus the superior 

 mandibular border between the base of the incisor and the alve- 

 olus of P 4 is broadly concave. 



The new species is named in honor of its discoverer, Mr. J. C. 



Sperry. 



Measurements. 



Length of skull, siipraoccipital to premaxillae inclusive 50 mm 



Interorbital width 6.5 



Width across zygomatic arches .■ 35 



Width of median portion of rostrum 11 



Depth of rostrum at incisive foramina 9.5 



Length of rostrum from base of P 4 to anterior end of premaxillae..24.5 



Length of nasals, approximate 23.5 



Length P 4 to M' inclusive, on alveolar border 11 



Length P 4 to M 3 inclusive, on alveolar border 8.5 



P 1 , antero-posterior diameter 2 



P 4 , transverse diameter 2.5 



M 1 , antero-posterior diameter 2 



M 1 , transverse diameter 3 



* E. D. Cope. Tertiary Vertebrata, p. 861. 



t Ibid. 



} E. D. Cope, Hid., p. 862. 



§E. D. Cope, ibid., p. 864, PI. LX1V, Fig. 5a. 



