'• 4 1 Sinclair. — John Day Rodents and Ungulates. 



141 



No.. '193 No.T9lS8 



Length M'-M" inclusive 39 mm 42 mm 



Length Pi-M 8 inclusive 81 



Length Mj-M., inclusive 45 



Width of skull at postorbital processes 83 



Depth of alveolar border at front of orbit 78 72 



Length of diastema between lower canine and P, 



(average of both sides) 16 



Depth of mandible below P 2 33.5 



Depth of mandible below M, 33.5 



P 4 , antero-posterior diameter 10 9 



P 4 , transverse diameter 10.5 11 



M l , antero-posterior diameter 12.5 12.75 



MP, transverse diameter 11 11 



MP, antero-posterior diameter 13.5 14 



MP, transverse diameter 11.5 11 



P 4 , antero-posterior diameter 12 



P 4 , transverse diameter 7 



M„ antero-posterior diameter 12 



Mj, transverse diameter 8 



M 3 , antero-posterior diameter 18.5 



M„ transverse diameter 9 



MESOHIPPUS ACUTIDENS, n. Sp. 

 PI. 18. 



Type. — Cranium, portion of the left fore limb, and a few vertebral 



fragments; No. 376, Univ. of Cal. Palaeont. Coll. 

 Locality.— Promerycochoerus beds ('?), Uprjer John Day. Powell's 



ranch on the Middle Fork of the John Day Kiver about five miles 



above Bitter, Grant Co., Oregon. 



Superior canines long and pointed, with acute anterior and 

 posterior edges. Metaloph hardly interrupted by metaconule, 

 sharply separated by a deep notch from the ectoloph. Protoloph 

 with well marked protoconule, united with ectoloph by a narrow 

 shape-edged ridge which widens in moderately worn teeth. 

 Parastyle broadly rounded except in M 3 where it is compressed 

 antero-posteriorly. M 3 with metaloph storter than protoloph 

 (i.e., as 8.5 mm. : 12.3 mm.), producing almost a triangular out- 

 line for the tooth crown. Mesostyle sharply defined and ribs 

 broadly rounded and prominent. The measurements seem also 

 to be characteristic. 



The moderately worn teeth indicate the fully adult condition 

 of the animal. The incisors show incipient cupping and are 

 marked by a slight depression in the center of the external face. 



