MESOHIPPUS. 



49 



ward at a sharp angle with ectoloph, to which fact the name M. obliquidens refers." This is one of the horses of relatively 

 larger size from the Upper Oreodon zone, possessing also relatively long-crowned molar grinding teeth. 



The type is an immature specimen and the adult jaw would be larger than that of the cotype of M. bairdii. Matthew 

 (1915) questions the validity of this species, regarding it as probably conspecific with M. bairdii. 



Fig. 28. Type of Mesohippus obliquidens Osborn, Am. Mus. 668. (Left) Original figures of type, after Osborn, 1904, 

 PI. v, C. (5) Side view of type skull, reconstructed in drawing. (Middle) Original figure of superior premolars, dp 2-4 , 

 and anterior molars, m 1-2 , after Osborn, 1904, fig. 4, p. 173. Skulls one-half natural size, teeth natural size. 



Species Attributed to Upper Oreodon Zone. 4. 



Mesohippus eulophus Osborn, 1904. 



Plates 1.6, 2.8. Text Fig. 29. 



Mesohippus eulophus, sp. nov., Osborn, Henry F. "New Oligocene Horses," Bull. Amer. Mus. Nat. Hist., Vol. XX, Art. XIII, 

 May 28, 1904, pp. 173-4, fig. 5. 



Horizon and locality. — Upper Oreodon zone (Horizon B) of Cedar Creek, Colorado. Type collected by F. B. Loomis, 

 Am. Mus. Expedition of 1901. 



Type. — Amer. Mus. 8791, a complete adult superior dental series of the left side and portion of cranium. Measure- 

 ments: p'-m 3 .076; m 1 - 3 .036; m 1 a.p. .0115, tr. .015; m 3 a.p. .0123, tr. .015. 



Type figure. — Plates 1.6, 2.8, text Fig. 29 of this Memoir. 



Characters. — (Osborn, 1904) "Distinguished from M. bairdi[i] by (1) deep preorbital [lachrymal] fossa, which is 

 deeper also than in M. hypostylus; (2) large size of m 3 ; (3) protoloph with very faint protoconule, and strongly connected 

 with parastyle, constituting a nearly perfect anterior crest; metaloph also continuous; (4) as in M. mctcidophus n^-m 3 

 exceed in linear measurement p 2 -p 4 ; (5) p 4 slightly narrower than m 1 ; (6) series of grinding teeth, m 2 -p 2 , narrowing 

 anteriorly." 



Additional specific characters. — P 2-4 of shorter length than p 1-3 . 



