56 



osborn: OLIGOCENE, MIOCENE, PLIOCENE EQTJID.E. 



Characters. — (Osborn, 1904, p. 177, 1917) P 24 apparently less than molars m 1-3 in length; (2) ectoloph elevated, 

 height .013; (3) parastyle broad, paraeone and metaeone ribs distinct; (4) metaloph short or else separated from ecto- 

 loph; (5) protoloph interrupted, protocone indented; (6) the hypostyle < shaped or triangular, connected with cingulum 

 and with a strong outward spur. (7) Lachrymo-malar fossa relatively deep and vertically broad, subdivided by a low 

 median ridge into anterior and posterior depressions; (8) cranial exceeds facial length. As compared with Mesohippus 

 bairdii this animal is a relatively large horse, standing not less than twenty-eight inches at the withers. 



Fig. 33. Miohippus validus, Osborn, Am. Mus. 1218. (H) Original figure of skull of type, exhibiting the vertically 

 deep lachrymo-malar fossa; cranial exceeding facial length. One-half natural size. After Osborn, 1904, PI. v, H. (5) 

 Crown view of superior molar-premolar teeth of type. Natural size. 



Miohippus gidleyi Osborn, 1904. 

 Plates 1.10, 3.4, 39.16,19, 51.8,12. Text Fig. 34. 



Mesohippus gidleyi, sp. nov., Osborn, Henry F., " New Oligocene Horses," Bull. Amer. Mus. Nat. Hist., Vol. XX, Art. XIII, May 28, 

 1904, p. 178, fig. S, PI. v G. 



Horizon and locality. — Badlands near Cheyenne River, South Dakota, Protoceras zone. Type collected by American 

 Museum Expedition of 1894. 



Type. — Amer. Mus. 1192, partly broken skull of young individual, with complete unworn grinding teeth, cervical 

 vertebrae associated. Measurements: P-m 3 .0975; m 1-3 .042; m 1 a.p. .0145, tr. .019. 

 Type figure. — Text Fig. 34 of this Memoir. 



Characters. — (Osborn, 1904, p. 178, 1918) (1) An animal of somewhat larger size than the type of Miohippus inter- 

 medins, which, however, it resembles in the presence of (2) a vertically deep lachrymo-malar fossa, and (3) in the 

 sharpness of the metaloph crest of the molars. It is more primitive than M. intermedins in (4) the somewhat larger size 



