54 



osborn: OLIGOCENE, MIOCENE, PLIOCENE EQUID.E. 



Characters. — (Osborn, 1904, 1917) The name refers (1) to the broad rounded parastyle, readily distinguishable 

 from the flattened angulate parastyle of Mcsohippus eulophus, Miohippus metevlophus, and Hypohippus. This species 

 is further distinguished by: (2) p 2 " 4 exceeding m 1-3 in length (the reverse occurs in M. eidophus); . (3) broadly depressed 

 proto- and metalophs; (4) protoloph interrupted, with large oval protocone and distinct protoconule uniting externally 

 with parastyle as in M . bairdii; (5) ectoloph with broad, prominent, rounded parastyle and well defined mesostyle, para- 

 and metacone ribs defined; (6) hypostyle connected with cingulum but giving off a strong outward spur. (7) A 

 vertically broad, shallow lachrymo-malar fossa (as compared with the narrow fossa in M. mctculophus); (8) facial 

 exceeds cranial length. 



(Osborn, 1904) This horse, which is an animal of larger size than Mcsohippus bairdii, appears to be one of its 

 successors although of larger size. In some respects it appears to be ancestral to the type of Miohippus intermedins of 

 the Protoceras zone, connected by a simpler intermediate stage (Amer. Mus. 1218). The molars approach the buno- 

 selenodont type, with resemblances to those of Miohippus crassicuspis, M. anceps, etc. 



Fig. 31. Original figures of type of Miohippus brachystylus Osborn, Amer. Mus. 11860. (Upper) Lateral view of 

 skull, one-half natural size. (Lower) Crown view of superior grinding teeth, p^m 3 , of the left side. Natural size. After 

 Osborn, 1904, skull PI. v, E, teeth fig. 6, p. 175. 



Miohippus intermedius Osborn and Wortman, 1895. 

 Plates 1.9, 3.3. Text Fig. 32. 



Mesohippus intermedius, sp. nov., Osborn, H. F., and Wortman, J. L., " Perissodactyls of the Lower Miocene White River Beds," 

 Bull. Amer. Mus. Nat. Hist. Vol. VII, Art. XII, Dec. 23, 1895, p. 355, fig. 4. 



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

 Museum Expedition, 1S94. 



Type. — Amer. Mus. Nat. Hist. 1196, skull and parts of skeleton. Measurements: basilar length, condyles to sym- 

 physis .218; p'-m 3 .088; m 1 " 3 .040; m 1 a.p. .0135, tr. .018. 

 Type figure. — Text Fig. 32 of this Memoir. 



Characters. — (Osborn and Wortman, 1895, Osborn, 1918) (1) Skull with large and apparently undivided lachrymo- 

 malar fossa of the shallow vertically broad type : (2) cranial exceeds facial length. (3) Premolars 3-4 exceeding molars in 



