160 



osborn: OLIGOCENE, MIOCENE, PLIOCENE EQUID.E. 



narrower than they would be in a greater degree of wear; (2) the simplicity of the enamel foldings, the small rounded 

 protocone, the degree of curvature of the tooth crown, resembling the northern species of Pliohippus; (3) the animal agrees 

 in size with P. spcdans Cope. 



(Matthew, 1913) (1) Size large, about equalling P. spcdans; (2) protocone larger than in P. spcdans, of flattened 

 oval shape; (3) fossettes not as wide as in P. spcdans; (4) distinguished from P. pcrnix by larger size and more hypso- 

 dont molars; (5) from P. spcdans by less reduction of protocone. 



A referred specimen is Amer. Mus. 13900a. 



Pliohippus lullianus Troxell, 1916. 

 Plate 27. Text Fig. 127. 



Pliohippus lullianus sp. nov. "An Early Pliocene One-Toed Horse, Pliohippus lullianus sp. nov." The Amer. Jour, of Sci. 

 (4), Vol. XLII, No. 250, Oct., 1916, pp. 335-348, figs. 1-7. 



Horizon and locality. — (Troxell, pp. 345, 346) "The skeleton of the new type was found in the eastern part of the 

 Rosebud Indian Reservation, near the town of Mission, South Dakota. This Reservation, at least the western part 

 in the Miocene formation of the valley of the Little White River, has long been a favorite hunting ground for specimens 

 of extinct animals. . . .The fauna of this Oak Creek formation corresponds closely with that of the Snake Creek Beds of 

 Western Nebraska; the latter, though resembling the Republican River Beds of Western Kansas, show a more modern- 

 ized type of animal life and are considered by Matthew and Cook to be intermediate between the Blanco of Texas and the 

 Upper Miocene. The Oak Creek formation, while in some respects like the Etchegoin of California, Middle Pliocene, 

 is not so far advanced and in all probability belongs to the Early Pliocene." Type collected by E. L. Troxell. 



Type. — Amer. Mus. 17225. (Troxell, p. 336.) "... .the skeleton of a young colt about ten months old. The milk 

 teeth are all visible and some are slightly worn; the first permanent true molar is well formed and about ready to be cut 

 — it has, however, no apparent cement. The loose epiphyses and the incompletely ossified bones also attest the imma- 

 turity of the individual." 



Type figure. — Text Fig. 127 of this Memoir. 



Characters. — (Troxell, pp. 341-343) "Metacarpals. — The especial character which distinguishes this specimen is 

 its monodactyly. It has commonly been predicted that one-toed specimens of the Protohippina? would be found, but 

 no positive evidence of this feature has, heretofore, been presented. The splints, Metacarpals II and IV, unlike those 

 of Equus, extend the lengths of the cannon bone, but like those of the modern horse they bear no digits on the ends. These 

 slender bones are large proximally, but at once decreasing in size they run at a uniform diameter to the middle; in the 

 next fourth of the distance they decrease to a width of about 3 mm. and a thickness of less than 1.5 mm. The distal ends 

 are enlarged to receive the pointed epiphyses, the larger one of which measures 6 mm. in length. They show no evidence . 

 of articular facets; in fact their very sharp ends eliminate the possibility of their ever having borne phalanges." 



PLIAUCHENIA-PERACERAS-PLIOHIPPUS NOBILIS ZONE. 14. LOWER PLIOCENE. 



The typical exposures of this zone are on the Republican River, western Kansas. 



Pliohippus nobilis sp. nov. 

 Plates 26.4, 2S.4. Text Fig. 128. 



Horizon and locality. — From the Republican River formation, Long Island, Phillips County, Kansas. Type col- 

 lected by American Museum Expedition of 1S94. 



Type. — Amer. Mus. 2668. An upper jaw containing p 3 -m 3 of the left side, also p 2 and m 2-3 of the right side. Teeth 

 about three-fifths worn. 



Type figure Plates 26.4, 28.4, text Fig. 128 of this Memoir. 



