130 



OSBORN: OLIGOCENE, MIOCENE, PLIOCENE EQUIDjE. 



the posterior four molars." P 4 -m 3 . Measurements: (Gidley, 1907, p. 882) p 4 a. p. .020, tr. .022, height of crown .036; 

 m 1 a.p. .0195, tr. .0215; m 3 a.p. .020, tr. .0175. Ncotypc. (Gidley, 1907, p. 882) "A nearly complete skull," Amer. 

 Mus. 10S3S. From the Little White River, near Rosebud Indian Agency, South Dakota. 

 Type figure. — Text Fig. 102 of this Memoir. 



Characters. — (Leidy, 185S) (1) The portion of jaw is like the corresponding part in the recent horse. (2) Molar 

 teeth with their crowns about one-half worn; (3) enamel folds even less complex than in the recent horse; (4) antero- 

 internal fold [protocone] of the same form, direction, and mode of continuation as the posterointernal fold [hypocone]. 

 (Gidley, 1907) (5) Moderately small size. (6) Laterally compressed and backwardly directed protocone and hypocone 



Fig. 102. Original figures of the type of Protohippus perditus Leidy, U. S. Nat. Mus. 619. After Leidy, 1869, PI. 

 xvii, figs. 1, 2. Natural size. 



of the upper molars. (7) Shallow, not sharply defined lachrymal fossa; (8) rudimentary condition or entire absence of 

 malar fossa. 



The specimen selected by Gidley as the neotype (Amer. Mus. 10838) does not clearly exhibit in its molar teeth the 

 characteristic specific features enumerated by Leidy. 



Protohippus parvulus Marsh 1868. 

 Text Figs. 104, 105. 



Equus parvulus, Marsh, O. C. "Notice of a New and diminutive species of fossil Horse (Equus parvulus), from the Tertiary of 

 Nebraska," Amer. Jour. Sci. and Arts (2) Vol. XLVI, No. 138, Nov. 1868, p. 374-375, no figure. 1 



Horizon and locality. (Marsh) " Antelope station on the Union Pacific Railroad, about 450 miles west of Omaha 



during the excavation of a well at a depth of sixty-eight feet." Type collected by O. C. Marsh, 1S68. 1 



1 Professor Marsh gave an account of this locality and its fossils before the National Academy of Sciences at the Northampton 

 meeting, August, 1868. Op. cit. p. 374. 



