122 



osborn : 



OLIGOCENE, MIOCENE, PLIOCENE EQUID^E. 



Type. — Univ. Cal. Pal. Coll. 21247. First superior molar of the left side, m 1 , from locality 2124; also from same 

 locality, between forty and fifty upper and lower molars, several incisors, limb and foot elements. (Merriam) "The upper 

 and lower molars seem all referable to a single species." Measurements: (Merriam, p. 201) m 1 a.p. .0187, tr. .0201, height 

 of mesostyle, worn, .0281. 



Type figure. — Text Fig. 96 of this Memoir. 



Characters. — ; (Merriam, 1915) (1) Molars of more slender form than in M. isonesus, otherwise in some respects 

 similar; (2) protocone separate from protoconule almost to base of crown, connected only in very old, much worn teeth; 

 (3) protocone round [oval] with a slight lateral compression [suboval]; (4) a spur extending toward protoconule; (5) enamel 



Fig. 96. (Upper) Type of Merychippus californicus Merriam, Univ. Cal. Pal. Coll. 21247, superior molar of left side, 

 m 1 . Crown, external, and internal views. (Lower) Original figures of a referred specimen of M. californicus Merriam, 

 Univ. Cal. Pal. Coll. 21217, m 1 of the left side. 3a Crown view, 3b posterior view, 3c internal view, 3d external view. 

 After Merriam, 1915, p. 197. 



folding moderately complex, approximating that of M. isonesus; (6) superior molars somewhat narrow in cross section 

 and somewhat more hypsodont than in M. isonesus; (7) type of upper molar leading toward llipparion; (8) lower cheek 

 teeth closely resembling those of M. isonesus in form and dimensions. 



Merychippus insignis Leidy 1857. 



Plates 17.5, 25.3. Text Fig. 97. 



Merychippus insignis, Leidy, Joseph. "Notices of Extinct Vertebrata Discovered by F. V. Hayden, during the Expedition to the 

 Sioux Country under the Command of Lieut. G. K. Warren," Proc. Acad. Nat. Sci. Phila. Vol. VIII, 1856 (sig. printed April or later, 

 1857), p. 311, no figure. "The Extinct Mammalian Fauna of Dakota and Nebraska," Jour. Acad. Nat. Sci. Phila. (2) Vol. VII, 1869, 

 pp. 296-299, PI. xvii, figs. 3-4. 



Horizon and locality. — (Leidy) "From the tertiary beds of Bijoux Hills on the Upper Missouri." Brule Co., So. Dak. 

 Lower Pliocene or Upper Miocene. Type collected by F. V. Hayden. 



