HIPPARION. 



197 



Hipparion leptode Merriam 1915. 



Text Fig. 161. 



Neohipparion leptode, n. sp., Merriam, John C. "New Species of the Hipparion Group from the Pacific Coast and Great Basin 

 Provinces of North America," Univ. Cal. Publ. Bull. Dept. Geol. Vol. 9, No. 1, June 29, 1915, pp. 3-4, fig. 3. 



Horizon and locality. — Locality 1101, Thousand Creek formation, Thousand Creek, Nevada, Lower-Middle Pliocene. 

 Name of collector not given. 



Type. — Univ. Cal. Pal. Coll. 19414. An inferior molar, m 2 . Measurements: (Merriam) a.p. .029+, tr. .011, a.p. 

 of metaconid-metastylid column .0146, greatest length of crown .066. 

 Type figure. — Text Fig. 161 of this Memoir. 



Characters. — (Merriam, 1915) (1) Resemblances to Hipparion eurystyle Cope from 

 the Clarendon formation, Paloduro Canon, Texas, but of larger size and differing in 

 details of structure; (2) crown rather elongate, slender, relatively straight, well ce- 

 mented, much compressed laterally; (3) metaconid-metastylid column long anteropos- 

 teriorly, narrow transversely, with wide, flat internal groove; (4) hypoconid ridge 

 prominent; (5) a strong external protoconid ridge present. 



Merriam observes that the type represents a species in many respects near //. 

 eurystyle and also resembling //. occidentale in many characters. The Thousand Creek 

 species is tentatively distinct. A referred upper molar (Univ. Cal. Pal. Coll. 12581) 

 presents characters which may be correlated with the structure of the lower molar 

 type. 



Hipparion montezuma Leidy 1883. 

 Text Fig. 162. 



Hippotherium montezuma, Leidy, Joseph. "On Remains of Horses," Proc. Acad. Nat. Sci. 3 

 Phila. Vol. XXXIV, 1882 (sig. dated Jan. 16, 1883), pp. 290-291, text fig. p. 291. 



Fig. 161 . Original figure of 

 the type of Hipparion leptode 

 Merriam, Univ. Cal. Pal. 

 Coll. 19414, m 2 . Natural 

 size. After Merriam, 1915, 

 fig- 3, p. 4. 



Horizon and locality. — (Leidy, p. 290) "The remaining specimens are of more 

 interest than the preceding, and consist of two bone fragments and three teeth (Nos. 

 1-5, 11629), which were obtained by Mr. Ellis Clarke, Jr., from near Lacualtipan, 

 Hidalgo, Mexico. According to the accompanying letter, they were discovered in a 

 thirty inch clay bed, lying between an upper four inch, and an under four feet stra- 

 tum of coal, overlying a limestone with small shells. The fossils belong to the three-toed horse, Hippotherium {Hipparion), 

 and are probably of pliocene age, though they may be miocene." ? Upper Miocene. 



Type — U. S. Nat. Mus. 3304. A superior premolar, p 3 or p 4 of the right side. Measurements: (Gidley, 1907) p 3 

 or p 4 a.p. .0195, tr. .017, height of crown, external, .047. 



Type figure. — Text Fig. 162 of this Memoir. 



Characters. — (Leidy, p. 291) (1) Type an animal about the size of H. venustum and of H. (Hippodon) speciosus; (2) 

 distinguished by differences in the enamel plications; (3) protocone greatly elongated anteroposteriorly, compressed 

 transversely; (Gidley, 1907) (4) relatively small size and comparative great length of crown; (5) in general related to 

 the H. whitneyi types; (6) plications confined to the metaloph and crochet region of the protoconule, the latter double 

 in prefossette and double opposite the protocone. 



