208 



osborn: OLIGOCENE, MIOCENE, PLIOCENE EQUID.E. 



Characters. — (Leidy, 1858, p. 26.) "... .has the same form [of upper molar] as the corresponding teeth of Anchi- 

 therium, except that the outer surfaces of its external lobes present no trace of median rising. It indicates an animal 

 larger than A. aurelianense and about the size of Paloeotherium crassum." 



(Gidley, 1906, pp. 135, 136) "Compared with the corresponding teeth in H. cquinus they show a marked progres- 

 sive stage, especially in (1) their greater size; (2) their proportionately longer crowns; and (3) the better development 

 of the metastylid which at its summit in the little worn teeth is slightly separated from the metaconid by a shallow 

 groove which extends but a short distance down the side of the metaconid pillar. The continuous external basal 

 cingulum is well developed in a broad heavy band of enamel." 



(Gidley, 1906) Only on the ground of equality in size, the height of the molar crowns, and its derivation from the same 

 formation and a locality not far removed from that of the type is the reference to this species of the lower teeth from Big 

 Spring Canon made. 14043 A. M. 



A referred specimen is Amer. Mus. 14043. 



12 



Fig. 169. Hypohippus affinis Leidy, U. S. National Mus. 573. (11, 12) Original figures of the type, natural size. 

 After Leidy, 1869, PI. xxi, figs. 11, 12. '(Right) Referred lower teeth, Amer. Mus. Nat. Hist. 10834. One-half natural 

 size. After Gidley, 1906, fig. 1, p. 135. 



Hypohippus nevadensis Merriam 1913. 

 Text Fig. 170. 



Hypohippus (Drymohippus) nevadensis, n. sub-gen. and n. sp., Merriam, John C. "New Anchitheriine Horses from the Tertiary 

 of the Great Basin Area," Univ. Cal. Publ. Bull. Dept. Geol., Vol. 7, No. 22, Dec. 16, 1913, pp. 420, 422, figs, la, 16, 2a, 2b. 



Horizon and locality. — (Merriam) "From the Stewart Valley Miocene, twenty-four miles northeast of Mina, 

 Nevada." Procamelus zone. Type collected by T. Holman Buck. 



Type. — Univ. Cal. Pal. Coll. 21056. (Merriam) "The type specimen consists of a small portion of the skull 

 with three milk molars, portions of all four limbs, and a number of scattered fragments of other skeletal parts. The 

 elements of the limbs were in part connected." Measurements: (Merriam) dp 2 a.p. .033, tr. .029; dp 3 a.p. .0318, tr. 

 .0305; dp 4 a.p. .0319, tr. .0314. 



Type figure. — Text Fig. 170 of this Memoir. 



Characters. — (Merriam, 1913, p. 421) (1) An animal approaching in size H. affinis, the largest described species. 

 (2) Milk teeth exceeding in dimensions those of H. osborni; (3) deciduous crown pattern in general resembling that of 

 permanent crown pattern in H. osborni; (4) metaloph not connected with ectoloph; (5) a crista extending inward from 

 ectoloph; (6) Limbs in general character and proportions near those of Hypohippus; (7) The proposed subgenus Drymo- 

 hippus distinguished from Hypohippus by the separation of the metaloph from the ectoloph in the milk dentition. 



