HIPPARION. 



175 



6. Antero-external cingulum fold of lower teeth prominent to the crown of the tooth. 



7. Crowns of the grinding teeth nearly straight, or curved (H. lenticulare, II. whitneyi). 



S. Lachrymal fossa deep and sharply defined or broadly shallow, malar fossa usually absent, present in a referred 

 //. (/ration. 



9. Limbs generally slender, feet anisotridactyl, terminal phalanges typically narrow. 



The grouping of the species, partly on progressive characters, partly on true phyletic distinctions, is tentatively pro- 

 posed by Gidley, Matthew, and Osborn as follows: 



Group I, with elongate protocones, the Neohipparion of 

 Gidley. Animals of large size. 



Hipparion occidentale Leidy. 



whitneyi Gidley. 



affine Leidy. 



sinclairi Wortman. 



molle Merriam. 



platystyle Merriam. 



■mohavcn.se callodonte Merriam, etc. 



gidieyi Merriam (near a.ffinc, J. C. M.) 



Group II, protocones same as in Group I. Animals of 

 small or diminutive size, molar crowns elongate. 



Hipparion gratwm Leidy. 



montezuma Leidy. 

 peninsulatum Cope. 



Group III, protocone, as in Group I. Animals of large 

 size, molar enamel plicate. 



Hipparion plicatile Leidy. 



Group IV, with round or oval protocones, as in the H. 

 gracile and //. prostylum of Europe. 



Hipparion venustum Leidy. 



ingenuum Leidy. 

 All of Florida. 



This grouping is preliminary and is by no means based upon a profound study of all parts of the animal. It is prob- 

 able that the skull structure, the preorbital fossa 1 , and possibly divergencies of foot structure will have to be considered 

 in separating the phyla of Hipparion. At present our knowledge of the foot structure and even of the skull structure is 

 very incomplete. 



Fig. 139. (Left) Original figure of the type of Hipparion condoni Merriam, Univ. Oregon Coll. 672, p 4 , mi. Outer 

 and occlusal views, fig. 4, p. (i. (Right) Referred mandibular symphysis of Hipparion condoni, Univ. Oregon ('oil. 668, 

 fig. 5, p. 6. All figures natural size. After Merriam, 1915. 



Hipparion condoni Merriam 1915. 

 Text Fig. 139. 



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

 vinces of North America," Univ. Cat. Publ. Bait. Dept. Gcol. Vol. 9, No. 1, June 29, 1915, p. 6, fig. 4. 



Horizon and locality. — Ellensburg formation, Kittitas County, Washington. Middle to Upper Miocene. Type 

 collected by Professor Thomas Condon. 



