HIPPARION. 



185 



Horizon and locality. — (Cope) Mulberry Canon, near Goodnight, Texas. Clarendon formation ("Goodnight beds"). 

 Type collected by F. A. Cummins. 



Type. — Univ. Texas Coll. (cast Am. Mus. 14390). (Cope) Two isolated superior molar teeth, obviously belong- 



Fig. 148. Neotype (Gidley) of Hipparion lenticulare Cope, Amer. Mus. 10584. Natural size. Drawing by S. Oka. 



A/C. /OS84- 



ing to different individuals: No. 1 (type) a right superior molar, diameters a.p. .021, tr. .019, height of crown .048; 

 No. 2, a left superior molar, fractured anteriorly, diameters a.p. .021, tr. .018, height of crown .044. Neotype (Gidley, 

 1907, p. 916), Amer. Mus. 10584, anterior portion of skull with full dentition from the 

 Clarendon beds of Donley County, Texas. 



Type figure. — Text Fig. 147 of this Memoir. 



Characters. — (Cope, 1893, Gidley, 1907) (1) Distinguished by the absolutely len- 

 ticular section of the protocone, which presents acute angles anteriorly and posteriorly 

 and convex surfaces internally and externally; (2) enamel borders of fossettes moder- 

 ately complex [relatively simple], in type only three folds projecting into prefossette 

 and three folds [in paratype] into postfossette; (3) crown quite strongly curved trans- 

 versely. (4) An animal about the size of Hippodon spedosus Leidy. 



Gidley observes that the sharply lenticulate form of protocone, pointed out by 

 Cope as distinctive of the species, is apparently due entirely to the little worn condition 

 of the tooth crown. The simple enamel foldings in the fossettes relate this species to 

 the Hipparion whitneyi type and to the referred specimen Amer. Mus. 10584 obtained 

 by Gidley in 1889 from the Clarendon beds of Donley County, Texas. 



Neotype characters. — (Gidley) (1) Corresponding teeth nearly identical in size 

 with those of the type molars, protocones of the less worn teeth, m 1 " 2 , lenticulate in form, while the others, p 2_1 , have a 

 suboval outline with a spur extending off anteriorly toward the convex apex of the protoconule, indicating that Cope 

 was correct in referring this animal to Protohippus; (2) in skull characters the palate high-arched, the muzzle compara- 

 tively long and slender, the cranium as compared with that of Protohippus perditus with a considerable vertical depth; 



(3) in the facial region, the lachrymal fossa especially well developed, sharply defined, and deeply pocketed posteriorly; 



(4) no trace of malar fossa. 



Fig. 148a. Section of crown 

 of the neotype of Hipparion 

 lenticulare Cope, Amer. Mus. 

 10584, p 4 . To show pattern 

 of the half-worn grinding 

 tooth. 



