i:;x 



osborn: OLIGOCENE, MIOCENE, PLIOCENE EQUID.E. 



premolar series, p 2 -m 3 , .135; molar series .062; m 1 , a.p. .020, tr. .023; p 4 a.p. .021, tr. .0245. Paratype. Am. Mus. 

 10871. (Gidley, 1907, p. 925) A portion of an upper jaw containing all the large cheek teeth except m 1 . 

 Type figure. — Plate 21.1, text Fig. 109 of this Memoir. 



Characters. — (Gidley, 1907, p. 925) (1) Allied to Protohippus pcrditus though somewhat larger and differing in the fol- 

 lowing characters: (2) protocones of a more progressive stage in their fuller development anteriorly, thus forming a deeper 

 infolding of the enamel between them and the protoconules; (3) fossettes narrower transversely than in P. perditus; (4) pre- 

 orbital or facial region relatively shorter and broader than in P. perditus; (5) incisive border but little curved, giving the 

 muzzle a rather truncate appearance; (6) palate broader and less arched than in P. pcrditus, especially in front of pre- 

 molars; (7) malar fossa wanting, as in P. pcrditus; (8) lachrymal fossa broader, much more shallow, and less sharply 

 defined than in P. perditus; (9) comparative great vertical depth of skull may be due in part to distortion. (Osborn, 

 1918) (10) Protocone strongly constricted and separated at the summit from protoconule; (11) evidence of a small pli 

 caballin, of one crochet enamel fold in prefossette, and of two enamel folds in postfossette. 



Protohippus pachyops Cope 1893. 

 Plates 23.1,la,2, 24.2,2a. Text Fig. 110. 



Protohippus pachyops Cope, Cope, E. D. Name and figure, no description, "On the Permanent and Temporary Dentitions of 

 Certain Three-toed Horses," Amer. Naturalist, Vol. XXVI, Nov., 1892, pp. 943, 944, pi. XXVI, fig. 1. "A Preliminary Report on the 

 Vertebrate Palaeontology of the Llano Estaeado," Fourth Ann. Rept. Geol. Surv. Texas, (1892) 1893, pp. 26-29, PI. iii, fig. 1, PI. ix, 

 figs. 2, 3. 



Horizon and locality. — (Cope) "Found by myself in the Loup Fork bed of Donley county, Texas." Clarendon 

 formation, Procamelus zone, Lower Pliocene. 



Type. — Geol. Surv. Texas Coll. (cast Am. Mus. 14391). (Cope) "Represented by a cranium witli lower jaw, from 

 which have been broken away all posterior to the orbits, and all anterior to the second premolars." (Gidley, 1907, p. 

 913). " But a more careful examination of the type shows it to be that of a colt still retaining the milk molars, with the first 

 true molar just coming into use and the second just protruding from the alveolus, the third not yet having made its appear- 

 ance." Measurements: (Cope) length of skull as preserved .290; m 1 a.p. .028, tr. .025. 



Type figure. — Text Fig. 110 of this Memoir. 



Characters. — (Cope) (1) Malar-maxillary ridge obtusely rounded; (2) no preorbital fossa, an oval maxillo-nasal 

 fossa which is strongly pronounced; (3) infraorbital foramen issuing above middle of m 1 ; (4) the deciduous premolar 

 crowns with protocone section greater longitudinally than transversely, junction with protoconule complete; (5) two 

 enamel folds in prefossette; (0) superior molars with elongate crowns, well curved transversely; (7) inferior with para- 

 conid and hypostylid well developed. 



Gidley observes (1907, p. 913) that (1) Cope's conclusions were based on a misconception of the age of the specimen; 

 (2) that the characters of the type are in general those of Protohippus but differ in several important details from any 

 previously described species; (3) that the young skull referred to this species by Cope agrees closely with that of [?] Proto- 

 hippus affinis. 



Protohippus tehonensis Merriam 1915. 

 Text Fig. in. 



Protohippus tehonensis, n. sp., Merriam, John C. "New Horses from the Miocene and Pliocene of California," Univ. Cat. Publ. 

 Bull. Dept. Geol. Vol. 9, No. 4, Nov. 22, 1915, p. 52, figs. 4a, 4b, 4c. 



Horizon arid locality. — From the Tejon Hills, southern end of San Joaquin Valley, California. Type collected by 

 J. P. Buwalda. 



Type. — Univ. Cal. Pal. Coll. 21779. A first or second superior molar of the left side. Measurements: (Merriam) 

 m ] a.p. .0225, tr. .0237. 



