156 



OSBORN: OLIGOCENE, MIOCENE, PLIOCENE EQUID/E. 



animal and of more robust proportions; (6) terminal phalanx well rounded, with the posteroexternal processes much 

 reduced as in the modern horse, but the plane of the proximal articular facet directed more backward as in the other 

 species of Miocene horses. (7) This species is not clearly distinguished from P. suprernus Leidy, with which it agrees in size 

 and general characters so far as they are known. 



(Matthew, 1913) P. robustus Marsh agrees witli P. suprernus Leidy. 



Pliohippus fossulatus Cope 1S93. 



Plate 23.1,1a, 24.1. Text Figs. 124, 125. 



Protohippus fossulatus Cope, Cope, E. D. "A Preliminary Report on the Vertebrate Paleontology of the Llano Estacado," Fourth 

 Ann. Iiept. Geol. Surv. Texas (1892) 1893, pp. 30-32, Pis. v, vi, vii. 



2 



Fig. 124. Original figures of (1) side view of the skull and (2) crown view of the right premolar-molar series (p :i -m 3 ) 

 of the type of Pliohippus fossulatus Cope, Univ. Texas Coll. (cast Amer. Mus. 14395). After Cope (1S92) 1893, PI. v. 

 Skull one-half natural size, teeth natural size. 



Horizon and locality. — (Cope) " . . .found by Mr. W. F. Cummins in the Loup Fork formation of Donley county, 

 Texas." Clarendon formation, Upper Miocene. 



Type. — Univ. Texas Coll. (cast Am. Mus. 14395). (Cope) "Represented by a cranium, which has lost all, 

 posterior to the posterior frontal region and anterior to the premaxillary border." Measurements: (Cope) length from 

 posterior border of orbit to extremity of nasal bones .235; m 1 a.p. .020, tr. .025; total length of molar series .145; length 

 of true molar series .069. 



Type figure. — Text Figs. 124, 125 of this Memoir. 



Characters. — (Cope) (1) Size between that of Pliohippus pachyops and P. mirabilis. (2) No fossa immediately in front 

 of the orbit, but there is a narrow and deep maxillo-nasal fossa [lachrymal!, the posterior extremity of which approaches 

 nearer to the superior part of the orbit than any other; (3) beneath it and immediately above the penultimate molar tooth 

 (m 2 ) a small but well pronounced fossa [malar] ; (4) immediately anterior to the infraorbital foramen is a wider and shal- 



