PLIOHIPPUS. 



167 



GLYPTOTHERIUM-PLIOHIPPUS SIMPLICIDENS ZONE. 17. FULL MIDDLE PLIOCENE. 



The typical exposures of this zone are the Blanco, Texas. It is characterized by the presence of 



SEVERAL SPECIES OF PLIOHIPPUS AND BY THE ABSENCE OF THE PhoTOHIPPUS STAGE. 



Pliohippus simplicidens Cope 1S92. 



Plates 24.5, 28.5. Text Fig. 134. 



Equus simplicidens sp. nov. Cope, Edw. D. " A Contribution to the Vertebrate Paleontology of Texas," Proc. Amcr. Philos. Soc. 

 Vol. XXX, No. 137, Mar. 30, 1892, pp. 124-125, tig. 1. 



Fig. 134. Pliohippus .simplicidens Cope, Univ. 

 Texas Coll. (cast Am. Mus. 143S8). (Left) Original 

 figure of the type true molar, of the left side. After 

 Cope, 1892, fig. 1. (Right) Drawing of type superior 

 molar under the direction of Osborn; crown, external, 

 and anterior views. All figures natural size. 



Horizon and locality. — (Cope, p. 123) "The formation has been named the Blanco Canyon bed by Mr. Cummins 

 (First Annual Report of the Geol. Survey of T&as, 1890, p. 190)." Crosby County, Texas. Type collected by W. F. 

 Cummins. 



Type and parahjpes. — Univ. Texas Coll. (type cast Am. Mus. 14388). (Cope, p. 124) "This species is repre- 

 sented by one nearly entire superior molar of an adult, and one of a young animal, with characteristic fragments of two other 

 superior molars, and several fragments of inferior molars. The size of the teeth is about that of the E. occidentalis and E. 

 caballus." Measurements: (Gidley, 1907) diameters of type molar, a.p. .032, tr. .026, height of crown .060. 



Type figure. — Text Fig. 134 of this Memoir. 



Characters. — (Cope, p. 124) (Type and cotype) (1) Size about that of E. caballus, (2) Internal column [proto- 

 cone] is of moderate anteroposterior extent, its posterior border marking the anterior third of the posterior lake [post- 



