384 University of California Publications in Geology [Vol. 12 



Description. — The angle of the external faces of the type specimen, 

 the transverse breadth of the anterior edge, the anteroposterior 

 length, and heaviness of the parastyle suggests P-. The type and 

 referred specimen are of large size in comparison with the teeth of the 

 subform and with the more typical Pliohippus teeth from the same 

 beds, compare third molars referred to type (figs. 104(i-1046) and to 



103f 105b 



Figs. 103a to 105b. Pliohippus osborni, n. sp. Premolar and molar teeth. 

 Figs. lOSa-lOSf, type, no. 23787: fig. 103a-103Z;, outer and front views, X %; fig. 

 103c', occlusal view, X 1; figs. 103d-103/, sections through m, n and o respectively. 

 Figs. 104o, 104b, referred M^, no. 23338: fig. 104a, outer view, X 1/2; fig. 104b, 

 occlusal view, X 1. Figs. 105a, 105b, Pliohippus osborni, subform A, small M-, 

 no. 23350: fig. 105o, outer view, X 1; fig. 105b, occlusal view, X 1. Eden beds, 

 California. 



subform A (figs. 105a-105&). The crowns are long and well curved. 

 The parastyle is relatively strong, the mesostyle well developed. The 

 protocone is large (the anteroposterior diameter being twice the trans- 

 verse), the cusp projects considerably anteriorly, and is slightly 

 indented in the inferior margin; the main postprotoconal valley is 

 relatively narrow, and is extended at the head, where a slight sub- 

 sidiary fold is developed. Cross-sections of the type specimen (figs. 



