1921] Frick: Faunas of Bautista Creek and San Timoteo Cafion 395 



protoconid, and the resulting unusual, rounded contour of the sides 

 of the valley that divides the parastylid and metastylid ; the consider- 

 able production of the fold between the protoconid and hypoconid 

 within the mouth of the metaconid-metastylid colunan of P^, and the 

 sudden and marked increase in the size and production of this fold 

 in Mj;. 



130 



131 



Figs. 130, 131. FPlioMppus osborni, subform A. Lower cheek teeth. Fig. 130, 

 two premolars and one molar associated, no. 23286, referred specimen, occlusal 

 view, X 1. Fig. 131, P; to M5, no. 23510, type, occlusal view, X 1; outer view, 

 X Eden beds, California. 



Measurements of P. osborni, subform A 



No. 23510 No. 23286 



Pj Mi M5 Mi 



Anteroposterior diameter of crown 27.3 mm. 28.5 mm. 25.2 mm. 



Transverse diameter of crown 12.6 mm. 12.7 11.1 13.3 



Anteroposterior length of pillar 13.6 15.1 13.5 15 



Discussion. — Except for the suggested sharpness of the gutter 

 of the metaconid-metastylid pillar, the teeth in the flatness of their 

 inner faces and the great anteroposterior extension of the metaconid- 

 metastylid would indicate the presence of an Hipparion form. This 

 elongation of the metaconid-metastylid column of the new teeth is 

 shown in comparison to that occurring in hipparions from the Rattle- 

 snake and Ricardo Pliocene, as well as in Merychippus and Pliohippus 

 in the following table. 



so Eipparion and Merychippus data through the kindness of Professor John C. 

 Merriam. 



