1921] Frick: Faunas of Bautista Creek and San Timoteo Canon 329 



Pliohippus francescana resembles the considerably smaller horse 

 (see below) occurring in the same horizon: (1) in the general propor- 

 tions of the protocone, slight amount of the projection of its anterior 

 corner, and the circular protocone section of the premolars : (2) in the 

 relative simplicity of the borders of the cement lakes. It differs mark- 

 edly from the smaller form by the much greater size and accompanying 

 heaviness of its styles as contrasted with the thin and slender ones of 



Figs. 38a to 396. Pliohippus francescana minor, n. subsp. Upper cheek teeth, 

 X 1. Fig. 38a, F-% no. 23275, referred to type, inner view with section; fig. 38b, 

 same tooth, occlusal view; fig. 39a, P^, no. 23263 of type specimen, occlusal view; 

 fig. 39b, Mi, no. 23264 of type specimen, occlusal view. San Timoteo beds, Cali- 

 fornia. 



the latter, the great size of its lakes, and the comparative broadness 

 of the postprotoconal valley of and ( versus the constriction 

 of the same in the smaller form). The interesting similarity of the 

 larger to the smaller series and their several strong points of common 

 primitiveness point either: (1) to a parallel development of two dis- 

 tinct forms of advanced Pliohippus type associating in the same range ; 

 or (2) to an exceptional sexual variation. The writer has placed the 

 small form, pending the securing of additional material, under the 

 name P. francescana minor. 



