1921] Frick: Faunas of Bautista Creek and San Timoteo Canon 333 



given in Gidley's description of P. sinus.-'' They also approach 

 Pliohippus intcrpolatus of Cope-^ (as seen in figures loaned by Pro- 

 fessor Osborn) in the same tendency to narrowness of the styles and 

 to constriction of the postprotoconal valley in the and M^, but 

 differ from figures of the molar of the less worn type specimen in the 

 University of Texas Collection through lack of the greater degree of 

 primitiveness shown in its smaller and rounder protocone. The 

 fossettes of P. interpolatus are more complicated than those of P. 

 francescana minor. 



The single small lower tooth (no. 23274, fig. -iO), is believed to 

 represent the lower dentition of P. francescana minor. The slope of 

 the exterior and interior faces refer it to the posterior portion of the 

 series, while the very slight degree of prolongation of the fold between 

 the protoconid and hypoconid place it not farther back than Pj. In 

 an Mj a similar lack of production in this fold would point to a degree 

 of advancement beyond the usual in an equine of corresponding 

 characters and size. The anteroposterior length of a P4 may be 

 taken as 26% to 27% of the total length of P3 to Ish inclusive (in 

 E. occiclentalis of the Univ. Calif. Coll. Vert. Pal. no. 12258, the same 

 figures 26%, in P. simpliciclens of Cope's illustration 26%, and in 

 P. francescana 271/2%) ; this would place the total length of the four 

 hypothetical lower teeth at 100 mm., a length which compares well 

 with a compiled length of 108 mm. for the small uppers. 



The specimen (figs. 40a-406) is considerably smaller than the teeth 

 figured in Professor Cope's lower series of Plioliippns simplicide ns . 

 Compared with the P. simplicidens series, and P3 in particular, the 

 groove of the metaconid-metastylid column is a trifle more open ; the 

 prolongation of the interprotoconid-hypoconid fold is slightly less; 

 the comparatively short parastylids are much the same ; the protoconids 

 have a certain resemblance in their exterior roundness, the present 

 form exceeding P. simplicidens in this character; and the hypoconids 

 are relatively flat. 



27 Gidley, J. W. Revision of the Miocene and Pliocene Equidae of North 

 America. Bull. Am. Mus. Nat. Hist., vol. 23, p. 925, 1907. 



28 Cope, Edw. D. Geol. Surv. Texas (1892), 1893. 



