1921] Frick: Faunas of Bautista Creek and San Timoteo Cafion 391 



PLIOHIPPUS EDENSIS, subform B 



Type. — A complete series from the right side of the upper jaw, Univ. Calif. 

 Coll. Vert. Pal. no. 23193 (figs. 121a-121b), Univ. Calif, loc. 3269. 



Bef erred material. — Second premolar, no. 2428.5 (fig. 122a) ; molar, no. 23219 



(fig. 123); cross section of no. 2335i (fig. 124); Mi, M2, no. 23327 (figs. 125a- 



1256), Univ. Calif, loc. 3301; all others, Univ. Calif, loc. 3269. All in Univ. 

 Calif. Coll. Vert. Pal. 



Characters. — The large size of the much worn teeth and the 

 transverse thickness and inflection of the inner margins of the proto- 

 cones, as compared with Pliohippus edensis, typical form, and with 

 P. edensis, subform A. 



Description. — The teeth are very much worn. They are of large 

 size, the protocones are more than relatively large, and their inner 

 borders have a more angular inflection than those of other Pliohippus 

 edensis teeth. The considerable size of the teeth is illustrated by 

 comparison of the P- of type series and of referred specimen no. 24285 

 (fig. 122a) with the small P. edensis-liVQ P-, no. 23234 (figs. 1225, c). 

 The inflection of the inner border of the protocone is illustrated by 

 comparison of the P- of type series and specimen 23219 (fig. 123) with 

 the P. edensis type tooth (fig. 111). Certain somewhat similar teeth 

 from the Eden representative of equally worn stages have protocones 

 tenting more to the P. edensis type (see cross-sections no. 23351, and 

 molars no. 23327, figs. 124, 125a-1256). These are only very tenta- 

 tively placed in this section. The series of the B subtype is believed 

 to represent a variation of the general Pliohippus edensis form. 

 Cross-sections (figs. 107, 103e, 108) show the protocones of specimens 

 of P. oshorni of a fully equal stage of wear still retaining a certain 

 amount of the typical anterior projection. 



Pliohippus Upper Milk Teeth 



Material. — A small section of an upper tooth, Univ. Calif. Coll. Vert. Pal. 

 no. 23220 (fig. 1266), Univ. Calif, loc. 3269. Two upper milk teeth, Univ. Calif. 

 Coll. Vert. Pal. nos. 23202, and 23330 (figs. 126a, c). 



Description. — The tooth no. 23220 is of very peculiar pattern, but 

 so fragmentary that the position of the section is undeterminable ; it 

 may represent a milk tooth. The protocone is remarkably oval in 

 cross-section and, like the hypocone, is' directed inward ; the post- 

 protoconid valley is greatly extended ; the lakes are long and narrow. 

 The tooth has some of the characters of the milk dentition ; in its 



