1921] Prick: Faunas of Bautista Creek and San Timoteo Canon 309 



are slightly lighter; (2) the protocones are shorter anteroposteriorly, 

 and considerably less extended both fore and aft; (3) the borders of 

 the cement lakes are less plicated ; (4) in the lower teeth the metaconid- 

 metastylid column has less anteroposterior extension, and its inner 

 groove is deep angular instead of shallow and flattened; and (5) the 

 outer faces of the protoconid are perhaps less flattened. 



Compared with Equus occidentalis Leidy, as seen in the Raneho 

 La Brea type, the premolars may be slightly heavier, though the cheek 

 teeth in general are of similar size. The new form generally differs as 

 follows: (1) the protocones average longer in fore-and-after diameter, 

 especially in the premolars, where their anterior production is most 

 marked; in the molar portion of the series the anterior corner of the 

 protocone is narrowed to pointed, instead of more oval in shape as 

 in E. occidentalis; the inferior border of the protocone tends to 

 be more deeply indented in the premolars, the postprotoconal valley 

 is broader, and the accessory fold more marked than in the Rancho 

 La Brea specimen; (2) the fossettes are broader and longer, and their 

 borders are plicated, in contrast to the simple margins of E. occi- 

 dentalis; (3) the lower cheek teeth average slightly narrower, and the 

 fold of the metaconid-metastylid column averages somewhat deeper; 

 (4) the outer faces of the protoconid and hypoconid are flatter than 

 the more rounded faces of E. occidentalis. 



Compared with Pliohippus proversus Merriam^^ the weight of 

 evidence indicates the more advanced stage represented by Equus 

 hautistensis : (1) of the type specimen is but slightly larger than 

 that of the P. proversus type specimen, its parastyle and mesostyle 

 are but slightly lighter, and the styles of the teeth of both forms 

 referred to the first molars are equal; (2) the protocone of the P- 

 has the greater anterior projection in the Bautista tooth, but the 

 protocone of the M- is as long anteroposteriorly in the Pliohippus 

 proversus type; (3) the borders of the cement lakes are more complex 

 and somewhat narrower in the Bautista form, though one specimen 

 of P. proversus (no. 22328) shows a very considerable incision of the 

 anterior lake margin; (4) in the lower teeth P3 of the E. hautistensis 

 appears of about equal size with that of the portion of the single large 

 tooth (no. 21332) referred to P. proversus; the groove of the meta- 

 conid-metastylid column of the Bautista form is markedly deeper and 



13 Merriam, John C. Eelationship of Equus to Pliohippus suggested by Char- 

 acters of a New Species from the Pliocene of California. Univ. Calif. Publ., 

 Bull. Dept. Geol., vol. 9, pp. 525-534, 1916. 



