56 



University of California Publications in Geology [Vol. 9 



rower and have a distinctly different form. The protocone is small and round. 

 In this particular specimen the protoloph and metaloph remain separate almost 

 to the base of the tooth. 



The nearest approach to the form seen in specimen no. 19789 is 

 that in a tooth type (no. 21341) from the Etchegoin Pliocene of the 

 North Coalinga region of California, on the western border of the 

 San Joaquin Valley. The Etchegoin form shows rather narrow fos- 

 settes, a very small, round protocone, and a weak connection of 

 protoloph and metaloph. The cheek-teeth of the Etchegoin species are 

 considerably narrower and less curved than the Ricardo form, and 

 appear to be specifically different. 



This species is named in honor of Dr. H. W. Fairbanks, who was 

 one of the earliest investigators to study the Ricardo Pliocene beds. 



EQUUS or PLIOHIPPUS, probably new 

 Equus or Pliohippus, sp. Merriam. Amer. Phil. Soc. Trans., n.s., vol.. 22, 

 pt. 3, p. 223, 1915. 



Upper and lower cheek-teeth, from beds in the upper portion of the Etche- 

 goin formation north of Coalinga. 



Cheek-teeth large, long-crowned, heavily cemented. Upper cheek-teeth with 

 heavy mesostyle, fossettes wide with moderately crinkled enamel borders. Pro- 

 tocone large, strongly compressed laterally, inner border convex. Metaeonid- 

 metastylid column of lower cheek-teeth often with wide inner groove. 



Of the described species this form most closely approaches Equus 

 or Pliohippus simplicidens of the Blanco Pliocene. It possibly differs 

 from Equus simplicidens in somewhat greater width of the fos- 

 settes of the upper cheek-teeth and in the greater anteroposterior 

 diameter of the protocone. The form of the protocone is not fully 

 shown on Cope's figure of the type specimen of E. simplicidens, but 

 this pillar is restored by Cope and Gidley as relatively shorter 

 than in the Coalinga species. According to Gidley the teeth of E. 

 simplicidens have the appearance of being comparatively short- 

 crowned. The lower teeth referred to E. simplicidens are char- 

 acterized by the angular nature of the groove on the inner side of the 

 metaconid-metastylid column. In a specimen, no. 21333, from North 

 Coalinga this groove is rather sharply angular. In specimen no. 21332 

 the groove is wider and approaches the form seen in Equus. 



Measurements of Type Specimen, No. 19789 



P 4 , height of crown on outer side '■ 



P 4 , anteroposterior diameter 



P\ transverse diameter ! 



oo 



25 

 26.4 



mm. 



