528 University of California Publications in Geology [Vol. 10 



short anteroposteriorly, the stage of anteroposterior abbreviation sug- 

 gesting that in PUohippus. As in Equus, the anterior border of the 

 protocone is prolonged anteriorly much beyond the isthmus, connecting 

 the protocone with the protoconule. The inner border of the proto- 

 cone is distinctly concave, as in Equus. The characters of this tooth 

 are those of Equus, with the exception of shortness of the protocone, 

 which suggests PUohippus. The characters of the anterior and inner 

 borders of this pillar are clearly those of Equus. Anteroposterior 

 shortness of the protocone occurs in a few species of Equus, especially 

 the earlier members of the group . 



An upper cheek-tooth, no. 22346 (fig. 4), was obtained at locality 

 3039, in bluffs assumed to be Idaho exposed along the north bank 

 of the Payette River, about four and one-half miles southeast of the 

 town of Payette. The anterior portion of the protocone of this speci- 

 men is broken away. The characters of this tooth do not seem in 

 any particular to differ from those of the Equus. The posterior 

 portion of the protocone column is shorter than this region often 

 appears in Equus, but matches the proportions commonly seen in 

 Equus occidcntalis. There is good reason for considering that this 

 tooth represents a typical Equus species not far removed from E. 

 occidcntalis. It differs from average specimens of E. occidcntalis in 

 greater lateral compression of the fossettes, and in the more pro- 

 nounced complication of the enamel borders of the fossettes. 



A lower premolar, no. 22347 (fig. 5), from locality 3036C in pre- 

 sumed Idaho beds at Froman Ferry represents a large and very ad- 

 vanced horse. The crown is long and heavily cemented ; the outer faces 

 of the protoconid and the hypoconid are flat. The metaconid-meta- 

 stylid column is long anteroposteriorly and the valleys anterior and 

 posterior to this column are narrow transversely. In all these char- 

 acters this tooth distinctly resembles Equus. In a single feature, 

 namely, in the acuteness of the inner fold of the metaconid-metastylid 

 column, this tooth shows resemblance to advanced forms of PUohippus. 

 In Equus the gutter is commonly broad and flat. Occasionally, how- 

 ever, it may be narrow and the inner end of the fold acute. On the 

 whole this tooth is of the Equus type with only a single suggestion of 

 PUohippus in its structure. 



Compared with the teeth of Equus from the Columbia River bluffs 

 near Ringold, 4 Washington, upper tooth 22348 is somewhat larger and 

 the protocone is much shorter anteroposteriorly. The upper tooth 



♦ Merriam, J. C, and Buwalda, J. P., Univ. Calif. Publ. Bull. Dept. Geo]., 

 vol. 10, p. 256. 1917. 



