19] 5] 



Merriam: New Species of the Hipparion Group 



5 



An upper molar 4 (no. 12581) from the same locality as the lower 

 molar no. 19414 presumably belongs also in or near the Hipparion 

 group. This tooth is long and nearly straight. The outer styles are 

 well developed. The mesostyle is of almost even width throughout its 

 whole length. The fossettes are unusually narrow transversely and 

 show a few strong plications. The inner side of the tooth is broken 

 away and it is not possible to determine the characters of the protocone. 



Measurements op No. 12581 



M 1 , anteroposterior diameter near base 21.7 mm. 



M l , length of slightly worn crown 65.8 



HIPPARION PLATYSTYLE, n. sp. 



Neohipparion, sp. Merriam, J. C, Univ. Calif. Publ., Bull. Dept. Geol., vol. 7, 

 p. 375, figs, la to lc, 1913. 



Type specimen no. 19830, a second upper premolar from the Orinda Pliocene 

 southwest of Mount Diablo, California. 



A single tooth obtained from the Orinda beds represents a member 

 of the Hipparion group not clearly identical with any known form. 

 The crown is large and well cemented. Though somewhat worn, the 

 form of the fossettes suggests that the crown was never greatly elon- 

 gated. The small protocone pillar is distinct and is flattened laterally. 

 The fossettes are slightly narrower than in Hipparion moliavense. 

 Their enamel walls are moderately crinkled. The outer styles are 

 heavy. 



This species most nearly approaches the Hipparion forms of the 

 Ricardo fauna. It differs from H. moliavense in its more strongly 

 flattened protocone and transversely narrower fossettes. The char- 

 acters of a single specimen (no. 19478) from the Ricardo fauna ap- 

 proach those of the Orinda specimen, but are not sufficiently near to 

 warrant the conclusion that the two are specifically identical. 



Measurements of Type Specimen 



P 2 , greatest anteroposterior diameter 25.8 mm. 



P-, greatest transverse diameter 21,6 



P 2 , anteroposterior diameter of protocone 8.2 



4 See Merriam, J. C, Fauna of Virgin Valley and Thousand Creek, Univ. Calif. 

 Publ. Bull. Dept. Geol., vol. 6, p. 263, figs. 32a and 32b, 1911. 



