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University of California Publications in Geology L VoL - 13 



No. 24241 is moderately worn but is slightly smaller than premolar 

 teeth of Hipparion mohavense from the Ricardo. The enamel pattern 

 in the specimen from the Siestan resembles somewhat that in teeth of 

 H. mohavense. The protocone approaches perhaps most nearly that 

 in teeth of H. mohavense callodonte from the Ricardo Pliocene. 



The single tooth from Orindan deposits southwest of Mount Diablo, 

 regarded by J. C. Merriam 3 as the type of the species Hipparion platys- 

 tyle, differs as much from the Siestan specimen as it does from teeth 



Fig. 1. Hipparion, near mohavense Merriam. P 1 ?, no. 24241, inner and oc- 

 clusal views, X 1. Siestan Pliocene, Berkeley Hills, California. 



of Hipparion mohavense. According to Dr. Merriam, H. platystyle 

 approaches closely the Hipparion forms from the Mohave Desert. A 

 second fragmentary specimen, no. 1324, apparently from Orindan beds 

 near Bolinger Canon, is regarded by Dr. Merriam 4 as representing a 

 form near Hipparion mohavense. The prefossette in this specimen is 

 narrow transversely, and the enamel border exhibits a number of pli- 

 cations. No. 1324 is a larger specimen than no. 24241. The protocone 



3 Merriam, J. C, New species of the Hipparion group from the Pacific Coast 

 and Great Basin Provinces of North America. Univ. Calif. Publ. Bull. Dept. 

 Geol., vol. 9, p. 5, 1915. 



* Merriam, J. G, op. cit., vol. 7, p. 375, figs. 3a, 3b, 1913. 



Merriam, J. C, Relationships of Pliocene mammalian faunas from the Pacific 

 Coast and Great Basin provinces of North America. Univ. Calif. Publ. Bull. 

 Dept. Geol., vol. 10, p. 426, 1917. 



