118 University of California Publications in Geology [Vol. 10 



able interest, as no remains representing the Rhinocerotidae have been 

 recognized in either the Barstow or the Ricardo fauna. A calcaneum 

 representing a member of this group is known in the fauna of the 

 Pinole Tuff Pliocene of middle California, and the group has been 

 reported from the Thousand Creek and Rattlesnake Pliocene of north- 

 ern Nevada and Oregon. It is possible that in late Tertiary time this 

 group did not range into the Mohave Desert area. 



NEOHIPPARION GRATUM TEHONENSE, n. subsp. 



Type specimen, no. 21780, from the Chanac formation of the Tejon Hills at 

 the southern end of the San Joaquin Valley, California. 



This species corresponds approximately in size and form to Neo- 

 hipparion gratum of the Great Plains region. It is doubtfully dis- 

 tinguished from the typical form of that species by the tendency to 

 show a more nearly circular cross-section of the protocone and by 

 somewhat dubious characters in width of crown and nature of the 

 enamel folds bordering the fossettes. 



The character of the protocone of the Chanac form (figs, la to lc) 

 suggests Hipparion plicatile of the Alachua clays of Florida, but the 

 crowns in that species seem larger and relatively wider than in the 

 Chanac species. H. ingenuum also of the Alachua clays is not widely 

 removed from the Chanac species, but the protocone is smaller. The 

 Chanac species differs from Neohipparion montezumae in its more 

 nearly circular section of protocone and possibly in a tendency to rela- 

 tively greater transverse diameter of the fossettes. 



The characters of the Chanac species represented by specimen 

 21780 are in general like those of Hipparion, mohavense of the Ricardo 

 Pliocene, but they are shown in a form with smaller dimensions, and 

 approaching the combination of characters of N. gratum. The species 

 is evidently very near the Great Plains form of N. gratum, and it is 

 not impossible that larger collections will exhibit a range of characters 

 making even subspecific separation inadvisable. 



An upper molar (figs. 8a to 8c) obtained by R. W. Pack of the 

 United States Geological Survey on the north side of Hospital Creek 

 (SE corner sec. 11, T 4 S, R 5 E) is similar to N. g. tehonense in 

 dimensions. In this specimen the protocone is very small and approx- 

 imately circular in cross-section. 



An upper cheek-tooth figured in the earlier paper on the Tejon 

 Hills fauna 5 may represent N. g. tehonense, or is possibly a more 

 primitive form. 



3 Merriam, J. C, op. cit., p. 286, fig. 1, 1915. 



