1916] Buwalda: Miocene Mammalian Faunas from Tehachapi Pass 83 



The horses of the Phillips Ranch fauna appear more primitive 

 than those of either the Mascall or the Virgin Valley. They may be 

 of a middle Miocene stage, but older than the stage of either the 

 Mascall or the Virgin Valley. The lower, or Phillips Ranch horizon, 

 appears to represent the oldest stage in the development of mammalian 

 life above the Oligocene known thus far in the region west of the 

 Wasatch. 



The Cache Peak fauna has been stated to be more advanced than 

 that from near Phillips Ranch. The Hypokippus of the Cache Peak 

 assemblage is probably specifically distinct from that found at Bar- 

 stow. The complete skull with dentition representing Merychippus 

 differs somewhat in the details of the facial region and in its dentition 

 from Merychippus calamarius, a common form at Barstow, but ap- 

 pears to be quite near that species. The Hipparion-like horse teeth 

 of the Cache Peak fauna have the protocone more distinctly separated 

 than it is in the nearest allied type in the Barstow fauna; this wide 

 separation is probably an advanced character. On the other hand, 

 the Barstow fauna contains horses which have longer and heavier lower 

 molars than any found in the Cache Peak assemblage. 



The Dromomeryx teeth from the Cache Peak horizon seem consid- 

 erably shorter and less advanced than the form found at Barstow. 

 The Merycodus cannot be compared satisfactorily. The Merycochoerus 

 form may be different, but the material is too fragmentary to permit 

 a certain comparison. 



Comparing the Cache Peak with the Ricardo, no form is known to 

 be common to the two faunas, although the Merycodus may be the 

 same. The horses in the lower part of the Ricardo section are mainly 

 very advanced types of Pliokippus and Hipparion. 



The horses obtained in the Cache Peak horizon are all different 

 from those so far known from the Tejon Hills, and probably represent 

 a stage somewhat older. 



The Cache Peak fauna is probably considerably older than the 

 Ricardo, probably somewhat older than the Tejon Hills, but probably 

 does not differ greatly in age from the Barstow. 



The Cache Peak fauna represents a stage in advance of that found 

 at Phillips Ranch. The Cache Peak fauna may be late middle Miocene 

 or upper Miocene; it may furnish a transition stage between the 

 Phillips Ranch and the Barstow faunas, but it is much nearer to the 

 Barstow than to the Phillips Ranch. 



