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University of California Publications in Geology [Vol. 9 



A calcaneum (no. 21481) from locality 2027 represents a Merv- 

 chippus-like species probably identical with that shown in the proximal 

 phalanges. 



The proximal end of a slender metatarsal (figs. 28a and 286 

 no. 21482) shows well-developed cuboid and mesocuneiform facets. 

 It differs from Merychippus, and from the larger forms of the Ricardo 

 referred to Hipparion and Pliohippus. The mesocuneiform facet is 

 large, but is somewhat smaller than the cuboid facet. Both cuboid 

 and mesocuneiform facets are nearly flat, or in the plane of the ecto- 

 cuneiform facet. This specimen may represent Hypohippus. It differs 

 from that genus in that the cuboid facet is nearly in the plane of the 

 ectocuneiform facet, while in Hypohippus, as known to the writer, the 

 cuboid facet slopes at an angle of near 45° from the plane of the 

 ectocuneiform facet. In Pliohippus there is a distinct mesocuneiform 

 facet, but the cuboid articulation is relatively larger. 



A lower molar (no. 19825, fig. 21) from locality 2029 represents 

 a protohippine horse of approximately the stage of evolution seen in 

 one form of Merychippus near calamarius of the Barstow fauna. The 

 crown is of moderate length and well cemented. The metaconid- 

 metastylid column is short anteroposteriorly. 



A fragment of an incisor (no. 22287, fig. 22) shows well-marked 

 cupping and abundant cement in the pit. The stage of evolution of 

 this tooth is approximately that of M. calamarius. 



PROTOHIPPUS?, sp. 



Several fragments of upper cheek-teeth from localities 1979, 1984, 

 2029, and 2025 represent protohippine forms (fig. 24) at least at 

 large as a very large Merychippus or Protohippus species of the 

 Barstow fauna. These specimens may represent an advanced Mery- 

 chippus, a Protohippus, or possibly a Hipparion. A rather narrow 

 fossette of an upper cheek-tooth shows considerable crinkling of the 

 enamel. It may represent a Merychippus or a Hipparion, 



A large incisor (fig. 25) with deep cement-filled pit is larger 

 than the incisors of any protohippine form known from the Barstow 

 fauna. It corresponds more nearly to the stage of advance of a large 

 Hipparion form of the Ricardo fauna. 



A fragment of a lower cheek-tooth (no. 21483, fig. 23) exceeds 

 the dimensions of the average of the largest protohippine form of 

 the Barstow fauna. The metaconid-metastylid column is short antero- 

 posteriorly. and of the Pliohippus rather than of the Hipparion type. 



