1919] Merriam: Tertiary Mammalian Faunas of Mohave Desert 475 



addition to difference in size the large form is distinguished by greater 

 width of the proximal face and by an anteroposteriorly longer unci- 

 form facet. One objection to referring it to Hypohippus is the fact 

 that it is associated with the distal end of a metapodial quite unlike 

 the better known forms of Hypohippus in possessing a complete distal 

 keel. 



Several relatively large proximal ends of meta- 

 tarsal IV differ from the common specimens evidently 

 representing Merychippus in the Barstow fauna, and 

 are presumably to be referred to Hypohippus. These 

 metapodials are distinguished from metatarsal IV 

 specimens referred to Merychippus in much larger 

 size ; relatively wider cuboid facet, position of the 

 median facet for contact with the metatarsal III more 

 nearly transverse to the plane of lateral compression 

 of the bone, and in apparent absence of a posterior 

 facet for articulation with metatarsal III. 



PABAHIPPUS? MOUBNINGI Merriam 



Parahippus mourningi Merriam, J. C, Univ. Calif. Publ. 

 Bull. Dept. Geol., vol. 7, p. 427, 1913. 



Pig. 32. Hypo- 

 hippus?. Prox- 

 imal end of 

 metacarpal 3, 

 no. 21406, X y 2 . 

 Barstow Mio- 

 cene, Mohave 

 Desert, Califor- 

 nia. 



A portion of a lower jaw with dentition (fig. 33) 

 obtained by Mr. Baker in 1911 has been described 

 by the writer as Parahippus mourningi, a horse with characters near 

 Parahippus and Hypohippus, but with size and stage of evolution 

 near Archaeohippus. The specimen differed, however, from the only 

 lower jaw material referred to Archaeohippus in several characters, 

 and especially in the absence of the strong internal cingulum shown 

 on teeth referred to Archaeohippus by Gidley. In January, 1913, a 

 second specimen, a maxillary (fig. 34) with Dm 3 , Dm 4 , and M 1 , rep- 

 resenting a very small brachyodont horse, was obtained in the Mohave 

 region by Buwalda and Mourning. An approximation of the dimen- 

 sions of the cheek-tooth series, as well as a comparison of individual 

 teeth, shows that the upper and lower jaw specimens represent animals 

 of very nearly the same size. The similarity of dimensions, considered 

 with similarity of relationship to other forms and similarity of occur- 

 rence, leaves lttle room for doubt that the two jaws represent the same 

 species. 



In the specimen representing the upper jaw, the well-preserved, 

 unworn, inner portion of M 1 shows the metaloph fully united with 



