280 University of California Publications in Geology [Vol. 8 



The various specimens of Merychippus taken collectively evidently 

 represent a species of Middle or Upper Miocene age. The species is 

 less advanced than some of the forms of the Mohave Upper Miocene. 

 While small Merychippus forms have been reported from the Snake 

 Creek Pliocene, that fauna also contains many advanced horses which 

 are not represented here. It seems improbable that the Merychippus 

 species from the McKnight locality represents a faunal stage later 

 than Upper Miocene. 



2 



Figs. 1 to 3. From Miocene beds, North Fork of Humboldt Kiver, north- 

 eastern Nevada. 



Fig. 1. Merychippus, sp. M,?, natural size. 



Fig. 2. Merychippus, sp. Phalanges one and two, natural size. 



Fig. 3. Merycodus?, sp. P 4 ?, X 2. 



Merycodus?, sp. 



A single lower premolar (fig. 3) represents P 3 or P 4 of a form 

 which is either Merycodus or Blastomeryx. The tooth is nearly iden- 

 tical in dimensions with P 4 of a specimen (no. 19805) associated with 

 Merycodus antlers and molars from the Cedar Mountain region, south- 

 east of Walker Lake, Nevada. It has been noted that in the Cedar 

 Mountain specimen the characters of the inferior premolars are rather 

 more primitive in some respects than in the Merycodus form of the 

 Mohave fauna. The degree of hypsodonty of the Cedar Mountain 



