GEOLOGIC HORIZONS AND LIFE ZONES. 



29 



Bone Valley Formation, Florida, Sellards. 



The type locality of this formation is Brewster, Polk County, Florida, which yields the type of Hipparion minor 

 Sellards. It is probable that the Bone Valley formation is contemporaneous with the Alachua Clays, Florida. 



Type of Hipparion minor Sellards, 1916.1. 



Petaluma, California, Merriam. 

 Type of Hipparion gidleyi Merriam, 1915.1. 



Age of Devil's Gulch, Niobrara River, Nebraska. 

 Including lower and upper beds. 



Lower levels. These exposures on the south side of the Niobrara River, twenty miles east of Fort Niobrara, as 

 reported by Barbour, Whitford, and Matthew, compare on the lower levels with the fauna of the Procamelus zone. 

 The types of Proboscidea discovered here by Barbour, namely, Tetrabehdon willistoni and Eubelodon, morrilli are much 

 more primitive than the T. campester of the Republican River. The lower levels contain also specimens referred to 

 Merychippus. 



Upper Levels. As described by Barbour (June 10, 1914) the [upper] fauna is regarded (Matthew) as of the age of the 

 Snake Creek or slightly more recent, and the upper levels contain a somewhat more recent fauna than the lower. The 

 upper fauna is reported to include a variety of camels, Alticamelus, Procamelus, Pliauchcnia, also Eubelodon morrilli, among 

 oreodonts Metoreodon, among horses Protokippus, Pliohippus, Hipparion. The new horse recorded here, Hypohippus 

 matthewi Barbour is somewhat near H. affinis Leidy. 



Type of Hypohippus matthewi Barbour, 1914. 



Pliohippus-Pliauchenia Zone, Second Phase of Lower Pliocene. 



This phase is distinguished by the absence of Hypohippus, Merychippus, Protokippus, by the disappearance of the 

 rhinoceroses, and by the abundance of Pliohippus of advanced type and of Hipparion. 



1. Ricardo, Southern California, bordering the Mohave Desert, Merriam, Buwalda, 1912, 1914. 



2. Rattlesnake, Ore., Merriam, Sinclair, 1901, 1907. 



3. Jacalitos, California, Merriam, 1915. 



4. Pinole Tuff, San Pablo Bay, Cal., Merriam, 1913. 



5. Orinda, resting upon Pinole Tuff, San Pablo Bay, Cal. (Merriam, letter Sept. 15, 1917). 



Ricardo, Fl Paso Range, Southern California. 

 Lower and Upper Levels, Merriam, 1912, 1914. 



The lower Ricardo fauna is still incompletely known. The upper Ricardo, 3,000 and 3,500 feet, is regarded by 

 Merriam as slightly more recent than Snake Creek. It contains no Merychippus. The other equines are regarded by 

 Matthew as less progressive than certain Snake Creek forms. Hipparion is abundant, also Pliohippus. 



Type of Pliohippus tantalus Merriam, 1913. Type of Hipparion mohavensc Merriam, 1913. 



" " " fairbanksi Merriam, 1915. " " " " callodonle Merriam, 1915.6. 



Pinole Tuff Formation, San Pablo Bay, California, Merriam 1913. 



This formation contains a great number of vertebrate remains, including horses of the Pliohippus type near Pliohippus 

 fairbanksi of the Ricardo Pliocene. This Pinole species is also very close to the Pliohippus species of the Rattlesnake 

 Pliocene. The Pinole Tuff belongs in the lower portion of the Pliocene. 



