GEOLOGIC HORIZONS AND LIFE ZONES 



31 



Pliohippus proversus Zone. 



Upper Etchegoin, North Coalinga Region, Merriam, 1915. 



The Upper Etchegoin, which was fully described by Merriam in 1915 {Trans. Amer. Philos. Soc, 1915, p. 222), is a 

 formation of considerable thjckness, containing an advanced vertebrate mammalian fauna, the species of which are 

 relatively close to those of the Pleistocene of Rancho La Brea; yet this Upper Etchegoin formation lies below the Tulare 

 formation, 3,000 feet in thickness, which is regarded as of Upper Pliocene age. The Tulare is almost exclusively fresh- 

 water; it includes a thin marine phase near the upper limit (Merriam, 1917). 



The feature of this horizon is the presence of camels near Carnelops or Pliquchenia, also of cervids resembling Odo- 

 coileus. Most distinctive also is the Pliohippus proversus Merriam, a horse almost as advanced as the Equus excelsus of 

 Leidy. Hywnognatkus is evidently from this Tulare formation above the Upper Etchegoin (Merriam, 1917). 



Type of Pliohippus proversus Merriam, 1916.1. 



Tulare Formation, North Coalinga Region, California. 



The Tulare rests above the Upper Etchegoin Pliohippus proversus beds of the North Coalinga Region in California. 

 It contains a large feline described as Machcerodus ischyrus (Merriam, 1917). 



Idaho Formation, southwest Idaho, Cope, 1883. 



Described by Cope in 1883, without giving type locality or type section. From these beds Cope described twenty- 

 three species of fishes, representing eight genera. Mammalian remains from beds presumed to represent Idaho include a 

 referred (Leidy) Mastodon mirificus and a referred Equus excelsus. In 1916 Merriam and Buwalda obtained from beds 

 representing the Idaho formation the type of Equus idahocnsis and a sabre-tooth resembling fMachwrodus ischyrus. The 

 Idaho is at present referred to a stage near that of the Tulare formation, which rests upon the Pliohippus proversus phase 

 of the Upper Etchegoin of the North Coalinga region in California (Merriam, letter Sept. 15, 1917). 



Type of Equus idahoensis, Merriam. 



Tehuichila, Vera Cruz, Hidalgo, Mexico, Cope, 1885. 



See also Tehuichila and Lacualtipan, Mexico. Later than Barstow and Santa Fe (Merriam, 1917). 



Type of Hipparion montczuma Leidy, 1883. Type of Hipparion rectidens Cope, 1886. 



" " " pcninsulatum Cope, 1885.2. " " tProtohippus castilli Cope, 1885. 



Ashley River, South Carolina. 

 A Lower Pleistocene composite fauna. Here occurs also, probably through redeposition, a Pliocene species, the 



Type of Hipparion venustum Leidy, 1859. 



Peace Creek, Florida. 

 Here occurs, also probably through redeposition, the Pliocene equine 



Type of Hipparion princcps Leidy, 1890, = Equus ffraternus Leidy, 1860, atict Gidley. 



