GEOLOGIC HORIZONS AND LIFE ZONES. 



25 



6. Santa Fe Marls, New Mexico, Cope, 1877. 



9. Clarendon beds, Llano Estacado, northwestern Texas, Gidley, 1903. 



10. Madison Valley beds, western Montana, Douglass, 1S99. 



12. Upper Pawnee Creek, northwestern Colorado, Matthew, 1913. 



13. Ellensburg, Washington, Merriam, 1915. 



14. Devil's Gulch (lower beds), Niobrara River, about forty miles east of Fort Niobrara, Barbour, 1914. 

 17. Esmeralda, Nevada, Merriam. 



Fort Niobrara, Niobrara River, Nebraska. 



This is the "Horizon F" of Hayden and Leidy (1869); it is the lower portion of the "Loup Fork" of Hayden. The 

 type of Hypohippits (Anchithcrium) affinis was collected here during the exploration of 1857. During the same year the 

 type of Parahippus {Anchithcrium) cognatus was recorded, namely, "Upper Niobrara River near Fort Niobrara;" also 

 the type of Protohippus (Equus) perditus and the type of Protohippus pladdus. In 1857 Hayden collected here also the 

 type of Merychippus mirabilis Leidy, since referred to Pliohippus mirabilis. To the Niobrara River Leidy (18G9) 

 attributed his type of Hipparion affine. In 1873 Clifford and Marsh collected from a locality further west or up the 

 river, probably above the mouth of Snake River, the type of Pliohippus pernix Marsh, also in the same year the type 

 of Pliohippus robustus Marsh. In 1906 Gidley collected the type of Protohippus niobrarcnsis from near Fort Niobrara. 



Type of Hypohippus affinis Leidy, 1858. 

 " " Parahippus cognatus Leidy, 1858. 

 " " Protohippus perditus Leidy, 1858. 

 " " " pladdus Leidy, 1869. 

 " " " niobrarensis Gidley, 1906.2. 



Type of Pliohippus mirabilis Leidy, 1858. 

 " " " pernix Marsh, 1874.1. 

 " " " robustus Marsh, 1S74.2. 

 " " lEipparion affine 1 Leidy, 1869.1. 



Little White River, South Dakota. 



In 1866 Hayden discovered on the Little White River of South Dakota the type of Pliohippus supremus Leidy. In 

 1905 Gidley collected here his type of Protohippus simus. In 1856 Hayden collected here the type of Hipparion. occidentale 

 Leidy. To the Little White River Leidy (1869) attributed the type of Hipparion gratum. On the Little White River 

 Gidley (1905) secured his neotype of Hipparion gratum. In 1902 Wells and Gidley collected the type of Hipparion whitneyi. 

 In 1903 Gidley collected at Big Spring Canon, Little White River, the type of Hipparion dolichops. 



Thus from the Little White River neither Merychippus nor Parahippus has been recorded. Hypohippus is repre- 

 sented only by some teeth found by Matthew at Big Spring Canon, a locality where admixture is not wholly excluded. 



Type of Protohippus simus Gidley, 1906.1. 

 " " Pliohippus supremus Leidy, 1869. 

 " " Hipparion occidentale Leidy, 1856. 

 " " Pliohippus lullianus Troxell, 1916.2. 



Type of Hipparion gratum Leidy, 1869.2. 

 « " " whitneyi Gidley, 1903. 

 " " « dolichops Gidley, 1906. 



Chanac Formation, Buwalda, 1915. 



Tejon Hills, San Joaquin Valley, Southern California. 



Of nearly the same Lower Pliocene or latest Miocene age as the lower portion of the Jacalitos Etchegoin of the North 

 Coalinga region and the Ricardo stage of the Mohave area (Merriam, 1916, op. cit., pp. 116, 117). It includes: 



Type of Protohippus tehonensis Merriam, 1915. 



Type of Hipparion (Neohipparion) gratum tehonense 

 Merriam, 1916.3. 



1 It is possible that Hipparion affine was derived from a younger zone (J. C. M. 1917). 



