GEOLOGIC HORIZONS AND LIFE ZONES. 



23 



Snake Creek, Sioux County, Western Nebraska (Lower Pockets). 



As described by Matthew, Cook (1909), and Sinclair (1915) these deposits contain a more ancient Parahippus, Mery- 

 chippus, Hypohippus horse fauna of Upper Miocene age, also a more modern Protohippus, Pliohippus, Hipparion fauna 

 of Lower Pliocene age, as well as Pliauchenia and Peraceras. See p. 28 below. 



Geologic Age of "Temblor" (Anderson, 1908), or Vaqueros. 

 North Coalinga, Kings County, So. Cal., Merriam, 1915. 

 Marine deposit, twelve miles north of Coalinga, California. 



The vertebrate collection representing the Merychippus fauna* was obtained in a zone at the upper limit of the 

 "Temblor," as explored by the University of California in 1913 (Moody and Douglass). The Merychippus zone yielded 

 here teeth of the Sirenian Desmostylus fhcsperus, and other marine forms, including Carcharodon. The fauna washed in 

 from the adjacent land included the type of Merychippus ccdifomicus Merriam, also mammalian teeth referred to Pros- 

 thennops, Procamelus, Tctrabelodon. It is probable that the Temblor containing the Turritclla ocoyana fauna is synchro- 

 nous with the marine Monterey, which by some invertebrate palaeontologists (James Perrin Smith) is regarded as Oligocene 

 or Lower Miocene. Merriam (Trans. Am. Philos. Soc, 1915) observes, however, that the Temblor cannot be earlier 

 than Middle Miocene because neither Merychippus nor Proboseidea are known earlier than the Middle Miocene. 



As described by Merriam this phase contains the type of Merychippus californicus, progressive species, indicating a 

 late phase of the Merychippus zone, all the genera occurring here. This is a marine littoral deposit, associated with an 

 invertebrate fauna referred to the marine Lower Miocene, and includes the Sirenian Desmostylus fhcsperus and the shark 

 Carcharodon, also the land mammals Tetrabelodon, Procamelus, Prosthenops. 



Type of Merychippus californicus Merriam. 1915.1. 



Bijou Hills, Brule County, South Dakota, Leidy, 1854. 



According to Matthew this is probably an outlyer of the beds north and east of Valentine, Niobrara River, Nebraska. 

 Beside the indecisive type of Mcrycodus nccatus Leidy the following types have been described from this locality. 



Type of Hippodon speciosus Leidy, 1S54. Type of Merychippus insignis Leidy, 1857. 



Procamelus-Hipparion Zone, Upper Miocene or Lower Pliocene. Pontian Stage of Europe. 



The type region of this very prolonged and important period of geologic deposition is along the Niobrara and Little 

 White Rivers of western Nebraska and South Dakota, as explored by Hayden in 1S57. 



1. Horizon F of Hayden and Leidy, 1S69, the "Loup Fork" of Hayden (lower portion only). 

 la. Niobrara River localities, Hayden, Leidy, Gidley. 

 16. Little White River localities, Hayden, Leidy, Gidley. 



2. " Loup Fork," Cope, Scott and Osborn in part, 1877-1894. 



3. Nebraska formation, Cosoryx (= Merycodus) beds, western Nebraska, Scott, 1894. 



4. Ogallala formation in part, western Nebraska, Darton,' 1899. 



5. Niobrara formation, King, 1878 (preoccupied, Cretaceous). 



7. Procamelus beds (= upper "Loup Fork"), Cope, 1883. 



8. Pliohippus beds, Marsh, 1896. 

 11. Protohippus zone, Osborn, 1907. 



15. Valentine beds, Barbour, Cook, 1917. Near Ft. Niobrara. 



18. Fort Niobrara formation, Osborn, 1918. Type locality on Niobrara River, near Fort Niobrara. 



16. Oak Creek formation, Troxell, 1916, near Mission, So, Dakota. 



