OF WESTERN NORTH AMERICA. 



83 



The fossiliferous horizon on Loup River in Nebraska whicli 

 yielded Dihelodon mirificus has not been recently explored. The 

 fauna is sparsely known from the Blanco formation of Texas. It 

 includes among Carnivora-Canidae, Borophagus, Amphicyon being 

 doubtfully present; among Mustelidge, Canimartes; among Felidse, 

 Felis hillianus, the earliest positively known appearance of Felis. 

 Among Proboscidea from this level is Dihelodon mirificus (Nebraska, 

 Texas); among Artiod^ctyla-Dicotylidse, the large cursorial peccary 

 Platyqonus first appears ; among Camelidae, Pliauchenia of very large 

 size; a^mongKqmddd, NeoMppaHon and ProtoMppus contimie; among 

 Edentata-Glyptodontia, Glyptotherium resembles PanocJithus of the 

 Pampean in type, but is less specialized; Megalonyx and Mylodon 

 occur. 



UPPER PLIOCENE OR LOWER PLEISTOCENE. 

 18. ELEPHAS IMPERATOR ZONE. 

 HOMOTAXIS. 



North America. — 1, Horizon F of Hayden and Leidy, upper part 

 only. 2, ''Loup River" of Meek and Hayden, 1861-62, Nebraska. 

 3, Certain formations (unnamed) in Texas and Mexico, containing 

 Elephas imperator. 



Europe. — In Europe the uppermost Pliocene is distinguished by 

 the disappearance of Hipparion and the advent of Elephas {E. meri- 

 dionalis) and Equus (E. stenonis). 



HISTORY AND SYNONYMY. 



According to the decision of the committee on geologic names of 

 the Geological Survey, the typical beds of this stage may for the pres- 

 ent be kno\^Ti as upper Pliocene or Elephas imperator zone. The 

 ground for this decision is the confusion in the application of the terms 

 ^'Loup River" and ''Loup Fork," which apply to the same stream; 

 also the confusion in the usage of the term ''Loup Fork." 



Horizon F, or the typical "Loup River beds," on "Loup Fork 

 of Platte River, extending north to Niobrara River and south to 

 an unknown distance beyond the Platte," were first characterized 

 by Meek and Hayden^ (1861-62) as follows: "Fine loose sand, with 

 some layers of limestone — contains bones of Canis, Felis, Castor, 

 Equus, Mastodon, Testudo, etc., some of which are scarcely distin- 

 guishable from living species." Of the bones collected in this locality 

 Leidy ^ observed in 1869 : ' ' Other remains of elephants, as Doctor Hay- 

 den supposes them to be, he observed in association with those of 

 Mastodon mirificus, Equus excelsus, and Hipparion at the head of the 

 Loup Fork branch of the Platte River; also between this point and 



oProc. Acad. Nat. Sci. Philadelphia, vol. 13, 1861 (1862), p. 433. 

 ^> Extinct mammalian fauna of Dakota and Nebraska, 1869, p. 255. 



