8 



250 TEN years' progress IX VERTEBRATE PALEONTOLOGY 



the Eocene upward in the history of American formations they become 

 more and more scattered, with an ever increasing number of interval 

 and breaks, thus: 



K()(ENIC ColltillUOUH 



Oi-i(ii)CKNK Nearly continuous. ^ 



MiotKNK Breaks between Lower, Middle, and T'ppev. 



I'j>iocKNE Wide and unHUed intervals. 



That all these intervals will be filled in time there can be little ques- 

 tion. Eich faunistic additions during the past decade are those indicated 

 in the column below in large capital letters. 



li'tje Zoiies: Forinations <iii<l States. Dale of BUcorertf. 



Ekphdn, Equus Peace Creek of Florida . . . Dall, 1891. 



" " Loup River of Nebraska. . .Meek, Ilayden, 1861-2. 



Glyptotlieriuin Llanco of Texas. 



lUngoceras, Splienoph'dus. . .TJKHisand Cieek of Nevada. .Merriani, Iii{)9-1 1 . 



Neutntgocems Snak k Ckei:k (Ogallala) of Matthew, 1909. 



Nebraska. 



Piiohippas, AlUcainelus Rattlksxakk of Oregon . . .Merriani, Sinclair, 1907. 



Peraceras Alachua Clays of Florida. . . Leidy, 1896. 



Feraceras Republican River of Kan- Cope, Sternberg, 18s2. 



sas. 



The base as well as the summit of our Pliocene still lacks definition in 

 comparison with that of Europe. The Snake Creek (Matthew, Cook, 

 1909)^^ and Thousand Creek fauna? have been compared by Matthew and 

 Merriam with that of the Pikermi, or Upper Miocene, of Greece. The 

 occurrence of Neotragoceras, the earliest bovine recorded in America in 

 the Snake Creek, and of several antelopine forms in the Thousand Creek, 

 are facts of prime importance in paleogeographic science; they indicate 

 an outlying connection with the great bovine and antelopine fauna of 

 southern Asia. 



Pleistocene 



The first physiographic or forest and plains subdivision of the Lower 

 Pleistocene fauna is that of Matthew (1902).-*^ The first attempt to 

 subdivide the entire American Pleistocene faunisticallyp is that of Os- 

 born^^ (1910) and is essentially a forecast, because Pleistocene divisions 



1^ W. D. Matthew and Harold J. Cook : A Pliocene Fauna from Western Nebraska. 

 Bulletin of the American Museum of Natural History, vol. xxvi, art. xxvii, September 3, 

 1909, pp. 361-414. 



20 W. D. Matthew : List of the Pleistocene Fauna from Hay Springs, Nebraska. Bulle- 

 tin of the American Museum of Natural History, vol. xvi, art. xxiv. September 25, 1902, 

 pp. 317-422. 



-1 H. F. Osborn : The Age of Mammals in Europe, Asia, and North America. 8vo. 

 The Macmillan Company, New York, October 25, 1910, 635 pages. 



