CENOZOIC MAMMALS OF WESTERN AMERICA 409 



of phyla. A great advance has been made in the Lower Eocene and 

 Paleocene faunas, the former representing, as I see it, the true beginnings 

 of the Tertiary mammalian succession in this country, while the latter, 

 whatever its precise geologic position may prove to be, is essentially the 

 culmination and close of a Cretaceous mammal fauna whose earlier evo- 

 lutionary stages are wholly unknown to us, either because they inhabited 

 upland areas, where their remains were not preserved, or because they 

 lived in some other region whose Cretaceous land faunas have not yet 

 been discovered.-^ 



In the Lower Eocene the most remarkable discovery is the Diatriima, 

 a gigantic ground bird resembling the Phororhachos of the South Amer- 

 ican Miocene, but not related to it and standing apart in a group by 

 itself.^2 



In the Oligocene Sinclair--^ has inaugurated an intensive stratigraphic- 

 faunal study of the typical White River badlands that will serve as a 

 foundation for comparison and correlation much more exact and accurate 

 than has been possible hitherto. A remarkable fossil quarry opened by 

 the Denver Museum-"^ in the Chadron formation of Colorado has yielded 

 already a large series of well preserved skeletons and appears to contain 

 still vast numbers. 



In the Lower Miocene the great collections of the Carnegie Museum 

 from the Agate fossil quarry have been described by Holland and Peter- 

 son in three fine memoirs,-^ and the excellent series of Moropus skeletons 

 obtained by the American Museum from the same quarry provide a com- 

 plete knowledge of this extraordinary animal. Large collections have 

 also been obtained from the Lower Miocene for the Yale, Amherst, and 

 Field museums. 



The later Miocene and Pliocene faunas are represented in the Snake 

 Creek quarries in Sioux County, Nebraska, which have been worked 



2MV. D. Matthew: (1913, 1917.) Bull. Amer. Mus. Nat. Hist., vol. xxxii, p. 307: vol. 

 xxxvil, pp. 569, 831 ; 1914, Bull, Geol. Soc. Amer., vol. 25, p. 381 ; 1921, Am. Jour. Sci.. 

 vol. ii, p. 209. 



22 W. D. Matthew and W. Granger: (1917.) The skeleton of Diatri/ma. Bull. Amer. 

 Mus. Nat. Hist., vol. xxxvii, pp. 307-326. 



23 W. .T. Sinclair: (1921-1922.) Four articles in Proc. Am. Phil. Soc. vols. Ix and Ixi. 

 2*. J. D. Figgins : (1921.) Ann. Rep. Colorado Mus. Nat. Hist., p. 16. 



2^0. A. Peterson: (1909.) Revision of the Entelodontidse. Mem. Carnegie Mus., vol. 

 iv., pp. 41-158, pis. liv-lxii ; 1910, Description of new carnivores from the Miocene of 

 western Nebraska, ibid., pp. 205-278, pis. Ixxiv-lxxxv ; 1920, The American Diceratheres. 

 ibid., vol. vii, pp. 399-476, pis. Ivii-lxvi. 



W. .J. Holland and O. A. Peterson: (1914.) Osteology of the Chalicotheroidea. 

 Mem. Carnegie Mus., vol. iii, pp. 189-406, pis. xlviii-lxxvii. 



