THE EOCENE OF EUROPE AND NORTH AMERICA 



105 



fessor Cope described as "Puerco marls" in 1875/ and from which he 

 listed the first mammalian fauna in 1881.' The formation overlies the 

 Upper Cretaceous (Laramie) and underlies the Wasatch (Sparnacian, 

 Ypresian). 



In 1895 Wortman observed a natural subdivision of the formation into 

 Lower or Puerco proper, and Upper or Torrejon, estimating the combined 

 thickness at 800 to 1,000 feet.-' In 1897 Matthew* separated the fauna of 



Fig. 27. — Badlands of northorn New Alcxii o, lnud of Toin'juii River. Jia.sal Eocene, 

 Torrejon-Pantolunilida Zone below. Lower Eocene, Wasatch-Coryphodon Zone above. From 

 photograph by American Museum of Natural History, 1896. 



the two levels, adopting Wortman's proposed designation Torrejon for 

 the upper beds, which are nearly of Upper Thanetian or Cernaysian age. 

 As distinguished by its mammalian life this division is as follows: 



Upper: Torrejon Formation (300 feet), zone of Pantolambda, the earliest 

 known member of the Ungulata-Amblypoda, with crescentic teeth, 

 ancestral to Coryphodon. 



Lower: Puerco Formation (500 feet), zone of Poly mastodon. 



In 1901 Douglass discovered in the Fort Union or great lignite forma- 

 tion of the upper Missouri River in northern Montana, a hcd of shale con- 



' Cope, E. D., Report on the Geology of Northwestern New Mexico, Examined During 

 1874, Append. LL, Ann. Rept. Chief Eng., Washington, 1875. 



^ Cope, E. D., On Some Mammalia of the Lowest Eocene Beds of New Mexico. Proc. 

 A?ner. Philos. Soc, Vol. XIX, 1881, pp. 484-4!)5. 



' Osborn, H. F., and Earle, Chas., Fo.ssil Mammals of the Puerco Beds. Collection of 

 1892. Bull. Amer. Mm. Nat. Hist., Vol. VII, Art. i, Feb., 1895. 



* Matthew, W. D., A Revision of the Puerco Fauna. Bull. Amer. Mus. Nat. Hist., Vol. IX, 

 1897, pp. 259-323. 



