10 INTllODUCTION. 



Mylopox Haiilani, Owen : Zool. Voy. Beagle, Tt. I., 1840, C8. 



Meyalonyx laqucatns, Harlan : Med. and Phys. Researches, 1835, 334. 



Ori/rtcrolhcrium Missouriois'; Ilarlan : Proc. Am. Phil. Soc., 1841, II. 119; Am. Journ. Sc, 1843, 

 XLIV. G9. 



Orj/cterotJiirium Orrgancnais, Perkins : Am. Journ. So., 1843, XLIV. 80. 

 Ereitodon priscus, Leidy : Proc. Ac. Nat. Sc, 1853, V. 241. 

 EuBRADYS ANTiQUUS, Lcidy : Ibid. 



Myahmt/x potens, Leidy: Proc. Ac. Nat. Sc, 1852, VI. 117. 

 Pelphinus vermontanus ? Thompson : Am. Journ. Sc, 1850, XI. 256. 

 TRicnECUS virginianus? Dekay : Nat. Ilist. New York, 1842, Pt. I., Zool. Mam., 56. 



Trichecus. Mitchell, Smith, and Cooper: An. Lye. Nat. Hist. N. York, 1828, II. 271. 



Tn'chrcus rosmarus (fossilis). Harlan : Med. and Phys. Researches, 1835, 277. 

 Manatus, Cuvier. Harlan : Journ. Ac. Nat. Sc, 1825, IV. 23G; Med. and Phys. Researches, 1835, 278. 

 RoRQUALis australis (fossilis). Dekay : Nat. Hist. New York, 1842, Pt. I., Zool. Mam. 99.' 



In addition to the species just enumerated, remains of numerous mammals and 

 other vertebrates have been discovered, by Prof. S. F. Baird, in various caves of 

 Pennsylvania and Virginia, and are now deposited in the Museum of the Smith- 

 sonian Institution." Tlie collection contains representatives of nearly all the 

 larger recent mammals and turtles of the United States, together with a few 

 extinct species. 



The particular object of the present memoir is the description of a large and 

 highly important collection of I'emains of mammalia and chelonia from an exten- 

 sive Eocene deposit, which immediately overlies the Green Sand of the Cretaceous 

 Period, in the Mauvaises Terres of Nebraska Tenitory. 



The Mauvaises Terres, or Bad Lands, as they are named, constitute a district of 

 country extending along the foot of the Black Hills, a spur of the Rocky Mountains, 

 situated between the Platte, or Nebraska, and the Missouri Rivers, at the head of 

 certain branches of the latter called the L'Eau-qui-court, White, Cheyenne, and 

 Moreau Rivers.^ 



Dr. Owen, in describing this region, from notes of a visit made to it by Dr. John 

 Evans, in his magnificent " Report of a Geological Survey of Wisconsin, Iowa, and 

 Minnesota, and incidentally of a portion of Nebraska," observes tliat it presents one 

 of the most extraordinary and picturesque sights that can be found in the whole 

 Missouri country.* 



* The following are erroneously reported as fossil remains : — 



Rhinoceroides Alleghaniensis, Featherstonhaugh : Journ. of Geol. 1831, I. 10. This is no animal 

 remain whatever, but is merely a fragment of stone. See Pe Blaiuville's Osteographie, article Rhino- 

 ceros, p. 172. Further confirmed by Dr. Isaac Hays and Mr. Isaac Lea, who have had an opportunity 

 of inspecting the specimen. 



OsTEOPERA PLATYCEPIIALA, Harlan : Fauna Amer., 12G. The cranium described under this name is 

 now preserved in the Cabinet of the Academy of Natural Sciences, and without the slightest doubt 

 belongs to the recent Cixhgenys paca, Rengger, of South America. 



Equus caballus ? 



Equus major, Dekay: Nat. Hist. New York, Pt. I., Zool. Mam., 108. 

 Eqaus curvidens, Owen. Leidy: Proc. Ac. Nat. So., 1847, III. 262. 

 " See Proceedings of the American Association, at Cambridge, 1849, II. 352. 

 ' Sec the map accompanying this memoir, for the use of which I am indebted to Dr. D. D. Owen. 



* P. 19G. 



