I) 11. LEIDY'S 



M E M 0 I R. 



The region of Nebraska Territory of the United States appears to be as rich in 

 the remains of Mammalia and Chelonia of the Eocene period as the deposits of the 

 same age of the Paris basin. Dr. Hiram A. Pront of St. Louis, described the first 

 mammalian fossil from Nebraska, in the American Journal of Science for 1847. 

 The specimen indicates a species of Palseotherium, or of a closely allied genus of 

 gigantic size, and has been named after its discoverer, Palseotherium Proutii, Owen, 

 Norwood, and Evans. Since the account of this fossil was published, an extraordi- 

 nary number of beautiful and highly important specimens, of new species and genera 

 of extinct Mammalia and Chelonia have been derived from the same locality, through 

 the combined influence and labours of Messrs. Joseph and Thaddeus Culbertson, 

 Professor Baird, Drs. D. D. Owen, Norwood, and Evans, and Dr. H. A. Prout and 

 Professor 0. Loghland. The most valuable collection, obtained by Dr. Owen's 

 survey, forms the basis of the following descriptions, and comprises numerous speci- 

 mens of eight species of six genera of Mammalia, and four species of the chelonian 

 genus Testudo. 



All the genera of Mammalia are distinct from those now in existence, and half of 

 the number are new to Pala3ontology. 



Among all the specimens which .have come under my observation from Nebraska, 

 one only belongs to a true carnivorous animal, and this is the Machairodus primae- 

 vus, Leidy and Owen. 



All the other mammalian fossils belong to the order Pachydermata, as Pala?othe- 

 rium and Rhinoceros, or to this order combined with ruminating characters, as 

 in the case of Oreodon and Eucrotaphus ; or to the same order in combination with 

 decided carnivorous characteristics, as in the Archasotherium. 



Most of the bones and their fragments are in a relatively good state of preserva- 

 tion, and are highly mineralized. Those of smaller animals are less fractured and 

 mutilated than those of larger animals. The latter in many cases are crushed, 

 while the fragments still retain their relative position, and the interstices filled 



