232 EIGHTH ANNUAL REPORT OP 



existence of four species of the ox, which were probably contempora- 

 neous with the Mastodon and the Megalonyx. Fossil remains of these 

 animals have been frequently found in the United States, and descrip- 

 tions of them are scattered through various works ; but no approach 

 has before been made to a correct view of the number and character 

 of the species. The present existing species of ox are found indige- 

 nous in every part of the world except South America and Australia ; 

 and this is the more remarkable, because the domestic ox introduced 

 into the former country by Europeans exists in immense herds on the 

 pampas in a wild state. There is a similar fact 'with regard to the 

 horse. America, at the period of its discovery, possessed no indigenous 

 quadruped of this kind, though the climate is highly favorable to its ex- 

 istence, an'd the remains of two extinct species are frequently found. 

 Two of the species of ox described by Dr. Leidy belong to the genus 

 Bison, and one of these is of gigantic size. The other two species be- 

 long to a new genus called Bootherium. 



5. Another memoir presented by the same author forms an interesting 

 addition to our knowledge of the extinct gigantic sloth tribe of North 

 America. It comprises a description of remains of the Megalonyx, 

 Mylodon, Megatherium, and of a new genus called Erijptodon. 



The scientific world is indebted for the first account of the remains 

 of a large extinct quadruped of the sloth tribe to President Jefferson. 

 Fragments of the bones of this animal were found in a saltpetre cave in 

 Greenbrier county, Virginia. They were regarded with little or no 

 interest by the persons who first observed them, and, as they encum- 

 bered the saltpetre bed, would probably have been thrown out and 

 suffered to decay, had not the news of their existence reached the 

 ears of the distinguished individual before mentioned. Though de- 

 voted to politics, he was too much of a philosopher not to see in these 

 mouldering fragments of a skeleton objects of high interest connected 

 with the past history of our globe. He described them in a memoir 

 published in the Transactions of the American Philosophical Society ^.t 

 Philadelphia in. 1797, and gave to the animal to which they belong the 

 name of Megalonyx, or the great claw. The materials in his possession, 

 however, were too scanty to allow of his determining the true character 

 of the quadruped. Dr. Wistar, of Philadelphia, suspected the animal 

 to have been a gigantic sloth; and this opinion was confirmed by 

 Cuvier, from the ample materials for comparison at his command. 

 The original bones described by Jefferson are preserved in the 

 collection of the Philosophical Society; but, besides these, Dr. Leidy 

 had access to specimens of the remains of the same animal, found in 

 different parts of the United States. From the study of these he has 

 been enabled to throw much additional light upon the characters of 

 the Megalonyx. He considers that the only remains of this animal yet 

 known are those found in the United States, and satisfactorily proves 

 that the lower jaw of an extinct quadruped discovered by Dr. Darwin 

 in South America, and referred by naturalists to the Megalonyx of Jef- 

 ferson, does not belong to an animal of the same genus. 



The remains of the Mylodon, or gigantic sloth, were first discovered 

 by Darwin in his researches in the southern part of South America. 

 Remains of another species found in North America were described 



