Paleontology 689 



The scientific world is indebted for the first account of the 

 remains of a large extinct quadruped of the sloth tribe to Presi- 

 dent Jefferson. He described them in a memoir published in 

 the "Transactions of the American Philosophical Society" in 

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

 belonged 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. Doctor 

 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, 

 Doctor Leidy had access to specimens of the remains of the 

 same animal found in different parts of the United States. 

 From the study of all these he was enabled to throw much 

 additional light upon the characters of Megalonyx. He con- 

 sidered that the only remains of this animal yet known were 

 those found in the United States, and satisfactorily proved 

 that the lower jaw of an extinct quadruped discovered by 

 Charles Darwin in South America, and referred by naturalists 

 to the Megalonyx of Jefferson, 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 by Doctor Harlan, but were erron- 

 eously referred to the Megalonyx. Doctor Leidy, in his 

 memoir, described the collection of the remains of this animal 

 belonging to the New York Lyceum. 



The Megatherium, which is the largest of all the extinct 

 sloth tribe, when full grown, was more than fourteen feet long, 

 including the tail, and eight feet high. It was first discovered 



