A MEMOIR 



EXTINCT SLOTH TRIBE OF NORTH AMERICA, 



ITIEGALOIVYX, Jefferson. 

 Megalonyx JcfIerJi$onii, Harlan. 



History. — The extinct genus of giant sloths, Megalonyx, was established by the 

 enlightened and philosophic American President, Thomas Jefferson, in a communi- 

 cation read to the American Philosophical Society, March 10, 1797, entitled "A 

 Memoir on the Discovery of certain Bones of a Quadruped of the Clawed Kind, in 

 the Western Parts of Virginia."^ The illustrious writer observes : " It is well known 

 that the substratum of the country beyond the Blue Ridge is a limestone, abounding 

 with large caverns, the earthy floors of which are highly impregnated with nitre. 

 In digging the floor of one of these caves belonging to Frederic Cromer, in the 

 county of Green Briar, the laborers at the depth of two or three feet, came to some 

 bones, the size and form of which bespoke an animal unknown to them." 



The bones which were preserved and obtained by Mr. Jefferson, consisted of a 

 fragment of an os femoris, a radius, an ulna, three claws, and several other bones 

 of one of the feet. 



From the general resemblance of form of the claws to those of carnivora, Mr. 

 Jefferson supposed the bones to have belonged to an animal of this character — a 

 mistake of much less importance than many made by the best naturalists. 



The specimens Mr. Jefferson subsequently presented to the cabinet of the American 

 Philosophical Society, and they were then more particularly described in its 

 Transactions, by Dr. Caspar Wistar.' The memoir of Dr. Wistar is accompanied 

 by very good figures, of which one represents the restoration of the fore median 

 digit, with its corresponding metacarpal bone. 



From the form and arrangement of the bones of the feet, Dr. Wistar suspected 

 the affmity of the Megalonyx to the recent sloths f and Cuvier,^ who afterwards 

 described the same bones, from casts sent to him by Mr. Peale, of Philadelphia, 



* Trans. Amer. Phil. Soc, 1799 ; IV, 246. "" Ibid. VI, 526. 

 » Ibid. 530. 



♦ Annales du Mus. V. 358 ; Ossem. fossiles, ed. 4, 1836, VIII, 304. 



