FOSSIJL MAMMALIA. 



135 



less rudimentary. The hind feet are smaller than the fore, 

 and are articulated with the tibia by a broad astragalus, in a 

 manner much more oblique than in the bradypi. In the 

 Madrid skeleton, but one of their toes is provided with a claw 

 at all comparable to those of the fore-feet. Next this toe are 

 two external rudimentary ones, and there is none visible on 

 the interior side. M. Cuvier suspects that these feet are not 

 completely reconstructed ; for it is a rule without any excep- 

 tion, that all unguiculated animals have five toes, either visible 

 or rudimentary. There is reason, then, to believe that the two 

 internal toes are wanting, and it is possible that all were pro- 

 vided with claws. According to the measurements reported 

 of the different parts of the megatherium, it must have been 

 pretty nearly about the magnitude of the rhinoceros. 



The megalonyx was thus named by Mr. Jefferson, the 

 celebrated President of America, who was the first describer 

 of some of its bones, in the thirtieth number of the " Transac- 

 tions of the Philosophical Society of Philadelphia." It has also 

 formed an object of the Baron's researches. 



Its debris were found, for the first time, at a depth of two 

 or three feet, in one of the caverns of the calcareous mountains 

 of Green-Briar, in Western Virginia. They consist of bones 

 of the extremities, particularly a fore-foot, the forms of which 

 are almost absolutely identical with the analogous parts of the 

 megatherium ; but these bones are one-third smaller, though 

 they bear evident marks of having belonged to an adult subject. 

 A tooth, reported to be American by M. Palisot de Beauvois, 

 has been recognised by Cuvier to be precisely and rigorously 

 the tooth of a bradypus. It was a simple cylinder of osseous 

 substance, enveloped in a case of enamel. Its coronal was 

 hollow in the middle, with projecting edges ; as to the form of 

 this tooth, the megalonyx differed remarkably from the mega- 

 therium, in which the coronal of the molars is marked with 

 transverse hillocks. 



In his memoir on the megalonyx, M. Cuvier has given tlie 



