411 



the ai. This is particularly the case with the long-descending apophysis 



placed at the anterior base of the zygomatic arch. This arch, which is 



interrupted in the sloths, is complete in the megatherium. The rising ^ 



branch of the lower jaw resembles that of the sloths ; but its lower part 



forms a convexity, of which but a slight resemblance is found in the 



elephant. 



The bony muzzle is more projecting in this fossil animal, the Mega- 

 therium, than in the ai, in consequence of the advancing of the sym- 

 phisis of the lower jaw. The bones of the nose are very short; which, 

 from what takes place in the elephant and tapir, gives reason for suspect- 

 ing that this animal had a trunk, which, however, there is also reason 

 for supposing must have been very short. 



The teeth are sixteen grinders, four on each side, in each jaw. They 

 are of a prismatic form, and have their crown crossed by a groove. Th?e 

 vertebrae are seven cervical, sixteen dorsal, and three lumbar. The 

 megatherium, therefore, differs in the number of cervical from the ai, 

 who we have seen differs in this respect from all the other quadrupeds, 

 but agrees with it exactly in the number of the dorsal and lumbar. The 

 number of the ribs are of course sixteen on each side. 



The relative proportions of the extremities of the megatherium differ 

 exceedingly from those of the sloths, and indeed from those of any 

 known animal. In the sloths, we have seen that the length of the fore 

 extremities is double that of the hinder ; but, in this animal, the dif- 

 ference is much less. But the great thickness of the bone of the thigh 

 observable in the sloths, tatous, and pangolins, is carried to a much fur- 

 ther extent in the megatherium ; the length of the femur of this animal 

 being only double its thickness. The inability of this animal for leap- 

 ing, or running, must be obvious : it could only have walked, and that 

 slowly. 



The scapula possesses, on a large scale, the same proportions as that 

 of the sloths ; and the clavicles which this animal possesses, with the 



