Fossil bones in Georgia. 269 



the fibula is on the left side. The following are the principal 

 dimensions in inches and tenths. 



From the anterior border of the upper extremity, to 



the anterior border of the lower, - 24.1 



From the posterior border of the upper extremity, to 



the posterior point of the lower, - , - - 25.6 



Breadth at its widest part, including fibula, - - 12.5 



Breadth at its narrowest part just below the foramen, 10.4 



These dimensions though somewhat longer, agree suffi- 

 ciently with those which M. Cuvier, calculating from the pro- 

 portions of the plates, assigns to the corresponding bone of 

 the Megatherium. The anatomists who examined the skele- 

 ton at Madrid, have omitted giving its dimensions. 



The other portion which I shall notice at present, is one 

 of the metacarpal bones, and is quite perfect. Upon comparing 

 it with the bones of the Megalonyx, of which there are good 

 casts in the cabinet of the Lyceum, I was immediately struck 

 with its great resemblance to that which M. Cuvier considers 

 as the metacarpal of the middle finger of the left hand ; and 

 a further examination satisfied me, that it was in fact the cor- 

 responding bone. This was a discovery of some interest, as 

 it enabled me to compare two corresponding parts of these 

 extraordinary animals, of which so little is known, and which 

 were supposed to be so nearly related, that some naturalists 

 have thought it advisable to include them in the same genus. 

 See Desmarest's Mammalogie, p. 3G5. 



The first thing that strikes us on making this comparison, 

 is the vast difference in size. Cuvier speaks of the " enorme 

 grosseur" of the metacarpal bones of the Megalonyx. But, 

 enormous as they are, this of the Megatherium is at least ten 

 times as large. It is not probable, however, that the same 

 relative proportions existed throughout the skeleton. In 

 other respects there is a great general resemblance, though 

 the bone from Georgia is shorter in proportion to its thick- 



