122 Megatherium of Georgia. 



enamel ; but where it is parallel to the cutting edges is nearly 

 a quarter the thickness of the whole tooth. Enclosed within 

 this is a second coating of enamel, which, like the first two,, 

 has two sides very thin. The other two sides are more than 

 a line thick, and terminate in the cutting processes, which by 

 this means are kept constantly sharp and prominent by the 

 wearing away of the softer ivory on each side of them. Where 

 these laminae of enamel terminate, on the anterior side of the 

 higher process, may be observed a semilunated truncation, 

 which is not seen on the lower process, although terminated in 

 a similar manner. 



The whole solid part of the tooth thus represents a prism of 

 bone, enveloped in three cases, two of enamel, and the third of 

 a substance similar to itself. There is therefore much analo- 

 gy between this structure and that of the teeth in the genus 

 Bradypus ; which, says M. Cuvier, are simply " un cylindre 

 d'os enveloppe d'email." In another passage he speaks of 

 this enamel as an " etui tubuleux." We have thus an addi- 

 tional circumstance to show the affinity of the Megatherium to 

 the Sloths. 



Fig. 3 represents a transverse section, natural size, of one of 

 the first molars, showing the arrangement and relative thick- 

 ness of the coats. 



Fig. 4, a longitudinal section of part of a larger tooth, 

 showing the manner in which the interior enamel terminates 

 the cutting processes. 



Of the four vertebra?, three have little remaining besides 

 the body, the processes being almost all entirely broken off. 

 The other, which appears to be one of the dorsal, perhaps the 

 third, is tolerably entire. It agrees with Bru's description of 

 those of the Megatherium, excepting that I am not able to find 

 the two holes which he describes in the atlas, and which, he 

 says, are common to all the other vertebrae. As, however, 

 this bone is much incrusted with various shells, they may 

 possibly be covered or filled up. 



