GEOLOGICAL SOCIETY 



41 



the other ; sometimes equally before and behind, leav- 

 ing two lateral points, all depending on the manner in 

 which the teeth meet and rub against each other. The 

 teeth of the sloths are of the most simple structure 

 imaginable. A cylinder of bone enveloped by enamel^ 

 and hollow at both ends, at the external end by detri- 

 tion, at the internal, by default of ossification, and for 

 the purpose of lodging the remains of the gelatinous 

 pulp; which served them for a nidus-— voila toute leur 

 description." 



" These animals do not possess, like the other herbi- 

 vora, plates of enamel, which penetrate the tooth in 

 various directions, and which render the crowns more 

 fit for grinding vegetables ; consequently their mastica- 

 tion ought to be very imperfect." 



ff It is still further necessary to remark that the plates 

 which compose their osseous substance, are but imper- 

 fectly united to each other. In sawing a tooth longi- 

 tudinally, these plates are observable, piled one on top 

 of the other, like pieces of money in a tube, and this 

 tubular case consists of enamel." 



The observations which I have made on the struc- 

 ture of the teeth in the sloths, lead to different results, 

 both as regards fact and inference. In the first place, 

 the two species of the Linns&an genus Bradypus, (B. 

 tridactylus, and B. didactylus, or the three-toed and 

 two-toed sloths,) differ considerably in their dental 

 structure, and in the form of the head. In reference 

 to the latter point, Illiger and F. Cuvier have arranged 

 these tardigrade animals under two distinct genera, the 



Vol, I— F 



