GEOLOGICAL SOCIETY. 43 



Anatomy of the Sloth, by R. Harlan, M. D, Am. 

 Monthly Journal of Geology, vol. i. p. 499. 



In the two-toed sloth* (B. didactylus, Lin. or chselo- 

 pus, Illig.) the form and structure of the teeth differ 

 from those of the former species, besides possessing true 

 canines, differing in form and size from the molars ; the 

 latter are nearly destitute of the external layer of ce - 

 ment, which consists only of a slight brush of this sub- 

 stance, of a black color, probably stained by the vege- 

 table juices on which the animal feeds ; the crowns of 

 the two middle molars display, by detrition, two irre- 

 gular concave triangular faces, anteriorly and posteriorly. 

 The central portion of the long pillar is of a softer struc- 

 ture, and differs in color from the rest of the bone. 



In the genus Dasypus, or Armadillo, although the 

 various subgenera and species, differ considerably in 

 their dental formula from each other, I have observed 

 nothing very remarkable in the structure of these or- 

 gans, in the species which I have examined ; they are 

 generally subconical, apparently destitute of cement, 

 surrounded by enamel, which, when worn off by fric- 

 tion, leaves the crown with a double concave semi- 

 elliptical surface, with a central depression, there being, 

 as in the B. didactylus? a central portion bone, of a 

 softer texture ; like the teeth of most of the animals com- 

 posing the order Edentata, those of the Armadillo, are 

 destitute of true roots or fangs, a structure which it is 

 supposed enables them to continue through life, grow- 

 ing from the inferior extremity, as the crown is worn 



