Second. 



Tliird. 



[n. Lines. 



In. 



Lines. 



9 











6 6 



6 



5 



2 



1 



11 



1 8 



1 



7 



Mr. Clift on the Megatherium. 441 



convex. From the thinness of the partitions of the sockets, the teeth closely 

 approximate; and from the direction of the sockets, the series on each side 

 is shg-htly convergent. 



The following' are the admeasurements of the most perfect teeth : 



Upper Jaw. First molar. 

 In. Lines. 



Length 7 



Circumference 4 



Transverse diameter 1 8 



Antero-posterior diameter . . 1 4 



from which it appears that they do not increase in size as they are situated 

 posteriorly, but that the second is at least larger than the third. 



Cuvier also describes two fangs to each tooth of Megatherium*, and ob- 

 serves that in this respect it differs from the Bradypodae, to which it is allied 

 in so many other respects ; but as there is not any appearance of fangs in 

 the teeth of the present specimen f, and as the resemblance in every other 

 particular with that on which his description is founded is complete, this can- 

 not be considered as a specific difference, but as depending most probably on 

 the imperfect state of the tooth in the Madrid specimen, from which Dr. Pan- 

 der's figure is taken ; and this is the more probable, as in the original work 

 of Garriga;};, a molar tooth is figured without these fangs; this deceptive ap- 

 pearance being merely owing to a dotted line, by which he has endeavoured 

 to indicate on the surface of the tooth the extent and shape of the cavity for 

 the secreting pulp within : which circumstance may have misled Messrs. 

 Pander and D'Alton, who probably had no opportunity of examining a tooth 

 separated from its socket, as their figure sufficiently implies §. 



The teeth ||, though simple in form, are complex in structure, being com- 

 posed of a central body of ivory extending across nearly the whole transverse 

 diameter of the tooth, but occupying only the middle two thirds of the antero- 

 posterior diameter. The ivory is surrounded by a thin layer of enamel not ex- 

 ceeding a line, and the rest of the tooth on the anterior and posterior surfaces 

 is made up of caementum ; hence, from the different degrees of density pos- 



[ * Ossemcns Fossiles, torn. v. PI. I. p. 1 79. See also ante, Note p. 438, on this subject. — W. C. 1 835. 



f Plate XLV. fig. 2. 



"l Tab. IV. fig. 5. " Descripcion del Esqucleto de un Quadrupedo muy corpulento y raro, que 

 se conserva en el Real Gabinete de Historia Natural de Madrid. Publicala Don Joseph Garriga, 

 Ciipitao de Ingenieros Cosmografos de Estado." Folio. Madrid, 179G ; with five folding Phites. 



§ Tab. III. fig. 15. ^^ Das Ricsen Faulthier, Dasypus Giganteus, von Dr. Chr. Pander uiul Dr. 

 E. D'Alton." Oblong folio. Bonn, 1821. 



11 Tab. IV. fig. 5. 



