10 



Rbtzius and myself into the structure of the teeth of the Mammalia generally, had 

 made me acquainted with the marked difference between the teeth of the Armadillos 

 and those of the Sloths in internal structure, and I now found that the Mega- 

 therium presented the same remarkable compound structure of the teeth as in the 

 Sloths, but with additional complexity, by which they still further departed from 

 the comparatively simple structure of the teeth of the Armadillos: the exami- 

 nation at the same time proved that there was no true enamel in the teeth of the 

 Megatherium*. 



Another important evidence of the affinity of the Megatherium to the Sloths was 

 brought to light by a fragment of the skull from Punta Alta, which demonstrated a 

 fifth small molar tooth on each side of the upper jaw, thus showing that in the 

 number as well as in the structure and the kind of teeth the Megatherium agreed 

 with the Bradypodidw, and especially with the Ai or Three-toed Sloth ; the anterior 

 pair of molars not "manifesting the excess of size and laniary form which characterize 

 them in the Unau or Two-toed species-f-. 



These additional evidences of the concordance of structure between the Mega- 

 therium and the Sloths, manifested by the hard and enduring parts which are most 

 intimately related to the food of the animal, induced me to reconsider the conclu- 

 sions of Cuvier, Pander and D'Alton, and Dr. Buckland relative to the sources of 

 its nutriment and its habits of life ; and ultimately to arrive at a conviction of the 

 correspondence of the food of the Megatherium with that of the Sloths, and of the 

 relation of the modified form of the Megatherium to its peculiar mode of obtaining 

 such food, the grounds for which conviction are given in my memoir on the 

 Mylodon robustus, published in 1842. 



By the analogy of this smaller species of the great extinct terrestrial Sloths of 

 South America, I endeavoured to dissipate some of the doubt and obscurity which 

 shrouded the true structure of the fore and hind feet of the Megatherium J; but the 

 light so obtained served rather to increase the desire to inspect the skeleton itself at 

 Madrid, and obtain, ex visu, a conviction of the accuracy of my views ; for I partici- 

 pated entirely in the doubts expressed by my experienced colleague Mr. Clift§ 

 relative to that skeleton, then unique in Europe, viz. as to " whether it had been 

 properly or improperly mounted, i. e. whether all the parts were of one or more indi- 

 viduals, whether they belong to the situation or position in which they are placed, 

 whether all the parts are genuine or partly modelled, or whether parts are eked out 

 by bones that do not belong to the part or situation in which they are collected :" 

 concurring at the same time with Mr. Clift, that " no blame was attributable to the 

 articulator, who, probably, had little or no guide in such a difficult task." 



* Zoology of the Voyage of Her Majesty's Ship ' Beagle,' Fossil Mammalia, 4to, 1838-40, p. 103, 

 pis. 31 and 32. fig. 1. f Ibib. p. 102. 



X Description of the Skeleton of the Mylodon robustus, 4to, pp. 102, 131-136. 

 i "Notice on the Megatherium," Geol. Trans. Second Series, vol. iii., description of plate 44. 



