MEGATHERIOIDS. 341 



ones in the upper jaw, have been assigned to each half of the lower 

 jaw of the Megatherium, by Garriga,(l) Pander and D'Alton,(2) and 

 Cuvier.(3) One cannot suppose, that the figures in the celebrated 

 works of these Authors err in the general form and proportions 

 of the four lower molars, which in a side view are not concealed 

 by the ascending ramus of the jaw : but, since we have proof, 

 that a small molar, posterior to the corresponding teeth in the upper 

 jaw has been overlooked, the same oversight may have been com- 

 mitted in regard to a corresponding small tooth in the lower jaw. (4) 



In the Collections of Megatherian remains, brought to this 

 country by Sir Woodbine Parish and Mr. Darwin, the following 

 teeth, which differ from those of the upper jaw, may with more 

 probability be referred to the lower jaw than to a distinct species 

 of Megatherium. 



That which most closely corresponds with the first molar in 

 the upper jaw, I have referred to the same part of the lower series 

 of molar teeth. The anterior surface is so much less convex than 

 in the first upper molar, that the entire tooth presents a tetragonal 

 rather than a semi-cylindrical figure ; the anterior facet, however, 

 being only two-thirds the breadth of the posterior one, by which it 

 differs from all the tetragonal teeth of the upper jaw. Both the inner 

 and outer sides which converge to the anterior surface are slightly 

 concave, whilst the inner side in the first upper molar is convex : it 

 has the same double curvature and transverse diameter as the first 

 upper molar. 



A molar tooth of a tetragonal form, but with the anterior facet 

 relatively broader and flatter than in the preceding tooth, and 

 narrower than in any of the tetragonal teeth of the upper jaw, may 

 be the second molar of the lower jaw. 



A third tetragonal molar resembles the third in the upper jaw, 



(1) Description del Esqueleto de un Quadrupedo muy corpulento y raro, &c. fol. 1796. 



(2) Das Riesen-Faulthier, Brady-pus giganteus, abgebildet, beschrieben, &c. fol. 1821. 



(3) Ossemens Fossiles, 4to. 1825, vol. v. pt. i. 



(4) Professor Daubeny kindly undertook, at my request, to examine the jaws of the celebrated 

 skeleton of the Megatherium at Madrid during his recent visit to Spain, with a view to determine 

 the actual number of teeth : but he found the specimen so inclosed in its glazed case, as to pre- 

 vent any examination of the interior of the mouth, and to exhibit only those teeth that are 

 obvious in the published figures. This may account for the oversight of the fifth superior 

 molar. Permission to open the case for a nearer inspection could not be obtained. 



