244 Royal Society. 



site to give due strength and stability totheslioulder-joint for varied 

 actions of the fore-arm, as in grasping, climbing and burrowing : 

 but they are not essential to scansorial or fossorial quadrupeds ; the 

 Bear and the Badger have not a trace of clavicles, and the mere rudi- 

 ments of these bones exist in the Rabbit and the Fox. We must seek, 

 therefore, in the other parts of the organization of the Megatherium, 

 for a clew to the nature of the actions by which it obtained its food. 

 In habitual burrowers the claws can be extended in the same plane as 

 the palm, and they are broader than they are deep. In the Mega- 

 therium the depth of the claw-phalanx exceeds its breadth, especially 

 in the large one of the middle finger; and they cannot be extended 

 into a line with the metacarpus, but are more or less bent. Thus, 

 although they might be used for occasional acts of scratching up 

 the soil, they are better adapted for grasping ; and the whole struc- 

 ture of the fore-foot militates against the hypothesis of Pander and 

 D' Alton, that the Megatherium was a burrowing animal. The 

 same structure equally shows that it was not, as Dr. Lund supposes, 

 a scrnsorial quadruped; for, in the degree in which the foot depart?; 

 from the structure of that of the existing Sloths, it is unfitted for 

 climbing ; and the outer digit is modified, after the ungulate type, 

 for the exclusive office of supporting the body in ordinary terrestrial 

 progression. It may be inferred from the diminished curvature and 

 length, and from the increased strength and the inequality of the claws, 

 especially the disproportionately large size of that weapon of the 

 middle digit, that the fore-foot of the Megatherium was occasionally 

 ap])lied by the short and strong fore-limb in the act of digging ; but 

 \\s analogy to that of the Ant-eaters teaches that the fossorial actions 

 were limited to the removal of the surface-soil, in order to expose 

 something there concealed, and not for the purpose of burrowing. 

 Such an instrument would be equally effective in the disturbance of 

 roots and ants ; it is, however, still better adapted for grasping than 

 for delving. But to whatever task the partially unguiculate hand of 

 the Megatherium might have been applied, the bones of the wrist, 

 fore-arm, arm and shoulder, attest the prodigious force which would 

 be brought to bear upon its execution. The general organization of 

 the anterior extremity of the Megatherium is incompatible with its 

 being a strictly scansorial or exclusively fossorial animal, and its 

 teeth and jaws decidedly negative the idea of its having fed upon 

 insects ; the two extremes in regard to the length of the jaws are 

 presented by the phyllophagous and myrmecophagous members of 

 the Edentate order, and the Megatherium in the shortness of its 

 face agrees with the Sloths. 



Proceeding then to other parts of the skeleton for the solution of 

 the question as to how the Megatherium obtained its leafy food, the 

 author remarks that the pelvis and hind limbs of the strictly bur- 

 rowing animals, e.g. the Mole, are remarkably slender and feeble, 

 and that they offer no notable development in the Rabbit, the Oryc- 

 terope, or other less powerful excavators. In the climbing animals, 

 as e.g. the Sloth and Orang, the hind-legs are much shorter than 

 the fore-legs, and even in those Quadrumana in which the pre- 

 hensile tail is superadded to the sacrum, the pelvis is not remarkable 



