146 



A palseontologist, who has earned a just celebrity by his successful exertions 

 in the discovery of the fossil Mammalia of Brazil, has pushed the hypothesis of 

 the climbing habits of the Megatherioids so far as to hazard the conjecture that 

 the Megalonyx, and in all probability the Megatherium, were furnished with a 

 prehensile tail. Those arboreal quadrupeds, however, which have the advantage 

 of this fifth hand, as it may be termed, such as the prehensile Porcupine, the 

 didactyle Ant-eater, and the Spider-Monkeys, have a light body, a small pelvis, 

 and slender hind extremities ; and the colossal proportions of these parts in the 

 Megatherioids would be still more enigmatical than they appear when applied to 

 the ordinary scansorial hj^pothesis, if the tail had really been so important an instru- 

 ment in the climbing actions as Dr. Lund conjectures. But it would seem from 

 this able naturalist's allusion to the claws of his Megalonyx Cuvieri, viz. " that they 

 are not compressed as in the Sloth," such compressed claws being, in fact, one of 

 the distinctive characters of Cuvier's genus Megalonyx, that the extinct Megathe- 

 rioid which Dr. Lund had in view was a species of Scelidotherium or Mylodon. 



Now we know that the Mylodon had a strong and powerful tail, but too short 

 for prehensile purposes ; its proportions being exactly such as to enable it to com- 

 plete, with the two hind legs, a tripod strong enough to afford a firm foundation 

 for the massive pelvis and adequate resistance to the forces acting upon and 

 from that great osseous centre. The large and thick transverse, and upper and 

 lower spinous processes, and especially the prolonged and capacious spinal canal, 

 indicate the bulli and strength of the muscular masses which surrounded the tail 

 and connected it with the pelvis : the natural co-adaptation of the articular sur- 

 faces shows that the ordinary inflection of the extremity of the tail was back- 

 wards, as in a ' cauda fulciens,' not forwards, as in a ' cauda prehensilis.' 



Viewing, then, the pelvis of the Mylodon as the fixed point towards which the 

 fore-legs and anterior parts of the body were to be drawn in the gigantic leaf-eater's 

 efibrts to uprend the tree that bore its sustenance, the colossal proportions of the 

 hind extremities and tail lose all their anomaly, and appear in just harmony with 

 the robust claviculate and unguiculate fore-hmbs, with which they combined 

 their forces in the Herculean labour. The uncommon length of the sole of the 

 foot, equalling in the Mylodon, perhaps surpassing in the Megatherium, the length 

 of the femur ; the prolongation of the os calcis which affords the strong posterior 

 fulcrum, and the very powerful claw of the middle toe by which the opposite 



