"276 FAMILY GRAVIGRADA ; MYLODON. 



earth, and which have been named GRAVIGRADA from their mas- 

 sive character. Of one of these, the Mylodon (of which there is 

 a magnificent skeleton in the Museum of the Royal College of 

 Surgeons, London), an elaborate account has recently been pub- 

 lished by Professor Owen ; in which the other animals of the 

 same group are also noticed. All of them appear, from the 

 structure of their teeth, to have been adapted to the same kind 

 of food with the comparatively pigmy Sloths of the present day ; 

 but instead of possessing limbs adapted for climbing trees, which 

 could not have borne their enormous weight, their feet were con- 

 structed for digging ; and the evidence adduced by Professor 

 Owen from the structure of their skeletons, together with the 

 beautiful chain of reasoning which he connects with this, leave 

 no room for doubt, that they obtained their food by digging 

 around the bases of the trees, and uprooting their trunks. 

 " Conceive of a Sloth of the size and bulk of a Rhinoceros or 

 Hippopotamus, but with bones infinitely more massive, muscles 

 infinitely more voluminous and powerful, with a thick tail acting 

 as a support, and forming with the hind limbs a firm tripod, 

 "while the animal thus raised upright, and exerting its enormous 

 strength, sways the tree to and fro, and lays it at last prostrate ; 

 and the reader will have a good idea of what this mighty 

 devastator (the Mylodon) of the primitive forests of South 

 America must have been." * It is an interesting circumstance, 

 that the skull of the specimen described by Professor Owen had 

 at some time been fractured and had healed, the animal living 

 long afterwards ; and it is evident that these animals must have 

 been unusually liable, from their habits, to blows from heavy 

 falling bodies. It appears to be for the sake of meeting these 

 accidents, that the outer and inner layers of the bones of the skull 

 are separated from each other by large air-cells; so that the 

 fracture of the outer table might occur without injury to the 

 brain. The same structure exists in the Sloths ; and is evidently 

 a provision against injury from the severe falls, to which these 

 animals must be occasionally liable, from the giving- way of the 

 branches to which they cling. 

 245. The Megatherium was an animal nearly allied to the 



* Pictorial Museum, Vol. I., p. 178. 



