1833.] EXTINCT QUADRUPEDS. 63 



and reddish mud, just such as the sea might now wash up on a 

 shallow bank. They were associated with twenty-three species 

 of shells, of which thirteen are recent and four others very 

 closely related to recent forms ; whether the remaining- ones are 

 extinct or simply unknown, must be doubtful, as few collections 

 of shells have been made on this coast. As, however, the recent 

 species were embedded in nearly the same proportional immbers 

 with those now living in the bay, I think there can be little 

 doubt, that this accumulation belongs to a very late tertiary 

 period. From the bones of the Scelidotherium, including even 

 the knee-cap, being intombed in their proper relative positions, 

 and from the osseous armour of the great armadillo-like animal 

 being so well preserved, together with the bones of one of 

 its legs, we may feel assured tiiat these remains were fresli 

 and united by their ligaments, when deposited in tlie gravel 

 together with tiie shells. Hence we have good evidence that 

 the above enumerated gigantic quadrupeds, more different from 

 those of the present day than the oldest of the tertiary quadru- 

 peds of Europe, lived whilst the sea was peopled with most of its 

 present inhabitants ; and we have confirmed that remarkable law 

 so often insisted on by Mr. Lyell, namely, that tlie " longevity 

 of the species in the mammalia is upon the whole inferior to that 

 of the testacea."* 



The great size of the bones of the Megatheroid animals, includ- 

 ing the Megatherium, Megalonyx, Scelidotlierium, and Mylodon, 

 is truly wonderful. The habits of life of these animals were a 

 complete puzzle to naturalists, until Professor Owenf lately 

 solved the problem with remarkable ingenuity. The teeth in- 

 dicate, by their simple structure, tliat these Megatheroid animals 

 lived on vegetable food, and probably on the leaves and small 

 twigs of trees ; their ponderous forms and great strong curved 

 claws seem so little adapted for locomotion, that some eminent 

 naturalists have actually believed, that, like the sloths, to which 

 they are intimately related, tliey subsisted by climbing back 

 downwards on trees, and feeding on the leaves. It was a bold, 



* Principles of Geology, vol. iv. p. 40. 



t This theoi-y was first developed in the Zoology of the Voyage of the 

 Beagle, and subsequently in Professor Oweu!s Memoir on JNlyJodon ro- 

 bustus. 



G 2 



