1833.] EXTINCT QUADRUPEDS. &3 
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 numbers 
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 that these remains were fresh 
and united by their ligaments, when deposited in the gravel 
together with the 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 the “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, Scelidotherium, and Mylodon, 
is truly wonderful. ‘Che habits of life of these animals were a 
complete puzzle to naturalists, until Professor Owent lately 
solved the problem with remarkable ingenuity. The teeth in- 
dicate, by their simple structure, that 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, they subsisted by climbing back 
downwards on trees, and feeding on the leaves. It was a bold, 
“* Principles of Geology, vol. iv. p. 40. 
+ This theory was first developed in the Zoology of the Voyage of the 
Beagle, and subsequently in Professor Owen’s Memoir on Mylodon ro- 
bustus. 
