104 13A1IIA BLANCA. 



The plain, at the clistance of a few miles from 

 the coast, belongs to the great Pampean formation, 

 which consists in part of a reddish clay, and in 

 part of a highly calcareous marly rock. Nearer 

 the coast there are some plains formed from the 

 wreck of the uj^per plain, and from mud, gi'avel, 

 and sand thrown up by the sea during the slow el- 

 evation of the land, of which elevation we have 

 evidence in upraised beds of recent shells, and in 

 rounded pebbles of pumice scattered over the coun- 

 tiy. At Punta Aha we have a section of one of 

 these later-formed little plains, which is highly in- 

 teresting fi-om the number and extraordinary char- 

 acter of the remains of gigantic land-animals em- 

 bedded in it. These have been fully described by 

 Professor Owen, in the Zoology of the voyage of 

 the Beagle, and are deposited in the College of 

 Surgeons. I will here give only a brief outline of 

 their nature. 



First, parts of three heads and other bones of 

 the Megatherium, the huge dimensions of which 

 are expressed by its name. Secondly, the Mega- 

 lonyx, a great allied animal. Thirdly, the Sceli- 

 dotherium, also an allied animal, of which I obtain- 

 ed a nearly perfect skeleton. It must have been 

 as large as a rhinoceros : in the structure of its 

 head it comes, according to Mr. Owen, nearest to 

 the Cape Ant-eater, but in some other respects it 

 approaches to the armadilloes. Fourthly, the My- 

 lodon Dai'winii, a closely related genus of little in- 

 ferior size. Fifthly, another gigantic edental quad- 

 ruped. Sixthly, a large animal, with an osseous 

 coat in compartments, very like that of an aiTnadil- 

 lo. Seventhly, an extinct kind of hoi-se, to which 

 I shall have again to refer. Eighthly, a tooth of a 

 Pachydermatous animal, probably the same with 

 the Macrauchenia, a huge beast with a long neck 



