86 BAHIA BLANCA chap. 



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 upper plain, and from mud, gravel, and sand 

 thrown up by the sea during the slow elevation of the land, of 

 which elevation we have evidence in upraised beds of recent 

 shells, and in rounded pebbles of pumice scattered over the 

 country. At Punta Alta we have a section of one of these 

 later -formed little plains, which is highly interesting from the 

 number and extraordinary character of the remains of gigantic 

 land-animals embedded 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 Megathe- 

 rium, the huge dimensions of which are expressed by its name. 

 Secondly, the Megalonyx, a great allied animal. Thirdly, the 

 Scelidotherium, also an allied animal, of which I obtained 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 

 Mylodon Darwinii, a closely related genus of little inferior 

 size. Fifthly, another gigantic edental quadruped. Sixthly, a 

 large animal, with an osseous coat in compartments, very like 

 that of an armadillo. Seventhly, an extinct kind of horse, to 

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

 Pachydermatous animal, probably the same with the Macrau- 

 chenia, a huge beast with a long neck like a camel, which I 

 shall also refer to again. Lastly, the Toxodon, perhaps one of 

 the strangest animals ever discovered : in size it equalled an 

 elephant or megatherium, but the structure of its teeth, as Mr. 

 Owen states, proves indisputably that it was intimately related 

 to the Gnawers, the order which, at the present day, includes 

 most of the smallest quadrupeds : in many details it is allied to 

 the Pachydermata : judging from the position of its eyes, ears, 

 and nostrils, it was probably aquatic, like the Dugong and 

 Manatee, to which it is also allied. How wonderfully are the 

 different Orders, at the present time so well separated, blended 

 together in different points of the structure of the Toxodon ! 



