FOSSIL MAMMALIA. 



Ill 



With respect to the geological contemporaneity of the fossils collected by 

 him, Mr. Darwin subjoins the following observations : — 



" The remains of the following animals were embedded together at Punta Alta 

 in Bahia Blanca:— The Megatherium Cuvierii, Megalonyx Jeffersonii, Mylodon 

 Daricinii, Scelidotherium leptocephalum, Toxodon Platensis (?) a Horse and a small 

 Dasypodoid quadruped, mentioned p. 107 ; at St. F6 in Entre Rios, a Horse, a 

 Mastodon, Toxodon Platensis, and some large animal with a tesselated osseous 

 dermal covering ; on the banks of the Tercero the Mastodon, Toxodon, and, 

 according to the Jesuit Falkner, some animal with the same kind of covering ; 

 near the Rio Negro in Banda Oriental, the Toxodon Platensis, Glossotherium, and 

 some animal with the same kind of covering. To these two latter animals the 

 Glyptodon clavipes, described by Mr. Owen in the Geological Transactions, 

 may, from the locality where it was discovered, and from the similarity of the 

 deposit which covers the greater part of Banda Oriental, almost certainly be 

 added, as having been contemporaneous. From nearly the same reasons, it is 

 probable that the Rodents found at Monte Hermoso in Bahia Blanca, co-existed 

 with the several gigantic mammifers from Punta Alta. I have, also, shown 

 in the Introduction, that the Macrauchenia Patachonica, must have been coeval, 

 or nearly so, with the last mentioned animals. Although we have no evidence 

 of the geological age of the deposits in some of the localities just specified, 

 yet from the presence of the same fossil mammifers in others, of the age of 

 which we have fair means of judging, (in relation to the usual standard of com- 

 parison, of the amount of change in the specific forms of the invertebrate inha- 

 bitants of the sea,) we may safely infer that most of the animals described in this 

 volume, and likewise the Glyptodon, were strictly contemporaneous, and that all 

 lived at about the same very recent period in the earth's history. Moreover, as 

 some of the fossil animals, discovered in such extraordinary numbers by M. Lund 

 in the caves of Brazil, are identical or closely related with some of those, which 

 lately lived together in La Plata and Patagonia, a certain degree of light is thus 

 thrown on the antiquity of the ancient Fauna of Brazil, which otherwise would 

 have been left involved in complete darkness." 



