GEOLOGY OF PATAGONIA 



affected only by upward movements : the extinct tertiary shells 

 from Port St. Julian and Santa Cruz cannot ha\e livedo 

 according to Professor E. Forbes, in a greater depth of water 

 than from 40 to 250 feet; but they are now covered with 

 sea-deposited strata from 800 to i 000 feet in thickness : hence 

 the bed of the sea, on which these shells once lived, must have 

 sunk downwards several hundred feet, to allow of the accumula- 

 tion of the superincumbent strata. What a history of geo- 

 logical changes does the simply-constructed coast of Patagonia 

 reveal ! 



At Port St. Julian,^ in some red mud capping the gravel 

 on the 90-feet plain, I found half the skeleton of the Macrau- 

 chenia Patachonica, a remarkable quadruped, full as large as a 

 camel. It belongs to the same division of the Pachydermata 

 with the rhinoceros, tapir, and paLxotherium ; but in the 

 structure of the bones of its long neck it shows a clear relation 

 to the camel, or rather to the guanaco and llama. P^rom recent 

 sea-shells being found on two of the higher step-formed plains, 

 which must have been modelled and upraised before the mud 

 was deposited in which the Macrauchenia was intombed, it is 

 certain that this curious quadruped lived long after the sea was 

 inhabited by its present shells. I was at first much surprised 

 how a large quadruped could so lately have subsisted, in lat. 

 49° 15', on these wretched gravel plains with their stunted 

 vegetation ; but the relationship of the Macrauchenia to the 

 guanaco, now an inhabitant of the most sterile parts, partly 

 explains this difficulty. 



The relationship, though distant, between the Macrauchenia 

 and the Guanaco, between the Toxodon and the Capybara, — 

 the closer relationship between the many extinct Edentata and 

 the living sloths, ant-eaters, and armadilloes, now so eminently 

 characteristic of South American zoology, — and the still closer 

 relationship between the fossil and living species of Ctenomys 

 and Hydrochaerus, are most interesting facts. This relation- 

 ship is shown wonderfully — as wonderfully as between the 

 fossil and extinct Marsupial animals of Australia — b\- the 



' I have lately heard that Capt. .Sulivan, R.N., has found numerous fossil 

 bones, embedded in regular strata, on the banks of the R. Gallegos, in lat. 51'' 

 4'. .Some of the bones are large ; others are small, anil appear to have belonged to 

 an armadillo. Tiiis is a most interesting and important discovery. 



