I §2 
GEOLOGY OF PATAGONIA 
CHAP. 
affected only by upward movements : the extinct tertiary shells 
from Port St. Julian and Santa Cruz cannot have lived, 
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 1000 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, 1 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 palseotherium ; 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. From 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 0 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—by the 
1 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 0 
4'. Some of the bones are large ; others are small, and appear to have belonged to 
an armadillo. This is a most interesting and important discovery. 
