72 GEOLOGY OF PATAGONIA. {cHaP. VIIL 
cliffs or escarpments, which separate the different plains as they 
rise like steps one behind the other. The elevatory movement, 
and the eating-back power of thesea during the periods of rest, 
have been equable over long lines of coast; for I was astonished 
to find that the step-like plains stand at nearly corresponding 
heights at far distant points. The lowest plain is 90 feet high ; 
and the highest, which I ascended near the coast, is 950 feet ; 
and of this, only relics are left in the form of flat gravel- 
capped hills. The upper plain of S. Cruz slopes up toa height 
of 38000 feet at the foot of the Cordillera. Ihave said that 
within the period of existing sea-shells Patagonia has been up- 
raised 300 to 400 feet: I may add, that within the period 
when icebergs transported boulders over the upper plain of 
Santa Cruz, the elevation has been at least 1500 feet. Nor 
has Patagonia been affected only by upward movements: the 
extinct tertiary shells from Port St. Julian and Santa Cruz cannot 
have lived, according to Professor E. Forbes, ina 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 accu- 
mulation 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 palzotherium; 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 
* T 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, and appear to have 
belonged to an armadillo. ‘This is a most interesting and important dis- 
covery. 
