172 GEOLOGY OF PATAGONIA. [chap. -vaii. 



cliffs or escarpments, V/iiich separate the different plains as they 

 rise like steps one beliind the other. The elevatory movement, 

 and tiie eating-back pov/er of the sea during- the periods of rest, 

 have been equable over long lines of coast ; for I was astoni>hed 

 to find tiiat the step-like plains stand at nearly correspojiding 

 heiglits at far distant points. The lowest plain is 90 feet high ; 

 and the higiiest, wliich 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 to a height 

 of i^OOO feet at tiie foot of the Cordillera. I have 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 ele\ation 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, 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 tjje accu- 

 mulation of tlie superincumbent strata. "What a iiistory of geo- 

 logical changes does the simply-constructed coast of Patagonia 

 reveal ! 



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

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

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

 camel. It belongs to the same division of the Pachydermata with 

 theriiinoceros, tapir, and palceotherium; but in the structure of the 

 bones of its long neck it shows a clear relation to the camel, or 

 raiher to the guanaco and llama. From recent sea-shells being 

 found on two of tiie higher step-formed plains, whicli must have 

 been modelled and upraised before the mad was deposited in 

 w^iiich the Macrauchenia was intombed, it is certain tiiat tliis 

 curious quadruped lived long after the sea was inhabited by its 



* 1 have lately hcaril that Capt. Sulivan, Tv.N., has found numerous fossil 

 bones, emhedlecl in regular strata, on the banks of the II. Gallegos, in lat. 

 ^1° 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. 



