﻿I860.] 



FORBES BOLIVIA AND PEKTT. 



47 



above them, and so analogous in character to those on the east side of 

 the fault (and which also I could find developed further west), 

 furnished me with a clue to the explication of the question as 

 represented in the section. I have further reason to believe this 

 to be correct from finding, much further to the west (as marked 

 in the section), coarser and pebbly beds and traces of the outcrop 

 of cupriferous beds, which, on examination, may possibly prove 

 to be the representatives of the western half of the dislocated 

 " vetas." * 



Before taking leave of Corocoro, I must mention the occurrence of 

 fossil wood in the beds of the mine of Quimse Cruz, in a carbonized 

 state, and occasionally having the pores filled with metallic copper ; 

 also the occurrence of a fossil skeleton of a Mammal in the mine of 

 Santa Eosaf in 1859, part of which I was enabled to obtain through 

 General Brown, and which Prof. Huxley, having kindly examined 

 it, pronounces to be the skeleton of a mammal of the Camel tribe, 

 allied to the Llama, but presenting marked differences from it : it 

 has been called by him Macrauchenia Boliviensis% . See p. 73. 



The occurrence of a Mammal of the post-pleistocene period in 

 strata considered as so much older appears only to be accounted for 

 on the supposition that the animal had fallen into a fissure in these 

 rocks, and been subsequently covered up by the crumbling sandy 

 debris of the adjacent rocks, which has gradually consolidated. The 

 mine of Santa Bosa being situated close to the fault, it might be also 

 possible that some portion of the fault itself has not been closed up, 

 and has thus left a fissure, which might account for the depth at 

 which these remains were found under the surface. The bones 

 themselves are in some instances almost converted into copper, or 

 at least the pores are filled with that metal, — a circumstance easily 

 accounted for in strata so highly impregnated with it. 



I have gone into this detailed description of the cupriferous forma- 

 tions of Corocoro, because they are at present the object of the most 

 important metallic explorations in the Permian rocks of Bolivia ; but 

 from all I can leam, the other mining districts in this formation 

 present quite analogous features, and in some cases, as at San Baxtolo 

 in the south of Bolivia, are developed on an equally large scale, — 

 the occurrence of the metallic copper in them being exactly as de- 

 scribed in Corocoro §. 



The disturbances or convulsions which have affected the Permian 



* I cannot but express here the obligations I am under to Fieldrnarshal 

 Brown, M. Pedro Saienz, and other friends at Corocoro for the kind assistance 

 they afforded me in my researches in this part of the country. 



t The former of these mines belongs to Mr. Teare, the latter to Mr. Griffiths. 



\ The occurrence of an animal allied to the only known larger mammals 

 of this part of Bolivia (the Llama, Alpaco, Guanaco, and Vicuna) is further in- 

 teresting as showing that the great Bolivian plateau, at so much earlier a period, 

 was inhabited by animals generically allied to those found there at present, and 

 two of which (the Llama and Alpaco) are known to be indigenous, and not to 

 occur elsewhere in the world. 



§ Mr. Abel of Copiapo has, in a letter, kindly forwarded me the following 



