406 Tertiary Formations : paet n. 



there is said to be a considerable calcareous deposit : a 

 few fossils have been described by M. d'Orbigny from 

 this place, namely : — 



1. Eostellaria Gaudichaudi, d'Orbig. 'Voyage Pal.' 



2. Pectunculus Paytensis, do. 



3. Venus petitiana, do. 



4. Ostrea Patagonica ? This great oyster (of which specimens 



have been given me) cannot be distinguished by Mr. Sowerby 

 from some of the varieties from Patagonia ; though it would 

 be hazardous to assert it is the same with that species, or 

 with that from Coquimbo. 



Concluding Remarks. — The formations described 

 in this chapter, have, in the case of Chiloe and probably 

 in that of Concepcion and Navidad, apparently been 

 accumulated in troughs formed by submarine ridges 

 extending parallel to the ancient shores of the continent ; 

 in the case of the islands of Mocha and. Huafo it is 

 highly probable, and in that of Tpun and Lemus almost 

 certain, that they were accumulated round isolated 

 rocky centres or nuclei, in the same manner as mud 

 and sand is now collecting round the outlying islets 

 and reefs in the West Indian archipelago. Hence, I 

 may remark, it does not follow that the outlying ter- 

 tiary masses of Mocha and Huafo were ever continuously 

 united at the same level with the formations on the 

 mainland, though they may have been of contempora- 

 neous origin, and been subsequently upraised to the 

 same height. In the more northern parts of Chile, the 

 tertiary strata seem to have been separately accumu- 

 lated in bays, now forming the mouths of valleys. 



The relation between these several deposits on the 

 shores of the Pacific, is not nearly so clear as in the 

 case of the tertiary formations on the Atlantic. Judging 

 from the form and height of the land (evidence which 

 I feel sure is here much more trustworthy than it can 

 be in such broken continents as that of Europe), from 



