CHAP. XII 



Age of. 411 



table on the previous page, in which the difference 

 between the extension in latitude of the fossil and existing 

 species is shown, is taken from M. d'Orbigny's work ; but 

 the range of the living shells is given on the authority 

 of Mr. Cuming, whose long-continued researches on the 

 conchology of South America are well known. 



When we consider that very few, if any, of the fifty- 

 nine fossil shells are identical with, or make any close 

 approach to, living species ; when we consider that some 

 of the genera do not now exist on the west coast of 

 South America, and that no less than twelve genera out 

 of the thirty-two formerly ranged very differently from 

 the existing species of the same genera, we must admit 

 that these deposits are of considerable antiquity, and 

 that they probably verge on the commencement of the 

 tertiary era. May we not venture to believe, that they 

 are of nearly contemporaneous origin with the Eocene 

 formations of the Northern Hemisphere ? 



Comparing. the fossil remains from the coast of Chile 

 (leaving out, as before, Concepcion and Chiloe) with 

 those from Patagonia, we may conclude, from their 

 generic resemblance, and from the small number of the 

 species which from either coast approach closely to 

 living forms, that the formations of both belong to 

 nearly the same epoch ; and this is the opinion of M. 

 d'Orbigny. Had not a single fossil shell been common 

 to the two coasts, it could not have been argued that 

 the formations belonged to different ages ; for Messrs. 

 Cuming and Hinds have found, on the comparison of 

 nearly 2,000 living species from the opposite sides of 

 South America, only one in common, namely, the Pier- 

 pura lapillus from both sides of the Isthmus of Panama : 

 even the shells collected by myself amongst the Chonos 

 Islands and on the coast of Patagonia, are dissimilar, 

 and we must descend to the apex of the continent, to 



