LIFE ON THE EARTH. 169 



England, Deshayes found about 40 per cent, of the 

 Crag shells identical with living species, and of these 

 nearly all occur in the neighbouring ocean 1 . In like 

 manner, the Tertiary fossils of the sub-Apennine region 

 of Italy are successfully compared with those of the 

 modern epoch, yielding, according to Deshayes, 41*8 

 per cent, of living species, a large proportion of them 

 from the neighbouring seas 2 . By observations of this 

 kind, the Tertiary Series is linked in easy harmony 

 with the actual period ; but if we make the same 

 kind of comparison of the Tertiary with preceding 

 Mollusca, but little of direct affinity can be traced ; 

 and the same remark applies to the common bound- 



1 See Lyell's Principles of Geology ; Wood, in Pal. Soc. 

 Memoirs. 



2 ' From the copious fauna which now tenants the Mediterra- 

 nean waters, a series of changes may be traced, through older 

 sea-beds of the same area, far back into bygone ages. Nowhere 

 do we find better illustration than here of the nature of the 

 changes which a fauna may undergo in time : the evidence is 

 consecutive. It is possible, however, that the Mediterranean 

 series, recent and fossil, may be imperfect, and that the earliest 

 periods of our European marine fauna are not represented there. 

 A comparison of the contents of the older Italian deposits, and 

 their equivalents containing the remains of the existing Atlan- 

 tic species of Testacea, with those of the Faluns of Bordeaux 

 and Touraine, suggests the probability that in these last we have 

 an earlier stage still in the history of our fauna, referable to the 

 time when the Mediterranean depression had not yet been opened 

 to the Atlantic waters.' Forbes and Godwin- Austen, Nat. Hist. 

 of European Seas, 1859. 



