LIFE ON THE EARTH. 207 



Surely this imperfection of the geological record 

 is overrated. With the exceptions of the two great 

 breaks at the close of the Palaeozoic and Mesozoic 

 periods, the series of strata is nearly if not quite com- 

 plete, the series of life almost equally so. Not indeed 

 in one small tract or in one section ; but on a com- 

 parison of different tracts and several sections. For 

 example, the marine series of Devonian life cannot 

 be found in the districts of Wales or Scotland, but 

 must be collected in Devonshire, Bohemia, Russia 

 and America. When so gathered it fills very nearly 

 if not entirely the whole interval between the Upper 

 Silurian and the Carboniferous Fauna. So in England 

 the marine intermediaries of the Oolitic and Creta- 

 ceous ages are not given : but the Neocomian Strata 

 supply the want. We have no Meiocene Strata in 

 England, but their place is marked in France and 

 America. 



Even the great breaks alluded to are bridged. 

 The Permian series of life contains some Mesozoic 

 interpolations ; and the Lias contains reliquiae of 

 some Palaeozoic genera. The upper chalk of Maes- 

 tricht and the South of France extends toward the 

 Tertiaries the reign of the Upper Mesozoic beds. 



On the whole, it appears that there exist ample 

 materials for testing any hypothesis of the sequence 

 of life which includes the marine races ; and that 



