300 THE POORNESS OF 



forgotten, namely, that very many fossil species are known 

 and named from single and often broken specimens, or 

 from a few specimens collected on some one spot. Only 

 a small portion of the surface of the earth has been geologi- 

 cally explored, and no part with sufficient care, as the im- 

 portant discoveries made every year in Europe prove. No 

 organism wholly soft can be preserved. Shells and bones 

 decay and disappear when left on the bottom of the sea, 

 where sediment is not accumulating. We probably take a 

 quite erroneous view, when we assume that sediment is being 

 deposited over nearly the whole bed of the sea, at a rate 

 sufficiently quick to embed and preserve fossil remains. 

 Throughout an enormously large proportion of the ocean, 

 the bright blue tint of the water bespeaks its purity. The 

 many cases on record of a formation conformably covered, 

 after an immense interval of time, by another and later 

 formation, without the underlying bed having suffered in 

 the interval any wear and tear, seem explicable only on the 

 view of the bottom of the sea not rarely lying for ages in 

 an unaltered condition. The remains which do become em- 

 bedded, if in sand or gravel, will, when the beds are up- 

 raised, generally be dissolved by the percolation of rain 

 water charged with carbolic acid. Some of the many kinds 

 of animals which live on the beach between high and low 

 water mark seem to be rarely preserved. For instance, the 

 several species of the Chthamalinse (a sub-family of sessile 

 cirripedes) coat the rocks all over the world in infinite num- 

 bers : they are all strictly littoral, with the exception of a 

 single Mediterranean species, which inhabits deep water, 

 and this has been found fossil in Sicily, whereas not one 

 other species has hitherto been 7 found in any tertiary for- 

 mation : yet it is known that the genus Chthamalus existed 

 during the Chalk period. Lastly, many great deposits, 

 requiring a vast length of time for their accumulation, are 

 entirely destitute of organic remains, without our being able 

 to assign any reason : one of the most striking instances is 

 that of the Flysch formation, which consists of shale and 

 sandstone, several thousand, occasionally even six thousand, 

 feet in thickness, and extending for at least 300 miles from 

 Vienna to Switzerland; and although this great mass has 

 been most carefully searched, no fossils, except a few vege- 

 table remains, have been found. 



With respect to the terrestrial productions which lived 

 (luring the $e§oi}c[ary and Palaeozoic periods, jt js superflu- 



