288 IMPERFECTION OF THE Chap. IX. 



sufficient care, as the important discoveries made every 

 year in Europe prove. No organism wholly soft can be 

 preserved. Shells and bones will decay and disappear 

 when left on the bottom of the sea, where sediment is 

 not accumulating. I believe we are continually taking 

 a most erroneous view, when we tacitly admit to our- 

 selves 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 enormous interval of time, by another and 

 later formation, without the underlying bed having 

 suffered in the interval any wear and tear, seem ex- 

 plicable only on the view of the bottom of the sea not 

 rarely lying for ages in an unaltered condition. The 

 remains which do become embedded, if in sand or gravel, 

 will when the beds are upraised generally be dissolved 

 by the percolation of rain-water. I suspect that but few 

 of the very many animals which live on the beach be- 

 tween high and low watermark are preserved. For in- 

 stance, the several species of the Chthamalmse (a sub- 

 family of sessile cirripedes) coat the rocks all over the 

 world in infinite numbers: they are all strictly littoral, 

 with the exception of a single Mediterranean species, 

 which inhabits deep water and has been found fossil in 

 Sicily, whereas not one other species has hitherto been 

 found in any tertiary formation : yet it is now known 

 that the genus Chthamalus existed during the chalk 

 period. The molluscan genus Chiton offers a partially 

 analogous case. 



With respect to the terrestrial productions which 

 lived during the Secondary and Palaeozoic periods, it is 

 superfluous to state that our evidence from fossil 



