The remark of that admirable palaeontologist, the late
Edward Forbes, should not be forgotten, namely, that numbers of our
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 geologically
explored, and no part with 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 ourselves 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
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
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 between
high and low watermark are preserved.
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