HE POORNESS OF PALAEONTOLOGICAL COLLECTIONS.

Now let us turn to our richest museums, and what a paltry display we
behold! That our collections are imperfect is admitted by every one. The
remark of that admirable palaeontologist, Edward Forbes, should never
be 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 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 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 embedded, if in sand or gravel,
will, when the beds are upraised, generally be dissolved by the
percolation of rain water charged with carbonic 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
Chthamalinae (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 this has been found fossil in Sicily, whereas not one other
species has hitherto been found in any tertiary formation: 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 th