There is thus established an intimate
and most interesting parallelism between the chalk and
the ooze of modern oceans. Both are formed essentially in
the same way, and the latter only requires consolidation to
become actually converted into chalk. Both are fundamentally
organic deposits, apparently requiring a great depth of water
for their accumulation, and mainly composed of the remains of
_Foraminifera_, together with the entire or broken skeletons
of other marine animals of greater dimensions. It is to be
remembered, however, that the ooze, though strictly
representative of the chalk, cannot be said in any proper sense
to be actually _identical_ with the formation so called by
geologists. A great lapse of time separates the two, and though
composed of the remains of representative classes or groups of
animals, it is only in the case of the lowly-organised
_Globigerinoe_, and of some other organisms of little higher
grade, that we find absolutely the same kinds or species of
animals in both.
[Illustration: Fig. 8.--Organisms in the Atlantic Ooze, chiefly
_Foraminifera_ (_Globigerina_ and _Textularia_), with _Polycystina_
and sponge-spicules; highly magnified. (Original.)]
[Illustration: Fig. 9.--Slab of Crinoidal marble, from the
Carboniferous limestone of Dent, in Yorkshire, of the natural
size. The polished surface intersects the columns of the Crinoids
at different angles, and thus gives rise to varying appearances.
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