The seas of this epoch included an immense number of Zoophytes, nearly
400 species of Mollusca, and a few Crustaceans and Fishes. Among the
Fishes, _Psammodus_ and _Coccosteus_, whose massive teeth inserted in
the palate were suitable for grinding; and the _Holoptychius_ and
_Megalichthys_, are the most important. The Mollusca are chiefly
Brachiopods of great size. The Productæ attained here exceptional
development, _Producta Martini_ (Fig. 53), _P. semi-reticulata_ and _P.
gigantea_, being the most remarkable. Spirifers, also, were equally
abundant, as _Spirifera trigonalis_ and _S. glabra_. In _Terebratula
hastata_ the coloured bands, which adorned the shell of the living
animal, have been preserved to us. The _Bellerophon_, whose convoluted
shell in some respects resembles the Nautilus of our present seas, but
without its chambered shell, were then represented by many species,
among others by _Bellerophon costatus_ (Fig. 54), and _B. hiulcus_ (Fig.
56). Again, among the Cephalopods, we find the _Orthoceras_ (Fig. 57),
which resembled a straight Nautilus; and Goniatites (_Goniatites
evolutus_, Fig. 55), a chambered shell allied to the Ammonite, which
appeared in great numbers during the Secondary epoch.
[Illustration: Fig. 47.--Lepidodendron Sternbergii.]
Crustaceans are rare in the Carboniferous Limestone strata; the genus
Phillipsia is the last of the Trilobites, all of which became extinct at
the close of this period. As to the Zoophytes, they consist chiefly of
Crinoids and Corals. The Crinoids were represented by the genera
_Platycrinus_ and _Cyathocrinus_. We also have in these rocks many
Polyzoa.
[Illustration: Fig. 48.--Pecopteris lonchitica, a little magnified.]
[Illustration: Fig. 49.--Neuropteris gigantea.]
[Illustration: Fig. 50.--Lonchopteris Bricii.]
[Illustration: Fig. 51.--Odontopteris Brardii.]
[Illustration: Fig. 52.--Sphenopteris artemisiæfolia, magnified.]
Among the corals of the period, we may include the genera
_Lithostrotion_ and _Lonsdalea_, of which _Lithostrotion basaltiforme_
(Fig. 58), and _Lonsdalea floriformis_ (Fig. 59), are respectively the
representatives, with _Amplexus coralloïdes_. Among the Polyzoa are the
genera _Fenestrella_ and _Polypora_. Lastly, to these we may add a group
of animals which will play a very important part and become abundantly
represented in the beds of later geological periods, but which already
abounded in the seas of the Carboniferous period. We speak of the
_Foraminifera_ (Fig. 60), microscopic animals, which clustered either in
one body, or divided into segments, and covered with a calcareous,
many-chambered shell, as in Fig. 60, _Fusulina cylindrica_. These little
creatures, which, during the Jurassic and Cretaceous periods, formed
enormous banks and entire masses of rock, began to make their
appearance in the period which now engages our attention.
[Illustration: Fig. 53.--Producta Martini. One-third nat. size.]
[Illustration: Fig. 54.--Bellerophon costatus. Half nat. size.]
[Illustration: Fig. 55.--Goniatites evolutus. Nat. size.]
[Illustration: Fig. 56.--Bellerophon hiulcus.]
[Illustration: Fig. 57.--Orthoceras laterale.]
[Illustration: Fig. 58.--Lithostrotion basaltiforme.]
[Illustration: Fig. 59.--Lonsdalea floriformis.]
The plate opposite (PLATE X.) is a representation of an ideal aquarium,
in which some of the more prominent species, which inhabited the seas
during the period of the Carboniferous Limestone, are represented. On
the right is a tribe of corals, with reflections of dazzling white: the
species represented are, nearest the edge, the _Lasmocyathus_, the
_Chætetes_, and the _Ptylopora_. The Mollusc which occupies the
extremity of the elongated and conical tube in the shape of a sabre is
an _Aploceras_. It seems to prepare the way for the Ammonite; for if
this elongated shell were coiled round itself it would resemble the
Ammonite and Nautilus. In the centre of the foreground we have
_Bellerophon hiulcus_ (Fig. 56), the _Nautilus Koninckii_, and a
_Producta_, with the numerous spines which surround the shell. (See Fig.
62.)
[Illustration: Fig. 60.--Foraminifera of the Mountain Limestone, forming
the centre of an oolitic grain. Power 120.]
[Illustration: Fig. 61.--Foraminifera of the Chalk, obtained by brushing
it in water. Power 120.]
On the left are other corals: the _Cyathophyllum_ with straight
cylindrical stems; some Encrinites (_Cyathocrinus_ and _Platycrinus_)
wound round the trunk of a tree, or with their flexible stem floating in
the water. Some Fishes, _Amblypterus_, move about amongst these
creatures, the greater number of which are immovably attached, like
plants, to the rock on which they grow.
[Illustration: X.--Ideal view of marine life in the Carboniferous
Period.]
In addition, this engraving shows us a series of islets, rising out
of a tranquil sea. One of these is occupied by a forest, in which a
distant view is presented of the general forms of the grand vegetation
of the period.
* * * * *
It is of importance to know the rocks formed by marine deposits during
the era of the Carboniferous Limestone, inasmuch as they include coal,
though in much smaller quantities than in the succeeding sub-period of
the true coal-deposit. They consist essentially of a compact limestone,
of a greyish-blue, and even black colour. The blow of the hammer causes
them to exhale a somewhat fetid odour, which is owing to decomposed
organic matter--the modified substance of the molluscs and zoophytes--of
which it is to so great an extent composed, and whose remains are still
easily recognised.
[Illustration: Fig. 62.--Producta horrida. Half natural size.]
In the north of England, and many other parts of the British Islands,
the Carboniferous Limestone forms, as we have seen, lofty
mountain-masses, to which the term _Mountain Limestone_ is sometimes
applied.
In Derbyshire the formation constitutes rugged, lofty, and
fantastically-shaped mountains, whose summits mingle with the clouds,
while its picturesque character appears here, as well as farther north,
in the _dales_ or valleys, where rich meadows, through which the
mountain streams force their way, seem to be closed abruptly by masses
of rock, rising above them like the grey ruins of some ancient tower;
while the mountain bases are pierced with caverns, and their sides
covered with mosses and ferns, for the growth of which the limestone is
particularly favourable.
The formation is _metalliferous_, and yields rich veins of lead-ore in
Derbyshire, Cumberland, and other counties of Great Britain. The rock is
found in Russia, in the north of France, and in Belgium, where it
furnishes the common marbles, known as Flanders marble (_Marbre de
Flandres_ and _M. de petit granit_). These marbles are also quarried in
other localities, such as Regneville (La Manche), either for the
manufacture of lime or for ornamental stonework; one of the varieties
quarried at Regneville, being black, with large yellow veins, is very
pretty.
In France, the _Carboniferous Limestone_, with its sandstones and
conglomerates, schists and limestones, is largely developed in the
Vosges, in the Lyonnais, and in Languedoc, often in contact with
syenites and porphyries, and other igneous rocks, by which it has been
penetrated and disturbed, and even _metamorphosed_ in many ways, by
reason of the various kinds of rocks of which it is composed. In the
United States the Carboniferous Limestone formation occupies a somewhat
grand position in the rear of the Alleghanies. It is also found forming
considerable ranges in our Australian colonies.
In consequence of their age, as compared with the Secondary and Tertiary
limestones, the Carboniferous rocks are generally more marked and varied
in character. The valley of the Meuse, from Namur to Chockier, above
Liège, is cut out of this formation; and many of our readers will
remember with delight the picturesque character of the scenery,
especially that of the left bank of the celebrated river in question.