The teeth (Fig. 141), which are the most important and characteristic
organs of the whole animal, are imbedded laterally in grooves, or
sockets, in the dentary bone; there are three or four sockets of
successional teeth on the inner side of the base of the old teeth. The
place thus occupied by the edges of the teeth, their trenchant and
saw-like form, their mode of curvature, the points where they become
broader or narrower which turn them into a species of nippers or
scissors--are all suitable for cutting and tearing the tough vegetable
substances which are also found among the remains buried with this
colossal reptile, a restoration of which is represented in PLATE XXI.,
p. 296.
* * * * *
The Cretaceous seas contained great numbers of Fishes, among which some
were remarkable for their strange forms. The _Beryx Lewesiensis_ (1),
and the _Osmeroides Mantelli_ (2) (Fig. 142), are restorations of these
two species as they are supposed to have been in life. The _Odontaspis_
is a new genus of Fishes which may be mentioned. _Ammonites rostratus_
(Fig. 140), and _Exogyra conica_ (Fig. 147), are common shells in the
Upper Greensand.
[Illustration: XXI.--Ideal scene in the Lower Cretaceous Period, with
Iguanodon and Megalosaurus.]
The seas of the Lower Cretaceous period were remarkable in a zoological
point of view for the great number of species and the multiplicity of
generic forms of molluscous Cephalopods. The Ammonites assume quite
gigantic dimensions; and we find among them new species distinguished by
their furrowed transverse spaces, as in the _Hamites_ (Fig. 132). Some
of the _Ancyloceras_ attained the magnitude of six feet, and other
genera, as the _Scaphites_, the _Toxoceras_, the _Crioceras_ (Fig. 125),
and other Mollusca, unknown till this period, appeared now. Many
Echinoderms, or sea-urchins, and Zoophytes, have enriched these rocks
with their animal remains, and would give its seas a condition quite
peculiar.
On the opposite page an ideal landscape of the period is represented
(PLATE XXI.), in which the Iguanodon and Megalosaurus struggle for the
mastery in the centre of a forest, which enables us also to convey some
idea of the vegetation of the period. Here we note a vegetation at once
exotic and temperate--a flora like that of the tropics, and also
resembling our own. On the left we observe a group of trees, which
resemble the dicotyledonous plants of our forests. The elegant
_Credneria_ is there, whose botanical place is still doubtful, for its
fruit has not been found, although it is believed to have belonged to
plants with two seed-leaves, or dicotyledonous, and the arborescent
Amentaceæ. An entire group of trees, composed of Ferns and Zamites, are
in the background; in the extreme distance are some Palms. We also
recognise in the picture the alder, the wych-elm, the maple, and the
walnut-tree, or at least species analogous to these.
* * * * *
The Néocomian beds in France are found in Champagne, in the departments
of the Aube, the Yonne, the Haute-Alps, &c. They are largely developed
in Switzerland at Neufchatel, and in Germany.
1. The Lower Néocomian consists of marls and greyish clay, alternating
with thin beds of grey limestone. It is very thick, and occurs at
Neufchatel and in the Drôme. The fossils are _Spatangus retusus_,
_Crioceras_ (Fig. 125), _Ammonites Asterianus_, &c.
2. _Orgonian_ (the limestone of Orgon). This group exists, also, at
Aix-les-Bains in Savoy, at Grenoble, and generally in the thick, white,
calcareous beds which form the precipices of the Drôme. The fossils
_Chama ammonia_, _Pigaulus_, &c.
3. The _Aptien_ (or Greensand) consists generally of marls and clay. In
France it is found in the department of Vaucluse, at Apt (whence the
name Aptien), in the department of the Yonne, and in the Haute-Marne.
Fossils, _Ancyloceras Matheronianus_, _Ostrea aquila_, and _Plicatula
placunea_. These beds consist here of greyish clay, which is used for
making tiles; there of bluish argillaceous limestone, in black or
brownish flags. In the Isle of Wight it becomes a fine sandstone,
greyish and slightly argillaceous, which at Havre, and in some parts of
the country of Bray, become well-developed ferruginous sandstones.
[Illustration: Fig. 143.--Cypris spinigera.]
[Illustration: Fig. 144.--Cypris Valdensis.]
We have noted that the Lower Néocomian formation, although a marine
deposit, is in some respects the equivalent of the _Weald Clay_, a
fresh-water formation of considerable importance on account of its
fossils. We have seen that it was either formed at the mouth of a great
river, or the river was sufficiently powerful for the fresh-water
current to be carried out to sea, carrying with it some animals, forming
a fluviatile, or lacustrine fauna, on a small scale. These were small
Crustaceans of the genus _Cypris_, with some molluscous Gasteropoda of
the genera _Melania_, _Paludina_, and acephalous Mollusca of the five
genera _Cyrena_, _Unio_, _Mytilus_, _Cyclas_, and _Ostrea_. Of these,
_Cypris spinigera_ (Fig. 143) and _Cypris Valdensis_ (Fig. 144) may be
considered as among the most characteristic fossils of this local fauna.
The Cretaceous series is not interesting for its fossils alone; it
presents also an interesting subject for study in a mineralogical point
of view. The white Chalk, examined under the microscope by Ehrenberg,
shows a curious globiform structure. The green part of its sandstone and
limestone constitutes very singular compounds. According to the result
of Berthier’s analysis, we must consider them as silicates of iron. The
iron shows itself here not in beds, as in the Jurassic rocks, but in
masses, in a species of pocket in the Orgonian beds. They are usually
hydrates in the state of hematites, accompanied by quantities of ochre
so abundant that they are frequently unworkable. In the south of France
these veins were mined to a great depth by the ancient monks, who were
the metallurgists of their age. But for the artist the important
Orgonian beds possess a special interest; their admirable vertical
fractures, their erect perpendicular peaks, each surpassing the other in
boldness, form his finest studies. In the Var, the defiles of Vésubia,
of the Esteron, and Tinéa, are jammed up between walls of peaks, for
many hundreds of yards, between which there is scarcely room for a
narrow road by the side of the roaring torrent. “In the Drôme,” says
Fournet, “the entrance to the beautiful valley of the Vercors is closed
during a part of the year, because, in order to enter, it is necessary
to cross the two gullies, the _Great_ and _Little Goulet_, through which
the waters escape from the valley. Even during the dry season, he who
would enter the gorge must take a foot-bath.
“This state of things could not last; and in 1848 it was curious to see
miners suspended on the sides of one of these lateral precipices, some
450 feet above the torrent, and about an equal distance below the summit
of the Chalk. There they began to excavate cavities or niches in the
face of the rock, all placed on the same level, and successively
enlarged. These were united together in such a manner as to form a road
practicable for carriages; now through a gallery, now covered by a
corbelling, to look over which affords a succession of surprises to the
traveller.
“This is not all,” adds M. Fournet: “he who traverses the high plateaux
of the country finds at every step deep diggings in the soil, designated
pits or _scialets_, the oldest of which have their sides clothed with a
curious vegetation, in which the _Aucolin_ predominates; shelter is
found in these pits from the cutting winds which rage so furiously in
these elevated regions. Others form a kind of cavern, in which a
temperature obtains sufficient to freeze water even in the middle of
summer. These cavities form natural _glaciers_, which we again find upon
some of the table-lands of the Jura.
“The cracks and crevasses of the limestone receive the waters produced
by falling rain and melted snow; true to the laws of all fluid bodies,
they filter through the rocks until they reach the lower and impervious
marly beds, where they form sheets of water, which in course of time
find some outlet through which they discharge themselves. In this manner
subterranean galleries, sometimes of great extent, are formed, in which
are assembled all the marvels which crumbling stalactites, stalagmites,
placid lakes, and headlong torrents can produce; finally, these waters,
forcing their way through the external orifices, give rise to those fine
cascades which, with the first gushing torrent, form an actual river.”
The _Albien_ of Alc. D’Orbigny, which Lyell considers to be the
equivalent of the _Gault_, French authors treat as the “_glauconie_”
formation, the name being drawn from a rock composed of chalk with
greenish grains of _glauconite_, or silicate of iron, which is often
mixed with the limestone of this formation. The fossils by which it is
identified are very varied. Among its numerous types, we find
Crustaceans belonging to the genera _Arcania_ and _Corystes_; many new
Mollusca, _Buccinum_, _Solen_, _Pterodonta_, _Voluta_, _Chama_, &c.;
great numbers of molluscous Brachiopods, forming highly-developed
submarine strata; some Echinoderms, unknown up to this period, and
especially a great number of Zoophytes; some Foraminifera, and many
Polyzoa (Bryozoa). The glauconitic formation consists of two groups of
strata: the _Gault_ Clay and the _glauconitic_ chalk, or Upper Greensand
and Chloritic Marl.