The Foraminifera are also represented by new genera, among which are the
Bolivina, Polystomella, and Dentritina.
Finally, the Crustaceans include the genera _Pagurus_ (or the Hermit
crabs); _Astacus_. (the lobster); and _Portunus_ (or paddling crabs). Of
the first, it is doubtful if any fossil species have been found; of the
last, species have been discovered bearing some resemblance to
_Podophthalmus vigil_, as _P. Defrancii_, which only differs from it in
the absence of the sharp spines which terminate the lateral angles of
the carapace in the former; while _Portunus leucodon_ (Desmarest) bears
some analogy to Lupea.
[Illustration: XXIV.--Ideal Landscape of the Miocene Period.]
* * * * *
[Illustration: Fig. 171.--Podophthalmus vigil.]
An ideal landscape of the Miocene period, which is given on the opposite
page (PLATE XXIV.), represents the Dinotherium lying in the marshy
grass, the Rhinoceros, the Mastodon, and an Ape of great size, the
_Dryopithecus_, hanging from the branches of a tree. The products of the
vegetable kingdom are, for the greater part, analogous to those of the
present time. They are remarkable for their abundance, and for their
graceful and serried vegetation; and still remind us in some respects,
of the vegetation of the Carboniferous period. It is, in fact, a
continuation of the characteristics of that period, and from the same
cause, namely, the submersion of land under marshy waters, which has
given birth to a sort of coal which is often found in the Miocene
formation, and which we call _lignite_. This imperfect coal does not
quite resemble that of the Carboniferous, or true Coal-measure period,
because it is of much more recent date, and because it has not been
subjected to the same internal heat, accompanied by the same pressure of
superincumbent strata, which produced the older coal-beds of the Primary
epoch.
[Illustration: Fig. 172.--Lupea pelagica.]
The _lignites_, which we find in the Miocene, as in the Eocene period,
constitute, however, a combustible which is worked and utilised in many
countries, especially in Germany, where it is made in many places to
serve in place of coal. These beds sometimes attain a thickness of above
twenty yards, but in the environs of Paris they form beds of a few
inches only, which alternate with clays and sands. We cannot doubt that
lignites, like true coal, are the remains of the buried forests of an
ancient world; in fact, the substance of the woods of our forests, often
in a state perfectly recognisable, is frequently found in the lignite
beds; and the studies of modern botanists have demonstrated, that the
species of which the lignites are formed, belong to a vegetation
closely resembling that of Europe in the present day.
Another very curious substance is found with the lignite--yellow amber.
It is the mineralised resin, which flowed from certain extinct
pine-trees of the Tertiary epoch; the waves of the Baltic Sea, washing
the amber out of the deposits of sand and clay in which it lies buried,
this substance, being very little heavier than water, is thrown by the
waves upon the shore. For ages the Baltic coast has supplied commerce
with amber. The Phœnicians ascended its banks to collect this beautiful
fossil resin, which is now chiefly found between Dantzic and Memel,
where it is a government monopoly in the hands of contractors, who are
protected by a law making it theft to gather or conceal it.
Amber,[91] while it has lost none of its former commercial value, is,
besides, of much palæontological interest; fossil insects, and other
extraneous bodies, are often found enclosed in the nodules, where they
have been preserved in all their original colouring and integrity of
form. As the poet says--
[91] See Bristow’s “Glossary of Mineralogy,” p. 11.
“The things themselves are neither rich nor rare,
The wonder’s how the devil they got there.”
The natural aromatic qualities of the amber combined with exclusion of
air, &c., have embalmed them, and thus transmitted to our times the
smaller beings and the most delicate organisms of earlier ages.
The Miocene rocks, of marine origin, are very imperfectly represented in
the Paris basin, and their composition changes with the localities. They
are divided into two groups of beds: 1. _Molasse_, or soft clay; 2.
_Faluns_, or shelly marl.
In the Paris basin the _Molasse_ presents, at its base, quartzose sands
of great thickness, sometimes pure, sometimes a little argillaceous or
micaceous. They include beds of sandstone (with some limestone), which
are worked in the quarries of Fontainebleau, d’Orsay, and Montmorency,
for paving-stone for the streets of Paris and the neighbouring towns.
This last formation is altogether marine. To these sands and sandstones
succeeds a fresh-water deposit, formed of a whitish and partly siliceous
limestone, which forms the ground of the plateau of La Beauce, between
the valleys of the Seine and the Loire: this is called the _Calcaire de
la Beauce_. It is there mixed with a reddish and more or less sandy
clay, containing small blocks of burrh-stone used for millstones, easily
recognised by their yellow-ochreous colour, and the numerous cavities
or hollows with which their texture is honeycombed.
This grit, or _silex meulier_, is much used in Paris for the arches of
cellars, underground conduits, sewers, &c.
The _Faluns_ in the Paris basin consist of divers beds formed of shells
and Corals, almost entirely broken up. In many parts of the country, and
especially in the environs of Tours and Bordeaux, they are dug out for
manuring the land. To the Falun series belong the fresh-water marl,
limestone, and sand, which composed the celebrated mound of Sansan, near
Auch, in the Department of Gers, in which M. Lartet found a considerable
number of bones of Turtles, Birds, and especially Mammals, such as
_Mastodon_ and _Dinotherium_, together with a species of long-armed ape,
which he named _Pithecus antiquus_, from the circumstance of its
affording the earliest instance of the discovery of the remains of the
quadrumana, or monkey-tribe, in Europe. Isolated masses of Faluns occur,
also, near the mouth of the Loire and to the south of Tours, and in
Brittany.
[Illustration: Fig. 173.--Caryophylla cyathus.]