During this period _terra firma_ has vastly gained upon the domain of
the sea; furrowed with streams and rivers, and here and there with great
lakes and ponds, the landscape of this period presented the same curious
mixture which we have noted in the preceding age, that is to say, a
combination of the vegetation of the primitive ages with one analogous
to that of our own times. Alongside the birch, the walnut, the oak, the
elm, and the alder, rise lofty palm-trees, of species now extinct, such
as _Flabellaria_ and _Palmacites_; with many evergreen trees (Conifers),
for the most part belonging to genera still existing, as the _firs_, the
_pines_, the _yews_, the _cypresses_, the _junipers_, and the _thuyas_
or tree of life.
The _Cupanioides_, among the Sapindaceæ; the _Cucumites_, among the
Cucurbitaceæ (species analogous to our bryony), climb the trunks of
great trees, and hang in festoons of aerial garlands from their
branches.
The Ferns were still represented by the genera _Pecopteris_, by the
_Tæniopteris_, _Asplenium_, _Polypodium_. Of the mosses, some
_Hepaticas_ formed a humble but elegant and lively vegetation alongside
the terrestrial and frequently ligneous plants which we have noted.
_Equiseta_ and _Charæ_ would still grow in marshy places and on the
borders of rivers and ponds.
It is not without some surprise that we observe here certain plants of
our own epoch, which seem to have had the privilege of ornamenting the
greater watercourses. Among these we may mention the Water Caltrop,
_Trapa natans_, whose fine rosettes of green and dentated leaves float
so gracefully in ornamental ponds, supported by their spindle-shaped
petioles, its fruit a hard coriaceous nut, with four horny spines, known
in France as _water-chestnuts_, which enclose a farinaceous grain not
unpleasant to the taste; the pond-weed, _Potamogeton_, whose leaves form
thick tufts of green, affording food and shelter to the fishes;
_Nympheaceæ_, which spread beside their large round and hollow leaves,
so admirably adapted for floating on the water, now the deep-yellow
flowers of the _Nenuphar_ now the pure white flowers of the _Nymphæa_.
Listen to Lecoq, as he describes the vegetation of the period:--“The
Lower Tertiary period,” he says, “constantly reminds us of the tropical
landscapes of the present epoch, in localities where water and heat
together impress on vegetation a power and majesty unknown in our
climates. The Algæ, which have already been observed in the marine
waters at the close of the Cretaceous period, represented themselves
under still more varied forms, in the earlier Tertiary deposits, when
they have been formed in the sea. Hepaticas and Mosses grew in the more
humid places; many pretty Ferns, as _Pecopteris_, _Tæniopteris_, and the
_Equisetum stellare_ (Pomel) vegetated in cool and humid places. The
fresh waters are crowded with _Naiades_, _Chara_, _Potamogeton_,
_Caulinites_, with _Zosterites_, and with _Halochloris_. Their leaves,
floating or submerged, like those of our aquatic plants, concealed
legions of Molluscs whose remains have also reached us.
“Great numbers of Conifers lived during this period. M. Brongniart
enumerates forty-one different species, which, for the most part, remind
us of living forms with which we are familiar--of Pines, Cypresses,
Thuyas, Junipers, Firs, Yews, and Ephedra. Palms mingled with these
groups of evergreen trees; the _Flabellaria Parisiensis_ of Brongniart,
_F. raphifolia_ of Sternberg, _F. maxima_ of Unger; and some
_Palmacites_, raised their widely-spreading crowns near the magnificent
_Hightea_; Malvaceæ, or _Mallows_, doubtless arborescent, as many among
them, natives of very hot climates, are in our days.
“Creeping plants, such as the _Cucumites variabilis_ (Brongn.), and the
numerous species of _Cupanioïdes_--the one belonging to the
Cucurbitaceæ, and the other to the Sapindaceæ--twined their slender
stems round the trunks, doubtless ligneous, of various Leguminaceæ.
“The family of Betulaceæ of the order Cupuliferæ show the form, then
new, of _Quercus_, the Oak; the Juglandeæ, and Ulmaceæ mingle with the
Proteaceæ, now limited to the southern hemisphere. _Dermatophyllites_,
preserved in amber, seem to have belonged to the family of the Ericineæ,
and _Tropa Arcturæ_ of Unger, of the group Œnothereæ, floated on the
shallow waters in which grew the _Chara_ and the _Potamogeton_.
“This numerous flora comprises more than 200 known species, of which 143
belonged to the Dicotyledons, thirty-three to the Monocotyledons, and
thirty-three to the Cryptogams.
“Trees predominate here as in the preceding period, but the great
numbers of aquatic plants of the period are quite in accordance with the
geological facts, which show that the continents and islands were
intersected by extensive lakes and inland seas, while vast marine bays
and arms of the sea penetrated deeply into the land.”
[Illustration: Fig. 149.--Branch of Eucalyptus restored.]
It is moreover a peculiarity of this period that the whole of Europe
comprehended a great number of those plants which are now confined to
Australasia, and which give so strange an aspect to that country, which
seems, in its vegetation, as in its animals, to have preserved in its
warm latitudes the last vestiges of the organic creations peculiar to
the primitive world. As a type of dicotyledonous trees of the epoch, we
present here a restored branch of _Eucalyptus_ (Fig. 149), with its
flowers. All the family of the Proteaceæ, which comprehends the
_Banksia_, the _Hakea_, the _Gerilea protea_, existed in Europe during
the Tertiary period. The family of Mimosas, comprising the _Acacia_ and
_Inga_, which in our age are only natives of the southern hemisphere,
abounded in Europe during the same geological period. A branch of
_Banksia_, with its fructification, taken from impressions discovered in
rocks of the period, is represented in Fig. 150--it is different from
any species of Banksia living in our days.
[Illustration: Fig. 150.--Fruit-branch of Banksia restored.]
Mammals, Birds, Reptiles, Fishes, Insects, and Molluscs, form the
terrestrial fauna of the Eocene period. In the waters of the lakes,
whose surfaces are deeply ploughed by the passage of large Pelicans,
lived Molluscs of varied forms, as _Physa_, _Limnæa_, _Planorbis_; and
Turtles swam about, as _Trionyx_ and the _Emides_. Snipes made their
retreat among the reeds which grew on the shore; sea-gulls skimmed the
surface of the waters or ran upon the sands; owls hid themselves in the
cavernous trunks of old trees; gigantic buzzards hovered in the air,
watching for their prey; while heavy crocodiles slowly dragged their
unwieldy bodies through the high marshy grasses. All these terrestrial
animals have been discovered in England or in France, alongside the
overthrown trunks of palm-trees. The temperature of these countries was
then much higher than it is now. The Mammals which lived under the
latitudes of Paris and London are only found now in the warmest
countries of the globe.
The Pachyderms (from the Greek παχυς, _thick_, δερμα, _skin_) seem to
have been amongst the earliest Mammals which appeared in the Eocene
period, and they held the first rank from their importance in number of
species as well as in size. Let us pause an instant over these
Pachyderms. Their predominance over other fossil Mammals, which exceed
considerably the number now living, is a fact much insisted on by
Cuvier. Among them were a great number of intermediate forms, which we
seek for in vain in existing genera. In fact, the Pachyderms are
separated, in our days, by intervals of greater extent than we find in
any other mammalian genera; and it is very curious to discover among the
animals of the ancient world the broken link which connects the chain of
these beings, which have for their great tomb the plaster-quarries of
Paris, Montmartre and Pantin being their latest refuge.
Each block taken from those quarries encloses some fragment of a bone of
these Mammals; and how many millions of these bones had been destroyed
before attention was directed to the subject! The _Palæotherium_ and the
_Anoplotherium_ were the first of these animals which Cuvier restored;
and subsequent discoveries of other fragments of the same animals have
only served to confirm what the genius of the great naturalist divined.
His studies in the quarries of Montmartre gave the signal, as they
became the model, for similar researches and restorations of the animals
of the ancient world, all over Europe--researches which, in our age,
have drawn geology from the state of infancy in which it languished, in
spite of the magnificent and persevering labours of Steno, Werner,
Hutton, and Saussure.
[Illustration: Fig. 151.--Palæotherium magnum restored.]
The _Palæotherium_, _Anoplotherium_, and _Xiphodon_ were herbivorous
animals, which must have lived in great herds. They appear to have been
intermediate, according to their organisation, between the Rhinoceros,
the Horse, and the Tapir. There seem to have existed many species of
them, of very different sizes. After the labours of Cuvier, nothing is
easier than to represent the _Palæotherium_ as it lived: the nose
terminating in a muscular fleshy trunk, or rather snout, somewhat like
that of the Tapir; the eye small, and displaying little intelligence;
the head enormously large; the body squat, thick, and short; the legs
short and very stout; the feet supported by three toes, enclosed in a
hoof; the size, that of a large horse. Such was the great Palæotherium,
peaceful flocks of which must have inhabited the valleys of the plateau
which surrounds the ancient basin of Paris; in the lacustrine formations
of Orleans and Argenton; in the Tertiary formations of Issil and
Puy-en-Velay, in the department of the Gironde; in the Tertiary
formations near Rome; and in the beds of limestone[82] at the quarries
of Binsted, in the Isle of Wight. Fig. 151 represents the great
Palæotherium, after the design, in outline, given by Cuvier in his work
on _fossil bones_.
[82] This limestone belongs to the Bembridge beds, and forms part of
the Fluvio-marine series. See “Survey Memoir on the Geology of
the Isle of Wight,” by H. W. Bristow.
[Illustration: Fig. 152.--Skull of Palæotherium magnum.]
The discovery and re-arrangement of these and other forms, now swept
from the face of the globe, are the noblest triumphs of the great French
zoologist, who gathered them, as we have seen, from heaps of confused
fragments, huddled together pell-mell, comprising the bones of a great
many species of animals of a former age of the world, all unknown within
the historic period. The generic characters of Palæotherium give them
forty-four teeth, namely, twelve _molars_, two _canines_, and
twenty-eight others, three toes, a short proboscis, for the attachment
of which the bones of the nose were shortened, as represented in Fig.
153, leaving a deep notch below them. The molar teeth bear considerable
resemblance to those of the Rhinoceros. In the structure of that part of
the skull intended to support the short proboscis, and in the feet, the
animal seems to have resembled the Tapir.
[Illustration: Fig. 153.--Skeletons of the Palæotherium magnum (_a_) and
minimum (_b_) restored.]
The geological place of the extinct Palæotherium seems to have been in
the first great fresh-water formation of the Eocene period, where it is
chiefly found with its allies, of which several species have been found
and identified by Cuvier. Dr. Buckland is not singular in thinking that
they lived and died on the margins of lakes and rivers, as the
Rhinoceros and Tapir do now. He is also of opinion that some retired
into the water to die, and that the dead carcases of others may have
been drifted into the deeper parts in seasons of flood.
The _Palæotherium_ varied greatly in size, some species being as large
as the Rhinoceros, while others ranged between the size of the Horse and
that of a Hog or a Roe. The smaller Palæotherium resembled the Tapir.
Less in size than a Goat, with slim and light legs, it must have been
very common in the north of France, where it would browse on the grass
of the wild prairies. Another species, the _P. minimum_, scarcely
exceeded the Hare in size, and it probably had all the lightness and
agility of that animal. It lived among the bushy thickets of the
environs of Paris, in Auvergne, and elsewhere.
All these animals lived upon seeds and fruits, on the green twigs, or
subterranean stems, and the succulent roots of the plants of the period.
They generally frequented the neighbourhood of fresh water.
[Illustration: Fig. 154.--Anoplotherium commune. One-twentieth natural
size.]
The _Anoplotherium_ (from ανοπλος, _defenceless_, θηριον, _animal_), had
the posterior molar teeth analogous to those of the Rhinoceros, the feet
terminating in two great toes, forming an equally divided hoof, like
that of the Ox and other Ruminants, and the tarsus of the toes nearly
like those of the Camel. It was about the size of the Ass; its head was
light; but what would distinguish it most must have been an enormous
tail of at least three feet in length, and very thick at its junction
with the body. This tail evidently served it as a rudder and propeller
when swimming in the lakes or rivers, which it frequented, not to seize
fish (for it was strictly herbivorous), but in search of roots and stems
of succulent aquatic plants. “Judging from its habits of swimming and
diving,” says Cuvier, “the Anoplotherium would have the hair smooth,
like the otter; perhaps its skin was even half naked. It is not likely
either that it had long ears, which would be inconvenient in its aquatic
kind of life; and I am inclined to think that, in this respect, it
resembled the Hippopotamus and other quadrupeds which frequent the water
much.” To this description Cuvier had nothing more to add. His memoir
upon the _pachydermatous fossils_ of Montmartre is accompanied by a
design in outline of _Anoplotherium commune_, which has been closely
followed in Fig. 154.
There were species of Anoplotherium of very small size. _A. leporinum_
(or the Hare-Anoplotherium), whose feet are evidently adapted for speed;
_A. minimum_ and _A. obliquum_ were of still smaller dimensions; the
last, especially, scarcely exceeded the size of a rat. Like the
Water-rats, this species inhabited the banks of brooks and small rivers.
[Illustration: Fig. 155.--Xiphodon gracile.]
The _Xiphodon_ was about three feet in height at the withers, and
generally about the size of the Chamois, but lighter in form, and with a
smaller head. In proportion as the appearance of the _Anoplotherium
commune_ was heavy and sluggish, so was that of _Xiphodon gracile_
graceful and active; light and agile as the Gazelle or the Goat, it
would rapidly run round the marshes and ponds, depasturing on the
aromatic herbs of the dry lands, or browsing on the sprouts of the young
shrubs. “Its course,” says Cuvier, in the memoir already quoted, “was
not embarrassed by a long tail; but, like all active herbivorous
animals, it was probably timid, and with large and very mobile ears,
like those of the stag, announcing the slightest approach of danger.
Neither is there any doubt that its body was covered with short smooth
hair; and consequently we only require to know its colour in order to
paint it as it formerly existed in this country, where it has been dug
up after so many ages.” Fig. 155 is a reproduction from the design in
outline with which Cuvier accompanied the description of this animal,
which he classes with the Anoplotherium, and which has received in our
days the name of _Xiphodon gracile_.
The gypsum-quarries of the environs of Paris include, moreover, the
remains of other Pachyderms: the _Chæropotamus_, or River-hog (from
χοιρος ποταμος), which has some analogy with the living Pecari, though
much larger; the _Adapis_, which reminds us, in its form, of the
Hedgehog, of which, however, it was three times the size. It seems to
have been a link between the Pachyderms and the Insectivorous Carnivora.
The _Lophiodon_, the size of which varied with the species, from that of
the Rabbit to that of the Rhinoceros, was still more closely allied to
the Tapir than to the Anoplotherium; it is found in the lower beds of
the gypseous formation, that is to say in the “Calcaire Grossier.”
A Parisian geologist, M. Desnoyers, librarian of the Museum of Natural
History there, has discovered in the gypseous beds of the valley of
Montmorency, and elsewhere in the neighbourhood of Paris, as at Pantin,
Clichy, and Dammartin, the imprints of the footsteps of some Mammals, of
which there seems to be some question, especially with regard to the
Anoplotherium and Palæotherium. Footprints of Turtles, Birds, and even
of Carnivora, sometimes accompany these curious traces, which have a
sort of almond-shape more or less lobed, according to the divisions of
the hoof of the animal, and which recall to mind completely, in their
mode of production and preservation, those imprints of the steps of the
Labyrinthodon which have been mentioned as occurring in rocks of the
Triassic period. This discovery is interesting, as it furnishes a means
of comparison between the imprints and the animals which have produced
them. It brings into view, as it were, the material traces left in their
walks upon the soil by animals now annihilated, but who once occupied
the mysterious sites of an earlier world. (See Fig. 1, p. 12.)
It is interesting to picture in imagination the vast pasturages of the
Tertiary period swarming with Herbivora of all sizes. The country now
surrounding the city of Paris belongs to the period in question, and not
far from its gates, the woods and plains were crowded with “game” of
which the Parisian sportsman little dreams, but which would nevertheless
singularly animate the earth at this distant epoch. The absence of great
Carnivora explains the rapid increase of the agile and graceful denizens
of the wood, whose race seems to have been so multiplied then, but which
was ultimately annihilated by the ferocious beasts of prey which
afterwards made their appearance.
The same novelty, riches, and variety which distinguished the Mammals of
the Tertiary period extended to other classes of animals. The class of
Birds, of which we can only name the most remarkable, was represented by
the curious fossil known as the “_Bird of Montmartre_.” The bones of
other birds have been obtained from Hordwell, as well as the remains of
quadrupeds. Among the latter the _Hyænodon_, supposed to be the oldest
known example of a true carnivorous animal in the series of British
fossils, and the fossil Bat known as the _Vespertilio Parisiensis_.
Among Reptiles the Crocodile, which bears the name of Isle of Wight
Alligator, _Crocodilus Toliapicus_. Among the Turtles the _Trionyx_, of
which there is a fine specimen in the Museum of Natural History in Paris
(Fig. 156).
[Illustration: Fig. 156.--Trionyx, or Turtle, of the Tertiary period.]
In the class Fishes we now see the _Pleuronectes_, or flat-fish, of
which _Platax altissimus_ and _Rhombus minimus_ are well-known examples.
Among the Crustaceans we see the earliest crabs. At the same time
multitudes of new Mollusca make their appearance: _Oliva_, _Triton_,
_Cassis_, _Harpa_, _Crepidula_, &c.
[Illustration: XXIII.--Ideal Landscape of the Eocene Period.]
The hitherto unknown forms of _Schizaster_ are remarkable among
Echinoderms; the Zoophytes are also abundant, especially the
_Foraminifera_, which seem to make up by their numbers for their
deficiency in size. It was in this period, in the bosom of its seas, and
far from shore, that the _Nummulites_ existed, whose calcareous
envelopes play such a considerable part as the elements of some of the
Tertiary formations. The shelly agglomerates of these Protozoan
Rhizopods constitute now very important rocks. The Nummulitic limestone
forms, in the chain of the Pyrenees, entire mountains of great height;
in Egypt it forms strata of considerable extent, and it is of these
rocks that the ancient pyramids were built. What an enormous time must
have been necessary to convert the remains of these little shells into
beds many hundreds of feet thick! The _Miliola_ were also so abundant in
the Eocene seas as to constitute the greater part of calcareous
rocks[83] out of which Paris has been built. Agglomerated in this
manner, these little shells form the continuous beds of limestone which
are quarried for building purposes in the environs of Paris, at
Gentilly, Vaugirard, and Châtillon.
[83] Similar beds of Miliolite limestone are found in the Middle
Bagshot beds on the coast of Sussex, off Selsey--the only
instance in England of the occurrence of such calcareous deposits
of Middle Eocene age.--H. W. B.
* * * * *
On the opposite page we present, in PLATE XXIII., an imaginary landscape
of the Eocene period. We remark amongst its vegetation a mixture of
fossil species with others belonging to the present time. The Alders,
the Wych-elms, and the Cypresses, mingle with _Flabellaria_; the Palms
of extinct species. A great Bird--a wader, the _Tantalus_--occupies the
projecting point of a rock on the right; the Turtle (_Trionyx_), floats
on the river, in the midst of Nymphæas, Nenuphars, and other aquatic
plants; whilst a herd of Palæotheria, Anoplotheria, and Xiphodon
peacefully browse the grass of the natural meadows of this peaceful
oasis.
With a general resemblance in their fossils, nothing can be more
dissimilar, on the whole, than the lithological or mineral characters of
the Eocene deposits of France and England; “those of our own island,”
says Lyell,[84] “being almost exclusively of mechanical
origin--accumulations of mud, sand, and pebbles; while in the
neighbourhood of Paris we find a great succession of strata composed of
limestones, some of them siliceous, and of crystalline gypsum and
siliceous sandstone, and sometimes of pure flint used for millstones.
Hence it is by no means an easy task to institute an exact comparison
between the various members of the English and French series. It is
clear that, on the sites both of Paris and London, a continual change
was going on in the fauna and flora by the coming in of new species and
the dying out of others; and contemporaneous changes of geographical
conditions were also in progress in consequence of the rising and
sinking of the land and bottom of the sea. A particular subdivision,
therefore, of time was occasionally represented in one area by land, in
another by an estuary, in a third by sea; and even where the conditions
were in both areas of a marine character, there was often shallow water
in one, and deep sea in another, producing a want of agreement in the
state of animal life.” The Eocene rocks, as developed in France and
England, may be tabulated as follows, in descending order:--
[84] “Elements of Geology,” p. 292.
English. French.
/ \ / Calcaire de la Beauce.
| Hempstead beds. | \ Grès de Fontainebleau.
| |
Upper Eocene. < | / Calcaire silicieux or
| Bembridge beds. >Fluvio-marine< Calcaire Lacustre
| | series. | Moyen. Gypseous
\ | \ series of Montmartre.
|
/ Osborne beds. | / Grès de Beauchamp
| Headon beds. / \ and Calcaire Marin.
|
| Upper Bagshot sand. Upper Sables Moyens.
|
Middle Eocene.< / Lower Sables Moyens,
| Barton clay. \ Middle < Lower Calcaire
| Bracklesham beds. / Bagshot. | Grossier, and
| \ Glauconie Grossière.
|
| Lower Bagshot / Lits coquillières.
\ beds. \ Glauconie Moyenne.
/ London clay. Wanting.
|
| Woolwich and \ / Argile Plastique.
| Reading beds, or > \ Glauconie Inférieure.
Lower Eocene. < Plastic clay. /
|
| Oldhaven beds.
|
\ Thanet sands. Sables Inférieurs.
The Woolwich and Reading Beds, or the Plastic Clay of older writers,
consists of extensive beds of sand with occasional beds of potter’s
clay, which lie at the base of the Tertiary formation in both England
and France. Generally variegated, sometimes grey or white, it is
employed as a potter’s earth in the manufacture of delf-ware.
In England the red-mottled clay of the Woolwich and Reading Beds in
Hampshire and the Isle of Wight is often seen in contact with the chalk;
but in the south-eastern part of the London basin, Mr. Prestwich shows
that the Thanet Sand (consisting of a base of fine, light-coloured sand,
mixed with more or less argillaceous matter) intervenes between the
Chalk and the Oldhaven Beds, or in their absence the Woolwich and
Reading beds, which lie below the London Clay. The Thanet Sands derive
their name from their occurrence in the Isle of Thanet, in Kent, in the
eastern part of which county they attain their greatest development.
Under London and its southern suburbs the Thanet sand is from thirteen
to forty-four feet thick, but it becomes thinner in a westerly
direction, and does not occur beyond Ealing.[85]
[85] “Memoir of the Geological Survey of Great Britain. The Geology of
Middlesex, &c.;” by W. Whitaker, p. 9.
The Woolwich and Reading beds in the Hampshire basin rest immediately on
the Chalk, and separate it from the overlying London Clay, as may be
seen in the fine exposure of the Tertiary strata in Alum Bay, at the
western extremity of the Isle of Wight, and in Studland Bay, on the
western side of the Isle of Purbeck, in Dorsetshire.
In the London basin the Woolwich and Reading beds also rest on the
Chalk, where the Thanet Sands are absent, as is the case, for the most
part, over the area west of Ealing and Leatherhead.
The beds in question are very variable in character, but may be
generally described as irregular alternations of clays and sands--the
former mostly red, mottled with white, and from their plastic nature
suitable for the purposes of the potter; the latter also of various
colours, but sometimes pure white, and sometimes containing pebbles of
flint.
The Woolwich and Reading beds are called after the localities of the
same names; they are fifty feet thick at Woolwich, and from sixty to
seventy feet at Reading.
The Oldhaven beds (so termed by Mr. W. Whitaker from their development
at the place of the same name in Kent) are a local deposit, occurring
beneath the London Clay on the south side of the London basin, from
Croydon eastward, at the most eastern part of Surrey, and through
Kent--in the north-western corner of which county they form some
comparatively broad tracts. The beds consist of rounded flint pebbles,
in a fine sandy base, or of fine light-coloured sand, and are from
eighty to ninety feet thick under London.
The London Clay, which has a breadth of twenty miles or more about
London, consists of tenacious brown and bluish-grey clay, with layers of
the nodular concretions, called Septaria, which are well known on the
Essex and Hampshire coasts, where they are collected for making Roman
cement. The London Clay has a maximum thickness of nearly 500 feet. The
fossils of the London Clay are of marine genera, and very plentiful in
some districts. Taken altogether they seem to indicate a moderate,
rather than a tropical climate, although the Flora is, as far as can be
judged, certainly tropical in its affinities.[86] The number of species
of extinct Turtles obtained from the Isle of Sheppey alone, is stated by
Prof. Agassiz to exceed that of all the species of Chelone now known to
exist throughout the globe. Above this great bed lie the Bracklesham and
Bagshot beds, which consist of light-yellow sand with an intermediate
layer of dark-green and brown clay, over which lie the Barton Clay (in
the Hampshire basin) and the white Upper Bagshot Sands, which are
succeeded by the Fluvio-marine series comprising the Headon, Bembridge,
and Hempstead series, and consisting of limestones, clays, and marls, of
marine, brackish, and fresh-water origin.[87] For fuller accounts of the
Tertiary strata of England, the reader is recommended to the numerous
excellent memoirs of Mr. Prestwich, to the memoir “On the Tertiary
Fluvio-marine Formations of the Isle of Wight,” by Professor Edward
Forbes, and to the memoir “On the Geology of the London Basin,” by Mr.
W. Whitaker.
[86] Prestwich. _Quart. Jour. Geol. Soc._, vol. x., p. 448.
[87] Detailed sections of the whole of the Tertiary strata of the Isle
of Wight have been constructed by Mr. H. W. Bristow from actual
measurement of the beds in their regular order of succession, as
displayed at Hempstead, Whitecliff Bay, Colwell and Tolland’s
Bays, Headon Hill, and Alum Bay. These sections, published by the
Geological Survey of Great Britain, show the thickness, mineral
character, and organic remains found in each stratum, and are
accompanied by a pamphlet in explanation.
At the base of the _Argile Plastique_ of France is a conglomerate of
chalk and of divers calcareous substances, in which have been found at
Bas-Meudon some remains of Reptiles, Turtles, Crocodiles, Mammals, and,
more lately, those of a large Bird, exceeding the Ostrich in size, the
_Gastornis_, which Professor Owen classes among the wading rather than
among aquatic birds. In the Soissonnais there is found, at the same
horizon, a great mass of lignite, enclosing some shells and bones of the
most ancient Pachyderm yet discovered, the _Coryphodon_, which resembles
at once both the Anoplotherium and the Pig. The _Sables Inférieurs_, or
Bracheux Sands, form a marine bed of great thickness near Beauvais; they
are principally sands, but include beds of calciferous clay and banks of
shelly sandstone, and are considered to be older than the plastic clay
and lignite, and to correspond with the Thanet Sands of England. They
are rich in shells, including many Nummulites. At La Fère, in the
Department of the Aisne, a fossil skull of _Arctocyon primævus_,
supposed to be related both to the Bear and to the Kinkajou, and to be
the oldest known Tertiary Mammal, was found in a deposit of this age.
This series seems to have been formed chiefly in fresh water.
The _Calcaire grossier_, consisting of marine limestones of various
kinds, and with a coarse, sometimes compact, grain, is suitable for
mason-work. These deposits, which form the most characteristic member
of the Paris basin, naturally divide themselves into three groups of
strata, characterised, the first, by _Nummulites_; the second by
_Miliolites_; and the third or upper beds by _Cerithia_. The beds are
also sometimes named Nummulite limestone, Miliolite limestone, and
Cerithium limestone. Above these a great mass, generally sandy, is
developed. It is marine at the base, and there are indications of
brackish water in its upper parts; it is called Beauchamp Sandstone, or
Sables Moyens (_Grès de Beauchamp_). These sands are very rich in
shells. The _siliceous limestone_, or lower travertin, is a compact
siliceous limestone extending over a wide area, and resembles a
precipitate from mineral waters. The _gypseous_ formation consists of a
long series of marly and argillaceous beds, of a greyish, green, or
white colour, in the intervals between which a thick deposit of gypsum,
or sulphate of lime, is intercalated. This gypsum bed is found in its
greatest thickness in France at Montmartre and Pantin near Paris. The
formation of this gypsum is probably due to the action of free sulphuric
acid upon the carbonate of lime of the formation; the sulphuric acid
itself being produced by the transformation of the gaseous masses of
sulphuretted hydrogen emanating from volcanic vents, into that acid, by
the action of air and water. It was, as we have already said, in the
gypsum-quarries of Montmartre that the numerous bones of Palæotherium
and Anoplotherium were found. It is exclusively at this horizon that we
find the remains of these animals, which seem to have been preceded by
the _Coryphodon_, and afterwards by the _Lophiodon_; the order of
succession in the appearance of these animals is now perfectly
established. It may be added that round Paris the Eocene formation, from
its lowest beds to the highest, is composed of beds of plastic clay, of
the _Calcaire grossier_ with its _Nummulites_, _Miliolites_, and
_Alveolites_, followed by the gypseous formation; the series terminating
in the Fontainebleau Sandstone, remarkable for its thickness and also
for its fine scenery, as well as for its usefulness in furnishing
paving-stone for the capital. In Provence the same series of rocks are
continued, and attain an enormous thickness. This upper part of the
Eocene deposit is entirely of lacustrine formation. Grignon has procured
from a single spot, where they were embedded in a calcareous sand, no
less than 400 fossils, chiefly formed of comminuted shells, in which,
however, were well-preserved species both of marine, terrestrial, and
fresh-water shells. Of the Paris basin, Sir Charles Lyell says: “Nothing
is more striking in this assemblage of fossil testacea than the great
proportion of species referable to the genus _Cerithium_. There occur no
less than 137 species of this genus in the Paris basin, and almost all
of them in the _Calcaire grossier_. Most of the living _Cerithia_ (Figs.
157 and 168) inhabit the sea near the mouths of rivers, where the waters
are brackish; so that their abundance in the marine strata now under
consideration is in harmony with the hypothesis that the Paris basin
formed a gulf into which several rivers flowed.”[88]
[88] “Elements of Geology,” p. 300.
To give the reader some idea of the formation, first come the limestones
and lower marls, which contain fine lignite or wood-coal produced from
vegetable matter buried in moist earth, and excluded from all access of
air, a material which is worked in some parts of the south of France as
actively as a coal-mine. In these lignites _Anodon_ and other
fresh-water shells are found.
From the base of Sainte-Victoire to the other side of Aix, we trace a
conglomerate characterised by its red colour, but which dies away in its
prolongation westward. This conglomerate contains land-snails (_Helix_)
of various sizes, mixed with fresh-water shells. Upon this conglomerate,
comprising therein the marls, rests a thick deposit of limestone with
the gypsum of Aix and Manosque, which is believed to correspond with
that of Paris. Some of the beds are remarkably rich in sulphur. The
calcareous marly laminæ which accompany the gypsum of Aix contain
Insects of various kinds, and Fishes resembling _Lebias cephalotes_.
Finally, the whole terminates at Manosque in a fresh series of marls and
sandstones, alternating with beds of limestone with _Limnæa_ and
_Planorbis_. At the base of this series are found three or four beds of
lignite more inflammable than coal, which also give out a very
sulphurous oil. We may form some estimate of the thickness of this last
stage, if we add that, above the beds of fusible lignite, we may reckon
sixty others of dry lignite, some of them capable of being very
profitably worked if this part of Provence were provided with more
convenient roads.
“The Nummulitic formation, with its characteristic fossils,” says
Lyell,[89] “plays a far more conspicuous part than any other Tertiary
group in the solid framework of the earth’s crust, whether in Europe,
Asia, or Africa. It often attains a thickness of many thousand feet, and
extends from the Alps to the Carpathians, and is in full force in the
north of Africa, as, for example, in Algeria and Morocco. It has been
traced from Egypt, where it was largely quarried of old for the building
of the Pyramids, into Asia Minor, and across Persia, by Bagdad, to the
mouth of the Indus. It occurs not only in Cutch, but in the mountain
ranges which separate Scinde from Persia, and which form the passes
leading to Caboul; and it has been followed still further eastward into
India, as far as eastern Bengal and the frontiers of China.”
[89] Ibid., p. 305.
“When we have once arrived at the conclusion,” he adds, “that the
Nummulitic formation occupies a middle place in the Eocene series, we
are struck with the comparatively modern date to which some of the
greatest revolutions in the physical geography of Europe, Asia, and
northern Africa must be referred. All the mountain chains, such as the
Alps, Pyrenees, Carpathians, and Himalayas, into the composition of
whose central and loftiest parts the Nummulitic strata enter bodily,
could have had no existence till after the Middle Eocene period.”
The Eocene strata, Professor Ramsay thinks, extended in their day _much
further_ west, “because,” he says, “here, at the extreme edge of the
chalk escarpments, you find outlying fragments of them,” from which he
argues that they were originally deposited all over the Chalk as far as
these points, but being formed of soft strata they were “denuded”
backwards.
The Beloptera represented in Fig. 195 are curious Belemnite-like
organisms, occurring in Tertiary strata, and evidently the internal bone
of a Cephalopod, having a wing-like projection or process on each side.
As a genus it holds a place intermediate between the Cuttle-fish and the
Belemnite.
[Illustration: Fig. 157.--Cerithium telescopium.
(Living form.)]