[Footnote 19: A singular fossil has been described by Professor Martin Duncan and Mr Jenkins from the Carboniferous rocks under the name of Palœocoryne, and has been referred to the Hydroid Zoophytes (Corynida). Doubt, however, has been thrown by other observers on the correctness of this reference.]
Amongst the Echinoderms, by far the most important forms
are the Sea-lilies and the Sea-urchins—the former from their
great abundance, and the latter from their singular structure; but
the little group of the "Pentremites" also requires to be noticed.
The Sea-lilies are so abundant in the Carboniferous rocks, that it
has been proposed to call the earlier portion of the period the
"Age of Crinoids." Vast masses of the limestones of the period are
"crinoidal," being more or less extensively composed of the broken
columns, and detached plates and joints of Sea-lilies, whilst
perfect "heads" may be exceedingly rare and difficult to procure.
In North America the remains of Crinoids are even more abundant
at this horizon than in Britain, and the specimens found seem
to be commonly more perfect. The commonest of the Carboniferous
Crinoids belong to the genera Cyathocrinus, Actinocrinus,
Platycrinus, (fig. 117), Poteriocrinus, Zeacrinus,
Fig. 117.—Platycrinus tricontadactylus, Lower
Carboniferous. The left-hand figure shows the calyx, arms, and
upper part of the stem; and the figure next this shows the surface
of one of the joints of the column. The right-hand figure shows
the proboscis. (After M'Coy.)
and Forbesiocrinus. Closely allied to the Crinoids, or
forming a kind of transition
between these and the Cystideans, is the
little group of the "Pentremites," or Blastoids (fig. 118).
This group is first known to have commenced its existence in
Fig. 118.—A, Pentremites pyriformis, side-view of the
body ("calyx"); B, The same viewed from below, showing the
arrangement of the plates; C, Body of Pentremites conoideus,
viewed from above. Carboniferous.
the Upper Silurian, and it increased considerably in numbers in
the Devonian; but it was in the seas of the Carboniferous period
that it attained its maximum, and no certain representative of the
family has been detected in any later deposits. The "Pentremites"
resemble the Crinoids in having a cup-shaped body (fig. 118, A)
enclosed by closely-fitting calcareous plates, and supported on
a short stem or "column," composed of numerous calcareous pieces
flexibly articulated together. They differ from the Crinoids,
however, in the fact that the upper surface of the body does
not support the crown of branched feathery "arms," which are
so characteristic of the latter. On the contrary, the summit of
the cup is closed up in the fashion of a flower-bud, whence the
technical name of Blastoidea applied to the group (Gr.
blastos, a bud; eidos, form). From the top of the
cup radiate five broad, transversely-striated areas (fig. 118, C),
each with a longitudinal groove down its middle; and along each
side of each of
these grooves there seems to have been attached a row of short
jointed calcareous filaments or "pinnules."
A few Star-fishes and Brittle-stars are known to occur in the
Carboniferous rocks; but the only other Echinodemls of this period
which need be noticed are the Sea-urchins (Echinoids).
Detached plates and spines of these are far from rare in the
Carboniferous deposits; but anything like perfect specimens are
exceedingly scarce. The Carboniferous Sea-urchins agree with those
of the present day in having the body enclosed in a shell formed
by an enormous number of calcareous plates articulated together.
The shell may be regarded as, typically, nearly spherical in
shape, with the mouth in the centre of the base, and the excretory
opening or vent at its summit. In both the ancient forms and the
recent ones, the plates of the shell are arranged in ten zones
Fig. 119.—Palœchinus ellipticus, one of the
Carboniferous Sea-urchins. The left-hand figure shows one of the
"ambulacral areas" enlarged, exhibiting the perforated plates.
The right-land figure exhibits a single plate from one of the
"inter-ambulacral areas." (After M'Coy.)
which generally radiate from the summit to the centre of the base. In
five of these zones—termed the "ambulacral areas"—the
plates are perforated by minute apertures or "pores," through which
the animal can protrude the little water-tubes ("tube-feet") by which
its locomotion is carried on. In the other five zones—the
so-called "inter-ambulacral areas"—the plates are of larger
size, and are not perforated by any apertures. In all the modern
Sea-urchins each of these ten zones, whether perforate or imperforate,
is composed of two rows of plates; and there are thus twenty rows of
plates in all. In the Palæozoic Sea-urchins, on the other hand,
the "ambulacral areas" are often like those of recent forms, in
consisting of two rows of perforated plates (fig. 119); but
the "inter-ambulacral areas" are always quite
peculiar in consisting each of three, four, five, or more rows of large
imperforate plates, whilst there are sometimes four or ten rows of
plates in the "ambulacral areas" also: so that there are many more than
twenty rows of plates in the entire shell. Some of the Palæozoic
Sea-urchins, also, exhibit a very peculiar singularity of structure
which is only known to exist in a very few recently-discovered
modern forms (viz., Calveria and Phormosoma). The
plates of the inter-ambulacral areas, namely, overlap one another
in an imbricating manner, so as to communicate a certain amount
of flexibility to the shell; whereas in the ordinary living forms
these plates are firmly articulated together by their edges,
and the shell forms a rigid immovable box. The Carboniferous
Sea-urchins which exhibit this extraordinary peculiarity belong
to the genera Lepidechinus and Lepidesthes, and
it seems tolerably certain that a similar flexibility of the
shell existed to a less degree in the much more abundant genus
Archœocidaris. The Carboniferous Sea-urchins, like
the modern ones, possessed movable spines of greater or less
length, articulated to the exterior of the shell; and these
structures are of very common occurrence in a detached condition.
The most abundant genera are Archœocidaris and
Palœchinus; but the characteristic American forms
belong principally to Melonites, Oligoporus, and
Lepidechinus.
Amongst the Annelides it is only necessary to notice the
little spiral tubes of Spirorbis Carbonarius (fig. 120),
Fig. 120.—Spirorbis (Microconchus) Carbonarius, of
the natural size, attached to a fossil plant, and magnified.
Carboniferous Britain and North America. (After Dawson.)
which are commonly found attached to the leaves or stems of the
Coal-plants. This fact shows that though the modern species of
Spirorbis are inhabitants of the sea, these old
representatives of the genus must have been capable of living
in the brackish waters of lagoons and estuaries.
The Crustaceans of the Carboniferous rocks are numerous,
and belong partly to structural types with which we are already
familiar, and partly to higher groups which come into existence
here for the first time. The gigantic Eurypterids of the
Upper Silurian and Devonian are but feebly represented, and make
their final exit here from the scene of life. Their place, however,
is taken by peculiar forms belonging to the allied group of the
Xiphosura, represented at the present day by the King-crabs
or "Horse-shoe Crabs" (Limulus). Characteristic forms of this
group appear in the Coal-measures both of Europe and America; and
though constituting three distinct genera (Prestwichia, Belinurus,
and Euproöps), they are all nearly related to one
another. The best known of them, perhaps, is the Prestwichia
rotundala of Coalbrookdale, here figured (fig. 121). The ancient
Fig. 121.—Prestwichia rotundata, a Limuloid Crustacean.
Coal-measures, Britain. (After Henry Woodward.)
and formerly powerful order of the Trilobites also undergoes
its final extinction here, not surviving the deposition of the
Carboniferous Limestone series in Europe, but extending its range
in America into the Coal-measures. All the known Carboniferous forms
are small in size and degraded in point of structure, and they are
referable to but three genera (Phillipsia, Griffithides,
and Brachymetopus), belonging to a single family. The
Phillipsia seminifera here figured (fig. 122, a)
is a characteristic species in the Old World. The Water-fleas
(Ostracoaa) are extremely abundant in the Carboniferous
rocks, whole strata being often made up of little else than the
little bivalved shells of these Crustaceans. Many of them are
extremely small, averaging about the size of a millet-seed; but
a few forms, such as Entomoconchus Scouleni (fig. 122,
c), may attain a length of from one to three quarters of
an inch. The old group of the Phyllopods is is likewise
still represented in some abundance, partly by tailed forms of a
shrimp-like appearance, such as Dithyrocaris (fig. 122,
d), and partly by the curious striated Estheriœ
and their allies, which present a curious
resemblance to the true Bivalve Molluscs (fig. 122, b).
Lastly, we meet for the first time in the Carboniferous rocks
with the remains of the highest of all the groups of
Crustaceans—namely, the so-called "Decapods," in
which there are five pairs of walking-limbs, and the hinder end
of the body ("abdomen") is composed of separate rings, whilst
the anterior end is covered by a head-shield or "carapace." All
the Carboniferous Decapods hitherto discovered resemble the
existing Lobsters, Prawns, and
Fig. 122.—Crustaceans of the Carboniferous Rocks. a,
Phillipsia seminifera, of the natural size—Mountain
Limestone, Europe; b, One valve of the shell of Estheria
tenella, of the natural size and enlarged—Coal-measures,
Europe; c, Bivalved shell of Entomoconchus Scouleri,
of the natural size—Mountain Limestone, Europe; d,
Dithyrocaris Scouleri, reduced in size—Mountain Limestone,
Ireland; e, Palœocaris typus, slightly
enlarged—Coal-measures, North America; f,
Anthrapalœmon gracilis, of the natural
size—Coal-measures, North America. (After De Koninck, M'Coy,
Rupert Jones, and Meek and Worthen.)
Shrimps (the Macrura), in having a long and well-developed
abdomen terminated by an expanded tail-fin. The Palœocaris
typus (fig. 122, e) and the Anthrapalœmon
gracilis (fig. 122, f), from the Coal-measures of
Illinois, are two of the best understood and most perfectly
preserved of the few known representatives of the "Long-tailed"
Decapods in the Carboniferous series. The group of the Crabs or
"Short-tailed"
Decapods (Brachyura), in which the abdomen is short, not
terminated by a tail-fin, and tucked away out of sight beneath
the body, is at present not known to be represented at all in
the Carboniferous deposits.
In addition to the water-inhabiting group of the Crustaceans, we
find the articulate animals to be represented by members belonging
to the air-breathing classes of the Arachnida, Myriapoda,
and Insecta. The remains of these, as might have been
expected, are not known to occur in the marine limestones of the
Carboniferous series, but are exclusively found in beds associated
with the Coal, which have been deposited in lagoons, estuaries, or
marshes, in the immediate vicinity of the land, and which actually
represent an old land-surface. The Arachnids are at present
the oldest known of their class, and are represented both by true
Spiders and Scorpions. Remains of the latter (fig. 123) have been
found both in the Old and New Worlds, and indicate the existence
Fig. 123.—Cyclophthalmus senior. A fossil Scorpion
from the Coal-measures of Bohemia.
in the Carboniferous period of Scorpions differing but very little
from existing forms. The group of the Myriapoda, including
the recent Centipedes and Galley-worms, is likewise represented
in the Carboniferous strata,
but by forms in many respects
very unlike any that are known to exist at the present day.
The most interesting of these were obtained by Principal Dawson,
along with the bones of Amphibians and the shells of Land-snails,
in the sediment filling the hollow trunks of Sigillaria,
and they belong to the genera Xylobius (fig. 124) and
Archiulus. Lastly, the true insects are represented by
Fig. 124.—Xylobius Sigillariœ, a Carboniferous
Myriapod. a, A specimen, of the natural size; b,
Anterior portion of the same, enlarged; c, Posterior
portion, enlarged. From the Coal-measures of Nova Scotia.
(After Dawson.)
various forms of Beetles (Coleoptera), Orthoptera
(such as Cockroaches), and Neuropterous insects resembling
those which we have seen to have existed towards the close of
Fig. 125—Haplophlebium Barnesi, a Carboniferous
insect, from the Coal-meastures of Nova Scotia. (After Dawson.)
the Devonian period. One of the most remarkable of the latter
is a huge May-fly (Haplophlebium Barnesi, fig. 125), with
netted wings attaining an expanse of fully seven inches, and
therefore much exceeding any existing Ephemerid in point of size.
The lower groups of the Mollusca are abundantly represented
in the marine strata of the Carboniferous series by Polyzoans
Fig. 126.—Carboniferous Polyzoa. a, Fragment of
Polypora dendroides, of the natural size, Ireland; a'
Small portion of the same, enlarged to show the cells; b,
Glauconome pulcherrima, a fragment, of the natural size,
Ireland; b', Portion of the same, enlarged; c, The
central screw-like axis of Archimedes Wortheni, of the
natural size—Carboniferous, America; c', Portion of
the exterior of the frond of the same, enlarged; c'',
Portion of the interior of the frond of the same showing the
mouths of the cells, enlarged. (After M'Coy and Hall.)]
and Brachiopods. Amongst the former, although a variety
of other types are known, the majority still belong to the old
group of the "Lace-corals" (Fenestellidœ), some of
the characteristic forms of which are here figured (fig. 126).
The graceful
netted fronds of Fenestella,
Retepora, and Polypora (fig. 126, a) are highly
characteristic, as are the slender toothed branches of
Glauconome (fig. 126, b). A more singular form,
however, is the curious Archimedes (fig. 126, c),
which is so characteristic of the Carboniferous formation of
North America. In this remarkable type, the colony consists of
a succession of funnel-shaped fronds, essentially similar to
Fenestella in their structure, springing in a continuous
spiral from a strong screw-like vertical axis. The outside of
the fronds is simply striated; but the branches exhibit on the
interior the mouths of the little cells in which the
semi-independent beings composing the colony originally lived.
The Brachiopods are extremely abundant, and for the most
part belong to types which are exclusively or principally
Palæozoic in their range. The old genera Strophomena,
Orthis (fig. 127, c), Athyris (fig. 127,
e), Rhynchonella (fig. 127, g), and
Spirifera (fig. 127, h), are still well
represented—the latter, in particular, existing under
numerous specific forms, conspicuous by their abundance and
sometimes by their size. Along with these ancient groups, we
have representatives—for the first time in any plenty—of
the great genus Terebratula (fig. 127, d), which
underwent a great expansion during later periods, and still exists
at the present day. The most characteristic Carboniferous
Brachiopods, however, belong to the family of the
Productidœ, of which the principal genus is
Producta itself. This family commenced its existence in
the Upper Silurian with the genus Chonetes, distinguished
by its spinose hinge-margin. This genus lived through the
Devonian, and flourished in the Carboniferous (fig. 127,
f). The genus Producta itself, represented in the
Devonian by the nearly allied Productella, appeared first
in the Carboniferous, at any rate, in force, and survived into
the Permian; but no member of this extensive family has yet been
shown to have over-lived the Palæozoic period. The
Productœ of the Carboniferous are not only
exceedingly abundant, but they have in many instances a most
extensive geographical range, and some species attain what may
fairly be considered-gigantic dimensions. The shell (fig. 127,
a and b) is generally more or less semicircular,
with a straight hinge-margin, and having its lateral angles
produced into larger or smaller ears (hence its generic
name—"cochlea producta"). One valve (the ventral) is
usually strongly convex, whilst the other (the dorsal) is flat
or concave, the surface of both being adorned with radiating
ribs, and with hollow tubular spines, often of great length.
The valves are not locked together by teeth, and there is no
sign in the
fully-grown shell of an opening in or between the valves for
the emission of a muscular stalk for the attachment of the shell
to foreign objects. It is probable, therefore, that the
Productœ, unlike the ordinary Lamp-shells, lived
an independent existence, their long spines apparently serving
to anchor them firmly in the mud or ooze of the sea-bottom; but
Mr Robert Etheridge, jun.; has recently shown that in one species
Fig. 127.—Carboniferous Braciopoda. a, Producta
semireticulata, showing the slightly concave dorsal valve;
a' Side view of the same, showing the convex ventral valve;
b, Producta longispina; c, Orthis resupinata; d, Terebratula
hastata; e, Athyris subtilita; f, Chonetes Hardrensis; g,
Rhynchonella pleurodon; h, Spirifera trigonalis. Most of
these forms are widely distributed in the Carboniferous Limestone
of Britain, Europe, America, &c. All the figures are of the
natural size. (After Davidson, De Koninck, and Meek.)
the spines were actually employed as organs of adhesion, whereby
the shell was permanently attached to some extraneous object,
such as the stem of a Crinoid. The two species here figured are
interesting for their extraordinarily extensive geographical
range—Producta semireticulata (fig. 127, a)
being found in the Carboniferous rocks of Britain, the continent
of Europe, Central Asia, China, India, Australia, Spitzbergen,
and North
and South America; whilst P. Longispina (fig. 127,
b) has a distribution little if at all less wide.
The higher Mollusca are abundantly represented in the
Carboniferous rocks by Bivalves (Lamellibranchs), Univalves
(Gasteropoda), Winged-snails (Pteropoda), and
Cephalopods. Amongst the Bivalves we may note the great
abundance of Scallops (Aviculopecten and other allied forms),
together with numerous other types—some of ancient origin,
others represented here for the first time. Amongst the Gasteropods,
we find the characteristically Palæozoic genera
Macrocheilus and Loxonema, the almost exclusively
Palæozoic Euomphalus, and the persistent, genus
Pleurotomaria; whilst the free-swimming Univalves
(Heteropoda)are represented by Bellerophon and
Porcellia, and the Pteropoda by the old genus
Conularia. With regard to the Carboniferous Univalves,
it is also of interest to note here the first appearance of true
air-breathing or terrestrial Molluscs, as discovered by
Dawson and Bradley in the Coal-measures of Nova Scotia and Illinois.
Some of these (Conulus priscus) are true Land-snails,
resembling the existing Zonites; whilst others (Pupa
vetusta, fig. 128) appear to be generically inseparable from
Fig. 128.—Pupa (Dendropupa) vetusta, a Carboniferous
Land-snail from the Coal-measures of Nova Scotia. a, The
shell, of the natural size; b, The same, magnified;
c, Apex of the shell, enlarged; d, Portion of the
surface, enlarged. (After Dawson.)
the "Chrysalis-shells" (Pupa) of the present day. All the
known forms—three in number—are of small size, and appear
to have been local in their distribution or in their preservation.
More important, however, than any of the preceding, are the
Cephalopoda, represented, as before, exclusively by the
chambered shells of the Tetrabranchiates. The older and simpler
type of these, with simple plain septa, and mostly a central
siphuncle, is represented by the straight conical shells of the
ancient genus Orthoceras, and the bow-shaped shells of the equally
ancient Cyrtoceras—some of the former attaining a
great size. The spirally-curved discoidal shells of the persistent
genus Nautilus are also not unknown, and some of these
likewise exhibit very considerable dimensions. Lastly, the more
complex family of the Ammonitidœ,
with lobed or angulated septa, and a dorsally-placed
siphuncle (situated on the convex side of the curved shells), now
for the first time commences to acquire a considerable prominence.
The principal representative of this group is the genus
Goniatites (fig. 129), which
commenced its existence in the Upper Silurian, is well represented
in the Devonian, and attains its maximum here. In this genus,
the shell is spirally curved, the septa are strongly lobed or
angulated, though not elaborately frilled as in the Ammonites,
and the siphuncle is dorsal. In addition to Goniatites,
the shells of true Ammonites, so characteristic of the
Secondary period, have been described by Dr Waagen as occurring
in the Carboniferous rocks of India.
| Fig. 129.—Goniatites (Aganides) Fossœ. Carboniferous Limestone. |
Coming finally to the Vertebrata, we have in the first
place to very briefly consider the Carboniferous fishes.
These are numerous; but, with the exception of the still dubious
"Conodonts," belong wholly to the groups of the Ganoids and
the Placoids (including under the former head remains which
perhaps are truly referable to the group of the Dipnoi or
Mud-fishes). Amongst the Ganoids, the singular buckler-headed
fishes of the Upper Silurian and Devonian (Cephalaspidœ)
have apparently disappeared; and the principal
types of the Carboniferous belong to the groups respectively
represented at the present day by the Gar pike (Lepidosteus)
of the North American lakes, and the Polypterus of the rivers
of Africa. Of the former, the genera Palœoniscus and
Amblypterus (fig. 130), with their small rhomboidal and
Fig. 130.—Amblypterus macropterus.
enamelled scales, and their strongly unsymmetrical tails, are
perhaps the most abundant. Of the latter, the most important are
species belonging to the genera Megalichthys and
Rhizodus, comprising large fishes, with rhomboidal scales,
unsymmetrical ("heterocercal") tails, and powerful conical teeth.
These fishes are sometimes said to be "sauroid," from their
presenting some Reptilian features in their organisation, and
they must have been the scourges of the Carboniferous seas. The
remains of Placoid fishes in the Carboniferous strata are
very numerous, but consist wholly of teeth and fin-spines,
referable to forms more or less closely allied to our existing
Port Jackson Sharks, Dog-fishes, and Rays. The teeth are of very
various shapes and sizes,—some with sharp, cutting edges
(Petalodus, Cladodus, &c.); others in the form of
broad crushing plates, adapted, like the teeth of the existing
Port Jackson Shark (Cestracion Philippi), for breaking
down the hard shells of Molluscs and Crustaceans. Amongst the
many kinds of these latter, the teeth of Psammodus and
Cochliodus (fig. 131) may be mentioned as specially
characteristic. The fin-spines are mostly similar to those so
common in the Devonian deposits, consisting of hollow defensive
spines implanted in front of the pectoral or other fins, usually
slightly curved, often superficially ribbed or sculptured, and
not uncommonly serrated or toothed. The genera Ctenacanthus,
Gyracanthus, Homacanthus, &c., have been founded for the
reception of these defensive weapons, some of which indicate
fishes of great size and predaceous habits.
In the Devonian rocks we meet with no
other remains of Vertebrated animals save fishes only; but the
Carboniferous deposits have yielded remains of the higher group
Fig. 131.—Teeth of Cochliodus contortus.
Carboniferous Limestone, Britain.
of the Amphibians. This class, comprising our existing
Frogs, Toads, and Newts, stands to some extent in a position
midway between the class of the fishes and that of the true
reptiles, being distinguished from the latter by the fact
that its members invariably possess gills in their early
condition, if not throughout life; whilst they are separated
from the former by always possessing true lungs when adult, and
by the fact that the limbs (when present at all) are never in
the form of fins. The Amphibians, therefore, are all
water-breathers when young, and have respiratory organs adapted
for an aquatic mode of life; whereas, when grown up, they
develop lungs, and with these the capacity for breathing air
directly. Some of them, like the Frogs and Newts, lose their
gills altogether on attaining the adult condition; but others,
such as the living Proteus and Menobranchus, retain
their gills even after acquiring their lungs, and are thus fitted
indifferently for an aquatic or terrestrial existence. The name
of "Amphibia," though applied to the whole class, is thus not
precisely appropriate except to these last-mentioned forms
(Gr. amphi, both; bios, life). The Amphibians also
differ amongst themselves according as to whether they keep
permanently the long tail which they all possess when young
(as do the Newts and Salamanders), or lose this appendage when
grown up (as do the Frogs and Toads). Most of them have naked
skins, but a few living and many extinct forms have hard
structures in the shape of scales developed in the integument.
All of them have well-ossified skeletons, though some fossil
types are partially deficient in this respect; and all of them
which possess limbs at all have these appendages supported by
bones essentially similar to those found in the limbs of the
higher Vertebrates. All the Carboniferous Amphibians belong to
a group which has now wholly passed away—namely, that of
the Labyrinthodonts. In the marine strata which form the
base of the Carboniferous series these creatures have only been
recognised by their curious hand-shaped footprints, similar
in character to those which occur in the
Triassic rocks, and which will be subsequently spoken of under
the name of Cheirotherium. In the Coal-measures of
Britain, the continent of Europe, and North America, however,
many bones of these animals have been found, and we are now
tolerably well acquainted with a considerable number of forms.
All of them seem to have belonged to the division of Amphibians
in which the long tail of the young is permanently retained; and
there is evidence that some of them kept the gills also throughout
life. The skull is of the characteristic Amphibian type (fig. 132,
a), with two occipital condyles, and having its surface
Fig. 132.—a, Upper surface of the skull of
Anthracosaurus Russelli, one-sixth of the natural size:
b, Part of one of the teeth cut across, and highly magnified
to show the characteristic labyrinthine structure; c, One
of the integumentary shields or scales, one-half of the natural
size. Coal-measures, Northumberland. (After Atthey.)
singularly pitted and sculptured; and the vertebræ are
hollowed out at both ends. The lower surface of the body was
defended by an armour of singular integumentary shields or scales
(fig. 132, c); and an extremely characteristic feature
(from which the entire group derives its name) is, that the walls
of the teeth are deeply folded, so as to give rise to an
extraordinary "labyrinthine" pattern when they are cut across
(fig. 132, b). Many of the Carboniferous Labyrinthodonts
are of no great size, some of them
very small, but others attain comparatively gigantic dimensions,
though all fall short in this respect of the huge examples of
this group which occur in the Trias. One of the largest, and
at the same time most characteristic, forms of the Carboniferous
series, is the genus Anthracosaurus, the skull of which
is here figured.
No remains of true Reptiles, Birds, or Quadrupeds have as yet been certainly detected in the Carboniferous deposits in any part of the world. It should, however, be mentioned, that Professor Marsh, one of the highest authorities on the subject, has described from the Coal-formation of Nova Scotia certain vertebræ which he believes to have belonged to a marine reptile (Eosaurus Acadianus), allied to the great Ichthyosauri of the Lias. Up to this time no confirmation of this determination has been obtained by the discovery of other and more unquestionable remains, and it therefore remains doubtful whether these bones of Eosaurus may not really belong to large Labyrinthodonts.
LITERATURE.
The following list contains some of the more important of the original sources of information to which the student of Carboniferous rocks and fossils may refer:—
Also numerous memoirs by Huxley, Davidson, Martin Duncan, Professor Young, John Young, R. Etheridge, jun., Baily, Carruthers, Dawson, Binney, Williamson, Hooker, Jukes, Geikie, Rupert Jones, Salter, and many other British and foreign observers.
CHAPTER XIV.
THE PERMIAN PERIOD.
The Permian formation closes the long series of the Palæozoic deposits, and may in some respects be considered as a kind of appendix to the Carboniferous system, to which it cannot be compared in importance, either as regards the actual bulk of its sediments or the interest and variety of its life-record. Consisting, as it does, largely of red rocks—sandstones and marls—for the most part singularly destitute of organic remains, the Permian rocks have been regarded as a lacustrine or fluviatile deposit; but the presence of well-developed limestones with indubitable marine remains entirely negatives this view. It is, however, not improbable that we are presented in the Permian formation, as known to us at present, with a series of sediments laid down in inland seas of great extent, due to the subsidence over large areas of the vast land-surfaces of the Coal-measures. This view, at any rate, would explain some of the more puzzling physical characters of the formation, and would not be definitely negatived by any of its fossils.
A large portion of the Permian series, as already remarked, consists of sandstones and marls, deeply reddened by peroxide of iron, and often accompanied by beds of gypsum or deposits of salt. In strata of this nature few or no fossils are found; but their shallow-water origin is sufficiently proved by the presence of the footprints of terrestrial animals, accompanied in some cases by well-defined "ripple-marks." Along with these are occasionally found massive breccias, holding larger or smaller blocks derived from the older formations; and these have been supposed to represent an old "boulder-clay," and thus to indicate the prevalence of an arctic climate. Beds of this nature must also have been deposited in shallow water. In all regions, however, where the Permian formation is well developed, one of its most characteristic members is a Magnesian limestone, often highly and fantastically concretionary, but containing numerous remains of genuine marine animals, and clearly indicating that it was deposited beneath a moderate depth of salt water.
It is not necessary to consider here whether this formation can be retained as a distinct division of the geological series. The name of Permian was given to it by Sir Roderick Murchison, from the province of Perm in Russia, where rocks of this age are extensively developed. Formerly these rocks were grouped with the succeeding formation of the Trias under the common name of "New Red Sandstone." This name was given them because they contain a good deal of red sandstone, and because they are superior to the Carboniferous rocks, while the Old Red Sandstone is inferior. Nowadays, however, the term "New Red Sandstone" is rarely employed, unless it be for red sandstones and associated rocks, which are seen to overlie the Coal-measures, but which contain no fossils by which their exact age may be made out. Under these circumstances, it is sometimes convenient to employ the term "New Red Sandstone." The New Red, however, of the older geologists, is now broken up into the two formations of the Permian and Triassic rocks—the former being usually considered as the top of the Palæozoic series, and the latter constituting the base of the Mesozoic.
In many instances, the Permian rocks are seen to repose unconformably upon the underlying Carboniferous, from which they can in addition be readily separated by their lithological characters. In other instances, however, the Coal-measures terminate upwards in red rocks, not distinguishable by their mineral characters from the Permian; and in other cases no physical discordance between the Carboniferous and Permian strata can be detected. As a general rule, also, the Permian rocks appear to pass upwards conformably into the Trias. The division, therefore, between the Permian and Triassic rocks, and consequently between the Palæozoic and Mesozoic series, is not founded upon any conspicuous or universal physical break, but upon the difference in life which is observed in comparing the marine animals of the Carboniferous and Permian with those of the Trias. It is to be observed, however, that this difference can be solely due to the fact that the Magnesian Limestone of the Permian series presents us with only a small, and not a typical, portion of the marine deposits which must have been accumulated in some area at present unknown to us during the period which elapsed between the formation of the great marine limestones of the Lower Carboniferous and the open-sea and likewise calcareous sediments of the Middle Trias.
The Permian rocks exhibit their most typical features in Russia and Germany, though they are very well developed in parts of Britain, and they occur in North America. When well developed, they exhibit three main divisions: a lower set of sandstones, a middle group, generally calcareous, and an upper series of sandstones, constituting respectively the Lower, Middle, and Upper Permians.
In Russia, Germany, and Britain, the Permian rocks consist of the following members:—
1. The Lower Permians, consisting mainly of a great series of sandstones, of different colours, but usually red. The base of this series is often constituted by massive breccias with included fragments of the older rocks, upon which they may happen to repose; and similar breccias sometimes occur in the upper portion of the series as well. The thickness of this group varies a good deal, but may amount to 3000 or 4000 feet.
2. The Middle Permians, consisting, in their typical development, of laminated marls, or "marl-slate," surmounted by beds of magnesian limestone (the "Zechstein" of the German geologists). Sometimes the limestones are degenerate or wholly deficient, and the series may consist of sandy shales and gypsiferous clays. The magnesian limestone, however, of the Middle Permians is, as a rule, so well marked a feature that it was long spoken of as the Magnesian Limestone.
3. The Upper Permians, consisting of a series of sandstones and shales, or of red or mottled marls, often gypsiferous, and sometimes including beds of limestone.
In North America, the Permian rocks appear to be confined to the region west of the Mississippi, being especially well developed in Kansas. Their exact limits have not as yet been made out, and their total thickness is not more than a few hundred feet. They consist of sandstones, conglomerates, limestones, marls, and beds of gypsum.
The following diagrammatic section shows the general sequence of the Permian deposits in the north of England, where the series is extensively developed (fig. 133):—
| GENERALISED SECTION OF THE PERMIAN ROCKS IN THE NORTH OF ENGLAND. |
| Fig. 133. |
The record of the life of the Permian period is but a scanty one, owing doubtless to the special peculiarities of such of the deposits of this age with which we are as yet acquainted. Red rocks are, as a general rule, more or less completely unfossiliferous, and sediments of this nature are highly characteristic of the Permian. Similarly, magnesian limestones are rarely as highly charged with organic remains as is the case with normal calcareous deposits, especially when they have been subjected to concretionary action, as is observable to such a marked extent in the Permian limestones. Nevertheless, much interest is attached to the organic remains, as marking a kind of transition-period between the Palæozoic and Mesozoic epochs.
The plants of the Permian period, as a whole, have a
distinctly Palæozoic aspect, and are far more nearly allied to
those of the Coal-measures than they are to those of the earlier
Secondary rocks; though the Permian species are mostly
distinct from the Carboniferous, and there are some new genera.
Thus, we find species of Lepidodendron, Calamites, Equisetites,
Asterophyllites, Annularia, and other highly characteristic
Carboniferous genera. On the other hand, the Sigillariods
of the Coal seem to have finally disappeared at the close of the
Carboniferous period. Ferns are abundant in the Permian rocks,
and belong for the most part to the well-known Carboniferous
genera Alethopteris, Neuropteris, Sphenopteris, and
Pecopteris. There are also Tree-ferns referable to the
ancient genus Psaronius. The Conifers of the Permian
period are numerous, and belong in part to Carboniferous genera.
A characteristic genus, however, is Walchia (fig. 134),
Fig. 134.—Walchia piniformis, from the Permian of
Saxony, a, Branch; b, Twig, (After Gutbier.)
distinguished by its lax short leaves. This genus, though not
exclusively Permian, is mainly so, the best-known species being
the W. Piniformis. Here, also, we meet with Conifers which
produce true cones, and which differ, therefore, in an important
degree from the
Taxoid Conifers of the
Coal-measures. Besides Walchia, a characteristic form of
these is the Ullmania selaginoides, which occurs in the
Magnesian Limestone of Durham, the Middle Permian of Westmorland,
and the "Kupfer-schiefer" of Germany. The group of the
Cycads, which we shall subsequently find to be so
characteristic of the vegetation of the Secondary period, is, on
the other hand, only doubtfully represented in the Permian
deposits by the singular genus Nœggerathia.
The Protozoans of the Permian rocks are few in number, and for the most part imperfectly known. A few Foraminifera have been obtained from the Magnesian Limestone of England, and the same formation has yielded some ill-understood Sponges. It does not seem, however, altogether impossible that some of the singular "concretions" of this formation may ultimately prove to have an organic structure, though others would appear to be clearly of purely inorganic origin. From the Permian of Saxony, Professor Geinitz has described two species of Spongillopsis, which he believes to be most nearly allied to the existing fresh-water Sponges (Spongilla). This observation has an interest as bearing upon the mode of deposition and origin of the Permian sediments.
The Cœlenterates are represented in the Permian by but a few Corals. These belong partly to the Tabulate and partly to the Rugose division; but the latter great group, so abundantly represented in Silurian, Devonian, and Carboniferous seas, is now extraordinarily reduced in numbers, the British strata of this age yielding only species of the single genus Polycœlia. So far, therefore, as at present known, all the characteristic genera of the Rugose Corals of the Carboniferous had become extinct before the deposition of the limestones of the Middle Permian.
The Echinoderms are represented by a few Crinoids, and by a Sea-urchin belonging to the genus Eocidaris. The latter genus is nearly allied to the Archœocidaris of the Carboniferous, so that this Permian form belongs to a characteristically Palæozoic type.
A few Annelides (Spirorbis, Vermilia, &c.) have been described, but are of no special importance. Amongst the Crustaceans, however, we have to note the total absence of the great Palæozoic group of the Trilobites; whilst the little Ostracoda and Phyllopods still continue to be represented. We have also to note the first appearance here of the "Short-tailed" Decapods or Crabs (Brachyura), the highest of all the groups of Crustacea, in the person of Hemitrochiscus paradoxus, an extremely minute Crab from the Permian of Germany.
Amongst the Mollusca, the remains of Polyzoa may
fairly be said to be amongst the most abundant of all the fossils
of the Permian formation, The principal forms of these are the
fronds of the Lace-corals (Fenestella, Retepora, and
Synocladia), which are very abundant in the Magnesian
Limestone of the north of England, and belong to various highly
characteristic species (such as Fenestella retiformis, Retepora
Ehrenbergi, and Synocladia virgulacea). The
Brachiopoda are also represented in moderate numbers in the
Permian. Along with species of the persistent genera Discina,
Crania, and Lingula, we still meet with representatives of
the old groups Spirifera, Athyris, and Streptorhynchus;
and the Carboniferous Productœ yet survive under
well-marked and characteristic types, though in much-diminished
numbers. The species of Brachiopods here figured (fig. 135) are
characteristic of the Magnesian Limestone in Britain and of the
Fig. 135.—Brachiopods of the Permian formation. a,
Producta horrida; b, Lingula Credneri; c, Terebratula elongata;
d and e, Camarophoria globulina. (After King.)
corresponding strata on the Continent. Upon the whole, the most
characteristic Permian Brachiopods belong to the genera
Producta, Strophalosia, and Camarophoria.
The Bivalves (Lamellibranchiata) have a tolerably varied development in the Permian rocks; but nearly all the old types, except some of those which occur in the Carboniferous, have now disappeared. The principal Permian Bivalves belong to the groups of the Pearl Oysters (Aviculidœ) and the Trigoniadœ, represented by genera such as Bakewellia and Schizodus; the true Mussels (Mytilidœ), represented by species which have been referred to Mytilus itself; and the Arks (Arcadœ), represented by species of the genera Arca (fig. 136) and Byssoarca. The first and last of these three families have a very ancient origin; but the family of the Trigoniadœ, though feebly represented at the present day, is one which attained its maximum development in the Mesozoic period.
The Univalves (Gasteropoda) are rare, and do not
demand special notice. It may be observed, however, that the
Fig. 136.—Arca antiqua. Permian.
Palæozoic genera Euomphalus, Murchisonia, Loxonema,
and Macrocheilus are still in existence, together with the
persistent genus Pleurotomaria. Pteropods of the
old genera Theca and Conularia have been discovered;
but the first of these characteristically Palæozoic types
finally dies out here, and the second only survives but a short time
longer. Lastly, a few Cephalopods have been found, still
wholly referable to the Tetrabranchiate group, and belonging
to the old genera Orthoceras and Cyrtoceras and
the long-lived Nautilus.
Amongst Vertebrates, we meet in the Permian period not
only with the remains of Fishes and Amphibians, but also, for
the first time, with true Reptiles. The Fishes are mainly
Ganoids, though there are also remains of a few Cestraciont
Fig. 137.—Platysomus gibbosus, a "heterocercal"
Ganoid, from the Middle Permian of Russia.
Sharks. Not only are the Ganoids still the predominant group
of Fishes, but all the known forms possess the unsymmetrical
("heterocercal") tail which is so characteristic of the
Palæozoic Ganoids. Most of the remains of the Permian Fishes
have been obtained from the "Marl-slate" of Durham and the
corresponding "Kupfer-schiefer" of Germany, on the horizon
of the Middle Permian; and the principal genera of the Ganoids
are Palœoniscus and Platysomus (fig. 137).
The Amphibians of the Permian period belong principally to the order of the Labyrinthodonts, which commenced to be represented in the Carboniferous, and has a large development in the Trias. Under the name, however, of Palœosiren Beinerti, Professor Geinitz has described an Amphibian from the Lower Permian of Germany, which he believes to be most nearly allied to the existing "Mud-eel" (Siren lacertina) of North America, and therefore to be related to the Newts and Salamanders (Urodela).
Finally, we meet in the Permian deposits with the first undoubted
remains of true Reptiles. These are distinguished, as a
class, from the Amphibians, by the fact that they are
air-breathers throughout the whole of their life, and therefore
are at no time provided with gills; whilst they are exempt from
that metamorphosis which all the Amphibia undergo in early
life, consequent upon their transition from an aquatic to a more
or less purely aerial mode of respiration. Their skeleton is well
ossified; they usually have horny or bony plates, singly or in
combination, developed in the skin; and their limbs (when present)
are never either in the form of fins or wings,
though sometimes capable of acting in either of these capacities,
and liable to great modifications of form and structure. Though
there can be no doubt whatever as to the occurrence of genuine
Reptiles in deposits of unquestionable Permian age, there is
still uncertainty as to the precise number of types which may
have existed at this period. This uncertainty arises partly from
the difficulty of deciding in all cases. whether a given bone
be truely Labyrinthodont or Reptilian, but more especially from
the confusion which exists at present between the Permian and
the overlying Triassic deposits. Thus there are various deposits
in different regions which have yielded the remains of Reptiles,
and which cannot in the meanwhile be definitely referred either
to the Permian series or to the Trias by clear stratigraphical
or palæontological evidence. All that can be done in such
cases is to be guided by the characters of the Reptiles themselves,
and to judge by their affinities to remains from known Triassic
or Permian rocks to which of these formations the beds containing
them should be referred; but it is obvious that this method of
procedure is seriously liable to lead to error. In accordance,
however, with this, the only available mode of determination
in some cases, the remains of Thecodontosaurus and
Palæosaurus discovered in the dolomitic conglomerates
near Bristol will be considered as Triassic, thus leaving
Protorosaurus[20] as the principal and most important
Fig. 138.—Protorosaurus Speneri, Middle Permian,
Thuringia, reduced in size. (After Von Meyer.) [Copied from
Dana.
representative of the Permian Reptiles.[21] The type-species
of the genus Protorusaurus is the P. Speneri(fig.
138) of the "Kupfer-schiefer" of
Thuringia, but other allied
species have been detected in the Middle Permian of Germany and
the north of England. This Reptile attained a length of from
three to four feet; and it has been generally referred to the
group of the Lizards (Lacertilia), to which it is most
nearly allied in its general structure, at the same time that it
differs from all existing members of this group in the fact that
its numerous conical and pointed teeth were implanted in distinct
sockets in the jaws—this being a Crocodilian character. In
other respects, however, Protorosaurus approximates closely
to the living Monitors (Varanidœ); and the fact that
the bodies of the vertebræ are slightly cupped or hollowed
out at the ends would lead to the belief that the animal was aquatic
in its habits. At the same time, the structure of the hind-limbs
and their bony supports proves clearly that it must have also
possessed the power of progression upon the land. Various other
Reptilian bones have been described from the Permian formation, of
which some are probably really referable to Labyrinthodonts, whilst
others are regarded by Professor Owen as referable to the order of
the "Theriodonts," in which the teeth are implanted in sockets,
and resemble those of carnivorous quadrupeds in consisting of
three groups in each jaw (namely, incisors, canines, and molars).
Lastly, in red sandstones of Permian age in Dumfriesshire have
been discovered the tracks of what would appear to have been
Chelonians (Tortoises and Turtles); but it would not be
safe to accept this conclusion as certain upon the evidence of
footprints alone. The Chelichnus Duncani, however, described
by Sir William Jardine in his magnificent work on the 'Ichnology
of Annandale,' bears a great resemblance to the track of a Turtle.
[Footnote 20: Though commonly spelt as above, it is probable that the name of this Lizard was really intended to have been Proterosaurus—from the Greek proteros, first; and saura, lizard: and this spelling is followed by many writers.]
[Footnote 21: In an extremely able paper upon the subject (Quart. Journ. Geol. Soc., vol. xxvi.), Mr Etheridge has shown that there are good physical grounds for regarding the dolomitie conglomerate of Bristol as of Triassic age, and as probably corresponding in time with the Muschelkalk of the Continent.]
No remains of Birds or Quadrupeds have hitherto been detected in deposits of Permian age.
LITERATURE.
The following works may be consulted by the student with regard to the Permian formation and its fossils:—
CHAPTER XV.
THE TRIASSIC PERIOD.
We come now to the consideration of the great Mesozoic, or Secondary series of formations, consisting, in ascending order, of the Triassic, Jurassic, and Cretaceous systems. The Triassic group forms the base of the Mesozoic series, and corresponds with the higher portion of the New Red Sandstone of the older geologists. Like the Permian rocks, and as implied by its name, the Trias admits of a subdivision into three groups—a Lower, Middle, and Upper Trias. Of these sub-divisions the middle one is wanting in Britain; and all have received German names, being more largely and typically developed in Germany than in any other country. Thus, the Lower Trias is known as the Bunter Sandstein; the Middle Trias is called the Muschelkalk; and the Upper Trias is known as the Keuper.
I. The lowest division of the Trias is known as the Bunter Sandstein (the Grès bigarré of the French), from the generally variegated colours of the beds which compose it (German, bunt, variegated). The Bunter Sandstein of the continent of Europe consists of red and white sandstones, with red clays, and thin limestones, the whole attaining a thickness of about 1500 feet. The term "marl" is very generally employed to designate the clays of the Lower and Upper Trias; but the term is inappropriate, as they may contain no lime, and are therefore not always genuine marls. In Britain the Bunter Sandstein consists of red and mottled sandstones, with unconsolidated conglomerates, or "pebble-beds," the whole having a thickness of 1000 to 2000 feet. The Bunter Sandstein, as a rule, is very barren of fossils.
II. The Middle Trias is not developed in Britain, but it is largely developed in Germany, where it constitutes what is known as the Muschelkalk (Germ. Muschel, mussel; kalk, limestone), from the abundance of fossil shells which it contains. The Muschelkalk (the Calcaire coquillier of the French) consists of compact grey or yellowish limestones, sometimes dolomitic, and including occasional beds of gypsum and rock-salt.
III. The Upper Trias, or Keuper (the Marnes irisées of the French), as it is generally called, occurs in England; but is not so well developed as it is in Germany. In Britain, the Keuper is 1000 feet or more in thickness, and consists of white and brown sandstones, with red marls, the whole topped by red clays with rock-salt and gypsum.
The Keuper in Britain is extremely unfossiliferous; but it passes upwards with perfect conformity into a very remarkable group of beds, at one time classed with the Lias, and now known under the names of the Penarth beds (from Penarth, in Glamorganshire), the Rhætic beds (from the Rhætic Alps), or the Avicula contorta beds (from the occurrence in them of great numbers of this peculiar Bivalve). These singular beds have been variously regarded as the highest beds of the Trias, or the lowest beds of the Lias, or as an intermediate group. The phenomena observed on the Continent, however, render it best to consider them as Triassic, as they certainly agree with the so-called Upper St Cassian or Kössen beds which form the top of the Trias in the Austrian Alps.
The Penarth beds occur in Glamorganshire, Gloucestershire, Warwickshire, Staffordshire, and the north of Ireland; and they generally consist of a small thickness of grey marls, white limestones, and black shales, surmounted conformably by the lowest beds of the Lias. The most characteristic fossils which they contain are the three Bivalves Cardium Rhœticum, Avicula contorta, and Pecten Valoniensis; but they have yielded many other fossils, amongst which the most important are the remains of Fishes and small Mammals (Microlestes).
In the Austrian Alps the Trias terminates upwards in an extraordinary series of fossiliferous beds, replete with marine fossils. Sir Charles Lyell gives the following table of these remarkable deposits:—
Strata below the Lias in the Austrian Alps, in descending order.
| Grey and black limestone, with calcareous marls having a thickness of about 50 feet. Among the fossils, Brachiopoda very numerous; some few species common to the genuine Lias; many peculiar. Avicula contorta, Pecten Valoniensis, Cardium Rhœticum, Avicula inœquivalvis, Spirifer Münsteri, Dav. Strata containing the above fossils alternate with the Dachstein beds, lying next below. | ||||||||||
| White or greyish limestone, often in beds three or four feet thick. Total thickness of the formation above 2000 feet. Upper part fossiliferous, with some strata composed of corals (Lithodendron.) Lower portion without fossils. Among the characteristic shells are Hemicardium Wulfeni, Megalodon triqueler, and other large bivalves. | ||||||||||
| Red, pink, or white marbles, from 800 to 1000 feet in thickness, containing more than 800 species of marine fossils, for the most part mollusca. Many species of Orthoceras. True Ammonites, besides Ceratites and Goniatites, Belemnites (rare), Porcellia, Pleurotomania, Trochus, Monotis salinaria, &c. | ||||||||||
|
| Among the fossils are Ceratites cassianus, Myacites fassaensis, Naticella costata, &c. | |||||||||
In the United States, rocks of Triassic age occur in several areas between the Appalachians and the Atlantic seaboard; but they show no such triple division as in Germany, and their exact place in the system is uncertain. The rocks of these areas consist of red sandstones, sometimes shaly or conglomeratic, occasionally with beds of impure limestone. Other more extensive areas where Triassic rocks appear at the surface, are found west of the Mississippi, on the slopes of the Rocky Mountains, where the beds consist of sandstones and gypsiferous marls. The American Trias is chiefly remarkable for having yielded the remains of a small Marsupial (Dromatherium), and numerous footprints, which have generally been referred to Birds (Brontozoum), along with the tracks of undoubted Reptiles (Otozoum, Anisopus, &c.)
The subjoined section (fig. 139) expresses, in a diagrammatic manner, the general sequence of the Triassic rocks when fully developed, as, for example, in the Bavarian Alps:—