FOSSIL STELLERIDÆ; COMPRISING THE CRINOIDEA OR LILY-LIKE ANIMALS; AND
THE ASTERIADÆ, OR STAR-FISHES.
The Radiata, or radiated animals, so designated because the parts of
which the body is composed are arranged around a common centre or
axis, are divided into three sub-classes; namely, 1, the _Polypifera_,
whose fossil remains were treated of in the previous chapter; 2. the
_Acalepha_, or Jelly-fishes, whose structures are so perishable as
to render it improbable that any vestiges of them will be found in a
fossil state, though imprints of the general outline of certain kinds
may possibly occur;[264] and, 3, the _Echinodermata_, comprehending
under that term the _Stelleridæ_, or Crinoids and Star-fishes, and the
_Echinoderms_, properly so called. This sub-class is the subject of the
present section; it comprises four orders, viz.
Crinoidea, or Lily-like Animals.
Asteriadæ, or Star-fishes.
Echinidæ, or Sea-urchins.
Holothuriadæ, or Sea-slugs.
[264] The impression of an Acaleph resembling an _Æquorea_ (a kind of
Medusa), is stated by M. Pictet to have been observed in a slab of
schistose rock, in Germany.
Vestiges of the Stellerida are among the earliest relics of animal
organization hitherto discovered. Many kinds of Crinoidea abound in
the Silurian rocks, and one genus of Star-fishes occurs in the same
deposits: the Echinidæ first appear in the Devonian formation.
The Echinodermata possess the radiated type of structure in an
eminent degree; especially the Asterioidæ and the Echinidæ, of which
the common Star-fish, and Sea-urchin, are familiar examples. The
external integument or skin is in many kinds protected by spines,
(hence the name Echinoderms or spiny-skin,) and perforated by numerous
foramina for the imbibition and transmission of sea-water, and for the
protection of minute soft tubular processes (called _pseudopodia_),
which constitute organs of adhesion and locomotion.
The first two orders have endo-skeletons, composed of numerous ossicula
or little calcareous bones: in the third order, the Echinidæ, the body
is inclosed in a calcareous case or shell, formed of numerous plates
closely adjusted to each other; in the fourth order, the Sea-slugs, the
body has only a tough outer integument without movable spines.
Diversified in form and external appearance as are the Invertebrata
thus grouped together, they are naturally related by their
organization. The Crinoidea may be regarded as Star-fishes fixed to one
spot by a jointed stem; the Star-fishes as free Crinoidea; the Echinidæ
as Star-fishes with the rays coalesced and united into a globular or
spherical case; and the Holothuriæ, as elongated Sea-urchins, destitute
of spines, and without a calcareous envelop.
[Sidenote: CRINOIDEA.]
Crinoidea.--The animals of this order are subdivided into families and
genera according to the number, form, and arrangement of the plates
composing the calcareous case or receptacle, and the structure of the
arms and column. In one living family, the _Comatulidæ_, the body is
free; and in one fossil genus, the _Marsupite_, the animal is capable
of locomotion through the water.
The essential character of the _Crinoidea_,[265]--so named because the
receptacle and anus of some kinds resemble when in repose a closed lily
or tulip,--are well exemplified in the recent _Pentacrinus_; the only
known living form that is identical in structure with the numerous
extinct tribes, that swarmed in the seas of the palæozoic and secondary
ages.
[265] From κρινον, _crinon_, lily, and ειδος, _eidos_, a form.
The Pentacrinus (_F. caput-medusæ_, _Wond._ p. 647), is an inhabitant
of the Caribbean Sea, and but rarely obtained; there are specimens in
the British Museum[266] and in the Hunterian Collection of the College
of Surgeons.
[266] Petrifactions, p. 77.
This animal has a long stem or column, which is composed of pentagonal
calcareous plates or ossicula, articulated to each other by radiated
surfaces, and is fixed by the base to a rock, or other firm body. The
column supports a vasiform receptacle or cup, formed of calcareous
plates in close apposition; in which the digestive and other viscera
are situated. The upper part of the receptacle is covered by an
integument in which there is an aperture for the mouth. From the margin
or brim proceed ten multi-radiate arms, which subdivide into branches
of extreme tenuity. On the upper and inner side of the arms are
numerous articulated feelers or pinnæ. The ova are situated externally
on and near the base of the arms, as in the Comatulidæ; a family of
living Star-fishes, or more properly Crinoids, which have a receptacle,
surrounded by articulated and multi-radiate arms, but are free animals,
being destitute of a column.
In the living state of Pentacrinus, the skeleton--for such are the
specimens in our museums--was of course covered and concealed by the
soft integuments and tissues by which it was secreted. The ossicula
composing the stem are pentangular, and very numerous; they have a
central perforation, and their articulating surfaces are ornamented
by pentapetalous striations. There are numerous side-arms sent off
from the column in groups of five, at uncertain distances. The mouth is
situated in the centre of a plated integument spread over the top of
the receptacle. The arms, which arise from the margin of the latter,
surround the mouth, and when spread out, with their numerous pinnæ
or feelers expanded, form a net for the capture of prey; and are the
organs by which the animal obtains food, and conveys it to the mouth.
[Sidenote: FOSSIL CRINOIDEA.]
Fossil Crinoidea.--The fossil crinoids, like the recent prototype above
described, consist of an articulated column, and a receptacle formed of
calcareous plates, and articulated arms or tentacula. They constitute
two groups; the _Encrinites_, in which the ossicula of the column
are subcylindrical and smooth; and the _Pentacrinites_, with a stem
composed of pentangular ossicles, as in the living Pentacrinus.
The petrified remains consist of the ossicula of the column, arms,
and tentacula; of the plates of the receptacle; and of the peduncle,
or process of attachment by which the animal was fixed to the rock.
The peduncle is in some species flat and expanded, like that of the
_Gorgonia_; in others, it consists of long jointed processes. These
several parts are commonly found detached, and intermingled with
detritus in the strata; throughout extensive beds of encrinital marble,
vestiges of the receptacle are but seldom discoverable. In some
localities the skeletons are preserved entire, and lie expanded on the
surface of the layers of shale, clay, or limestone, as if the animals
had been enveloped by the soft deposit when alive in their native seas.
These remarks will serve to convey a general idea of the nature of the
crinoidal remains which are scattered through certain rocks in such
inconceivable quantities; for, much as the columns may differ in form,
the ossicula in their markings, and the plates of the receptacle in
their configuration and ornament, the same general type of structure
prevails throughout the family.
[Illustration: Lign. 90. Stems of Encrinites and Pentacrinites.
Fig. 1.--Screw or Pulley-stone. _Derbyshire._
2, 4.--Articulating surfaces of Encrinital ossicula.
3, 5.--_Entrochites_, or portions of stems of Encrinites.
6, 8, 10.--Portions of Pentacrinital stems.
7, 9.--Articulating surfaces of ossicula of Pentacrinites.
]
Fossil Stems and Ossicula of Crinoidea.--(_Bd._ pl. xlix-lii. _Pict.
Atlas_, pl. xlvii.)--The detached ossicula and stems are so common in
many places, that they attracted the notice of the earlier collectors,
by whom the single pieces were termed _trochites_ (wheel-stones), and
the united series _entrochites_. In the north of England these fossils
are called _Fairy-stones_, and the circular perforated ossicula _Saint
Cuthbert's beads_; the latter were worn as ornaments by the ancient
Britons, and are occasionally found in tumuli.
These petrifactions present considerable variety in form, and in the
markings on their articulating surfaces, which are often radiated and
sculptured in floriform and stellular figures (_Lign. 90, fig. 7,
9_, and _Lign. 91, fig. 3, 4_). The central perforation is small in
some species, and large and pentagonal in others. The ossicula of the
Encrinites often vary in size in the same column, being circular and
elliptical, and thick or thin, alternately, as in the upper part of
the column of the Lily Encrinite, _Lign. 91, fig. 6_; by which great
flexibility and freedom of motion were obtained.
The pentagonal stems also display many modifications; some have five,
others but four sides (_Lign._ 90, _fig._ 6, 8, 10, and 91, _fig._ 7,
9); in some the angles are acute, in others rounded.
Pulley-stones. _Lign. 90, fig. 1._--The circular, or pentagonal
channel formed by the united ossicula of the column, has given rise to
the curious fossils called in Derbyshire the Screw, or Pulley-stones,
which are flint casts of those cavities that occur in the beds of
chert, interstratified with the mountain limestone. The siliceous
matter, when fluid, must have filled up the channel and invested the
stem: the original calcareous ossicles have since been dissolved,
and the casts, now solid cylinders of flint, resembling a pulley,
remain. The masses of chert are often impressed with the ornamented
articulating surfaces of the trochites.
In the quarries on Middleton Moor, near Cromford, Derbyshire, where
extensive beds of limestone composed of crinoideal remains are worked
for chimney-pieces and other ornamental purposes, beautiful examples
of these fossils may be obtained.[267] The cavities of the column and
ossicles are often filled with white calcareous spar, while the ground
of the marble is of a dark reddish brown colour; in other varieties of
the Derbyshire encrinital limestones, the substance of the fossils is
white, and the ground dark grey or brown,[268] A slab of this marble,
with portions of columns lying in relief, and a polished section
showing the inclosed entrochites, are figured _Wond._ p. 650.[269]
[267] See Excursions around Matlock, Part IV. of this work.
[268] Pict. Atlas, pl. xlix. figs. 1, 3, 6.
[269] Upwards of 80 figures of Encrinital remains are given in Pict.
Atlas, pl. xlvii.
[Illustration: Lign. 91. Illustrations of Crinoidea.
Fig. 1.--Group of Living Comatulæ; _nat._ (_Dr. Thompson._)
1_a_.--A single Comatula of the same group, magnified.
2.--Pentremites pyriformis. _Silurian, Ohio._
3, 4.--Surfaces of two pentapetalous ossicula.
5.--A single Ossicle of an Apiocrinus. _Chalk._
6.--Encrinus liliiformis; the receptacle with part of the
column attached; 1/2 _nat._ _From Brunswick._
7.--Pentacrinital stem with four angles.
8.--Entrochite, composed of five smooth ossicles.
9.--Quadrangular stem of seven ossicles.
10.--Cyathocrinus tuberculatus. (_Sil. Syst._)
11.--Receptacle of Bourqueticrinus; _from the Chalk. Lewes._
]
The _receptacle_ which contained the viscera is extremely diversified
in form, and in the number, shape, and arrangement of its plates: the
annexed figure 2, _Lign. 92_, illustrates the several pieces that enter
into its composition. The genera, or sub-genera, are based on the
modifications of shape and structure of the receptacle; and their names
are composed of the termination _crinus_, or _crinites_ (signifying
stone-lily), with a term prefixed expressive of the generic character:
thus we have _Apiocrinus_, or _Apiocrinites_, Pear Encrinite.[270]
[270] The termination _crinus_ is now generally employed, instead of
_crinites_; the latter is preferable, as it indicates the fossil nature
of the specimens. A more expressive name than _Encrinite_ was suggested
by Mr. Martin, of Derbyshire; that of _Stylastritæ_ or Column-Stars.
The receptacle being round and inflated, and composed of pieces
articulated with the stems, and supporting the arms by similar
articulations, are the generic characters of _Apiocrinites_ of
Miller. When round but not inflated--_Encrinus_, when pentagonal,
_Pentacrinus_. When the receptacle is composed of angular plates united
at the edges and forming several series or stages, it constitutes the
basis of the following genera: viz,--
_Platycrinus_; two series, the one of three, the other of five plates.
_Pateriocrinus_; three series each of five plates.
_Cyathocrinus_; three series of five plates, the last with five
intercalated pieces.
_Actinocrinus_; several series of plates: the first composed of three,
the second of five, and the others of many pieces.
_Rhodocrinus_; several series of plates that are covered externally
with radiated ridges. The first course consists of three, the second
of five, the third of ten, and the others of many plates.
_Eugeniacrinus_; of five pieces united into one receptacle.
This brief explanation will enable the student to comprehend the
nature of the almost infinite variety of figure and ornament which the
fossil crinoidea present, and the principles of nomenclature generally
adopted by modern authors. To attempt an enumeration even of the genera
would be inadmissible in these volumes. The late Mr. Miller's "Natural
History of the Crinoidea or Lily-shaped Animals,"[271] will afford the
student satisfactory information on this class of organic remains.[272]
[271] Published in 1 vol. 4to. 1821, with coloured plates.
[272] A beautiful "Monograph on the Recent and Fossil Crinoidea," by
Messrs. Austin, in 4to. is in course of publication, of which but eight
numbers have appeared.
Apiocrinus (_A. Parkinsoni_). _Lign. 92, fig. 4._ (_Wond._. p.
652.)--The Apiocrinite or Pear-Encrinite of Bradford, from its size, and
the abundance of its remains in one particular locality, is the most
generally known of all the British fossil Crinoids. It abounds in the
beds of oolite, in the quarries on the heights above the picturesquely
situated town of Bradford, in Wiltshire. The receptacle, detached
ossicula, and the pedicle, are very common; and in some instances the
entire endo-skeleton, from the peduncle to the extremities of the arms,
is preserved. The late Channing Pearce, Esq., of Bradford, by unremitting
attention to the collection of these fossils, obtained the beautiful
specimens deposited in the British Museum.[273]
[273] Petrifactions, Room II. Wall-case G.
This Apiocrinite has a smooth receptacle of a pyriform shape, composed
of large thin plates with radiated articulating surfaces; the stem
is short and strong; the arms are simple, resembling those of the
_Marsupite_; the peduncle spreads out into an expanded base, which
is firmly attached to the rock, like that of the Gorgonia, and is
generally of a rich purple colour.[274]
[274] Pictorial Atlas, pl. xlix. Pulley-stones and Encrinital marbles;
pl. 1. Apiocrinites.
[Illustration: Lign. 92. Fossil Crinoidea.
Fig. 1.--Eugeniacrinus. _Switzerland._
2.--Cyathocrinus planus. _Mountain Limestone._
_a._ Basal plate of the _receptacle_.
_b._ One of the plates composing the walls of the pelvis.
_c._ Costal plate.
_d._ Intercostal plate.
_e._ Scapula, or ossicle that receives the arm.
_f._ First ossicle of the arm.
3.--Marsupites Milleri (G. A. M.). _Chalk, Brighton._
_a._ The semilunar cavity for an attachment of the arm.
4.--Apiocrinus rotundus, _Pear-Encrinite. Bradford._
_a._ First ossicles of the arms.
]
Sir Charles Lyell mentions an interesting fact relating to the
occurrence of these fossils in the Oolitic limestone at Bradford. In
Burfield quarry, on the heights that overlook the town, a bed of
limestone was exposed, the upper surface of which was incrusted with
the stony peduncles or roots of Apiocrinites; upon this stratum was
a layer of clay, in which were innumerable remains of receptacles
and ossicula of stems and arms; some of the stems were erect, others
prostrate, and throughout the clay were the dismembered remains. This
submarine forest of Crinoideans must therefore have flourished in
the clear sea-water, till invaded by a current loaded with mud that
overwhelmed the living zoophytes, and entombed them in the argillaceous
deposit in which their fossil remains are imbedded.[275]
[275] Burfield quarry, on the heights of Bradford, is the locality
referred to; but I believe it is rarely that any specimens of the
Apiocrinite are to be found in an erect position. I could not learn
from any of the local collectors, that an example had been seen by
them. When I visited the quarry in June, 1848, no good section of the
beds was apparent: a few detached plates of Apiocrinites were the only
relics we could meet with. Mr. Reginald Mantell, when engaged on the
construction of the railway near Bradford, sought repeatedly, but in
vain, to discover any Apiocrinites in an erect position, or as if lying
on the spot where they grew.
The constituent substance of the ossicula and plates of the Bradford
Encrinite is calcareous, and has an oblique fracture; the colour is
generally a light ochre, or a bluish grey.[276]
[276] Pict. Atlas, pl. 1. contains figures of the Bradford Encrinites.
[Sidenote: APIOCRINITE OF THE CHALK.]
Apiocrinus ellipticus. _Lign. 93._--Detached ossicula of this small
encrinite are abundant in the White Chalk; the receptacle is known
to the quarrymen by the name of "_bottle_." The pieces composing the
column are cylindrical in the upper part, and elliptical and angular
in the lower, and are articulated by a transversely-grooved surface.
The two upper joints are enlarged, and support the receptacle, which is
smooth and round (_fig._ 1). The column has articulated side-arms, and
the base numerous jointed processes of attachment, which, when found
apart from the column, have been mistaken for a distinct type, and
named "_Stag's-horn Encriniter_."[277] The specimens figured _Lign.
93_, show the essential characters of this crinoid; when perfect, this
species must have borne a general resemblance to the Pear Encrinite of
Bradford.
[277] Pict. Atlas, pl. xlvii. _fig._ 31, p. 113. In the same plate there
are figures of several specimens of detached portions of the stem of
this species from the Kentish Chalk.
[Illustration: Lign. 93. Apiocrinites. _Chalk, Lewes._
Fig. 1.--Apiocrinus ellipticus, × 3.
1_a_.--Part of the elliptical portion of the column, with a
side-arm.
1_b_.--Portion of the same, magnified.
1_c_.--The articulating surface of an ossicle.
2.--Ossicle of A. flexuosus. (_M. D'Orbigny._).
3.--Portion of the cylindrical stem.
]
Bourqueticrinus (D'Orbigny). _Lign. 91, fig. 11._--Detached ossicles
of other species belonging to the same genus, or to allied genera,
are frequently met with in the Kentish and Sussex chalk. A common
form is that figured in _Lign. 91_, which is part of the receptacle
of a crinoid, named as above; it differs from the other Apiocrinites
of the chalk in the articulating surfaces of the ossicles not being
radiated, and in the receptacle, which is small and pyriform, not
having a distinct cavity; there is only a median canal, which is seen
in a vertical section: but the entire structure of the summit does not
appear to be shown in any specimens hitherto observed.
Encrinus liliiformis (_Lily Encrinite_). _Lign. 91, fig. 6._--This
exquisite Crinoid is equally interesting and attractive to the amateur
collector and the naturalist. Its remains do not occur in the British
strata, and are only known in the muschelkalk of Lower Saxony. The
specimens in this country are chiefly from Erkerode, in Brunswick;
they are found in a layer, about eighteen inches thick, of a soft
argillaceous cream-coloured limestone, chiefly made up of trochites,
detached ossicula, and a few fragile shells and corals.
The receptacle of the Lily Encrinite is smooth, and in the form of a
depressed vase; its base is composed of five plates, upon which are
placed three successive series of other plates, with the uppermost of
which the arms articulate. The stem is formed of numerous perforated
round ossicles, articulated to each other by radiated grooved surfaces,
and becoming somewhat pentangular, and alternately larger and smaller,
towards the summit, to which the receptacle is fixed; a construction
admitting great freedom of motion.[278]
[278] Mr. Miller's work should be consulted for details of structure.
This Encrinite when lying in relief on the rock, with its receptacle
entirely or partially closed (see _Wond._ p. 548), so strikingly
resembles the bud or expanding flower of a Lily or Tulip, as to justify
the popular name of Stone-lily. An exquisite specimen is figured by Mr.
Parkinson;[279] the British Museum possesses some fine examples.[280]
[279] Pict. Atlas, pl. xlviii.
[280] Petrifactions, p. 77.
Mr. Parkinson detected the animal membrane in ossicles of this crinoid,
by immersing them in dilute hydrochloric acid.[281] My friend Mr.
Frederick Harford has repeated the experiment with success.
[281] See Pict. Atlas, pl. xlvii. _fig._ 47.
[Sidenote: PENTACRINITES.]
Pentacrinites.--The description of the recent _Pentacrinus_
_caput-medusæ_ (_ante_, p. 282), illustrates the characters of the
crinoideans whose fossil remains are so familiar to the palæontologist,
under the name of Pentacrinites. In these animals the pieces composing
the receptacle are firmly articulated together; the rays of the disk
are fixed immediately to the summit of the column by special ossicula;
and the stem is composed of angular pieces, which are generally
pentagonal. The receptacle is small, and situated deep between the
bases of the arms; it is closed above by an integument covered by
minute plates or flat ossicles (_Lign. 94, fig. 2_). The fossil
remains of several species are abundant in the Lias and Oolite of
Dorsetshire, Somersetshire, &c. Slabs of limestone may be extracted
with the surface covered with these crinoideans, spread out as if
floating in their native element; very commonly they are transmuted
into sulphuret of iron, or have a coating of brilliant pyrites.[282] The
neighbourhoods of Lyme Regis, and Charmouth, are celebrated for these
organic remains. A small specimen of the arms of a pentacrinite on Lias
shale is figured in _Lign. 94, fig. 3._
[282] Pictorial Atlas, pl. li. lii.
The arms in many of the plumose pentacrinites are very long and thickly
beset with side-arms, and minute pinnæ, all of which are composed of
separate articulated ossicles, so that the number of bones in a single
endo-skeleton of those crinoids amounts to from fifty to one hundred
and fifty thousand distinct pieces. The Briarean Pentacrinite,[283] so
named from its numerous tentacula, is literally a tuft of articulated
processes, appearing like a delicate fibrous plume attached to a
stem. The _Pentacrinus Hiemeri_ is a beautiful example of this type
of crinoids, of which there is a noble group, comprising upwards of
thirty individuals, on a slab in the British Museum,[284] exposed on
the surface of the stone in as perfect a state as if just dredged up
from the bottom of the sea. The pentacrinites are for the most part
entire; the peduncle being fixed, and the column extending upwards
in gentle undulations, and supporting the receptacle, from which the
arms are gracefully outspread in various attitudes. The structure of
the receptacle, and of the arms, and the extreme delicacy of the finer
tentacula made up of countless minute ossicula, are admirably shown in
this unique and most instructive fossil.
[283] Pictorial Atlas, pl. xlvii. The Briarean Pentacrinite is fully
illustrated and described in detail in Dr. Buckland's Bridge water
Essay, p. 484.
[284] This species was named and figured by M. König in his "_Icones
Fossilium sectiles_," pl. iii. _fig._ 29, in 1826. See Petrifactions,
p. 88.
[Illustration: Lign. 94. Actinocrinites, or Nave Encrinites.
Fig. 1.--Actinocrinus Parkinsoni. (_Org. Rem._ ii. pl. xvii. _Pict.
Atlas_, pl. li.)
2.--Section of an Actinocrinus, (_Miller's Crinoideæ_, pl. ii.)
a. Proboscideal protrusion of the plate and integument.
b. Sections of the folded or closed arms.
3.--Arms of a Pentacrinite, on Lias-shale; _Lyme Regis_.
]
[Sidenote: ACTINOCRINUS. CYATHOCRINUS.]
Actinocrinus (_Nave Encrinite_). _Lign. 94, fig. 1, 2._ (_Wond._
p. 585. _Bd._ pl. xlvii.)--The column is formed of numerous round
ossicula, possesses side-arms, and is fixed by root-like processes.
The receptacle is of an irregular subspherical form, the arms passing
off at right angles like the spokes from the nave of a wheel; hence
the name. The base is composed of three plates which support five
hexagonals and one pentagonal, and on these are three other series;
from the upper margin of the last, five arms are given off. The
receptacle is closed by a dome-shaped tesselated covering (_Lign. 94,
fig. 2_), having on one side the opening for the mouth and vent. The
specimen, _fig. 1_, is a receptacle without a stem, and with but a few
joints of the arms; this is the usual state in which these fossils are
obtained. _Fig. 2_ is an _Actinocrinite_ in which part of the brim of
the receptacle and of the arms has been removed in front, leaving a
portion of the coalesced arms partially surrounding the proboscideal
plated integument that covers the upper part of the receptacle; the
figure is from Mr. Miller's work, and is introduced to illustrate the
structure of these crinoideans.[285]
[285] Miller's Crinoidea, _fig._ N. pp. 98-100.
The external surface of the plates of the receptacle in the
Actinocrinites, is generally covered with radiated markings and
ridges, so that detached plates have been mistaken for those of
Marsupites; see the restored figure of a Nave Encrinite, _Wond._ p.
654. In some species the receptacle is richly ornamented; but in the
specimen figured, _Lign. 94, fig. 1_, the surface has been defaced in
consequence of the fossil having been immersed in strong acid.
Cyathocrinus (_Cup-like Encrinite_). _Lign. 95_, and _Lign. 92, fig.
2_.--The column is formed of round, depressed, perforated joints,
articulating by radiated surfaces; pentagonal near the summit. The
receptacle is composed of five pieces, succeeded by two successive
series of five plates, with intervening plates, and supports five
bifurcating, radiated arms.
[Illustration: Lign. 95. Cyathocrinites planus; _nat._
_Mountain Limestone, Clevedon._]
The Encrinites of this genus have a light and elegant appearance: the
forms of the plates composing the pelvis, and of the ossicula of the
arms, are shown in _Lign. 92, fig. 2_; which represents a specimen of
_C. planus_, from the magnesian limestone of Somersetshire; a beautiful
example of the same species is figured in _Lign. 95_. The receptacle
resembles in shape a depressed vase; its upper part was probably
covered by a plated integument, having an aperture in the centre as in
the Actinocrinites. Cyathocrinites occur in the Silurian, Devonian, and
Carboniferous formations.[286]
[286] A figure of Cyathocrinus rugosus is given in Pict. Atlas, pl.
xlix. _fig._ 4. The same work contains coloured figures of Pentacrinus
scalaris (Goldfuss), pl. xlvii. figs. 57, 64, 66; Pentacrinus
basaltiformis, pl. xlvii. _fig._ 47.
A remarkable receptacle, with the tentacula partially introverted, is
figured Pict. Atlas, pl. xlvi. _fig._ 2, from Gloucestershire; and
several beautiful examples of the arms, tentacula, &c. of Pentacrinites
in Lias limestone and shale, in pl. li. figs. 9, 15, 16, and pl. lii.
figs. 1, 2, 3, from Charmouth.
Rhodocrinus. (_R. verus._ _Pict. Atlas_, pl. xlix. _fig._ 7, 8.)--A
beautiful form, allied to the Antinocrinoids, occurs in the palæozoic
rocks, and is named the Rose-encrinite by Miller. The column is
cylindrical and traversed by a pentagonal canal. The rays or arms
arise by a single ossicle and then bifurcate: the receptacle is
formed of three, five, ten, and more numerous series of plates, which
are ornamented externally. A fine example of a crinoid of this type
(_Hypanthocrinus_) from the Wenlock limestone, is figured in the London
Palæontological Journal, pl. xxi.
In Sir R. Murchison's Sil. Syst. all the crinoids of the Silurian
deposits, then known, are figured. Several new genera are described by
Professor McCoy, in the Synopsis of British Palæozoic Fossils.
Eugeniacrinus (_Clove-like Encrinite_). _Lign. 92, fig. 1._--These
little crinoids, which resemble a clove in form, are found at Mount
Randen, in Switzerland, in Oolitic limestone. The receptacle is simple
in structure, for it has but one series of plates; its cavity is very
small. It had five arms: the articulating surface of the ossicles is
radiated. When perfect this crinoidean must have somewhat resembled the
Lily Encrinite, but the plates are all anchylosed, or blended together,
which Mr. Miller attributed to an early stage of growth.
[Sidenote: PENTREMITES PYRIFORMIS.]
Pentremites pyriformis (_Pear-shaped angular Encrinite_). _Lign.
91, fig. 2._--The column of this remarkable crinoid is short, and
formed of cylindrical, perforated ossicula, with radiated surfaces,
and has irregular side-arms. The receptacle is composed of polygonal
plates, divided by five perforated grooves or furrows, which are of
an elongated petalous form, and converge in a rosette on the summit.
The marginal longitudinal rows of minute pores are not however for the
passage of soft membranous feelers, as in the ambulacra of echinoderms,
as was formerly conjectured, but are channels for the transit of
vessels that supply an infinite number of delicate simple tentacula,
composed of extremely minute calcareous ossicula, as in the other
Crinoidea, but not subdivided as in the Pentacrinites and Encrinites.
These articulated tentacula are arranged close together in longitudinal
rows on the ambulacral spaces; there being two rows, each consisting
of fifty tentacula, on every space. They are directed upwards towards
the vertex of the receptacle, and appear to be the instruments for the
capture and conveyance of food to the mouth.[287]
[287] See Dr. Fred. Röemer on jointed tentacles found on the ambulacral
spaces of _Pentremites_, "Geol. Journal," vol. v. p. 8.
There are several species of Pentremites, some of which swarm in the
cherty limestones of Kentucky. Mr. Say, to whom we are indebted for the
first satisfactory investigation of these fossils, mentions that such
is their abundance, that he has observed, on a piece of rock not larger
than three inches by two-and-a-half, above twenty specimens lying in
relief
Cystidea.--In the ancient fossiliferous strata there occurs a
remarkable family of crinoideans, which is supposed to be restricted
to the palæozoic ages; these fossils have been named by Von Buch,
_Cystideæ_, from the body of the animal being wholly inclosed in a
cyst, or box. The receptacle is of a spherical form, and composed of
polygonal plates, articulated to each other; it has distinct apertures
for the mouth, vent, and oviduct; the orifice of the latter is closed
by valves. It has a short pedicle, but no arms have been discovered,
and the Cystideæ are generally described as Crinoids without appendages
of this kind. But in some members of this group, there are not only
arms and tentacula, but likewise certain organs connected with the
plates, which Prof E. Forbes terms, "pectinated rhombs," the functions
of which are not obvious. The arms more closely resemble those of
the Ophiuridæ than of the Crinoidea.[288] This order comprises several
genera, and is the type under which the Crinoidea first appear in
the natural records of our planet, according to the present state of
our knowledge, and which becomes extinct before the advent of the
Pentacrinites.
[288] See a memoir on the British Cystidea, by Prof. Ed. Forbes; in the
Mem. Geological Survey, vol. ii.
[Sidenote: MARSUPITES MILLERI.]
Marsupites Milleri. _Lign. 92, fig. 3, Lign. 96._ (_Wond._ p.
652.)--The fossil remains of a genus related to the Encrinites, but
separated from them by being unattached and free, having no column
of support, were first described by the late Mr. Parkinson under the
name of "_Tortoise Encrinite_" (_Org. Rem._ vol. ii. pl. xiii. _fig._
24, _Pict. Atlas_, pl. xlvii.); but misled by the resemblance of some
of the plates to those of certain species of Actinocrinites, Mr.
Parkinson supposed the original to have possessed a jointed column. The
examination of specimens obtained from the Chalk of Lewes and Brighton,
enabled me to determine the true characters of the original; the
purse-like form when the arms are closed suggested the name Marsupites
(_purse-like_), by which it is now generally known; the specific name
_Milleri_, is in commemoration of the late excellent and able author of
the Natural History of the Crinoidea.
The receptacle of the Marsupite is of a sub-ovate shape, and rounded
and entire at the dorsal extremity; a large central plate forms
its base, on which is placed a successive series of pentagonal and
hexagonal plates, the margins of which are in contact, but not
anchylosed nor firmly united; to the periphery of this cup are
articulated five arms, which subdivide into ten rays, or tentacula. The
top of the receptacle was closed by an integument, covered by numerous
small semilunar plates, in the centre of which was situated the oral
aperture. The external surfaces of the plates of the receptacle are
generally granulated and radiated, as in _Lign. 92, fig. 3_; but in
some specimens the surface is quite smooth, a character which possibly
may be specific. Some examples have the surface granulated and rugous,
and these Mr. Miller regarded as distinct, and named _M. ornatus_. I
have not of late years been able to obtain specimens to determine this
question.
The Marsupites vary in size, from an inch to three inches in length,
exclusive of the arms. The receptacle is relatively very capacious
compared with that of other crinoideans. The central plate is large,
and of a pentagonal form, without the slightest indication of any
column or process of attachment: five pentagonal plates are united
to the sides of the basal plate, and above these a like number of
hexagonals, which receive the five upper plates that constitute the
margin; these have each a semilunar depression, to articulate with the
first bones of the arms, or brachial appendages.
[Illustration: Lign. 96.--Marsupites Milleri, _nat._
_Chalk, Lewes._]
Detached plates and ossicula of marsupites are not uncommon in the
Chalk of Kent and Sussex; nearly entire receptacles, filled with chalk
or flint, are occasionally found in the pits near Lewes and Brighton;
but examples with remains of the arms are extremely rare; and I have
seen but one specimen (which I collected from the Sussex chalk), in
which the plates of the integument that covered the opening of the
receptacle are preserved.[289]
[289] It is figured in my _South D. Foss._ pl. xvi. _fig._ 6.
The Marsupite is an exceedingly interesting type, in a zoological
point of view, since it forms a link that unites the Crinoidea with
the Comatulæ, or feather-stars, which we shall presently notice. Its
general form and habits are sufficiently indicated by the numerous
specimens that have been collected in the Chalk of the south-east of
England.
The body of the animal was inclosed in a crustaceous case formed
of large plates, articulated to each other by suture; the mouth or
oral aperture was situated in the centre of the plated integumental
cover of the receptacle. The organs of locomotion and prehension
consisted of five arms or brachial appendages, formed of ossicula
as in the crinoidea, and the whole was invested with soft tissue or
integuments. When floating in the water, the creature could spread
out its tentacula, and form a net to capture its prey, and by closing
them, secure it, and convey it to its mouth. The figure, _Lign. 96_,
is restored from specimens which separately exhibit the parts here
represented in connexion.
* * * * *
Fossil Asteriadæ.
[Sidenote: FOSSIL ASTERIADÆ.]
The radiated animals, popularly called _Star-fishes_, from their
stellular forms, are so abundant on our coasts, that the common
five-rayed species must be familiar to all my readers who indulge
in rambles on the sea-shore, and will serve as an illustration of
the general appearance and structure of the beings whose petrified
remains now claim our attention. This species belongs to the division
of Asteriadæ, in which the rays are elongated, and far exceed in
length the diameter of the disk; in another group (_Goniastea_, or
Cushion-star), the body is angular, and the lobes or rays are short,
and not longer than the diameter; while in a third subdivision
(_Comatula_ and _Ophiura_), the arms are distinct from the body, and
articulated, elongated, and ramified, as in the _Crinoidea_.
The external surface of the common Star-fish is soft, and attached to
a tough coriaceous integument, investing a skeleton composed of an
infinite number of calcareous ossicula, arranged in regular series
along the margins of the rays. Each ray has a longitudinal furrow,
perforated at the sides by alternating rows of pores, through which
tubular tentacula are protruded. The mouth is situated in the centre
of the under surface. Now if we imagine a Star-fish placed with
its mouth upwards, and the five rays fringed with long articulated
tentacula, as in the Comatula, and fixed by the centre of its dorsal
surface upon a jointed stem, we shall have the essential characters
of a crinoidean; and the animals of one recent tribe of _Asteriadæ_
are actually in this condition in the earlier stage of their
existence: these are the _Comatulæ_, or Feather-stars, in some of
which (the _Euryale_), the arms are as numerously subdivided as in the
Pentacrinites.[290]
[290] The reader interested in this subject should peruse the charming
volume on British Star-fishes and other Echinoderms, by Professor
Edward Forbes. 1 vol. 8vo. John Van Voorst. 1841.
From the importance of the Crinoidea in the economy of the ancient
world, the history of the only type at present inhabiting Europe, the
ancient seas of which swarmed with numerous forms of these beautiful
creatures, presents many points of interest. The receptacle of the
soft body of the _Comatula_, like that of the Crinoideans, consists
of a cup-shaped calcareous base, which sends off from its margin five
arms, that quickly subdivide, and are beset on each side with rows of
articulated pinnæ; on the convexity there are also numerous slender,
jointed, simple, tentacula. The mouth is situated in the centre of
the area surrounded by the arms, and is capable of being elongated
into a proboscis. In the young state, the Comatulæ are attached by a
jointed stem to other bodies, as shown in _Lign. 91, _fig. 1_, which
represents several of the natural size; _fig. 1a_ is an enlarged
view of an individual, and closely resembles an expanded Crinoidean.
The stem is composed of about eighteen joints, which are pentangular;
after a few weeks the Feather-star becomes detached from its peduncle,
and ranges the sea in freedom.[291]
[291] The researches of J. V. Thompson, Esq. first brought to light
these interesting facts in the Natural History of the Comatula; this
eminent naturalist first observed pedunculated Comatulæ in the Cove of
Cork. When this discovery was first made known to me, I suspected that
the _Marsupite_ might have been pedunculated when young; but as very
small specimens of this Crinoid are equally free from all traces of
a stem as the adult, I was led to relinquish that opinion: still the
collector, when searching for Crinoidean remains, should bear in mind
the possibility of this having been the case.
In the Comatulidæ, the arms are distinct from the body; these animals
therefore closely approach the Crinoideans: in the true Star-fish,
the angular processes, or arms, are an integral part of the body,
containing a portion of the stomach, ova, &c., and are furnished with
rows of pseudopodia.
Fossil Comatulæ have been discovered in the Solenhofen slate; and it is
not improbable that some of the numerous Crinoideans may be Asteriadæ
in the early stages of development.
In another group, Asteriadæ, (named _Ophiuræ_ or Serpent-stars,) the
rays are long and slender, and without grooves or tentacula, and are
distinct from the body. These organs are extremely flexuous, and in
some species beset with spines, and enable the animal to seize and
entwine round its prey. The mouth is central, and there is an ovarian
aperture at the base of each of the five arms.
Though the fossil Star-fishes comprise many extinct genera, they
belong to the same families as the recent; and Comatulæ, Ophiuræ,
and Asteriadæ, occur in the Lias, Oolite, and Chalk, in considerable
numbers. Professor Edward Forbes has determined many of the British
species, and it is to be hoped, will publish a monograph on the
Fossil Asteriadæ, as a companion to his delightful work on the recent
Star-fishes.
[Sidenote: FOSSIL OSSICULA OF STAR-FISHES.]
Fossil Ossicula of Star-fishes.--From the immense number of little
bones which enter into the composition of the skeleton of a single
Star-fish, and which are but slightly held together after the death of
the animal and the decomposition of the soft parts, we can understand
how layer upon layer of ossicula of Asteriadæ may have been formed at
the bottom of the cretaceous seas; as we find them in the quarries near
Arundel, Worthing, &c. Whoever has witnessed the hauling up of the
dredge off our coasts, and seen the mass of living Star-fishes which it
brings up, as if the sea-bottom were a living bank of these Radiata,
will not be surprised at the vast quantities of their fossil remains.
This profusion of the living animals of this family, serves also to
account for the enormous amount of those kindred but extinct forms,
whose relics were the subject of investigation in the former part of
the present chapter.
The ossicula vary in shape in different parts of the skeleton, and
Prof. E. Forbes affirms, that the careful determination of their
characters is of great importance, since they are the only paints of
the animals likely to be preserved, and the shape of an ossicle is as
truly indicative of a genus or species, as is that of a bone among the
vertebrata. There is one ossicle situated on the side of the centre of
the disk, which is worthy of remark, because it often occurs in the
chalk mingled with the debris of the rest of the skeleton, and should
be preserved by the collector. It differs from all the other bones in
being marked with radiating grooves, and is called the madreporiform
tubercle; it appears to be the analogue of the stem of the Crinoideæ,
in other words, a rudimental condition of an organ, which is fully
developed in that order of radiata.
[Sidenote: OPHIURA.]
Ophiura. _Lign. 97, fig. 1._--Several species of this genus, which is
distinguished by the long, slender, serpent-like arms, and the circular
disk covered with plates and spines, have been found in a fossil state:
one species was discovered in the Lower Silurian deposits by Prof.
Sedgwick, and other forms have been obtained from all the succeeding
formations. The Lias near Lyme Regis and Charmouth has yielded many
beautiful examples of _Ophiura Egertoni_. Professor John Phillips has
figured a species (_Oph. Milleri_, Geol. York, pl. xiii.) from the
marlstone of Yorkshire, and a species from the Oxford Clay has been
described as _Ophiura Prattii_. In the Cretaceous formation, remains
of several species have been found. The first specimen from the Sussex
Chalk that came under my notice, was discovered many years since, by
my son, in a quarry at Preston, near Brighton; the rays were admirably
preserved, as shown in the portion figured in _Lign. 97._ An example
of this species, with the disk entire, and portions of five arms, was
found by Henry Catt, Esq. and is represented in pl. xxiii. _fig._ 2, of
Mr. Dixon's work.[KF]
[292] Three plates are devoted to the Cretaceous Star-fishes: the
descriptions by Prof. E. Forbes comprise twenty-five species, belonging
to the genera Oreaster, Goniaster, Stellaster, Arthraster, and Ophiura,
all from the Chalk of Sussex and Kent.
[Illustration: Lign. 97. Fossil remains of Star-fishes.
Fig. 1_a_.--Part of the ray of Ophiura serrata; _nat._ _Chalk, Preston._
(_Mr. Walter Mantell._)
1.--Portion of the same magnified.
2.--Goniaster Hunteri. _Chalk. Gravesend._
]
[Sidenote: GONIASTER--ASTERIAS.]
Goniaster. _Lign._ 97 and 98.--The star-fishes of this genus, popularly
called Cushion-stars, are of a pentagonal form, and have a double
series of large marginal plates, bearing granules or spines; the latter
are seldom preserved in the fossils. The upper surface is nodulose.
[Illustration: Lign. 98. Fossil Star-fish. _Chalk, Kent._ Goniaster
Mantelli. (_sp Forbes._[293])]
[293] Dixon's Cret. Foss. p. 332.
The detached ossicula of the skeletons of Cushion-stars are frequent
in the White Chalk; and the large central bone, the _madreporiform
tubercle_, which is present in the dorsal aspect of all star-fishes,
is large, and therefore often observed, and may be easily mistaken for
the base of a crinoidean receptacle. The layers in the Sussex Chalk
composed of the exuviæ of star-fishes, as previously mentioned, are
chiefly made up of ossicula of goniasters.
There are two species not uncommon in the Chalk, of which portions may
generally be obtained from the pits near Gravesend; and occasionally
very fine examples of the entire goniaster are met with. Mr. Dixon's
work contains figures of several exquisite fossils of this kind. These
organic remains were familiar to the early collectors: Mr. Parkinson
figures several in Org. Rem. vol. iii. pl. i. and ii.[294]
[294] Pict. Atlas, pl. liii.
_Goniaster Hunteri_ (_Lign. 97_), has the body obtusely pentagonal, and
the sides nearly straight; the superior intermediate marginal plates
are four, equal, broadly oblong, coarsely mamillato-punctate; the
ossicula of the disk hexagonal.[295] This species is common in the upper
chalk.
[295] Prof. Forbes, Dixon's Cret. Foss. p. 331.
In _Goniaster Mantelli_, _Lign. 98_, the body is pentagonal, but the
sides are curved, with projecting angles; the ossicula of the disk
are punctated. The superior intermediate marginal plates are oblong,
narrow, punctate, marginate, and six in number.[296]
[296] Ibid. p. 332.
Specimens of these Goniasters are sometimes met with attached to a
nodule of flint, in an extraordinary state of freshness; sharp imprints
of the external surface, the skeleton having perished, are also found
in flints, and, rarely, casts in pyrites. The whetstone of Dorsetshire
often bears distinct moulds of Goniasters! I have found ossicula of
this form of Star-fish in the London Clay of the Isle of Sheppey.
Asterias. _Lign. 99._--The animals of this genus, of which the common
Star-fish is the type, are stellate in form; the rays are flat, and
extend from the body, of which they are a prolongation--not mere
appendages. They have deep grooves or furrows bordered by marginal
plates, which are continued to the extremities.
The Lias of Germany has yielded several species of Asterias; one of
which is figured, _Lign. 99_. A very large species occurs in the
Cornbrash of the Oolite of England. A magnificent specimen of _Asterias
arenicola_ (Goldfuss), from the calcareous grit, near Pickering,
Yorkshire, measuring 10-1/2 inches from the extremity of one ray to
that of another, is figured in the London Palæontological Journal, pl.
xvii. The same work contains admirable figures of _Ophiura Egertoni_,
and _Oph. senatu_ in flint, pl. xix.; _Oph. Milleri_ in Staithes
marlstone, and _Oph. Murravii_, pl. xx.; and two specimens of _Oph.
Milleri_ on the same slab of Lias from Staithes, near Whitby, pl. viii.
The Star-fishes of the British palæozoic strata are described by Prof.
E. Forbes in the Memoirs of the Geol. Survey, _Decad._ 1.[297]
[297] See also Prof. M'Coy's Lower Palæozoic Fossils, p. 58.
[Illustration: Lign. 99. Fossil Star-fish. _Lias, Wirtemberg._
Asterias prisca. (_Goldfuss._)]
[Sidenote: GEOLOGICAL DISTRIBUTION OF CRINOIDEA.]
Geological distribution of the Crinoidea.--The great number of extinct
forms of this order of Radiata in the most ancient fossiliferous
deposits, is a remarkable fact, which has already been incidentally
adverted to. In the palæozoic seas--including the Silurian, Devonian,
Carboniferous, and Permian--the Crinoidea were represented by upwards
of fifty genera, whose existence began and ended during that geological
cycle.
According to the present state of our knowledge all those peculiar
types of radiated animals were created, and each lived through the
destined period alloted to its race, and died out ere the deposition
of the New Red Sandstone; not a single species, not a relic of the
innumerable individuals that swarmed in the palæozoic oceans, has been
observed in any strata above the Permian.
The Trias, which ranks as the earliest of the secondary formations, is
characterized by the advent of two typical genera; the true Encrinus or
Lily-encrinite, and the Pentacrinus; the former is unknown in any other
deposits; the duration of its race was comprised within the Triassic
epoch. The Pentacrinus, on the other hand, has been perpetuated through
all the succeeding periods, and one species inhabits the present seas;
the sole existing representative of the most ancient type of this order.
In the Oolite, another living form, the Comatula, first appears.
The ocean of the Cretaceous epoch was inhabited by five genera of
Crinoids, unknown elsewhere; among them is that remarkable genus, the
Marsupite.
The Crinoidea of the Tertiary seas are as few in number and variety as
those of the present day; not a vestige of any of the ancient tribes
has been discovered. M. D'Orbigny's _Tab._ 12 presents the phenomena
thus briefly noticed, in a striking point of view.
* * * * *
From this review of the fossil Crinoidea and Asteriadæ, the student
will be in some measure prepared for the collecting of instructive
specimens from the immense accumulation of remains imbedded in certain
strata of the Oolitic, Liassic, Carboniferous and Silurian rocks.
The British species of fossil Crinoidea amount to more than two
hundred, and when the great number of bones that enter into the
composition of the skeleton of a single Pentacrinite or Encrinite is
considered, the prodigious quantity of the fossil remains of these
zoophytes in the ancient deposits may be readily conceived. Polished
slices of the encrinital marbles of Derbyshire, and of the Lias
limestones from Lyme Regis and Charmouth, should be obtained, as they
show sections of the imbedded crinoidal stems and detached ossicula;
and sometimes of the receptacles.