93, _imbricated_; 94, _pectinated_; 95, _plicated_; 96, _decussated_; 97,
_muricated_; 98, _foliated_.]
By the foregoing general observations and explanations, it is trusted that
the reader will be prepared for the following exposition of the general
arrangement of Lamarck, and the principles upon which it is founded.
* * * * *
GENERAL ARRANGEMENT
ACCORDING TO LAMARCK.
In Lamarck's "Histoire Naturelle des Animaux sans Vertebres," he divides
the invertebrata into classes, the 9th, 10th, and 11th of which include
animals possessed of shells properly so called. These are the ANNELIDES,
the CIRRIPEDES, the CONCHIFERA, and the MOLLUSCA.
The class ANNELIDES constitutes the 9th, and is divided into three orders,
namely, the "Apodes," "Antennees," and "Sedentaires"; the last of which,
_Sedentaria_, alone contains testaceous animals. This order includes
tubular shells, which, with the exception of Dentalium, are irregularly
twisted, and attached to each other, or to extraneous substances. The first
family _Dorsalia_, contains the genus Siliquaria (plates, fig. 1), known
from the Serpulæ, by the slit which passes through the whole length of the
shell on the upper surface of the tube. The second family, _Maldania_, has
the genus Dentalium (plates, fig. 2), a species of which are commonly known
by the name of "tooth shells"; these are regularly formed, curved conical
tubes, open at both extremities. The third family, _Serpulacea_, includes
the genera Serpula, Spirorbis, Galeolaria, Vermilia, Spiroglyphus, and
Magilus. The only shell that a learner would be likely to place among these
incorrectly, according to the system, is the Vermetus (plates, fig. 345),
which being regularly spiral at the apicial extremity, has been placed
among the Mollusca; to which situation the whole of the shells under
consideration have a better title than is generally supposed. It should be
mentioned that the Serpulacea are provided with opercula.
Class CIRRIPEDES.
This class constitutes the tenth of invertebrated animals, and receives its
name from the jointed and ciliated branchia which protrude between the
opercular valves. They are Multivalve shells, and were all included in the
single genus Lepas in the system of Linnæus, and are commonly known by the
name "Barnacles." Lamarck has, however, divided them into two distinct
orders. First, the _Sessile_ Cirripedes or those which being composed of
several valves, joined to each other, side by side in a circle, are
attached to each other, or to submarine bodies by the basal portion of
their own substance, and form a hollow, irregular cone, with the aperture
above closed by an operculum consisting of two or more valves. Secondly,
the _Pedunculated Cirripedes_, which are composed of valves placed in pairs
against each other, so as to form a flattened disc attached by means of a
tendinous tube called a peduncle. The first of these orders includes the
genera Tubicinella, Coronula, Platylepas, Clitia, Conia, Elmineus,
Catophragmus, Octomeris, Balanus, Creusia, Nobia, Savignium, Pyrgoma, Adna,
Megatréma. The second contains the genera Pentelasmis, Scalpellum, Smilium,
Pollicipes, Bisnæus, Lithotrya, Ibla, Octolasmis, Cineras, Otion.
Conchological writers are not agreed as to the propriety of allowing the
above to enter into the present science.
Class CONCHIFERA.
The shell of a conchiferous animal is always bivalve, composed of two
pieces placed opposite to each other, joined at the dorsal margins by an
elastic hinge. All true bivalve shells belong to animals of this class; and
the correspondence between the shell and the animal is so true that on
examining an empty bivalve shell we can not only determine that its
inhabitant belonged to this class, but also decide on the particular order
and family in which it should be placed, without seeing the soft parts.
The first general division of Conchifera is that which results from
observing the muscular impressions, or marks made on the inner surface of
the valve by the insertion of the adductor muscles. All Conchifera are
divided into two orders, as follows:
First Order, _Conchifera Dimyaria_.
Having two adductor muscles, and consequently two impressions in each
valve. They are separated into the following families:
1. _Tubicolæ_ (plates, fig. 44 to 54), having shelly tubes besides the
valves. This family contains the genera Aspergillum, Clavagella,
Teredina, Teredo, Xylophaga, Fistulana, and Gastrochæna.
2. _Pholadaria_ (plates, fig. 55 to 59), cylindrical, living in holes
in rocks pierced by the animals. Lamarck places in this family the
genera Pholas and Gastrochæna, the last of which belongs more properly
to the family Tubicolæ, as placed above.
3. _Solenacea_ (plates, fig. 60 to 68), longitudinally (transversely,
Lam.) elongated, open at the anterior and posterior extremities. This
family contains the genera Solen, Pholadomya, Panopæa, Glycimeris
(Solecurtus) and Solenimya.
4. _Myaria_ (plates, fig. 69 to 76), ligament internal. A spoon-shaped
ligamentary pit in one or both valves. Shell generally gaping at one or
both extremities. This family includes the genera Anatina, Mya,
Anatinella, Lyonsia, Myochama, Cleidotherus.
5. _Mactracea_ (plates, fig. 77 to 88), the cartilage placed in a
trigonal pit, with a small external ligament. The genera Lutraria,
Mactra, Crassatella, Erycina, Ungulina, Amphidesma, and Solenimya
belong to this family, the last of which ought to have been placed
among the Solenacea, as above.
6. _Corbulacea_ (plates, fig. 89, 90), inequivalve, with an internal
ligament resembling the Mactracea, but differing in having one valve
deeper than the other, although regular shells. This small family
contains only the genera Corbula and Pandora.
7. _Lithophagidæ_ (plates, fig. 91 to 97), irregular, terebrating,
living in holes of rocks. The genera are Saxicava, Petricola, and
Venerirupis.
8. _Nymphacea_ (plates, fig. 98 to 110), ligament external, generally
placed upon a prominent fulcrum, which passes from the inside to the
outside of the hinge; valves generally gaping at the extremities. This
family contains the genera Sanguinolaria, Psammobia, Psammotæa,
Tellinides, Corbis, Lucina, Donax, Capsa, and Crassina.
9. _Conchacea_ (plates, fig. 111 to 121), regular, having several
cardinal teeth and sometimes lateral teeth. The Conchacea constitute
one of the most beautiful and numerous families of the class; they
present equivalve shells, which are always regular, unattached, and in
general closed, especially at the sides; they are always more or less
inequilateral. They are divided into the _fluviatile_ and _marine
Conchacea_, the first containing the genera Cyclas, Cyrena, and
Galathæa, found in rivers; and the second, Cyprina, Cytherea, Venus,
and Venericardia.
10. _Cardiacea_ (plates, fig. 122 to 130). This family, which resembles
the last in some general characters, are also regular and equivalve,
and are generally provided with radiating ribs, which are seldom seen
in the Conchacea. The genera enumerated in this family are Cardium,
Cardita, Cypricardia, Hiatella, and Isocardia.
11. _Arcacea_ (plates, fig. 131 to 138). These are known by having a
row of numerous small teeth on the cardinal hinge in each valve. The
genera included are, Cucullæa, Arca, Pectunculus, Nucula.
12. _Trigonacea_ (plates, fig. 139 and 140). It is doubtful whether
this family should remain distinct. As of the two genera placed in it,
the first, Trigonia, is thought by some naturalists to have strong
affinities with Nucula, in the family of Arcacea; and the latter,
Castalia, certainly belongs to the Nayades.
13. _Nayades_ (plates, fig. 141 to 152). These are fresh-water shells,
covered on the outside by a thick horny epidermis, and pearly within.
They include the genera Unio, Hyria, Anodon, Iridina.
14. _Chamacea_ (plates, fig. 153 to 155), inequivalve, irregular,
foliaceous, attached; containing the genera Diceras, Chama, and
Etheria.
Second Order, _Conchifera Monomyaria_.
Having one adductor muscle, and therefore only one impression in each
valve. They are separated into the following families:--
1. _Tridacnacea_ (plates, fig. 156 & 157), transverse, equivalve, with
an elongated muscular impression, near the centre of the ventral
margin; margin undulated at the termination of the radiated large ribs.
The genera Tridacna and Hippopus are included.
2. _Mytilacea_ (plates, fig. 158 to 162), generally regular, with the
hinge linear, without teeth, occupying the greater part of the dorsal
margin. This family includes the genera Modiola, Mytilus, Pinna.
3. _Malleacea_ (plates, fig. 163 to 170), shell generally thin,
inequivalve, irregular, foliaceous, with the hinge linear. This family
contains the genera Crenatula, Perna, Malleus, Avicula, Meleagrina.
4. _Pectinides_ (plates, fig. 171 to 178). The Pectinides are generally
regular or nearly so, with the shell solid; the greater part of them
are auriculated at the dorsal margin, and generally characterized by
ribs radiating from the umbones. The genera are Pedum, Lima,
Plagiostoma, Pecten, Plicatula, Spondylus, Podopsis.
5. _Ostracea_ (plates, fig. 180 to 192). The shells of this family are
irregular, generally attached and foliaceous. They compose the genera
Gryphæa, Ostræa, Vulsella, Placuna, Anomia.
6. _Rudistes_ (plates 193 to 200). This family is composed of a
particular association of shells, which appear on one side to be
connected with the Ostracea; and on the other to approach the
Brachiopoda. They differ from Ostracea in having no hinge or ligament,
and only resemble them in their irregularity and foliaceous structure.
The following six genera are placed by Lamarck in this
family:--Sphærulites, Radiolites, Calceola, Birostrites, Discina,
Crania. Of these, Calceola, Discina, and Crania are shewn to belong to
the Brachiopoda.
7. _Brachiopoda_ (plates, fig. 201 to 219). The shells of this family
are inequivalve, equilateral, and attached to marine bodies by a tendon
passing through one of the valves. The animals have, near their mouth,
two elongated, ciliated arms, which are spirally rolled when at rest.
The following genera are enumerated by Lamarck, Orbicula, Terebratula,
Lingula.
MOLLUSCA.
Lamarck applies, or rather restricts, this name to those invertebrated
animals, which while they are inarticulate in all their parts, have the
head sufficiently advanced at the anterior part of the body to be
distinguished; which is not the case with the Conchifera. All the shells
are univalve, and are divided into six orders, namely, the PTEROPODA, which
have wing-shaped natatory organs or fins, and have _light_, _thin
transparent_, _nearly symmetrical_ shells; the GASTEROPODA, with the foot
not distinguishable from the rest of the body, have _patelliform_, _open_,
and _scarcely spiral_ shells; the TRACHELIPODA with the foot distinct and
attached to the neck of the animal, have _spiral_, _non-symmetrical_
shells. The CEPHALOPODA, with arms covered by suckers surrounding the head
of the animal, have generally _symmetrical convolute_ shells. The
Cephalopoda are divided into _C. polythalamia_, which have the internal
cavity divided into chambers by septa, as in the Nautilus; and the _C.
Monothalamia_, which are not so divided, as the Argonauta. The order
_Heteropoda_ contains the genus Carinaria alone.
Order _Pteropoda_.
This order, containing hyaline, symmetrical, non-spiral shells, as above
described, is not divided into families, but contains the following genera,
Hyalæa, Cleodora, Limacina, Cymbulia; the first of which, although composed
of a single piece, resembles a bivalve so nearly, that Linnæus actually
placed it in his genus Anomia.
Order _Gasteropoda_.
With the exception of the genus Bulla and Vitrina, the last of which forms
a passage into the next order, the shells contained in this order are
_patelliform_, _open_, _and scarcely spiral_. They are divided into the
following families:--
1. _Phyllidiana_ (plates, fig. 227 to 231), containing the genera
Chiton, Chitonellus, and Patella, the two former of which present the
only exception to the statement above made, that all the shells of
Mollusca were univalve.
2. _Semiphyllidiana_ (plates, fig. 232 and 233). Of the two genera
contained in this family, Pleurobranchus is broad, thin, and slightly
spiral at the apex, and Umbrella is flat, circular, with a central
apex.
3. _Calyptracea_ (plates, fig. 234 to 246). The patelliform shells of
this family, although united by no other general characters, are
brought together by the characters of the animals which produce them.
The genera are Parmophorus, Emarginula, Siphonaria, Fissurella,
Pileopsis, Calyptræa, Crepidula, Ancylus.
4. _Bulleana_ (plates, fig. 247 to 253), contains the genera Bulla and
Bullæa.
5. _Aplysiacea_ (plates, fig. 254 and 255). The genera Aplysia and
Dolabella are both expanded, somewhat flattened shells, with the apex
placed at one extremity, and slightly spiral.
6. _Limacinea_ (fig. 256 to 263). Many of the animals (slugs) are
without shells; some, as the Limax, or common garden slug, have a
slightly developed calcareous piece, hidden beneath the mantle, and of
others the shells are scarcely spiral. The genera included in this
family are, Parmacella, Limax, Testacella, Vitrina.
Order _Trachelipoda_.
All the remaining spiral non-symmetrical shells are arranged in this order,
which is divided into the following families:--
1. _Colimacea_ (plates, fig. 264 to 307). With the exception of the few
contained in the family of Limacina, which ought not to be separated
from this order, the whole of the land-shells are contained in this
family, and although it is difficult to notice any one character by
which terrestrial shells may be distinguished from others, few at all
conversant with the subject are liable to mistake them. There is a
general lightness and simplicity of form, which, though not clearly
definable, is generally understood. The following distribution of
genera by Lamarck, is generally acknowledged to require numerous
modifications; the genera are Helix, Carocolla, Anostoma, Helicina,
Pupa, Clausilia, Bulinus, Achatina, Succinea, Auricula, Cyclostoma.
2. _Lymneana_ (plates, fig. 308 to 312). The shells of this family are
found in fresh water, wells, ditches, and ponds. They are of a light
horny structure, and simple form. The genera Planorbis, Physa, and
Lymnea are placed in this family by Lamarck.
3. _Melaniana_ (plates, fig. 313 to 317). These are also found in fresh
water, principally in rivers; they are thicker than those of the last
family; and the greater part of them have elevated spires composed of
numerous whorls. This family contains the genera Melania, Melanopsis,
Pirena.
4. _Peristomata_ (plates, fig. 318 to 322). These are also fresh-water
shells, having opercula, and covered by a smooth green, or
greenish-brown epidermis. They differ from the last family in having
the peritreme entire. The genera are Valvata, Paludina, and Ampullaria.
5. _Neritacea_ (plates, fig. 323 to 333). The peculiarity of the shells
of this family consists in the inner lip being flattened and rather
straight at the inner edge. The genera are Navicella, Neritina, Nerita,
Natica, and Janthina, the last of which forms an exception to the
general character, and is placed by De Blainville in a family by
itself.
6. _Macrostomata_ (plates, fig. 334 to 341), so named, on account of
the large open aperture which they present in comparison to the spire.
The shells of this family, which contains the genera Stomatia,
Stomatella, and Haliotis, are pearly within.
7. _Plicacea_ (plates, fig. 342 to 344), contains the genera Tornatella
and Pyramidella.
8. _Scalariana_ (plates, fig. 345 to 352). The genera Vermetus,
Scalaria and Delphinula, seem to have been placed in this family by
Lamarck, on account of the whorls being distinct from each other.
9. _Turbinacea_ (plates, 353 to 371). The shells contained in this
family are all more or less globose, or angular, thickened and pearly
within. The following genera are included in this division by Lamarck,
Solarium, Rotella, Trochus, Monodonta, Turbo, Planaxis, Phasianella,
and Turritella.
10. _Canalifera_ (plates, fig. 372 to 401). The numerous genera of
which this family is formed, namely, Cerithium, Pleurotoma, Turbinella,
Cancellaria, Fasciolaria, Fusus, Pyrula, Ranella, Murex, Triton, are
distinguished by having at the anterior termination of the aperture, a
more or less elongated canal.
11. _Alatæ_ (plates, fig. 402 to 406). These are known by having the
outer lip more or less expanded and generally a posterior canal leaning
towards the spire. The genera are Rostellaria, Strombus, and
Pteroceras.
12. _Purpurifera_ (plates, fig. 407 to 429). In these, the canal, if
such it may be called, is extremely short, and turning abruptly
backwards, produces a kind of varix at the lower part of the whorl. The
genera enumerated in this family are Cassidaria, Cassis, Ricinula,
Purpura, Monoceras, Concholepas, Harpa, Dolium, Buccinum, Eburna,
Terebra.
13. _Columellata_ (plates, fig. 430 to 433). The shells of this family
are emarginated at the anterior extremity of the aperture, and the
inner lip is characterized by plates or folds, which, with the
exception of those on Columbella, are distinct. The genera are Mitra,
Voluta, Marginella, Volvaria, Columbella, the latter of which would be
better placed among the Purpurifera.
14. Convolutæ (plates, fig. 444 to 462). The well-known shells
contained in this family are distinguished for the small proportion of
the spire, if any, which remains uncovered by the last whorl. They
might be well divided into two groups, the first containing the genera
Ovulum and Cypræa, under the name of Cypræadæ, which are truly
convolute, having the spire entirely hidden; and the second containing
the genera Oliva. Ancillaria, and Conus.
Order _Polythalamous, or Chambered Cephalopoda._
The greater part of the shells belonging to this order are symmetrical, and
the internal cavity is divided into separate compartments, by plates called
_Septa_. It is divided into the following families:--
1. _Orthocerata_ (plates, fig. 463 to 470), containing the genera
Belemnites, Orthoceras, Nodosaria, Hippurites, and Conilites.
Hippurites certainly has no affinity with the Cephalopoda, but is
ascertained to be a bivalve shell, properly belonging to the family
Rudistes; the other genera are straight, elongated, and conical.
2. _Lituacea_ (plates, fig. 471), containing the genera Spirula,
Spirulina, and Lituola, the two latter of which are microscopic.
3. _Cristacea_, containing the microscopic genera Renulina, Orbiculina,
and Cristellaria.
4. _Spherulacea_, containing the microscopic genera Miliola, Gyrogona,
and Melonia.
5. _Radiolacea_, containing the microscopic genera Rotalites,
Lenticulina, Placentula.
6. _Nautilacea_ (plates, fig. 472 to 476). This family contains the
following genera--Discorbites, Siderolites, Polystomella, Vorticialis,
Nummulites, and Nautilus; the two latter of which alone are now
received in cabinets of shells, the four former belonging to that class
of microscopic fossils, now termed Foraminifera; the genus Nummulites,
although large, may probably belong to the same class, and perhaps it
would have been better to have included the remaining genus, Nautilus,
in the next family, from which it differs in having the septa which
divides the chambers simple at their edges.
7. _Ammonacea_ (plates, fig. 477 to 484). The edges of the septa of
these are all more or less sinuous and complicated. This family
contains the following genera, Ammonites, Ammonoceras, Baculites, and
Turrilites, the latter of which presents a singular anomaly in having
an oblique spire, like that of the order Trachelipoda, while it is
divided into chambers by sinuous septa.
Order _Monothalamous Cephalopoda_.
The only shells included in this order belong to the genera Argonauta
(plates, fig. 485), placed here by Lamarck, and Bellerophon (plates, fig.
486 and 487), a fossil genus subsequently added.
Order _Heteropoda_.
The singular and beautiful transparent shell contained in this order, under
the generic name Carinaria, forms a covering to a small portion of an
animal, equally remarkable and equally distinct from those of all other
orders.
The above arrangement, although far from perfect, and requiring numerous
modifications, is perhaps liable to as few objections as any other yet
proposed, and will certainly be more easily understood by those who have
not the opportunity of studying the soft parts of the animal.
* * * * *
CONCHOLOGICAL MANUAL.
ABIDA. Leach. A genus founded on a species of PUPA, which has the
peristome slightly reflected, and numerous plaits in the aperture. Pupa
Juniperi, Pupa secale, Draparnaud. Great Britain; also Central and
Southern Europe.
ABRA. Leach. A genus composed of AMPHIDESMA tenue, prismaticum, and
other small thin species. British Channel and Mediterranean. _Fam._
Mactracea.
ABSIA. Leach. LITHOTRYA, Sowerby. _Fam._ Pedunculated Cirripedes.
ACAMAS. Montfort. BELEMNITES multiforatus, Blainville. A species
described as being perforated at the apex, by a stellated perforation.
No species of Belemnite at present known agreeing with the description;
it is supposed to have been taken from a broken specimen.
ACANTHOCHETES. A name given to a species of Chiton having bunches of
bristles at the sides of the valves.
ACARDO. Commerçon. Described from a pair of bony plates, taken from the
vertebræ of the Whale, and mistaken for a bivalve shell, destitute of a
hinge.
ACARDO. Swainson. A generic term applied by Swainson to the nearly
toothless species of Cardium, named C. edentulum by some authors; C.
Greenlandicum by others: fig. 123*.
ACASTA. Leach. _Order_, Sessile Cirripedes, _Lamarck_. BALANUS
_Montagui_, Sowerby. A small genus separated from Balanus, on account
of the cup-shaped base, but re-united by Sowerby, who shews, in his
Genera of Shells, that this is a merely accidental circumstance,
resulting from the situations in which the shells acquire their growth.
If, for instance, the Balanus be attached to a flat surface, in an open
situation, the base will be short and flat; if it be placed in a hollow
among other growing substances, it will be lengthened out in order that
the aperture of the shell may be even with the outer surface of the
surrounding mass; and if, as in the Acastæ, it be imbedded in a soft
and loose substance, the base, being left to itself, will take a
regular form. The Acastæ are found imbedded in sponges. _Ex._ Balanus
Montagui, of Great Britain, fig. 26. Also found in the Pacific ocean
and Philippines.
ACAVUS. Montfort. _Fam._ Limacinea, Blainville; Colimacea, Lamarck. A
division of the genus Helix, which may be considered synonymous with De
Ferrusac's sub-genus Helicogena. De Montfort has given H. Hæmastoma, as
an example. Fig. 267.
ACCESSARY VALVES, are the smaller or less important testaceous plates,
found on the hinge or dorsal margins of the true valves of some shells.
Example, the small plates on the hinge of Pholas, fig. 55, a. The
Pholades were placed by Linnæus and Bruguière among multivalve shells.
ACEPHALOPHORA. Blainville. (_a_, without; [Greek: kephale], head.) The
third class of the type Malacozoaria, Bl. including all bivalve shells,
the animals of which have no distinct head. This class corresponds with
the Conchifera of Lamarck, and is divided into the orders
Palliobranchiata, Rudistes, Lamellibranchiata, and Heterobranchiata,
the last of which contains no genera of testaceous Mollusca.