Text emphasis is displayed as _Italics_.
[Illustration: Rudiments of Conchology.]
INTENDED AS A
FAMILIAR INTRODUCTION TO THE SCIENCE.
REFERENCES TO THE COLLECTION OF SHELLS IN THE BRITISH MUSEUM.
BY THE AUTHOR OF
"THE GEOGRAPHICAL PRESENT," &c.
[Illustration: A new and improved Edition.]
DARTON AND HARVEY,
PRINTED BY JOSEPH RICKERBY, SHERBOURN LANE.
The Compiler of the following pages has derived the greater part of the information contained in them from "The Conchology of Lamarck," from "Burrows's Elements of Conchology," and other introductory treatises.
In the present Edition of this little Work many alterations and additions have been made, with the hope of rendering it more useful to the young student.
[Note: Corrections were applied.]
Page 3, _for_ Plate 1, _read_ Plate 2.
Page 16, line 8, _for_ squamosa, _read_, squamosus.
Page 20, _for_ candidas, _read_ candida; and _for_ Plate 3, _read_ Plate 2.
Page 25, _for_ Plates 4 and 5, _read_ Plates 3 and 5; and _for_ gædaropus, _read_ gæderopus.
Page 27, _for_ epiphippium _read_ ephippium.
Page 35, line 12, _delete_ not.
Page 36, line 14, _read_ Plate 2.
Page 42, _read_ Bruguieres; and _for_ Pollicepes, _read_ Pollicipes.
Page 64, line 3, _read_ Parmophorus--line 6, _read_ Plate 3.
Page 68, line 5 from bottom, _read_ Carocolla.
Page 76, line 6, _for_ Valvata _read_ Voluta.
Page 90, line 4, _read_ anglicanum.
"A box full of shells!" said Charles to his sister Lucy, who was looking over her treasures with great attention. "What can you want so many little shells for?"
"This box and its contents are the gifts of my cousin Jane," replied Lucy: "she said that I might have her whole collection, if I could find any pleasure in looking at shells without knowing anything about them. But I am not _quite_ ignorant of the subject."
"Shells are pretty enough," said Charles; "but how troublesome to distinguish the differences between each kind! I like plants better than shells."
[Sidenote: MULTIVALVES, BIVALVES, UNIVALVES.]
"Probably because you are better acquainted with plants," observed his father, Mr. Elliot, who had just entered the room: "however, the great naturalist, to whom you are indebted for your knowledge of plants, did not consider shells as objects beneath his attention."
"You mean Linnæus," said Lucy; "then he, I suppose, separated shells into the three different divisions--_Multivalves_, _Bivalves_, and _Univalves_."
"You are right, Lucy," replied her father.
"Pray show me some bivalve shells," said Charles; "I want to know their forms. A _bivalve_ is a shell with two openings, as I should imagine: yes, I see that I am right, for you have given me an oyster and a cockle."
"Here are also _Venus_, _Tellìna_, _Donax_, _Arca_, and _Pinna_," observed Mr. Elliot, "all very easy to distinguish."
"'The anchor'd pinna and his cancer friend,'"
repeated Charles. "So the _Pinna_ is a bivalve; but what has _Venus_ to do with the matter?"
"That is very easy to understand," said Lucy: "the genus called by her name is remarkable for beauty."
"Now, Charles," said Mr. Elliot, "do you clearly comprehend the verse that you have just repeated?"
[Sidenote: THE PINNA AND THE CANCER.]
"I have heard that the _Pinna_ is a shell-fish, attended by a _crab_, 'his cancer friend;' but why it is called _anchor'd_ I do not know, but _cancer_ is Latin for crab."
"Here is a species of _Pinna_," said his father, opening a cabinet; "and these silken threads are the means by which it fastens itself to the rocks. The animal is provided with a long foot, with which it draws out the threads, or _byssus_. The _Pinna_ is sometimes called the silk-worm of the sea. Lucy, do you know a univalve shell?"
"Oh yes, many!" replied Lucy, "here are rock-shells, cowries, limpets, and cones. I know the difference between a cowry and a cone; but I am not yet acquainted with a multivalve shell--will you show me one?"
"_Chiton_, or coat of mail, is a good example," said Mr. Elliot; "_Pholas_ is another genus of the same division; it has the appearance of a bivalve. In the _Chiton_ are several _lamina_, or plates, which are connected by a membrane while the living animal is in the shell; the membrane is pliant, and the inhabitant has the power of contracting itself into a ball, when it would avoid injury, like the insect millepes, that we find under stones in damp places. (Plate 2.) The curious barnacle-shell, _Lepas_, is another multivalve." (Plate 1.)
"I think we cannot have a more agreeable pursuit for our leisure hours," said Lucy, "than the study of shells. One can bring them out or remove them so easily, that they can cause little inconvenience, which garden-pots often do in town; and then the plants are almost sure to die, whatever care I take of them."
[Sidenote: LAMARCK'S SYSTEM.]
"Collections of shells are frequently to be seen in London," said Mr. Elliot, "which are intended for sale. There are now many places where shells are sold at moderate prices, and young collectors like yourselves can easily avail themselves of the means thus afforded, to obtain even a single specimen. While we remain in town you may visit the British Museum, and become familiar with the rare species of each genus, of which there are many costly specimens. The arrangement adopted for that collection is Lamarck's. You will find the work of this celebrated naturalist on my shelves; it is entitled, '_Histoire Naturelle des Animaux sans Vertèbres_.' The three last volumes contain the Conchology."
"It is in French and Latin!" exclaimed Lucy, as she opened a volume.
"Why do you both look so serious?" asked their father. "Are you not students in those useful languages? To what purpose do you learn a language if it be not with a view to reading the works of learned men, whose labours have opened a wide field of knowledge?"
[Illustration: Plate 1.]
[Sidenote: USE OF THE LATIN LANGUAGE.]
"But so many works on science are written in Latin," said Lucy. "Linnæus, however, has been translated, I know; and as for _British_ botany, we have our own authors in my own dear language."
"The Latin language being universally studied by men of science, it has become the medium of communication between the learned of most countries," observed Mr. Elliot. "I should consider a young person of your age, Lucy, very ignorant who could not read and understand the general style of Lamarck with the occasional aid of the dictionary."
"Do not be discouraged, brother," said Lucy, "my father will assist us: remember how frequently he helps us with our lessons now, provided we do our best. I am resolved to obtain some knowledge of shells this winter."
"A very good resolution," said Mr. Elliot; "and I predict that your usual delight on revisiting our favourite country dwelling will be somewhat increased next spring."
"Because I shall carry down my little collection with the pleasure of knowing more than I did last year."
"Our own coasts, rivers, and ponds afford a variety of shells. The hedge-banks, heaths, and other places, possess their inhabitants."
[Sidenote: PLEASURE OF SEARCHING FOR SHELLS.]
"Oh," exclaimed Lucy, "I quite forgot the very pretty snails I have so often admired on the heath on a dewy morning: why, we may learn conchology in the open fields as well as botany!"
"Well, then," replied Mr. Elliot, "to-morrow we will apply ourselves to the needful instruction. I must, however, remind you that I do not approve of any animal's life being taken away in order to obtain its habitation. Empty shells are to be found, which will serve perfectly well for specimens; and should the colour not be so bright as you could wish, you will have the delightful consciousness that your amusements have been free from cruelty, and that you have not destroyed the life of any living, harmless creature, in the pursuit of pleasure. Indeed there is as much or more gratification in searching among the rocks, or digging into the sea-sand, with a view to watch the animal in its natural place, as in possessing its empty shell: and who knows what grand discoveries you may both make!
"But I must leave you now--be ready for me after our usual dinner-hour."
[Sidenote: INHABITANTS OF SHELLS.]
"Conchology," said Mr. Elliot, on resuming the conversation with his children, "is that branch of natural history which comprehends the study of testaceous animals, or animals with _shell-coverings_, and includes those of the seas, the rivers, and the land.
"All shells are formed of carbonate of lime. This you may easily prove by applying a little acid to a shell, and you will find that an effervescence takes place.
"The animals that inhabit shells are bloodless, without bones, but provided with a heart, lungs, and mouth, together with other organs needful to their conformation.
"Testaceous animals have the power of enlarging their habitations; they can also repair any injury that may occur to them.
"Many kinds of shell-fish are made use of by man, and form a valuable article of food, such as oysters, cockles, muscles, scallops. The whelk is also used, and a species of murex.
[Sidenote: FOSSIL SHELLS.]
"A species of cowry is in use for money among some people of Africa; and pearls, so much valued as articles of ornament, are obtained from the oyster and mussel genera.
"Within a few years, conchology has become a study of considerable importance, from its close connexion with geology. Students in the latter science must be well acquainted with fossil-shells, because they form so large a portion of organic remains. Species of recent shells, or those still existing, are also often found in a fossil state, while many fossil genera are now totally unknown in our earth and waters.
"Thus you perceive that while you are obtaining knowledge in one science, you are preparing yourselves for making advances in another, most interesting and wonderful. You, Charles, who are likely to become a traveller, will perhaps in future years find the advantage of my present brief lessons.
"I shall first endeavour to make you acquainted with the system of Linnæus; it is easily learned, and you should be familiar with it, as it is still adopted by some writers on conchology.
"But in order to understand my instructions, you must have a clear idea of the terms that I use in describing a shell; now, therefore, give me your attention while I explain some of those terms to you.
[Illustration: Plate 2.]
[Sidenote: TERMS FOR PARTS OF MULTIVALVES.]
"To begin with the first division, _Multivalves_. There is a group of _Lepades_, it is the species called goose-barnacle, of which so many strange and silly tales have been told in former times. (Plate 2, _Lepas anatifera_.) This species is furnished with a kind of stem, like a bladder, and is called the _peduncle_, (_c_) and is fastened to other bodies. The _feelers_ (_d_) are feathery projections, which the animal keeps in continual motion, for the purpose of catching its food. Here is a group of another kind; (Plate 2, _Lepas tintinnabulum_;) these are without a peduncle, and are called _sessile_. The _base_ (_a_) is that part of the shell by which it is fixed to other bodies: (_a_) the _operculum_ is formed of four small valves on the summit. (_b_).
* * * * *
"In the shells of the second division, _Bivalves_, we shall find a greater number of parts. _Valves_ are the different pieces that compose a shell. When both the valves are alike in form, the shell is called _equivalve_: when the valves are different in the same shell, it is called _inequivalve_. _Mya_, _Solen_, _Tellina_, are equivalves: _Ostrea_, _Anomia_, _Pinna_, &c. are inequivalves.
"The _hinge_ is formed by the teeth of one valve inserting themselves between those of the other valve, in some genera; in others, by the teeth fitting into the _cavities_ of the other valve (Plate 3., _a_.) When the teeth are placed in the centre of the hinge they are called _cardinal teeth_. _Lateral teeth_ are situated on the sides of the valves, and are generally long and flat, sometimes hollow. Some hinges are straight, others curved. Here is the hinge of _Arca_, furnished with many small teeth. (Plate 3, _b_.)
"The _ligament_ is a membrane that connects the valves, and keeps the hinge in its proper place: it is always situated near the beaks. The ligament is very perceptible in the cockle, in _Pecten_, or scallop, in _Tellina_, &c.
"The _beaks_ are the most pointed parts of the bivalve shell (Plate 3, _c_.); when the valves are closed, the line where they meet is called the _seam_. (Plate 3, _d_.)
"The _anterior slope_ is that part of the shell where the ligament is placed, and is also called the _area_. (Plate 3, _e_.) The _posterior slope_, or _areola_, is the other side of the beaks. (_f._)
"The _lunula_ is a crescent-like depression on either the area or areola. The edge of the valve is called the _margin_; it is often finely _crenulated_, or toothed. The interior of the valve is called the _cavity_. (_g._) In the valves of this ark-shell here are two broad marks, shining and glossy. (_g._) In those of the oyster and muscle that I now show you, there is but one. These marks are _muscular_ impressions; they are the parts where the muscles of the animal have been affixed, and are termed _cicatrix_.
[Illustration: Plate 3.]
"_Ears_ are two processes on each side of the beak; the _Pecten_, or scallop, is an example. (Plate 3, _i_.)
"_Sinus_, in _bivalve_ shells, is a small hollow in the hinge.
"_Byssus_, or beard, is an appendage composed of silky threads, by which the muscle and _Pinna_ fasten themselves to the rocks. (Plate 3, _f_.)
"_Cordiform_ is a term applied to heart-shaped shells.
"A _cartilage_ is the same as a ligament. When the valves of a shell are very nearly flat, they are said to be _compressed_: when a valve has teeth, it is said to be _dentated_.
"When the valves of a shell do not shut close, they are said to be _gaping_. (Plate 4, _Mya_.)
"A _muscle_ is a fleshy, pliant organ, by which the animal is attached to its shell. I have already pointed out to you the impressions of those muscles within bivalve shells.
"A _suture_ is a toothed joint, in bivalves.
"A shell with ears is said to be _auricled_.
* * * * *
"The third division, _Univalve_ shells, have also their several parts. The first section has a regular spire. Here are two shells of this section, _Voluta_ and _Buccinum_, both sawed asunder, in order to show the interior structure of the shell. (Plate 3.) The aperture, or opening, being turned _towards you_, the front of a univalve is seen; reverse it, and you see the back.
"The top, or highest part, is the _apex_; (_a_) the lowest part is the _base_ of the shell. (_b._)
"The _spire_ (_c_) is formed of wreaths, or whorls, (_ddd_) which terminate in the apex: the lowest whorl is the body of the shell. (_e._)
"The _aperture_, opening or _mouth_, (_f_) as it is sometimes called, is on the right-hand when the front of the shell is turned towards you. The aperture is an important distinction in univalves: some genera have a circular opening, as the _Turbo_, or periwincle; some longitudinal, as the cowry; others semi-lunar, as the _Helix_, or snail genus. (For examples of these apertures see Plates 1 and 7.)
"The _beak_ is the lengthened process (_g_) at the lower part of the shell.
"The _canal_, or _gutter_, runs through the beak. (Both these parts are perceptible in _Murex_ and _Strombus_, Plate 7.)
"_Sutures_ are spiral lines which separate the whorls; they are sometimes crenated, or notched, sometimes sulcated, or furrowed.
"The _columella_, or _pillar_, extends through the centre of the shell withinside. The _Buccinum_ and _Voluta_ both show the columella. (Plate 3.)
"The _pillar-lip_ of the aperture, or columella margin, is on the left-hand side of the shell; the _outer_ lip on the right-hand. Occasionally this order is reversed, but not commonly.
"The _operculum_, or lid, in univalves is that part which fits exactly into the aperture, and incloses the animal; it serves as a door to the shell. (Plate 3.) The operculum is either horny, like that of the periwincle, or of a harder substance, like the shell itself.
"The _umbilicus_ is a circular hole in the body of the shell. This perforation produces a very curious effect when it is very large. When the umbilicus is wanting, the shell is called _imperforate_.
"If the spire is truncated, it is _decollated_; if it is surrounded with spires, it is _coronated_, or crowned.
* * * * *
"Second section, without a regular spire. The _teeth_ in univalve shells, as the cowry, are ridges upon the aperture. (Plate 1.) In _Voluta_ they are regular folds or plaits upon the columella.
"A _fissure_ is a notch or slit, as in _Patella fissura_. (Plate 3.)
"Some shells of this section are internally lipped, as _Patella equestris_; (_Calyptræa_ of other authors, Plate 3;) some are chambered, as the slipper-limpet; some are cap-shaped, having the apex much curved--these are the cap-limpets.
"The _vertex_ in _Patella_ is as the superincumbent part of the shell.
"The _epidermis_ is the outward skin that covers the surface of some shells.
"_Fauces_ are narrow entrances, as at each end of the cowry.
"_Tubercles_ are protuberances, or knobs, on the surfaces of shells.
"_Striæ_ are raised or flat lines upon the surfaces of shells. When the surface is marked with lines longitudinally and transversely, it is _decussated_.
"_Sulci_ are furrows.
"_Fornicated_ signifies arched, greatly excavated.
"_Umbo_ is the swelling part near the beak of bivalve shells; the same as _boss_.
"_Longitudinal_, running nearly the whole length of the shell in univalves.
"_Concentric_, having the same centre.
"_Convolute_, when the exterior whorls spirally involve the interior.
"_Varices_, longitudinal, gibbous sutures formed in the shell, at certain distances on the whorls.
"_Carinated_, having the form of the keel of a boat."
[Sidenote: SYSTEM OF LINNÆUS.]
"As you both assure me," said Mr. Elliot, "that you do not fail to make yourselves familiar with the _nomenclature_, or terms, used in conchology, I shall proceed this morning to the arrangement of Linnæus.
"This system is established upon the _outward_ appearances, or external characters, of the covering bestowed by nature upon the animal, not upon the form of the animal itself.
"The three principal divisions you are already acquainted with, namely, _Multivalves_, shells composed of several parts called valves; _Bivalves_, formed of two parts; and _Univalves_, composed of one part or piece only.
"These divisions contain several _genera_, and the genera usually include many individual shells, but occasionally only one.
"The characters of every genus are permanent, and are therefore to be observed in every one of the species contained in the genus.
"Species are determined by shape, colours, or appearances on the surface of the shell: there are sometimes many varieties of the same species.
[Sidenote: LINNÆAN GENERA.]
"The Linnæan genera are thirty-six. I have copied a list of them for you. In that tray are the specimens mentioned in your list:
ARRANGEMENT OF LINNÆUS.
First Division--_Multivalves_: 3 genera.
* _Chiton_, coat of mail, example, _C. squamosus_.
* _Lepas_, acorn-shell or barnacle, ex. _L. anatifera_ and _tintinnabulum_.
* _Pholas_, stone-piercer, ex. _P. candida_.
Second Division.--_Bivalves_: 14 genera.
* _Mya_, trough-shell, ex. _M. truncàta_.
* _Solen_, razor-sheath, ex. _S. siliqua_.
* _Tellìna_, wedge-shell, ex. _T. Feroensis_.
* _Cardium_, cockle, ex. _C. cardissa_.
* _Mactra_, kneading-trough, ex. _M. stultòrum_.
* _Donax_, wedge-shell, ex. _D. trunculus_.
* _Venus_, Venus, ex. _V. Paphia_.
_Spondylus_, thorny-oyster, ex. _S. gæderopus_.
_Chama_, clamp-shell, ex. _C. gigas_.
* _Arca_, ark-shell, ex. _A. Noæ_.
* _Ostræa_, oyster, ex. _O. isognomon_.
* _Anomia_. antique lamp, ex. _A. ephippium_.
* _Mytilus_, muscle, ex. _M. edulis_.
* _Pinna_, wing-shell, ex. _P. pectinàta_.
[Sidenote: LINNÆAN GENERA.]
Third Division: 2 sections.--1st. _Univalves_ with a regular spire: 14 genera.
_Argonauta_, paper-sailor, ex. _A. argo_.
_Nautilus_, sailor, ex. _N. pompilius_. Conus, cone, ex. _C. Hebræus_.
* _Cypræa_, cowry, ex. _C. monèta_.
* _Bulla_, dipper, ex. _B. naucum_.
* _Voluta_, wreath, ex. _V. utriculus_.
* _Buccinum_, whelk, ex. _B. reticulatum_.
* _Strombus_, screw, ex. _S. pes-pelicàni_.
* _Murex_, rock-shell, ex. _M. ramòsus_.
* _Trochus_, top-shell, ex. _T. bifaciàtus_.
* _Turbo_, wreath, ex. _T. muricàtus_.
* _Helix_, snail, ex. _H. nemoràlis_.
* _Nerìta_, nerite, ex. _N. striàta_.
* _Haliòtis_, ear-shell, ex. _H. tuberculàta_.
* * * * *
2nd Section, without a regular spire: 5 genera.
* _Patèlla_, limpet, ex. _P. vulgàta_.
* _Dentàlium_, tooth-shell, ex. _D. elephantìnum_.
* _Sérpula_, worm-shell, ex. _S. triquétra_.
_Terèdo_, ship-worm, ex. _T. navàlis_.
* _Sabella_, Sabella, ex. _S. Belgica_.
Total number of genera in the arrangement of Linnæus, thirty-six.
The genera marked with an asterisk, contain species found in Britain.
[Sidenote: CHITON. LEPAS.]
"Multivalves may be divided into two kinds, the _pedunculated_, or those fixed to other bodies, as rocks, stones, planks, &c.; or _free_, as the _Chiton_ and _Pholas_.
"Our first genus is _Chiton_. The shell is easily known. The fixed character is, many valves placed over each other along the back. I have already noticed the membrane which connects the valves, which is also a permanent character. It is elastic: the sides are either scaly, as in _C. squamòsus_, (Plate 1,) and hairy, or spinous. The species are determined by the margins. Some of the Chiton genus are common upon our own coasts; they are frequently found among seaweed and stones, rolled up like a ball. _C. fasciculàris_ and _C. lævis_ are British; there are some other British species. The animal adheres to rocks, like the _Patella_, or limpet. The number of species forty.
"Second genus, _Lepas_. Shell multivalve, fixed at the base; valves erect, or _upright_.
"Observe how much the situation of the valves differs in _Chiton_ and _Lepas_. It is scarcely possible to mistake the one for the other. The feathery tentacula, or feelers, of _Lepas anatifera_ are worthy notice, and in a state of motion must be yet more beautiful. (Plate 2.) The common acorn-shell, _L. balanus_, is to be seen very frequently upon the shells of muscles, oysters, periwincles, whelks, in large groups. I see that you are examining the different appearance of the pedunculated and the sessile _Lepades_. Linnæus made two divisions; later writers have separated them into several distinct genera, which will be noticed when we attend to Lamarck's system. The species are forty-five, of which several are found on the British shores, as _L. tulipa_, _L. diadema_, _L. tintinnabulum_, _L. balanus_, _L. anatifera_, &c. The Indian, American, and Atlantic oceans afford numerous species.
"Third genus, _Pholas_. Generic character: shell bivalve, gaping or divaricated, with several smaller hinges situated upon the hinge; hinge recurved, with an incurved tooth."
"Father," said Charles, "I must say that the _Pholas_ shell is very unlike those of the multivalve division: I think it should rank with bivalves."
"So many conchologists have judged; nevertheless it possesses more than _two_ valves, and, according to the system, it must be forced into the division of multivalves.
"The _Pholades_ are found in company, but each individual occupies a distinct habitation, which the animal excavates for itself, either in rocks, in wood, coral, or sponge; but the finest specimens are usually to be seen in chalk. In proportion as the animal increases in size, it enlarges the cavity in which it is stationed. The animal is supposed to effect this operation by means of a corroding fluid that is secreted in the body, and which it has the power of ejecting upon the substance into which it has entered.
"The _Pholas_ has the power of emitting a phosphoric liquor, which shines with brilliancy in the dark.
"I must remind you that the accessory valves are fixed to the margin of the shell by a gelatinous substance; this decays after the death of the animal, and consequently the smaller valves are frequently wanting.
"The number of species is twelve. Several of them are found on our coasts. The _Pholas_ genus is without colour, but the reticulations in some species are exceedingly delicate. _Pholas candida_ (Plate 2) is found on the shores of Kent; you will be pleased with the shells. _Pholas dactylus_ is larger and coarser, and not at all uncommon.
"We have now finished our first division, and must proceed to the bivalves."
Second Division.--_Bivalves_: 14 genera.
"I fear," said Charles, "that this new division will be rather difficult, for my father tells me that we must pay particular attention to the _hinges_ of bivalve shells."
"Then _apply_ yourself to the study of hinges, Charles, and your difficulties will chiefly disappear," answered Mr. Elliot.
"The hinge of _Mya_, the first on the list, is easily known. The generic characters are, shell gaping at one end, hinge mostly with one thick spreading tooth, not inserted into the opposite valve. The _Mya_ race burrow in the sand. Here is _Mya arenaria_, a large thick shell, frequent on the shores of Kent: the large tooth is sufficiently plain in _this_ species. _Mya truncata_ (Plate 4) is as common, and the curious membranous case, which you will find attached to one end of the shell, is a guide to the species. Both these species are without colour, and have little to attract in their outward appearance. The genus, however, according to Linnæus, varies exceedingly, and contains forty-one species.
[Sidenote: SOLEN. TELLINA.]
"_Solen._ Shell bivalve, open at both ends, tooth of the hinge subulate, or awl-shaped, reflex, often double.
"In this genus, the great length, in comparison with the breadth of the shells in many of the species, is remarkable: some are exceedingly brittle. Our example, _Solen siliqua_ (Plate 1) is a British species. The hinge is not in the centre of the shell, but nearer to one end of it. Some are shaped like the handle of a knife or a razor, others are bent resembling the blade of a scimitar. The _Solen_ lives in the sands of the sea-shore, often burying itself two feet deep, and retaining its shell in a vertical position: thirty-five species.
"The genus _Tellìna_ is remarkable for the beauty of the shells, and, according to the arrangement of Linnæus, contains ninety-seven species. The exterior is sometimes marked with radiations: the surface of some shells is very finely polished, while in others it is covered with striæ and undulations. The species that you have placed before me, Lucy, is _Tellìna Feroensis_; the shell is finely striated, and has also radiations. (Plate 4.)
"The generic characters are chiefly these: shell compressed towards the anterior slope, teeth of the hinge mostly three, the lateral ones smooth, in one valve. Two or three small species are common on our coasts. I should also observe that there is a convex fold on one valve and a concave fold upon the other. Many of the _Tellìna_ genus are found buried in the sea-sands.
[Sidenote: CARDIUM. MACTRA.]
"_Cardium._ Generic character: shell equivalve, convex, ribbed, striated, or grooved, the margin toothed: hinge with two teeth near the beak, and a lateral one on each side: fifty-four species.
"Observe how the beaks of this common _Cardium_, cockle, turn inwards, and the bosses project. Another striking character is the ribs, that are generally longitudinal, and not concentric or transverse, as in _Tellìna_, and, as you will see, in _Venus_. _C. aculeatum_ has small spines on the valves; _C. costatum_, the ribbed cockle, is one of the finest species of this genus, and _C. cardissa_ is a beautiful shell. (Plate 4.) The common cockle is _Cardium edule_.
_Mactra._ Generic character: shell bivalve, unequal sided, middle tooth of the hinge complicated, with a small hollow on each side, and lateral side-teeth: thirty-seven species.
"The shells of this genus are usually thin, brittle, and remarkably light. _Mactra stultorum_ is a common species. (Plate 4.)
[Sidenote: DONAX. VENUS.]
"_Donax._ Margin of the shell often crenulate, the anterior slope very obtuse; hinge with two cardinal teeth, and one lateral tooth.
"The most striking characteristic of _Donax_ is the broad, thick extremity of one end, gradually lessening towards the other. A rich purple tint is very frequent in these shells. _Donax denticulatus_ and _trunculus_ are common British examples. (Plate 4.) You must remark the ligament of _Donax_, which is exterior.
"Our next genus ranks highest for beauty among the bivalves, and takes its name from the goddess _Venus_. The species amount to one hundred and sixteen in the Linnæan system, but other authors have formed several new genera.
"Shell bivalve, having the lips incumbent on the anterior margin; hinge with three teeth, all approximate, the lateral ones diverging at the lip.
"I am afraid," said Lucy, "that we shall find this genus very difficult: I wish you would tell us the new genera that have been formed out of it."
"Learn first to know the general appearance of _Venus_, and remark especially the _teeth_. You may also bear in mind that the _beaks_ are almost always turned _to_ the posterior slope, and _from_ the ligament. The area and areola are also very conspicuous: the area is generally large, and differently coloured to the disk. _Venus Paphia_ is pretty. (Plate 4.) The spinous species, _V. Diòne_, is more beautiful, and is the only shell of the genus that has spines. The brown Venus, _V. chionè_, is very smooth and polished; both species are frequent in collections. The British shells of this genus are neither numerous nor very beautiful.
[Illustration: Plate 4.]
"_Spondylus._ Valves unequal, rough; hinge with two recurved teeth, with a hollow between them; shell sometimes eared. (See Plates 3 and 5.)
"I think," said Lucy, "that the English name, _thorny-oyster_, is not very suitable: it is more like a scallop; but it differs from both in having two strong teeth in the hinge, and I observed this morning that neither the oyster nor the scallop have any hinge."
"So that was the object you had in view," said Charles, "when you were so quietly handling those shells in the kitchen: I confess I could hardly help laughing; and now my father will say that _you_ are '_Eyes_,' and I the '_No Eyes_,' of 'Evenings at Home.'"
"Perhaps I might have made the observation," replied Mr. Elliot; "but you have reproved yourself, which is far better.
"_Spondylus_ can scarcely be mistaken from any other bivalve shell. The species _gæderopus_ is remarkable for its projecting beak; the surface is rough, with either tubercles or spines. Some authors reckon only four species, others thirteen. The _Spondyli_ are frequently found attached to rocks at some depth in the ocean. The animal is eaten on the coasts of the Mediterranean. We have no British _Spondylus_.
[Sidenote: CHAMA. ARCA. OSTREA.]
"_Chama._ Shell thick; hinge with a thick tooth, sometimes crenate, obliquely inserted into a corresponding channel. (Plate 5.) The shells of this genus vary greatly, which you will perceive upon comparing _C. gigas_ and _C. cor_. (See Plate 9, _Isocardia cor_.) The _Chama_ genus is usually ribbed, foliated, or scaly. _C. Lazarus_ is a beautiful species: _C. cor_ is a British species, and the only one. The whole number is twenty-five.
"Here is _Noah's-ark_, an example of the genus _Arca_, and is found on our own coasts. The long hinge beset with sharp teeth, inserted into each other, renders the genus sufficiently marked; but in some species the hinge is curved. The form varies exceedingly. The number of species is forty-five. (Plate 5.)
"_Ostrea._ In this well-known genus we lose sight of the _toothed_ hinge. Take that _Pecten_, or scallop, which belongs to one division of _Ostrea_ in this system, and tell me what holds the valves together. Charles is silent; what says Lucy?"
"Here are the remains of the same kind of substance which we saw in _Donax_ and in _Venus_. I think it is called the _ligament_."
[Illustration: Plate 5.]
"Very well remembered," continued her father. "The generic character of this very large portion of bivalves is, shell bivalve, usually with unequal valves: hinge without teeth, having a hollow cavity or sinus, and sometimes grooved. Here is a young common oyster, and, according to the rule of our present system, this shell, _Ostrea isognomon_, is of the same genus. (Plate 5.) The number of species is eighty-four, of which thirteen are British. The old shells of common oysters are often covered with _Serpula_, _Lepas_, and _Anomia_, and some kinds of corallines.
[Sidenote: ANOMIA. MYTILUS.]
"The next genus, _Anomia_, is remarkable for the thin, delicate, and almost transparent appearance of the shells. The valves are unequal, and frequently perforated near the apex; hinge toothless; in the flat valve, two bony rays.
"_Anomia ephippium_ has a large perforation, through which the animal passes a ligament, and attaches itself to other substances. These shells are often to be found on oysters. (Plate 5.) Species thirty-two.
"_Mytilus._ The principal characters are, shell bivalve, rough, often affixed by a thick byssus, or beard; hinge without teeth, with a hollow line extending lengthways. (Plate 3.)
"The common muscle, _Mytilus edulis_, must be well-known to you, and also the fine polish that the shells will take when cleared of the rough exterior by artificial means, _Mytilus barbatus_ is not unfrequent on our shores; the colour is brown, and the shell is shaggy. Number of species, forty-nine.
"Our last bivalve genus is _Pinna_. The generic characters--shell bivalve, brittle, erect, gaping at one end, throwing out a byssus; hinge without teeth. (Plate 6.)
"The _Pinna_ race are found plentifully in the Mediterranean, the Indian, American, and Atlantic oceans: the British seas afford three species. The genus is noted for producing a fine byssus, that is manufactured in Italy into various articles, as gloves. The animal is sometimes used as an article of food.
"An ancient writer asserts that the _Pinna_ is attended by a crab, that finds a habitation in its shell, and repays the favour by giving notice, by a gentle nip, when a fish comes within reach; the _Pinna_ opens the valves of the shell, and secures the prey, which serves for the food of both. Now, Charles, you know the whole sense of the quotation--
"'The anchor'd pinna and his cancer friend.'"
"Father," said Lucy, the next time they met to pursue their study, "I think we have made ourselves familiar with the various hinges of the bivalve shells, which are becoming favourites with us; but from the variety of fine specimens which you have on your table, I see that we shall be much gratified in examining the univalve division."
"My first genus is very beautiful," replied Mr. Elliot; "it is _Argonauta_, or paper-sailor. The shell is univalve, involute, unilocular, or without chambers: the aperture cordate. (Plate 6.) These shells are spiral, and remarkably brittle. The argonauts are supposed to be the shells that taught mankind the use of sails in the earliest ages of society. In calm weather the animal rises with its shell to the surface of the water, and spreads its arms over the edge; these arms answer the purpose of oars. It then spreads a membrane for a sail, which can be turned in any direction, and is impelled forwards by the breeze: two other arms serve as rudders to direct the course. The animal first raises itself to the surface of the sea by ejecting a quantity of water; if danger occurs, it absorbs water, and thus, by making itself heavier, sinks to the bottom. The species are few in number.
[Sidenote: NAUTILUS. CONUS.]
"_Nautilus_, pearly sailor, has several characteristics of _Argonauta_; but the former is concamerate, the latter without chambers in the shell. The generic characters of _Nautilus_ are, shell univalve, divided into several compartments, communicating with each other by an aperture. _Nautilus pompilius_ is often cut through, or bisected, to display the chambers of the shell. In the East, the shells are formed into drinking-cups. Sometimes the outer coat of the shell is removed, and the pearly surface finely carved. This genus, according to Linnæus, consists of fifty-eight species, some of which are fossil. (Plate 6.)
"In the following genera we must pay particular attention to the _aperture_ of the shell, which is a generic distinction in most univalves.
[Illustration: Plate 6.]
"The first is _Conus_, a large and beautiful genus, including many rare and valuable species. Shell univalve, turbinate, aperture effuse, or having the lips separated by a sinus, linear, without teeth, pillar smooth. In their natural state the shells are usually covered with an epidermis; but will bear a brilliant polish. _C. textilis_, cloth of gold, is valuable. _C. generalis_ is sometimes sold for twenty guineas. The example on the table is _C. Ebræus_, or Hebrew cone. (Plate 6.) Species one hundred and fifty-five; not one British. The greater number are brought from the Indian Ocean; some from the seas of Africa and from the South Sea.
[Sidenote: CYPRÆA. BULLA.]
"The shells of the genus _Cypræa_, cowry, are general favourites: the species are fifty-eight; one British, _C. pediculus_. _C. moneta_ (Plate 1) is very common. The generic characters are, shell univalve, involute, obtuse, smooth; aperture linear, the whole length of the shell; effuse at both ends, toothed on each side.
"Look carefully at those three shells: do you perceive much resemblance between them? 'Not much, if any,' you reply, yet they are all of the genus _Bulla_. Here is _B. lignaria_, _B. terebellum_, (see Frontispiece,) and _B. naucum_. (Plate 6.) There are other forms, as the _B. ovum_, _B. volva_, the first somewhat like a cowry; but it is toothed only on one side of the aperture; the second has two long beaks.
"This genus is confessedly ill-determined. _B. naucum_ and _B. ampulla_ are examples of the common characters of the genus. The species are sixty-one.
[Sidenote: VOLUTA. BUCCINUM.]
"_Voluta_ is also a large genus, containing one hundred and eighty-six species. Shell univalve, aperture without a beak, and somewhat effuse; columella _plaited_. This latter character we meet with for the first time. Here is the common _Voluta_. (Plate 6.) The genus has been much diminished by forming other very striking genera out of it, as I shall soon show you, under the names of _Mitres_, _Olives_, _Gondolas_, &c. _Voluta musica_, the music-shell, is remarkable, and not at all rare.
"_Buccinum_ is another large genus. The shell univalve, spiral, gibbous; aperture ovate, ending in a canal turning to the _right_, with a short beak; pillar-lip expanded. Species, one hundred and seventy-two.
"You must recollect that when the apex of the shell is turned _downwards_ the canal turns to the right, when it is turned _upwards_ the canal will be to the left hand. My example is _Buccinum reticulatum_, a very common species upon our own shores." (Plate 7.)
"Is not this genus reduced by other authors?' asked Charles.
"Greatly," replied Mr. Elliot: "you will meet with tuns, helmets, harps, and needles. Species of the _Buccinum_ genus are found in the African, American, Indian, European, and Southern oceans. Eighteen occur upon our coasts.
[Sidenote: STROMBUS. MUREX.]
"_Strombus_ contains forty-four species. Shell univalve, spiral, aperture much dilated, the lip expanding, ending in a canal inclining towards the left.
"You must notice the sinus in the outer lip, near the base of the shell. _Strombus gigas_, the West Indian conch, is very large. Some species have the lip ending in claws. _Strombus pes-pelicani_, the pelican's-foot, has four palmated claws: (Plate 7.) it is a British shell. The city of Santa Cruz, in America, is paved with the shells of _Strombus gigas_.
"The genus _Murex_ is both large and beautiful. Shell univalve, spiral; aperture oval, ending in a straight canal.
"These shells are of very unequal form; their surfaces frequently covered with spines, knobs, or foliations. Some are remarkable for the great length of the beak, (Frontispiece,) such as the woodcock, the snipe's-head, and Venus's-comb. The _Murex_ before you is foliated. (Plate 7.) The species are one hundred and seventy-one. Several are found on British coasts, but they are not remarkable for beauty.
"The top-shell, _Trochus_, is univalve, conic, spiral; the aperture either angular or rounded; columella oblique: some of the apertures have a tooth-like projection. (Plate 7.) Species, one hundred and thirty. Several kinds occur in Britain. New Zealand, Friendly Isles, Red Sea, and most other seas, afford the various species. Two of this genus have the power of collecting parts of shells and other testaceous substances, which adhere strongly to the whorls of the shell: it is called the Conchologist. The other, named Mineralogist, is loaded with stones, pebbles, ores, &c. When heavily laden they are considered rarities.
[Sidenote: TROCHUS. TURBO. HELIX.]
"There is a great similarity between the genera _Turbo_ and _Trochus_. You must observe the generic distinction carefully. Shell univalve, spiral; aperture contracted, orbicular, entire. The one hundred and sixty-seven species have been much divided by other writers. The golden-mouthed _Turbo_ is a very fine shell. This genus also contains the common periwincle, an inhabitant of most European shores. Sailors report that if the animal is seen creeping high up the rocks, it foretells stormy weather. _Turbo muricatus_ is a pretty shell." (Plate 7.)
"Now we can tell the next genus," said Lucy. "_Helix_, snail. But what a number of different shapes, father, those shells have! they are not all snails, I should think, that you have placed on the table."
[Illustration: Plate 7.]
"According to Linnæus they are all of the genus _Helix_, which contains two hundred and sixty-seven species. Many kinds are land-shells; others live in fresh water; few inhabit the sea.
"Shell univalve, spiral, brittle; aperture contracted, semi-lunar, or roundish. The common snail is well-known to most persons. _Helix nemoralis_, the wood-snail, is very pretty; sometimes it is pink, with brown bands, or plain yellow, or yellowy banded with brown. (Plate 7.) The greater part of this genus consists of shells remarkable for their thin, brittle, and semi-transparent substances.
[Sidenote: NERITA. HALIOTIS.]
"The _Nerìta_ genus is very pretty: (Plate 7.) the texture of the shell is in general much thicker than that of _Helix_. The shell is spiral, gibbous, pillar-lip transversely truncated, flattish. Seventy-six species. _Nerìta polìta_ is a handsome species: those most valued are from the South Sea.
"We have now lost sight of the pillar-lip, and in the genus _Haliòtis_ we find a flat, ear-shaped shell, the spire nearly hidden, the disk perforated lengthways with pores. Species twenty-one. The animals that inhabit the ear-shells fasten themselves so firmly to the surfaces of rocks, that much force is needful to disengage them: during the fine nights of summer, the animal feeds on the herbage that grows on the sea-shore. The sea-ear from New Zealand, and that from California, are superb shells of considerable size. The British species, _Haliòtis tuberculàta_, is not uncommon. (Plate 8.)
Without a regular spire: 5 genera.
[Sidenote: PATELLA. DENTALIUM. SERPULA.]
"You are well acquainted with _Patella_, the limpet: one species of this genus is very common on the rocks by the sea-side. (Plate 1.) In the _Patella_ genus we lose sight of a spire; the shell is nearly conic, and shaped like a basin. The species are very numerous, exhibiting great variety of form; the number is two hundred and forty.
"The form of _Dentalium_ is easily known. The shell is univalve, nearly straight, tubular, not chambered, and open at both ends.
"The species called elephant's-tooth is slightly curved, the colour green, (Plate 2.) It is found in the European and Indian seas. There are only twenty-two species. _Dentalium entails_, the dog's-tooth, is very common.
"The _Serpula_ genus is remarkable. The shells are tubular, frequently closed at one end. They are often found in clusters, adhering to rocks, stones, fuci, shells, &c.
"There is _Serpula triquetra_ upon a _pecten_, (Plate 8.)
[Sidenote: TEREDO. SABELLA.]
"From the appearance of this piece of timber you may form some idea of the devastation committed by the _Teredo_, or ship-worm. (Plate 8.) The shell is tubular and flexuose; two valves at each end, and penetrating through wood. There are four species.
[Illustration: Plate 8.]
"_Sabella_ is the last genus, and a very remarkable one. The species are twenty-five, several of which are British, (Plate 8.)
"Shell tubular, formed of sandy and calcareous particles, agglutinated, and inserted in a membranous sheath. _Sabella Belgica_ is found in Britain. _S. chrysodon_ is found buried in sea-sand, often several inches long; it is covered with fragments of shells, and so brittle that it is not easy to obtain a complete specimen.
"We have now finished our Linnæan genera, and here we must pause for the present. If you wish for any assistance in your study of the thirty-six examples that I have given you, I shall be ready to afford you both any help that lies in my limited power."
[Sidenote: SYSTEM OF LAMARCK.]
"Lucy and I have been collecting a variety of species," said Charles to his father, "since our last lesson in conchology. We have also seen several large collections of shells, one of which was arranged according to Lamarck. I was much pleased with the new genera taken from _Buccinum_, _Bulla_, _Turbo_, and others.
"We are desirous of gaining information on this new system, if you can spare a little time to attend to us."
"Willingly," replied Mr. Elliot; "I anticipated such a request, and have been making lists of the genera belonging to each system; so that, upon meeting with a new genus, you may be able to ascertain with some accuracy its place in the old arrangement.
"Lamarck founds his system upon the structure and form of the animals, so far as they have been ascertained, and with which the exterior, or shell, must necessarily coincide. The conchology occupies the three last _classes_, and _one order_ of another class, in the well-known work which I have before mentioned to you.
[Sidenote: ANNULARIA. SEDENTARIA.]
"To begin with the 3rd Order of the 9th Class:--
Class, _Annularia_. Order, _Sedentaria_, Annulated Worms.
_Siliquaria_, taken from _Serpula_. _Dentalium_, ---- _Dentalium_. _Pectinaria_, ---- _Sabella_. _Sabellaria_, ---- _Sabella_. _Spirorbis_, } _Serpula_, } ---- _Serpula_. _Vermilia_, } _Galeolaria._ _Magilus._
"There has been much variation in the opinions of naturalists respecting the proper place of genus _Dentalium_. Cuvier, a very celebrated writer, agreed nearly with Lamarck; but still more recently it has been considered as nearest to a new genus, _Fissurella_, (_Patella_.) The fossil-shells are found in London clay in great numbers; in the marle at Folkstone, &c.
"_Spirorbis._ All the species are minute, fixed upon sea-weeds, and other marine substances. The animal which inhabits them is of a deep red colour.
"_Galeolaria_ is a New Holland genus.
"_Magillus_ is found in the Isle of France; the shell is sometimes three feet in length.
* * * * *
[Sidenote: CIRRHIPEDA--FIRST ORDER.]
"Class 10th. _Cirrhipeda_, contains two orders: the first, _sessile_, or placed upon some other body; the second, _pedunculate_, and fixed at the extremity of the pedicle to other substances.
"The class takes its name from the _Cirrhi_, or feathery tentacula. The genus _Lepas_ only is contained in the _Cirrhipeda_ class.
* * * * *
"1st Order. Shells Sessile.
_Tubicinella._ } _Coronula._ } _Balanus._ } _Acasta._ } All included in _Lepas_. _Creusia._ } _Pyrgoma._ }
"The first genus contains but one species; the shell is buried up to its aperture in the skin and fat of whales.
"The second, _Coronula_, is found inserting itself in the sea-turtle, &c.
"_Balanus_ is known to you as the acorn-shell; a genus widely diffused; abounding on rocks, shells, and wood, in large colonies.
[Sidenote: CIRRHIPEDA--SECOND ORDER.]
"_Acasta_ is found upon sponge.
"For examples of _Creusia_, we must examine our _madrepores_, and other corals; the shells of this genus are either affixed or buried in them.
"_Pyrgoma_ likewise adheres, or penetrates into corals.
"In the 'Penny Cyclopædia,' under the word _Cirrhipeda_, you will find much useful information, and some plates that will give you a good idea of this class. In the British Museum you may see many of the species, and may thus make yourselves familiar with them.
* * * * *
"2nd Order. Shells pedunculated.
_Pentalasmis_, (_Anatifera_.) } _Pollicipes_. } _Lepas._ _Cineras._ } _Otion_, ear-barnacle. }
"We have already noticed _Pentalasmis_, or barnacle, (Plate 2.) The generic name is changed by later writers; so are those of the two last.
"_Pollicipes_ resembles _Pentalasmis_, with a shorter pedicle, which is rough. The natives of Goree are said to eat a large species of _Pentalasmis_."
"I think we shall not fail to recollect the _Cirrhipeda_ class," said Lucy; "the forms of the shells are remarkable: and those that live on _Madrepores_ I shall search for immediately; but what a number of new genera are taken from the single one of _Lepas_!"
"Since the time of Linnæus," replied Mr. Elliot, "many more observations have been made upon the shells that he had examined; many new shells, both genera and species, have been found; and there is little doubt that, if Linnæus had now been living, he would have found his own genera inadequate, and would have established new ones. I fear you will have to regret the opposite extreme, and complain of the multiplicity of new genera, and new names. Our object is to become familiar with the shells, and by knowing the Linnæan name, and that bestowed by Lamarck, two authorities very generally cited, you may understand what species is alluded to by modern conchologists. The names of Bruguieres, Leach, Gray, and Sowerby will often occur among many others.
"For example: let us take the plate of a remarkable multivalve; you find that it is named _Scapellum vulgare_, and that it is so called by Leach. Below, you find '_Pollicipes scapellum_, Lamarck;' and on referring to our comparative lists we find that the shell was a _Lepas_, (_L. scapellum_ of Linnæus.)"
"But they have kept the specific name," observed Charles.
"And made it the generic," said Mr. Elliot; the peculiarities and variations are deemed insufficient to found a new genus.
"Here we shall pause for the present; and then proceed to the 11th Class."
Two Orders.--1st. _Bimusculosa_, two muscular impressions.
2nd. _Unimusculosa_, one muscular impression.
[Sidenote: CONCHIFERA, SHELL-BEARERS.]
"This class," observed Mr. Elliot, "contains all the bivalves of Linnæus, and some genera taken from the univalves and multivalves.
"The animals of this class are _shell-bearers_ or _carriers_, they remain constantly fixed in their habitations: the body is fastened to the shell by one or two strong muscles: when the shell is vacant we find the _cicatrix_. Refer to your explanation of terms, and you will find the word.
"The body is soft, without joints, without head or eyes; it is wrapped in a mantle or tunic. The mouth, always hidden in the tunic, is merely an opening to admit food, without jaws or teeth. The shell is always bivalve; the valves united by a hinge or a ligament; sometimes there are accessory pieces to the valves.
[Sidenote: CONCHIFERA. UNIMUSCULOSA.]
"Some of the _Conchifera_ are furnished with a kind of foot, which enables them to move with their shells, to draw out fibres by which they fasten themselves to marine bodies. The muscles that fasten the animals to their shells are thick and strong; their use is, to close the valves by contracting; when the muscle is relaxed, the elastic ligament is sufficient to open them. The _Conchifera_ are all aquatic; some inhabit fresh water, the others dwell in the sea.
"The class contains nineteen families and two orders. The first order, _Bimusculosa_, contains thirteen families. The first includes genera that you will scarcely expect to find among the bivalve shells.
* * * * *
"1st Family, _Tubicolaria_, contains,
_Aspergillum_, Watering-pot _Serpula._ _Clavagella_ ------- _Firtuluna_ _Septaria_ _Serpula._ _Teredina_ Fossil genus. _Teredo_ _Teredo._
"_Aspergillum Javanum_ is a rare and curious shell from the Indian seas, (Plate 9.) The whole family is remarkable, and was referred, you perceive, to a very different order. _Clavagella_ was till lately considered as existing only in a fossil state. The researches of recent travellers have discovered _Clavagella_ at Port Jackson, in Australia.[A] There is a specimen in the British Museum. The valves are enclosed in the tube.
[A] See Penny Cyclopædia, article Clavagella.
"The valves of _Teredo_ are noticed as forming part of the Linnæan generic character, you will recollect. Lamarck considers them as true _Conchifera_. In many specimens of _Teredo_ the valves are wanting, and the tube only remains.
* * * * *
"The family _Pholadaria_ contains,
_Pholas._ _Pholas_, stone-piercer. _Gastrochæna_ _Pholas_ and _Mya_.
"Notwithstanding the accessory pieces of the hinge, _Pholas_ is placed among bivalve shells, the essential character of which is to have two valves united by a hinge. The _Pholas_ has a foot or strong muscle, very thick and short. In the next genus, composed of _Pholas hians_ and _Mya dubia_ there are no secondary valves.
"Allied to this family is _Xylophaga dorsalis_, a curious shell. One specimen has been lately found at Gravesend, upon a stick.
* * * * *
[Sidenote: SOLENACEA. MYARIA. MACTRACEA.]
_Solen_ _Solen._ _Panopæa_ _Mya._ _Glycimeris_ _Mya._
"The _Solen_ is furnished with a muscle, called by some writers a tongue. By the aid of this instrument they descend two feet deep in the sand. The tongue is first projected from the shell, and cuts a hole. It then assumes the form of a hook, and draws down the shell into the hole. This operation is repeated until the shell disappears. _Panopæa_ is a large shell--it is in the Museum.
* * * * *
"4th Family, _Myaria_.
_Mya_ _Mya_, or gaper. _Anatina_ _Mya._
"The animal of _Mya_ has also a foot: it buries itself in the sand. You know the broad tooth of the _Mya_ genus. _Anatina_ has a tooth on each valve.
* * * * *
"Second Section contains four families.
"_Mactracea_ has the following genera:
_Lutraria_ _Mactra._ _Mactra_ _Mactra._ _Crassatella_ _Mactra_. _Erycina_ ---- _Ungulina_ ---- _Solenomya_ _Mya_. _Amphidesma_ _Tellìna_.
"_Crassatella_ is a genus from the seas of New Holland. The shell is very thick, with a brown epidermis. A fossil species is found at Hordwell cliff. There are several species also found in the chalk. _Mactra_, _Lutraria_, and _Erycina_ are found in a fossil state. _Crassatella sulcata_ is common in London clay.
* * * * *
[Sidenote: CORBULA. LITHOPHAGA.]
"The family _Corbula_ contains two genera.
_Corbula_ ---- _Pandora_ _Tellìna_.
"_Corbula_ comes chiefly from the Asiatic Seas. There is _one_ species, formerly _Mya inequivalvis_, from the British Ocean; fossil species several. _Pandora rostrata_ is British, and is said to be met with at Weymouth. It is a pretty shell. The ligament of these is internal.
* * * * *
_Saxicava_ _Mytilus_. _Petricola_ _Venerupis_, or Venus of the rocks.
[Sidenote: VENERUPIS PERFORANS. PSAMMOBIA.]
"These genera consist mostly of small shells, inhabiting stones, into which they bore holes. _S. rugosa_ is British. _Venerupis perforans_ is found on our coasts in stones. The valves of these shells have no accessory pieces like _Pholas_.
* * * * *
"_Nymphacea_ is the next family, containing, in the first section,
_Sanguinolaria_ _Solen_. _Psammobia_ _Tellina_. _Psammotæa_ ----
"In the genus _Psammobia_ we find our _Tellina Feroensis_. (Plate 4.) The shells of this and the preceding genus resemble the solens in a trifling degree, being a little open at the sides. In form they are near _Tellina_, but have not the fold on the anterior valve, but an angle on _each_ valve. The ligament is exterior.
* * * * *
"In the second section are--
_Tellina_ _Tellina_. _Tellinides_ _Tellina_. _Corbis_ _Venus_. _Lucina_ _Venus_ and _Tellina_. _Donax_ _Donax_. _Capsa_ _Donax_. _Crassina_ _Venus_.
[Sidenote: CORBIS. LUCINA. CAPSA. CYCLAS.]
"There is but one species of _Tellinides_ from the island of Timor. The genus _Corbis_ is fossil, with one exception, _Corbis fimbriata_, from the Indian Ocean. _Lucina_ is a pretty genus of shells. _L. carnaria_ is frequently found in collections. The interior of the valves is of a deep red colour: the muscular impressions are very distant from each other; one is greatly lengthened out; the valves delicately striated. _Capsa_ is taken, you perceive, from _Donax_.
"_Tellina_ is found fossil on the borders of the Red Sea, also in the county of York. Of _Donax_ and _Mactra_ the fossil species are few.
"In the third section of this order we find six families. 1st. _Conchæ_, which are of two kinds, fluviatic, living in fresh-waters; and marine, or living in the sea. Of the first are,
_Cyclas_, taken from _Tellina_. _Cyrene_, partly from _Tellina_ and _Venus_. _Galathea_, _Venus paradoxa_, (one species.)
"_Cyclas rivicola_ (Plate 9.) will give you an idea of this genus: it is _Tellina cornea_ of Linnæus. The species are very common in lakes, rivers, and ponds: it abounds in river-sand, from which you may often procure perfect specimens. Lamarck observes that it is rare in France; but appears common in the Thames.
[Illustration: Plate 9.]
[Sidenote: POTAMOPHILA. ASTARTE. PULLASTRA.]
"_Cyrene_ is a foreign genus.
"In the _Conchæ marìnæ_ the genera are very numerous. They are all assembled under the _Venus_ of Linnæus. Lamarck reduced the genus; but it has been yet further divided by later writers.
_Cyprina_, } _Cytherea_, } From _Venus_, Lamarck's genera. _Venus_, } But _Pullastra_, _Astarte_, _Venerupes_, and _Potamophila_ have been since withdrawn from the original genus.
* * * * *
"_Pullastra_ was the name of a species, and includes _V. pullastra_, _V. papilionacea_, _V. decussata_, _V. litterata_, _V. virginea_.
"_Astarte_ includes some British species, _V. Scotica_, &c.
[Sidenote: VENUS. CYTHEREA. ISOCARDIA.]
"_Potamophila_ is a scarce river-shell from Ceylon. Some species have also been brought from Congo by African travellers. The form is triangular, very thick, covered with an olive-green epidermis. Lamarck's two genera have been still further reduced; but I shall refer you to the Museum for their new names. Observe, in _Venus_ there are three cardinal teeth, close together, on each valve, with divergent lateral teeth. _V. lamellata_ is rare and beautiful, from the seas of New Holland. There are many species of _Venus_ in a fossil state. In _Cytherea_ we find four cardinal teeth on the _right_ valve, three of them near together, the fourth quite apart. The _left_ valve has three cardinal teeth. _C. Dionè_, the thorny Venus, is a pretty shell with spines. You may easily procure it.
"_Astarte_ has some fossil species in the crag and green sand: _A. obliquata_ is one species.
"_Venericardia_ is wholly a fossil genus: one species is found in the crag, _V. senilis_.
* * * * *
"The family _Cardiacea_ contains
_Cardium_ _Cockle_ _Cardita_ _Chama_ (some species.) _Cypricardia_ ------ _Hiatella_ _Mya_. _Isocardia_ _Chama_.
"_Isocardia cor_ is British. (Plate 9.) There is a beautiful species, _Isocardia moltkiana_ from the East Indies, which is much valued by collectors.
* * * * *
"In the family _Arcacea_ we find,
_Cucullea_ _Arca_. _Arca_ _Arca_, ark-shell. _Pectunculus_ _Arca_. _Nucula_ _Arca_.
[Sidenote: ARCA. PECTUNCULUS. NUCULA. NAYADA.]
"The hinge of _Arca_ in this arrangement is always _straight_, furnished with a number of teeth; the ligament is external. The shells are open at one end, for the animal throws out at the aperture a number of threads, by which it fastens itself to the rocks. The species are thirty-seven, and also several fossil.
"The orbicular form of _Pectunculus_, and its arched hinge, distinguish this genus from the preceding one. They are allied to the Pectens by their form, and their crenulated internal margin.
"The hinge of _Nucula_ is set with little teeth on each side, like a comb. It is pearly within, and sometimes small pearls are found in the shell. _Pectunculus costatus_ is found in London clay.
"_Trigoniana_ is a small family containing _Trigonia_ and _Castalia_. The first is a fossil genus chiefly. Some species are found in the Portland stone, or oölite beds.
"The next family contains the _Nayada_, chiefly composed of fluviatic, or fresh-water shells. They are covered with an olive-brown epidermis, which is constantly found eroded, or destroyed at the beaks. The muscular impressions are lateral and much separated; one of them is formed of two or three distinct irregular impressions.
_Unio_, taken chiefly from _Mya_. _Hyria_ _Mya_. _Anodon_ _Mytilus_. _Iridina_ Very rare genus.
[Sidenote: UNIO. ANODON. DICERAS.]
"_Unio_ has two teeth on each valve; one is cardinal, the other lengthened out. The ligament is exterior--the shell pearly. _Unio pictorum_ is common in rivers. The shell is used to hold small masses of gold or silver for artists, under the name of _shell-gold_.
"_Anodon_ is also to be met with in our rivers.
"_A. anatina_ is eaten by ducks and crows. The latter, when the shell proves too hard to penetrate, mount with it into the air, and letting it fall, pick out the fish from the broken shell.
* * * * *
"_Chamacea_ has only three genera.
_Diceras._ _Chama_ _Chama_.
_Etheria_, a rare genus, from the Indies and Madagascar.
* * * * *
"_Diceras_ is a fossil genus--only two species known according to Lamarck.
"Linnæus had assembled in his genus, _Chama_, shells with equal and with unequal valves, shells fixed to other marine bodies, with those that are free; some with _one_, others with _two_ muscular impressions. In the present genus, _Chama_, the shells are irregular, thick, scaly, or spinous. The hinge has one thick tooth, often notched: the beaks are bent inwards. They are found in the Indian, American, and Mediterranean seas. There are several fossil species.
"The first order, _Bimusculosa_, is finished. In our next lesson we shall proceed to the families and genera contained in the second, _Unimusculosa_."
[Sidenote: UNIMUSCULOSA. TRIDACNA. MODIOLA.]
"1st family, _Tridacnacea_.
_Tridacna_ _Chama_. _Hippopus_ _Chama_, (one species.)
"In the first genus we find the great _Tridacna gigas_, the largest and heaviest shell yet known. It sometimes weighs five hundred pounds. The hinge has two teeth, the lunula is open, the valves equal, the ligament exterior.
* * * * *
_Modiola_ _Mytilus_. _Mytilus_ _Mytilus_. _Pinna_ _Pinna_.
"The greater part of these genera attach themselves to marine substances by a byssus. The _Modiola_ genus are rarely found fixed. The ligament internal, lodged in a marginal gutter. Beaks nearly lateral; hinge without teeth. The genus _Pinna_ is unaltered. Small crustaceous bodies, resembling the crab, are sometimes found in the shells of the _Pinna_.
* * * * *
[Sidenote: PINNA. PERNA. AVICULA.]
_Crenatula_ Rare and little known. _Perna_ _Ostrea_. _Malleus_ _Ostrea_, hammer-oyster. _Avicula_ _Mytilus_. _Meleagrina_ _Mytilus_.
"The first genus is found in the seas of warm climates. The shells are thin and foliated. The hinge of _Perna_ differs widely from that of the oyster. It is linear, formed of sulcated teeth. There is a sinus under the extremity of the hinge, for the passage of the byssus. Compare _P. isognomon_ with the common oyster, and you will find few points of resemblance between them. (Plate 5.) _Perna ephippium_ is also a curious species, very pearly within. The _hammers_ are rugged and singular in form. They are all foreign, from the oriental seas.
"_Avicula_, or Swallow, so called from the resemblance of the shells to a bird flying, was considered as a single species by Linnæus. Lamarck makes eighteen species in his new genera. _Meleagrina_ has two species. The pearl-bearing muscle, as it is called, is found in the Persian Gulf, the Gulf of Mexico, &c. The interior of the shell is coated with thick pearl, and within it are formed those globular substances known by the name of pearls.
* * * * *
[Sidenote: MELEAGRINA. LIMA. PECTEN.]
"Family, _Pectenida_: genera--
_Pedum_ Only species, from India, rare. _Lima_ _Ostrea_. _Plagiostoma._ _Pecten_ _Ostrea_, scallop. _Plicatula_ _Spondylus_. _Spondylus_ _Spondylus_, thorny-oyster. _Podopsis._
"The genus _Lima_ is longitudinal, auricled, or eared; hinge without teeth, with a hollow receiving the ligament. These are very pretty shells, generally white, almost transparent, resembling the _Pecten_. _Lima_ comes from the American seas, and is a species easily obtained. There are also several fossil species.
"_Plagiostoma_ is wholly a fossil genus, of which several species are found in this country, in lias, &c.
"The pectens are so easily known that I need only mention some fine species, such as _P. pallium_, a splendid shell, from the Indian seas: _P. pleuronectes_ is a finely polished, smooth species from the Indian Ocean.
"The genus is divided into sections, viz. ears equal, ears unequal. You may find some common species on our own shores, and you may procure fossil species: they are numerous.
[Sidenote: PLICATULA. OSTREA.]
"_Plicatula_ is a genus taken from _Spondylus_. _Spondylus gæderopus_, from the Mediterranean, is a common shell in collections.
"_Podopsis_ is a fossil genus.
"The oysters and pectens differ so widely that they do not even rank in the same family.
* * * * *
"In the _Ostracea_ are,
_Gryphæa_ _Ostrea_. _Ostrea_ The same. _Vulsella._ _Placuna_ _Anomia_. _Anomia_ The same--Antique lamp.
"There is but one recent species of the first genus; but many fossil.
"The oyster is said to possess the most limited faculties of all shelly tribes. Immovable upon the rock or marine substance to which it is fastened, it receives no other nourishment than what the waves contribute, and indicates no other sign of life than opening and closing the valve of the shell. This genus still retains a great number of species: one section has the margin of the shell either _simple_, or _waved_, the other _folded_. _O. edulis_, common oyster, belongs to the first division.
"_O. folium_ is of the second; a curious species, from the Indian and American seas: the shell is fixed to wood and to the roots of trees on the sea-shores.
"_Vulsella_ is a foreign genus, from the Indian and other seas.
[Sidenote: PLACUNA. ANOMIA.]
"_Placuna_ does not adhere to any marine substance. The valves are flat, thin, and transparent; the very small space between them shows that the animal must be extremely flattened: there are two singular ribs at the hinge in the form of a V.
"_P. placenta_, Chinese window-glass, is so transparent when young, that it serves instead of that material in China.
"_Anomia._ The shells of this genus are fixed, like the oyster, to marine bodies. They live and perish on the spot where they are at first produced. I have noticed the muscle by which they attach themselves. Lamarck informs us that a hard, small operculum is to be seen at the extremity of this muscle, and fills up the _hole in the flat valve_ when the muscle is contracted. (Plate 5.)
"The family _Rudista_ contains only a few genera, which will be quite uninteresting to you at present.
"The next, _Brachiopoda_, has
_Crania._ _Orbicula_ _Patella_. _Terebratula_ Some from _Anomia_. _Lingula_ _Patella_."
Lucy could not forbear interrupting her father upon hearing the name of _Patella_. "How can that genus be mixed with the _Conchifera_?" she inquired.
"The shell is _bivalve_," he replied; "raised upon a fleshy peduncle, and fixed to marine substances; the hinge is without teeth, having the form of a duck's beak; the colour a greenish tint. It is found near the Molucca isles.
[Sidenote: HIPPONYX MITRATA.]
"Yet more remarkable is the _Hipponyx mitrata_, a common shell, known as _Patella mitrata_, long supposed to be a univalve, the upper valve only being known. A French naturalist discovered the lower valve, and _both_ have one muscular impression in the form of a horse-shoe.
"I think that it will be best to pause a little before we enter upon the study of the twelfth class, _Mollusca_, which contains most of the univalves of Linnæus."
[Sidenote: MOLLUSCA. CLEODORA.]
"As I have observed that you have been very diligent in studying Lamarck since our last lesson," said Mr. Elliot, "I propose to make you acquainted with the variations in the univalve genera.
"The animals of the _Mollusca_ are soft, without joints, generally possessing a head, eyes, and tentacula, or feelers. They have also a fleshy membrane, called a foot, which they use for climbing. The orders, excepting the first, are named from the position of this foot. They are five in number. The first order contains very few genera. One genus, named _Cleodora_, contains a species brought from Africa. The shell is curious, transparent, and shaped like the head of a halberd.
"The animals of the second order, _Gasteropoda_, have a muscular foot, or disk, on which they rest. The families are seven. The first, _Tritonia_, I shall pass over.
"_Phyllidiana_ includes the genera--
_Phyllidia._ _Chitonella._ _Chiton_ Coat of mail. _Patella_ _Patella_, or limpet.
[Sidenote: CHITON. PATELLA.]
"The _Chiton_ moves like the _Patella_, upon a disk, or foot.
"The body of _Patella_ is entirely covered by the shell. You may have many opportunities of examining the British species. _P. pellucida_ is very transparent, with blue lines.
* * * * *
"The family _Semi-phyllidiana_ contains
_Pleurobranchus._ _Umbella_ _Patella_.
"The _Umbella_ shell is flat and white, and is sometimes four inches in diameter. It is common in the Isle of France: there is another from the Mediterranean.
* * * * *
"_Calyptracea_ is a larger family: it has many genera taken from _Patella_:
_Parmorphorus_, Thracian-shield. _Emarginula_, } _Fissurella_, } _Pileopsis_, } _Patella_. _Calyptræa_, } _Crepidula_, } _Ancylus_, }
[Sidenote: FISSURELLA. PILEOPSIS. BULLA.]
_Parmophorus_ is found in the seas of New Holland and New Zealand. The margin of the next genus is distinguished by a slit: the shell is conic. (Plate 3.) _Fissurella_ has the top of the shell perforated; it is called the _key-hole_ limpet, from the shape of the aperture. _Pileopsis_ is obliquely conic. It was with this division that the curious _Hipponyx_ ranked.
"_Calyptræa_ is very thin and brittle, with an internal lip. (See Frontispiece.)
"_Crepidula_ has the shell partly covered, or arched: it looks like a little slipper.
"_Ancylus spina-rosa_ is a pretty species from the south of France: the genus is fluviatic. _A. lacustris_ and _fluviatilis_ are both natives of our fresh-waters.
* * * * *
"The next family, _Bullæana_, has
_Acera_ _Bulla_. _Bullæa_ _Bulla_. _Bulla_ The same.
"_Acera_ and the following genus have each but one species, _Bulla carnosa_ and _B. aperta_ of Linnæus. The original genus _Bulla_ was composed of an assemblage of shells of various characters, having little resemblance except in their gibbous form. _Bulla naucum_ is an example of the genus of Lamarck's system; so is _B. lignaria_. (See Frontispiece.) _B. ampulla_ and _B. striata_ are common in collections.
* * * * *
[Sidenote: APLYSIA. DOLABELLA.]
"_Aplysiana_ is a small family, containing
_Aplysia_, or Sea-hare. _Dolabella._
"One species of _Aplysia_ is found on the Devonshire coast: the name Sea-hare marks the singularity of the two tentacula, which resemble the ears of the hare. The body is folded up in a loose skin, or mantle: upon the middle of the back it carries a circular shield, thin, transparent, and yellowish, in which it resembles the slug. These animals swim with ease.
"_Dolabella_ resembles the _Aplysia_ in some degree; the genus is foreign, and one species is known to inhabit the bays of the Isle of France, where it covers itself with a portion of mud."
"I cannot understand why animals related to the slugs should find a place here," said Charles.
"Have not slugs the characteristics of the _Mollusca_ class?" asked his father. "And are you quite sure that they are without a shell?
[Sidenote: ONCHIDIUM. LIMAX.]
"Our next family, the _Limacina_, has
_Onchidium._ _Parmacella._ _Limax_, slug. _Testacella._ _Vitrina._
"_Onchidium_ is a genus from the shores of the Indian seas. The animals have a shield: they live near the sea, and some are known to swim, often coming to the surface to breathe the air.
"_Parmacella_ was found by an English traveller in Mesopotamia. It has a shell covered by a shield. But you have not answered my question respecting the _Limax_, or slug."
"I do not recollect," replied Charles; "yet how often we see slugs!"
"If I may be allowed to answer," said Lucy, "I think that the slug has what I now understand to be a _shield_. I have often watched the animal contract itself, and seen a broad, flat piece upon the back, which I thought was a kind of shelter for it."
"The _Limax_, or slug," continued Mr. Elliot, "is, in fact, provided with a coriaceous escutcheon, or shield, beneath which the animal partly conceals itself. The _Limax agrestis_, or spinning-slug, has the power of suspending itself by a kind of thread, formed of the viscid substance that covers the body.
[Sidenote: TESTACELLUS. COLIMACEA.]
"_Testacellus_ is a very interesting genus, lately found in England: the animal has a resemblance to the common slug: it carries the shield on the hinder part of the body.
"_Testacellus scutellum_ feeds on earth-worms, and can so much lengthen the body that it follows them under-ground.
"Our next order will show great alterations in the very large genus _Helix_. I shall name to you those of Lamarck.
"The third order of _Mollusca_, _Trachelipoda_, begins with a well-known genus, the snail, _Helix_. The term signifies that the _foot_ is situated under the neck, or anterior part of the body. The families in this order are numerous: they are divided into two sections; the first includes those that breathe only in the air; the second those that can exist only in the water, and are furnished with a syphon.
* * * * *
[Sidenote: HELIX. CUROCOLLA. ANOSTOMA.]
"First section: family _Colimacea_; genera numerous; animals live upon land only; tentacula generally four; during winter they enclose themselves in their shells, with a false operculum.
_Helix_, snail _Helix_. _Carocolla_ _Helix_. _Anostoma_ _Helix_. _Helicina_ _Helix_. _Pupa_ _Helix_. _Clausilia_ _Helix_. _Bulimus_ _Helix_. _Achatina._ _Succinea_ _Helix_. _Auricula_ _Voluta_. _Cyclostoma._
"What a number of new genera!" said Lucy. "I see the forms of the shells vary very much; and how beautiful these little transparent shells are!"
"They will find a place shortly. Here is a well-known species, _H. aspersa_, in most of its varieties; _H. pomatia_, the apple-snail, now naturalized in the county of Surrey; _H. ericetorum_, white with brown bands, very frequent on chalky soils; _H. citrina_, transparent, pale yellow, sometimes with one dark band; _H. muralis_, from the walls of Rome; _H. bidentalis_, from Teneriffe; and the little _Helix hispida_, which you may search for in your own garden; it is small, dark brown, and rough.
"_Carocolla_ has the shells more flattened than _Helix_.
"_Anostoma depressa_ is a rare and curious shell.
"_Helicina_ is a West Indian genus. You saw them just now. We shall find Helix in two other families.
[Sidenote: PUPA. BULIMUS. AURICULA.]
"_Pupa_ is a curious genus. The shells resemble a chrysalis. A few minute species are found in Britain. _P. muscorum_ I have found buried among damp moss. The larger species are natives of tropical regions. These shells are often found _decollated_.
"_Clausilia papillaris_ is a pretty shell. (Plate 9.)
"_Clausilia rugosa_ is found in some parts of Britain, under old hedges, at the foot of old trees, and similar places. It is a tapering shell, with the aperture reversed, or left-handed, and bi-dentated: the colour red-brown. It is to be found in the vicinity of Dorking, in Surrey.
"_Bulimus_ is a large genus. A common small species is the _Gaudaloupe Bulimus_.
"The largest land-shells are found in the genus _Achatina_. The greater number are African.
"_Succinea_ contains a few species. One of them, _S. amphibia_, is common near fresh-water.
"_Auricula_ has some resemblance to a _Voluta_. The aperture is longitudinal: the columella has one or more folds.
"The forms of the species in _Cyclostoma_ are variable; but the aperture is circular, and the margin revolute, or rolled back. _C. elegans_ is often to be found on hedge-banks or chalk soils. It is a pretty shell, sometimes white, often tinted with purple.
"In the family _Lymænana_, the species are amphibious; inhabiting fresh-water; but rising to the surface to breathe the air. They have but two tentacula.
"As several species are British, you may have the satisfaction of examining them for yourselves.
* * * * *
"The genera are,
_Planorbis_ _Helix_. _Physa_ _Bulla_. _Lymnæa_ _Helix_.
"_Planorbis_ is a discoid shell, and one peculiarity of the genus is, that they are all reverse shells. In a discoid shell the spire is depressed; when held up, the whorls turn from right to left, and the aperture is left-handed. The largest species is _P. cornu-arietis_,[B] which is a native of Brazil. _P. corneus_ is common in ponds and ditches. Empty shells are to be found at the edge of the water. (Plate 9.) If you take the animal to examine, and study its habits, remember that you have no right to injure it, and that you have already promised me that no kind of cruelty shall take place.
"_P. vortex_ is a smaller species. The outer valve is carinated.
"_Physa_ is found in fresh-water upon aquatic plants. They are small shells.
[Sidenote: LYMNÆA. MELANOPSIS. VALVATA.]
"The animal of the _Lymnæa_ genus has two flat tentacula. _L. stagnalis_ is a very pretty spiral shell, common in ponds.
"_L. auricularia_ is also frequent. It is much smaller than the first species. The last whorl is swelling, and the aperture very wide. They are both thin and brittle.
* * * * *
"The family _Melaniana_ are chiefly foreign. The shells are covered with a dark-coloured epidermis. They are operculated.
_Melania_ _Helix_. _Melanopsis._ _Pirèna._
"A species of _Melanopsis_ inhabits the river Orontes, in Syria.
* * * * *
"There is yet another family connected with _Helix_, the _Peristomata_, containing
_Valvata._ _Paludina_ _Helix_. _Ampullaria_ _Helix_, partly.
"Some of the _Valvata_ genus are found in fresh-water in Britain and other European countries. The shells are small; they are discoid or conoid, and have an operculum. In the shells of this family the margin of the aperture is carried completely round. In _Paludina_ the whorls are convex. They generally inhabit fresh-waters.
"_P. vivipara_ is found in rivers. Quantities of empty shells may be taken from the sand of the Thames.
"Fossil species abound--Petworth marble is full of them."
[Sidenote: NERITACEA. NERITINA.]
"The family of the _Neritacea_," said Mr. Elliot, as he renewed his lessons to Charles and Lucy, "are remarkable in their form. Their left-margin is truncated, without any appearance of a columella. They possess an operculum, and are either marine or fluviatic. The genera are,
_Navicella._ _Neritìna_ _Nerìta_, Nerite, or hoof-shell. _Nerìta_ _Nerìta_. _Natìca_ _Nerìta_.
"You will recollect that the order _Trachelipoda_ is still continued.
"_Navicella_ is a foreign genus from the Indian rivers.
[Sidenote: NERITINA. NERITA.]
"_Neritìna_ is a pretty genus of shells, from the European, the East and West Indian rivers. They resemble the _Nerìta_ genus, but are all fresh-water shells; thin, smooth, and variously marked; without any tooth or notch on the right-margin of the aperture.
"_N. virginea_ is common in collections; it is marked with various lines and dots.
"_N. fluviatilis_ is common in our rivers: you may find plenty in river-sand, of red and brown colours, and various sizes.
"_N. zebra_ and _N. meleagris_ are also pretty shells. The little _Neritìna viridis_, from the West Indian streams, is one of the smallest species, of a pale pellucid green.
"_Nerìta_ is a marine genus. The shells are solid and semi-globose; the left-margin is truncated, the right-margin toothed, or crenulated. This genus is never umbilicated.
"_N. polìta_ is a handsome shell: it is thick, polished, and variously marked; the base of the aperture is yellowish.
"_N. peloronta_, the bleeding-Nerite, is marked with a crimson spot.
"_N. tessellata_ is sulcated, or furrowed, chequered with black and white.
"_Natìca_ differs from the former genera in these particulars: the shell is umbilicated; the left-margin oblique, not toothed, callous, the callosity sometimes covering the umbilicus. The species are numerous, and several are common in collections. "_N. aurantius_ and _N. millepunctata_ are good shells.
[Sidenote: IANTHINA. SIGARETUS. STOMATELLA.]
"_Ianthina_ is the last of the snail-like genera. Its beautiful purple colour renders the shell a favourite. They are marine, though so fragile and transparent. The animal floats upon the surface of the sea, by means of a vesicular appendage to the foot, which, it is said, may be inflated or contracted at pleasure. _Ianthina_ shines by night. _I. communis_ is found in abundance in the Atlantic and in the Mediterranean.
* * * * *
"The family _Macrostoma_ contains,
_Sigaretus_ _Helix_? _Stomatella._ _Stomatia._ _Haliòtis_ _Haliòtis_, sea-ear.
"These genera form a beautiful family, and all bear a resemblance to the human ear.
"_Sigaretus_ is white and pearly; the shell is enveloped in the folds of the mantle belonging to the animal. There are several species, one or two of which were ranked among the _Helix_ race.
"_Stomatella_ is also very pretty; the shells are pearly. _S. auricula_, from New Holland, has the appearance of a little _Haliòtis_.
"_Stomatia_ is a small genus.
[Sidenote: HALIOTIS. VERMETUS. SCALARIA.]
"With the genus _Haliòtis_ you are already acquainted. The animal appears to be very elegantly formed, if the plate I have seen of it be correct.
"There is a number of fine specimens in the British Museum.
* * * * *
"The family _Plicacea_ contains only,
_Tornatella_ _Voluta_, chiefly. _Pyramidella._
"All the species have plaits, or folds, on the columella. The shells are marine and foreign in both genera. (Plate 9.)
* * * * *
"Our next family, _Scalariana_, contains the genera
_Vermetus._ _Scalaria_ _Turbo_. _Delphinula_ _Turbo_.
* * * * *
"The single species of the first genus, _Vermetus lumbricalis_, inhabits the sea near to Senegal. The shell is tubular, thin, twisted spirally; it is fixed on marine substances by the end of its thin, pointed spire. The shells are usually found in groups.
"The genus _Scalaria_ is one of the most elegant among univalve shells. The singularity of the numerous ribs renders the shells easily known from all other genera of turreted _Mollusca_. The aperture is nearly round, the whorls gibbous, or inflated with carinated ribs: the colour is usually pink or white. It is very costly. (Plate 9.) These shells are brought from the East Indies.
"The fossil species are very elegant: they are found in the strata above the chalk.
"Two other species are common, _S. communis_ and _S. lamellosa_. The first is a British species, and is called the _false Wentletrap_.
[Sidenote: DELPHINULA. SOLARIUM.]
"The shells of the genus _Delphinula_ are solid, thick, somewhat discoid, often armed with spines, without any apparent columella. The recent species inhabit the Indian Ocean. There are several fossil species of _Delphinula_.
"The _Turbinacea_ family contains many genera, with which you will soon become familiar. I believe you are already acquainted with this shell, which, from the time it was first known to collectors, has always been celebrated for beauty. It is now called _Solarium perspectivum_. (Plate 9.) The large, spiral, crenated umbilicus is its great peculiarity. The French call the shell _Cadran_, _dial_. In its natural state the shell is covered with an epidermis. There are a few fossil species, one in the oölite of our own country. The English name is _staircase trochus_.
* * * * *
[Sidenote: ROTELLA. TROCHUS. TURBO.]
"The genera of _Turbinacea_ are,
_Solarium_ _Trochus_. _Rotella_ _Trochus_--wheel-shell. _Trochus_ _Trochus_--top shell. _Monodonta._ _Turbo_ _Turbo_. _Planaxis_ _Buccinum_. _Phasianella_ _Turbo_. _Turritella_ _Turbo_.
"The genus _Rotella_ contains small, flattened, wheel-shaped shells, common in most collections. They are smooth and polished.
"_Trochus_ is still a large genus. _Trochus marmoràtus_ is a fine species from the Indian Ocean. There are several handsome species on our own shores. _T. magus_ is one of them; it has a large, deep umbilicus, or perforation; the spire is flattened; the whorls are crowned with tubercles. The _Trochi_ of tropical climates are thinner than those of northern latitudes.
"When any of these shells are placed upon their _base_, their axis is always inclined: of course they never stand perfectly upright.
"There are several fossil species.
"The genus _Monodonta_ holds a middle place between _Trochus_ and _Turbo_, differing from the former in the aperture, and from the latter in the columella, which is arched and truncated at the base. They are all marine shells.
[Sidenote: LITORINA. TURBO. PHASIANELLA.]
"From the well-known genus _Turbo_, a new one has been formed, called _Litorina_, which includes all the shells of our own coasts that formerly ranked under _Turbo_. Consequently we find the periwincle has changed its generic name, and from _Turbo_ it is altered into _Litorina_. _T. muricata_ is now of the same new genus, _Litorina muricata_. (Plate 7.)
"_Turbo pica_ is a large pearly shell known as the magpie. The golden-mouthed _Turbo_ is very brilliant; the aperture appears as if gilded, so fine is the yellow tint. It comes from the Molucca Isles. _Turbo smaragdus_, from New Zealand, is a rare and beautiful species of a bright green colour.
"_Phasianella_ is a beautiful genus of shells, formerly very costly. A small but elegant species is found on our own shores, _P. pullus_, _Turbo pullus_ of some authors. The colour is pink.
"_Phasianella bulimoides_, from New Holland, is the largest of the species, and once a very rare shell.
"The term _Turritella_ will give you an idea of the form of our last genus in the family _Turbinacea_. The shells are like _little towers_, with a circular aperture. The older conchologists gave the name of _screw_ to all turreted shells, without attending to the form of the aperture. Hence we find screws among _Turbo_, _Buccinum_, and _Strombus_ (spindle).
"_Turritella duplicata_ is a heavy shell, often more than four inches long. It is sulcated and carinated; the colour is yellow-white. _T. bicingulata_ is white, marbled with yellow; the whorls are girded with two ridges. There are several fossil species of this genus in London clay."
"I think," said Lucy, "that three or four genera have been taken out of _Turbo_--_Scalaria_, _Delphinula_, _Litoralia_, and _Turritella_, and that _Litoralia_ is not Lamarck's genus."
"You are correct," replied her father, "and indeed so many alterations are continually taking place in the generic names of shells, that I cannot enter into all the niceties of modern conchologists. However, the generic name of a shell, according to Linnæus or Lamarck, is usually given, therefore I hope you will not be greatly at a loss upon meeting with some apparently unknown genus."
[Sidenote: RANELLA. VOLUTA. OVULA.]
"What is Charles drawing from his pocket with a look of so much importance," said Mr. Elliot, the next time they met.
"There is _Ranella crumena_, thorny-frog; _Ovula gibbosa_, the shuttle; and _Voluta musica_, the music-shell," said Charles.
"Oh, who gave you those nice shells?" asked Lucy, "and how do you know the names?"
"Let my father say if I am correct, first," replied Charles.
"Perfectly," answered his father; "but I fancy that I can guess how you obtained your information. You have been buying these specimens, and had the names from the shell-vender. I hope your purchase did not cost much, for they are not rare shells?"
"No; I should not choose to spend a large sum, even from my purse, until I am a better judge of the value of shells. But as our collection is but small, I thought that Lucy would be glad to see an addition to the stock."
[Sidenote: CANALIFERA, CERITHIUM.]
"Thank you, brother," said Lucy, "you never forget me in your purchases or your pleasures."
"Let us return to our subject," said Mr. Elliot, "and notice the families of the next section, which are all carnivorous, living on animal substances. They have a projecting syphon, which conveys the water to them: they are all marine. The syphon passes through the base of the aperture, either into a canal, or channel, or a narrow, recurved margin. The mouth is furnished with a trunk.
* * * * *
"_Canalifera_ contains in the first section,
_Cerithium_ Chiefly _Murex_. _Pleurotoma_ _Murex_. _Turbinella_ _Voluta_ and _Murex_. _Cancellaria_ _Voluta_. _Fasciolaria_ _Murex_. _Fusus_ _Murex_. _Pyrula_ _Murex_ and _Bulla_.
[Sidenote: FOSSIL CERITHIUM. TURBINELLA.]
"The naturalist Bruguieres established the fine genus _Cerithium_, mixed by Linnæus among those of _Murex_, _Strombus_, and _Trochus_. These shells are always turreted, having a short canal at the base; the aperture oblong, oblique, with a gutter turned backwards. (See Frontispiece.) Many are girded with zones, that are granulated, or beset with little tubercles. It is remarkable that _Cerithium giganteum_, a species more than a foot in length, is found fossil in France, and as a living species in the seas of New Holland. _C. telescopium_ is a fine shell from the East Indies. _C. vertagus_ is smooth, tawny-white, with a recurved canal. It comes from the Moluccas. Many species occur fossil in London clay and in plastic clay: the Woolwich pits afford specimens, and also of _Turritella_.
"_Pleurotoma_, formerly united with _Murex_, is distinguished by the singular _notch_ in the right-margin of the shell. One species, the Tower of Babel, is well-known, and another is common under the name of _Murex javanus_. The fossil species are numerous.
"_Turbinella_ is taken from _Murex_ and _Voluta_: some species are thick, heavy shells, from the Indian seas.
"_Cancellaria_ is an elegant genus: the shells are varicose, reticulated, or cancellated; the columella has folds upon it, varying in number, the right-margin sulcated within. There are several fossil species, which are considered very beautiful.
"_Fasciolaria trapezium_, the Persian robe, is a fine shell from the Indian seas, very common in collections.
[Sidenote: FUSUS. PYRULA. RANELLA.]
"The genus _Fusus_ consists of spindle-shaped shells, of which _Fusus colus_, the distaff, will give an idea. They are covered with an epidermis which conceals, in some species, the fine colours beneath.
"_Fusus despectus_ (_Murex_ of Linnæus) is the largest of the British turbinated shells, and very common: it is the large whelk.
"_Fusus contrarius_, the reverse whelk, is found fossil in the Essex crag.
"Among the shells of the _Pyrula_ genus we find _P. ficus_, the fig, placed by Linnæus among the _Bulla_ race. _P. spirillus_ is a pretty species, with a long canal and a flattened spire, having a tubercle at its termination.
* * * * *
"Second section of _Canalifera_: shells with a varix on the right-margin.
_Struthiolaria_, } _Ranella_, } _Murex_. _Murex_, } _Triton_, }
"_Struthiolaria_, ostrich-foot, is a remarkable shell from New Zealand.
"_Ranella_, thorny-frog, is frequent in collections: there are several species: _R. crumena_ is easily obtained--you must purchase a specimen.
[Sidenote: MUREX. TRITON.]
"Notwithstanding the great reductions of the _Murex_ genus, it is still large, and contains very fine species. The shells have _three or more_ varices upon each whorl; those in _Ranella_ but _two_; while _Struthiolaria_ has a varix only on the right-margin. The species are numerous, and common in collections. _M. saxatilis_ is white, and zoned with rose-colour or purple. The foliations, or branches, are erect. The Rose-bush is pretty; and the wagtail, _M. motacilla_, will, doubtless, be a favourite with you, as well as the scoop, _M. haustellum_.
"Notwithstanding the resemblance of the genus _Triton_ to those of _Murex_ and _Ranella_, there are permanent differences which make them distinguishable at first sight. I have already noticed the varices of the preceding genera; in _Triton_ they never form longitudinal ranges, but are alternate, few, and nearly solitary on each whorl of the spire; these varices are generally smooth and without spines.[C] _Triton variegatum_, the marine trumpet, is a large, handsome species, from the Asiatic seas. _T. lampas_ and _T. lotorium_ are common. _Triton anus_ is very remarkable.
"In the next family, _Alata_, we must notice a remarkable fact: the shells, while they are young, assume a different form to those more advanced in growth.
[Sidenote: ROSTELLARIA. PTEROCERA. STROMBUS.]
"The genera are three--
_Rostellaria_, } _Pterocera_, } _Strombus_, wing-shell. _Strombus_, }
"In the first genus the shells are terminated below by a canal, or pointed beak; the right-margin entire, or toothed, more or less dilated with age, and having a sinus contiguous to the canal. There is a specimen from our own coast, _Rostellaria pes-pelicani_, the pelican's-foot: it was _Strombus_ of Linnæus. (Plate 7.) There are many of this species found in a fossil state.
"The _Pterocera_ genus is easily known by the digitated, or fingered, appearance of the right-margin. The greater part of the species become very large. Here we find the scorpion, with seven digitations, from India; the spider, with the same number, a large and fine shell, also from India.
"_Strombus_ has a short canal, the right-margin dilated with age into a simple wing, having, at the lower part, a sinus, separated from the canal at the base of the shell.
"All the species are natives of hot climates; some attain a very large size, such as _S. gigas_, so frequently seen in shops, and as ornaments in a room. _S. gibbèrulus_ is a pretty little shell; the white, gibbous whorls render it remarkable; the interior of the lip is pink. _S. lineàtus_ has dark lines round the shell. _S. vittàtus_ has a very long spire; the colour is tawny, girded with white: you may easily meet with this species.
[Sidenote: CASSIDARIA. CASSIS.]
"The family _Purpurifera_ is composed of genera taken chiefly from the large Linnæan genus _Buccinum_.
* * * * *
"It is thus divided:
"First, the genera with the canal ascending, or turned towards the back of the shell--
_Cassidaria_, } _Cassis_, } _Buccinum_, helmets.
"_Cassidaria_ is not a very common genus; but the helmets, _Cassis_, are both numerous and plentiful in most collections. The straight aperture slightly reminds you of a _Cypræa_ perhaps, but the short canal, abruptly turned back, is a clear distinction; the right-margin generally toothed; the columella folded, or wrinkled, transversely.
"_C. cornuta_, _C. flummea_, _C. arèola_ and _vibex_, are all well-known species, _C. cornuta_ has large tubercles like horns round the tip of the shell. _C. arèola_ is marked with chequers. _C. rufus_, from the Moluccas, is a fine shell, with a deeply coloured red aperture.
"In the next division the canal is oblique, and directed backwards.
[Sidenote: NASSA. RICINULA. PURPURA.]
_Ricinula_ _Murex_. _Purpura_, } _Monoceros_, } _Concholepas_, } _Harpa_, } _Buccinum_. _Dolium_, } _Buccinum_, } _Eburna_, } _Terebra_, }
"To these genera another has been added, called _Nassa_, of which _Buccinum arcularia_ will furnish an example. The columella has a callosity very evident in the species _Pullus_ and _Thersites_.
"_Ricinula horrida_ has a ringent aperture of a fine violet colour; the shell is thick, and covered with large black tubercles. The genus takes its name from a resemblance to the seeds of _Ricinus_.
"_Purpura_ is a large genus: in certain of the species the colouring-matter exists of which the ancients formed their famous purple dye. It is the last genus that offers any appearance of a canal at the base of the aperture.
"_P. patula_, the scoop, from the Atlantic and Mediterranean, has the aperture remarkably dilated, the margin sulcated.
"_P. lapillus_ is a common British shell among the chalk-cliffs of the coast; the colour varies, sometimes white, at others yellowish.
[Sidenote: MONOCEROS. CONCHOLEPAS. HARPA.]
"I shall describe a species of the singular genus _Monoceros_, by which you will scarcely fail to recognise it.
"The columella is flattened like _Purpura patula_; just within the outer lip is a row of small teeth; but the principal peculiarity is a process, or horn, near the outer part of the lower lip, and close to the canal, from which the genus derives its name _Monoceros_, _one-horn_. It is brought from the seas of America.
"_Concholepas Peruviana_, the only species, is also a remarkable shell. The aperture is very large, almost equal to the shell itself; the spire is near the edge; the outside is marked with ribs, or costæ; there are two short teeth on the right-margin. This shell was placed among the _Patella_.
"The beautiful genus _Harpa_, harp-shell, is remarkable for its elevated ridges on the back of the shell, its large aperture, and its fine colouring. They are East Indian shells. _H. ventricosa_ is a common species. _H. nobilis_ is very fine, and also _H. costata_.
"Equally well-known are the Tuns, _Dolium_, by their globose form, the right-margin toothed, and a canal below. They reach a large size, and are light shells in proportion to their bulk. _Dolium galeum_ is sometimes the size of the human head. _D. perdix_ is a choice species.
[Sidenote: DOLIUM. BUCCINUM. EBURNA.]
"_Buccinum_ contains some British species, as _B. reticulatum_, (Plate 7,) _B. anglicanum_, _B. undatum_, which is very common. In connexion with this species I wish you to know that a marine substance, called by sailors _sea-wash balls_, by others sea-sponge, and extremely common on all our sea-coasts, is the egg-cases of the _Buccinum undatum_. The mass is remarkably light, and composed of numerous little cells, each of which has an opening. The colour varies from yellow to white."
"I know them well," exclaimed Lucy, "how often I have asked the name of those nests, but never could I obtain a reply worth having! And now, father, give me leave to interrupt you a few minutes. What are those black, stiff, marine substances, with a horn-like projection at each of the four corners; they are all hollow, and open at each end, I think, and usually inflated?"
"The egg-cases of the scate."
"Thank you, father, I will examine them again carefully when I am at the sea-side."
"The genus _Eburna_," continued Mr. Elliot, "is remarkable from the smoothness of the shells. _E. spirata_, the Joppa whelk, has the whorls deeply channelled. (See the Frontispiece.) The columella is umbilicated, and has a canal beneath it.
[Sidenote: TEREBRA. COLUMBELLA.]
"The _Terebra_ genus is turreted; very acute at the apex. (Plate 9.)
"The family _Collumellaria_ is next in order. The _canal_ now disappears at the base of the shell, but there is a slope and folds on the columella. We have reached the large genus _Voluta_ of Linnæus, greatly reduced by withdrawing the following genera:
_Columbella_, } _Mitra_, } _Cymba_, } _Melo_, } _Voluta_. _Voluta_, } _Marginella_, } _Volvaria_, }
"The shells of _Columbella_ are of small size; two species are very common in collections. _C. mercatoria_ is a little shell striated transversely; the outer lip is thickened in the middle, and toothed; the columella is plaited: the animal is furnished with an operculum.
"_Columbella nitida_ is another pretty species, smooth and shining: you may perceive the generic marks if you look closely--two small folds on the pillar-lip, and the swelling, toothed, outer margin. They are all West Indian marine shells.
[Sidenote: MITRA. CYMBA. MELO.]
"_Mitra_ is a large genus, and it is believed that there are three times as many species yet undescribed. The mitres are natives of warm climates, and few are common. The pillar-lip of _Mitra_ is parallel, with transverse folds; the base has a slope, but no canal; the margin of the columella is thin and rolled back. _M. episcopalis_, the bishop, is white with red spots; the columella-folds are four. (Plate 9.) _M. papalis_, the pope's-mitre, has five; the upper whorls are broken into a kind of crown.
"In _Cymba_, the gondola, the spire ends in a tubercle, and scarcely appears; the aperture is wide: they are very pretty shells.
"_Melo_, the melon, from the Indian Ocean, is a very fine genus; here the spire is evident.
"_Voluta musica_ will serve as an example of the genus. The animal is carnivorous.
"_Marginella_ is an oblong, smooth, and polished shell; its peculiar character is the thickened outer lip; it is a neat, small species, prettily coloured.
"_Volvaria_ is a cylindrical shell, convolute, the spire nearly hidden; the aperture straight, as long as the shell. There is a fossil species found in London clay. _V. monilis_ is sometimes strung for necklaces. It comes from Senegal.
"The last family of the order _Trachelipoda_ is _Convoluta_, which contains many very fine genera.
"They are the following:
_Ovula_ _Bulla_. _Cypræa_ The same. _Terebellum_ _Bulla_. _Ancillaria._ _Oliva_ _Voluta_. _Conus_ The same.
"The general characters of this family are the following:
"Shell without a canal, the base of the aperture sloping, or effuse, the spire compressed, the last volution almost covering the rest.
"_Ovula_, you will recollect, was formerly confounded with the _Bulla_ genus: the form is egg-shaped, the outer lip toothed in one division, smooth in the other; the shells are white and polished, particularly _O. oviformis_, the poached-egg, from the Moluccas.
"_O. volva_, the weaver's-shuttle, is a rare and highly-valued species. It is nearly globular in the middle, and is terminated at each extremity by a long beak: it comes from the West Indies. _O. gibbosa_ is a common species; the shape is oblong, with a ridge in the centre.
[Sidenote: CYPRÆA. TRIVIA.]
"You can be at no loss on seeing the shells of _Cypræa_, a large and beautiful genus, which remained unchanged for a long time. Lately, we find a few of the small species are become a new genus, _Trivia_.
"The character of the _Cypræa_ is a longitudinal aperture, toothed, in the adult state, on each side. The spire is scarcely to be seen.
"While the shells are young they have the appearance of a _Voluta_ or a cone; the aperture spreads more, and is without teeth.
"The individuals of each species pass through three different states:
"In the first, the form is very imperfect; it is like a thin cone, and shows no character of the genus; hence young students are perplexed if they chance to have a young cowry in their collection.
"In the second state, the shell is still thin, with a _projecting_ spire; but attains its proper form.
"In the third, or adult state, the shell is thick, the colours are perfected, and the spire is very nearly concealed.
"When the animal becomes too large for its habitation, it has the power of leaving it, and forming a new one.[D]
"The inhabitant of the _Cypræa_ shells has two tentacula of a conic form, and finely pointed; the foot discous, and sometimes tongue-shaped. The mantle is two-lobed, with wing-like margins, capable of being turned back over the shell: this mantle preserves the shell from injury when the animal issues forth in search of food. The genus abounds both in the old and new world; but the larger kind chiefly in warm climates. They live on the coast, and are generally found under stones or rolled coral. A very few species are natives of the European seas.
"The tiger-cowry is before you; a large and very common species in collections; it also frequently adorns the mantel-piece. There is a remarkable line extending along the back of the shell; at this part the edges of the _mantle_, that I have before noticed, meet: this line is conspicuous in many species.
"_C. aurora_ is a costly shell from Otaheite and New Zealand; the colour orange, with the base and extremities white. It is large, and has been sold for 60_l._ when a specimen has been obtained without any perforation. The shell is worn by the New Zealand chiefs as a badge of honour.
"_C. exanthema_ changes its appearance greatly as it advances in growth. While young, three bands extend over the back, which in its adult state disappear, and the fawn-coloured ground is spotted over with numerous white circular marks.
"_C. mauritania_, the moor, is a fine species, with very black sides, and tawny-yellow back with spots. It is a native of Java.
"_C. caput-serpentis_, the serpent's-head, has dark sides, with white fauces: the back is covered with net-work colouring: the fauces, you must remember, are the narrow entrances at each end of the shell.
"_C. Isabella_, the orange-tip, with pale flesh-colour back, and the fauces orange-colour.
"_C. Arabica_ is a common species in collections.
"_C. mappa_ is varied with deep brown or yellow lines and spots: the dorsal line is laciniated.
"_C. talpa_, the mole, has the back fawn-colour, with three zones of pale yellow; the base and sides sometimes nearly black. It comes from Madagascar.
"_C. vitellus_, the fallow-deer, is fawn-colour, covered with small white spots: from the Indian Ocean.
"The wasp, _C. asellus_, is white, with three brown bands.
"_C. helvola_, the star-cowry, has the sides dark orange; the fawn-coloured back studded with small spots. It comes from the Maldives.
"_C. moneta_, the money-cowry, is generally white, sometimes yellow.
[Sidenote: TÆREBELLUM. OLIVA. TRIVIA.]
"_C. annulus_, the ring-cowry, has a yellow mark round the top of the shell. The fowl-cowry, _C. moneta_, is used for money by the natives of Siam and Bengal.
"_C. pediculus_ is changed to _Trivia_, a new sub-genus from _Cypræa_. We find the following characters:--form of the columella internally concave, ribbed; shell sub-globular, cross-ribbed. _T. carnea_, flesh-coloured shell; thin, pure rose-coloured, with very thin, distant ribs; lips whitish: it has sometimes an indistinct dorsal groove.
"_Trivia Europæa_ (_Cypræa_ of authors) is a globose shell, ash or flesh-coloured, with three black dots and a whitish dorsal streak; ribs close, rather thick, and whitish; base white; outer lip wide. The variety has the back without spots. _T. pediculus_ has six square dorsal spots; the colour of the shell pale red; ribs rather thick-covered; dorsal line narrow; base reddish. Only one species, _C. Europæa_ (or _Trivia_) is a native of our shores.
"There are several fossil species of _Cypræa_.
"We now pass on to a genus in which there is but one recent species, _Terebellum subulatum_, _Bulla_ of Linnæus. (See Frontispiece.) A fossil _Terebellum_ is found in London clay.
[Sidenote: ANCILLA. CONUS.]
"The _Oliva_ genus contains smooth, shining shells, common, and therefore little valued; nevertheless they are beautiful, and of various colours.
"The columella is obliquely striated; the aperture longitudinal and straight. The olives were placed by Linnæus among the _Volutæ_, on account of the striæ on the columella, without regard to the peculiarity of the _canal_, by which the olives are known from all other shells. This canal separates the _volutions_ of _Oliva_. Many species are prettily marked by nature, others are rendered handsome by polishing. _O. subulata_ is small, and pointed like a mitre. The common olive is white, with brown, waved lines. _O. irrisans_ is ornamented with yellow zigzag lines: it has two brown zones. _O. oriza_, the little rice-olive, is white.
"I should have noticed the small genus _Ancilla_, formerly _Ancillaria_, which is very near both to _Terebellum_ and _Oliva_. The columella has a varix at the base, which distinguishes it from _Terebellum_, and it wants the canal which separates the volutions of _Oliva_.
"There are several fossil species.
"The concluding genus of the third order is very large, and contains rare and costly shells. This is _Conus_, scarcely to be mistaken for any other genus except _Voluta_, and that only at a first glance.
"The species are covered with an epidermis, sometimes very thick; the spire has various degrees of elevation, sometimes almost flat; the operculum very small and horny. They are natives of southern and tropical seas: the animal is carnivorous: found in sandy mud, at various depths of the ocean. The species are very numerous--Lamarck makes 181 recent. Some new species have lately been discovered. Many of the cones are very beautiful, both in shape and colour, and the genus has been always in estimation among collectors. The _gloria-maris_, _cedonulli_, _ammiralis_, and some others, have been sold at very high prices, and some of the finest of these are now in England.
"Lamarck makes two divisions: in the first is comprehended the species with coronated spires; the second those with simple spires; the latter division contains far the greater number.
"Fossil cones occur, in London clay and crag, in England.
"No recent species are found upon our own coasts.
"_Conus Hebræus_, the Hebrew-cone, is easily known: (Plate 6:) it has a white ground, and square black markings.
"_Conus virgo_ is white, with a purple base.
"_C. marmoreus_ is a fine shell. Numerous species are within reach of your purses, and I do not doubt that you will soon acquire a good collection at a moderate price. You, Charles, will find more pleasure in a cone than in a top; and Lucy, who never found much pleasure in toys except in taking them to pieces, has always a ready sixpence either for a poor neighbour in distress, or for some harmless pleasure.
"We have yet two more orders of _Mollusca_ to notice, the _Cephalopoda_ and the _Heteropoda_.
"At our next lesson I shall mention the genera that are most likely to come under your observation, either fossil or recent."
[Sidenote: ARGONAUTA. NAUTILUS.]
"So many families of the fourth order, _Cephalopoda_, are found only in a fossil state, and which you will not easily meet with, that I shall not consider it needful to give you the whole catalogue," observed Mr. Elliot to his young pupils at the beginning of the next lesson.
"But we are exceedingly interested about fossils," replied Charles; "pray do not pass any species that we may be likely to find."
"And I," said Lucy, "have much wished to ask whether the _snake-stone_ ever was a shell? it is something like a _Planorbis_, but heavy and imperfect."
"I will answer your question presently," said her father. "Tell me what genera remain to be noticed among the univalves of Linnæus?"
"_Argonauta_ and _Nautilus_," was the ready reply.
"The animals inhabiting these shells are _Cephalopoda_. The word indicates the position of the feet, or more properly _arms_ of the animal, which are ranged round the head like a crown. The body is thick and fleshy, contained in a kind of bag, whence the head issues, surrounded by these arms, which vary in different genera.
[Sidenote: CUTTLE-FISH. BELEMNITE. SPIRULA.]
"The common _cuttle-fish_, a native of our seas, will give you an idea of a cephalopode.
"In the first family a fossil-shell occurs that is very frequently met with.
"Family, _Orthocerata_; genus, _Belemnite_, thunder-stone, or arrow-head. These fossil-shells occur abundantly in the chalk formations. Many superstitious notions have been attached to this extinct marine animal: of these you will find an account in the 'Penny Cyclopædia.'
"In the family _Lituolita_ we meet with the delicate and remarkable little shell _Spirula Peronii_, distinct from _Nautilus_ by the separation of the volutions: it is nearly covered by the body of the animal. The colour is white; the texture thin and brittle: it has a lateral syphon, the orifice of which is very clearly to be seen as each compartment is taken off. There is but one species; it is found in the Southern Ocean and the Moluccas. The shells are seen floating on the surface of the water when the animal is dead, and are sometimes carried to the shore. (Plate 9.)
[Sidenote: AMMONITE. NAUTILUS.]
"Another family of this order, _Nautilacea_, contains, among many other genera, the celebrated _Nautilus_. This genus, you are already informed, is distinguished from _Argonauta_ by its shells being many-chambered. Two or three fossil species have been found in London clay.
"Among the various fossil-shells abounding in different strata, not known in a recent state, the one most remarkable and frequently occurring is the Ammonite, _Cornu Ammònis_, so called from the resemblance it bears to the convoluted horns of Jupiter Ammon, in mythological history. This is your _snake-stone_, Lucy, a local name, which you had better change for Ammonite. Various legends are connected with this fossil, of which you may obtain information by consulting the before-mentioned publication.
"As you are desirous of studying geology, a knowledge of the Ammonites is very requisite, since whole sections of the genus are characteristic of certain strata.
"They are nearly allied to the _Nautilus_. The species are very numerous; one hundred and twenty according to some authors--two hundred and seventy species are enumerated by others. They occur in Europe, Asia, and America: they have been found in the chalk with a diameter of three feet.
"In the second division of this order the genus _Argonauta_ occurs: the shell has been already described, and retains its original name. (Plate 6.)
[Sidenote: OCTOPUS. LOLIGO. SEPIA.]
"In the third division is the family _Sepiaria_, containing _Octopus_, _Lolìgo_, and _Sepia_. This section contains animals without shells. _Octopus vulgàris_ is common in the European seas. In hot climates it grows to a very large size. The animal has sufficient strength to draw a boat under water.
"_Lolìgo_ also is found in our seas; the thin, transparent rib, called the _dorsal blade_, you may probably find on the shore, the flesh that covered the blade being cleared entirely from it. The colour is either white or brown. It is called _sea-sleeve_.
"The bone of the cuttle-fish, _Sepia officinalis_, is so frequently thrown on shore by the waves, that few persons visiting the sea-coast can be ignorant of its form. You have a large collection there I see, Lucy; and you are doubtless aware that this calcareous bone affords the _pounce_ of the stationers, when finely pulverized: it also forms one ingredient of tooth-powder.
"The ink of this marine animal is contained in a bag: the use of the fluid is to colour the water around, in order to conceal itself from hostile attack. The flesh of some of these animals is used for food, and is frequently seen in the market at Naples. In the British isles it is not put to any culinary purpose. The ink of _Sepia_ can be prepared for a pigment, or paint.
"The fifth and last order of the twelfth class is _Heteropoda_, which contains only a few genera, one of which I shall notice.
"_Carinaria_, the glass-nautilus, is a rare and very precious genus, containing but three species. The first, _Carinaria ritrea_, has been found in the Southern Ocean. There is a model of the shell in the British Museum; that of Paris possesses the shell itself.
"_C. Mediterranea_ is found in the neighbourhood of Nice, and is frequent in the summer months. So thin and delicate is the shell that it is seldom found entire.
"The shell of _Carinaria_ is wholly external, and is attached to the upper part of the body, apparently to protect the organs of respiration. The body is transparent, dotted with elevated points; on the lower part is a beautiful reticulated fin, of a reddish colour; with the end of this fin it floats along, carrying its delicate shell. The habit of the animal, which swims upon its back, reverses the natural position of the shell, which is on the upper part of the body when at rest."
"That is one of the most remarkable creatures you have yet mentioned," said Charles; "I may chance to meet with a specimen when I travel."
"Probably," replied Mr. Elliot; "but our lessons are now concluded--_Carinaria_ is the last genus."
"How greatly we are obliged to you, father!" said Lucy: "but I hope you will still give us a little advice and assistance: we shall often be unable to determine the genera of some shells, I am sure, especially among the bivalves."
[Sidenote: METHOD OF CLEANSING SHELLS.]
"Most willingly: but tell me if you know the easiest method of cleaning shells when they become soiled, or when you purchase them in the natural state?"
"That is a question I wished to ask."
"A little warm water and soap will cleanse and render them bright. Some collectors rub Florence oil over their shells, which prevents them from becoming dry. A weak solution of gum-arabic is sometimes applied, in order to produce a polished and bright appearance.
"Nitric or muriatic acid, diluted, is used to take off the epidermis, or any extraneous matter; but it must be done carefully, and the shell plunged in water after the acid has been applied. But do not make a practice of polishing; shells are best in their natural state, generally speaking."
"Thank you, father!" said both the young people.
"You are welcome to any instruction I can give you," he replied; "and now farewell for to-night."
A LIST OF SPECIES
_That may be purchased at a moderate Price._
Examples of the genera that may be easily obtained from the British Coast, or which are expensive, are omitted.
_Dentalium entalis._ _Pectinaria Belgica._[E] _Balanus tintinnabulum._ _Pentalasmis anatifera._ _Corbula nucleus._ _Psammobia virgata._ _Lucina carnaria._ _Cyprina Islandica._ _Cytherea chionè._ _Venus tigerina._ _Isocardia cor._ _Arca Noæ._ _Pectunculus marmoratus._ _Chama arcinella._ _Tridacna crocea._ _Pinna muricata._ _Perna ephippium._ _Meleagrina margaritacea._ _Lima squamosa._ _Spondylus gæderopus._ _Chiton squamosus._ _Emarginula fissura._ _Fissurella Græca._ _Pileopsis Hungarica._ _Calyptræa equestris._ _Bulla ampulla._ _Helix melanotragus._ _Pupa mummia._ _Bulimus ovatus._ _Achatina virginea._ _Neritina corona._ _Nerìta polìta._ _Natìca alba._ _Iànthina communis._ _Sigaretus haliotoideus._ _Pyramidèlla dolabrata._ _Scalària commùnis._ _Delphinula lacinìata._ _Solarium perspectivum._ _Trochus tuber._ _Monodonta labio._ _Turbo pica._ _Phasianella bulimoìdes._ _Cerithium vertagus._ _Pyrula ficus._ _Ranella crumèna._ _Murex haustèllum._ _Triton lotorium._ _Pterocera lambis._ _Strombus lineàtus._ _Cassis arèola._ _Ricinula horrida._ _Purpura patula._ _Monoceros imbricatum._ _Concholepas Peruvianus._ _Harpa ventricosa._ _Dolium maculàtum._ _Eburna spiràta._ _Terebra maculàta._ _Columbella mercatòria._ _Mitra episcopàlis._ _Voluta musica._ _Volraria monìlis._ _Ovula oviformis._ _Cypræa cribària._ _Terebellum subulàtum._ _Oliva utriculus._ _Conus virgo._ _Nautilus hians._ _Spirula Peronii._
[E] Or _Sabella_.
Acasta, 41 Acera, 64 Achatina, 69 Alata, 85 Ammonite, 103 Anatina, 47 Ancilla, 98 Ancylas, 64 Anodon, 54 Anomia, 29 Anostoma, 68 Annularia, 39 Aplysia, 65 Arca, 53 Argonauta, 29 Aspergillum, 45 Auricula, 69 Avicula, 57
Balanus, 40 Belemnite, 102 Bimusculosa, 44 Brachiopoda, 61 Buccinum, 32 Bulimus, 69 Bulla, 31
Calyptræa, 64 Cancellaria, 83 Capsa, 50 Caracolla, 68 Cardium, 23 Carinaria, 105 Cassis, 87 Cassidaria, 87 Cephalopoda, 101 Cerithium, 82 Chama, 26 Chamacea, 54 Chiton, 18 Cineras, 41 Cirrhipeda, 40 Clausilia, 69 Clavagella, 46 Cleodora, 62 Columbella, 91 Conchæ, 50 Conchifera, 44 Concholepas, 89 Conus, 30 Corbis, 50 Corbula, 48 Coronula, 40 Crassatella, 48 Crepidula, 64 Creusia, 41 Cyclas, 50 Cyclostoma, 69 Cymba, 92 Cypræa, 31 Cytherea, 52
Delphinula, 77 Dentalium, 36 Diceras, 54 Dolabella, 65 Dolium, 89 Donax, 23
Eburna, 90 Erycina, 48 Etheria, 54
Fasciolaria, 83 Fissurella, 64 Fusus, 84
Galeolaria, 40 Gasteropoda, 62 Gryphæa, 59
Haliotis, 35-75 Harpa, 89 Helix, 35-68 Heteropoda, 105 Hipponyx, 61
Ianthina, 74 Isocardia, 52
Lepas, 18 Lima, 58 Limax, 66 Lingula, 61 Litorina, 79 Loligo, 104 Lucina, 50 Lutraria, 48 Lymnæa, 71
Mactra, 23 Mactracea, 47 Magillus, 40 Melanopsis, 71 Meleagrina, 58 Melo, 92 Mitra, 92 Modiola, 56 Mollusca, 62 Monoceros, 89 Monodonta, 78 Murex, 35 Mya, 21 Myaria, 47 Mytilus, 27 Mytilacea, 56
Natica, 74 Navicella, 73 Nassa, 88 Nautilus, 30-103 Nerita, 35 Neritina, 73 Nucula, 53 Nymphacea, 49
Octopus, 104 Oliva, 98 Onchidium, 66 Orthocerata, 102 Ostrea, 26 Otion, 41 Ostracea, 59 Ovula, 93
Paludina, 72 Pandora, 48 Panopæa, 47 Parmacella, 66 Parmophorus, 64 Patella, 61-63 Pecten, 58 Pectunculus, 53 Perna, 57 Pentalasmis, 41 Phasianella, 79 Pileopsis, 64 Pinna, 57 Planorbis, 70 Placuna, 60 Plagiostoma, 58 Pleurotoma, 83 Plicatula, 59 Podopsis, 59 Pollicipes, 41 Potamophila, 51 Psammotæa, 49 Pterocera, 86 Pullastra, 51 Pupa, 69 Purpurifera, 87 Pyrgoma, 41 Pyrula, 84
Ranella, 84 Ricinula, 88 Rostellaria, 86 Rotella, 78 Rudista, 60
Sabella, 37 Scalaria, 76 Scapellum, 42 Serpula, 36 Sepia, 104 Siliquaria, 39 Sigaretus, 75 Solarium, 77 Solen, 22 Solenacea, 47 Spirorbis, 39 Spirula, 102 Spondylus, 25 Stomatia, 75 Stomatella, 75 Strombus, 33 Struthiolaria, 84 Succinea, 69
Tellina, 22-30 Terebellum, 97 Teredo, 46 Terebra, 91 Testacellus, 67 Trachelipoda, 67 Tridacna, 56 Trigoniana, 53 Trivia, 97 Triton, 85 Trochus, 78 Tubicinella, 40 Turbinella, 83 Turbo, 79
Umbrella, 63 Unio, 54 Unimusculosa, 56
Valvata, 71 Venus, 24-52 Venericardia, 52 Venerupis, 49 Vermetus, 76 Volvaria, 92 Voluta, 31 Vulsella, 60
Joseph Rickerby, Printer, Sherbourn Lane.
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All illustrations were moved so as to not split paragraphs. Words with accented vowels were not standardized.