The Project Gutenberg eBook ofRudiments of ConchologyThis ebook is for the use of anyone anywhere in the United States and most other parts of the world at no cost and with almost no restrictions whatsoever. You may copy it, give it away or re-use it under the terms of the Project Gutenberg License included with this ebook or online atwww.gutenberg.org. If you are not located in the United States, you will have to check the laws of the country where you are located before using this eBook.Title: Rudiments of ConchologyAuthor: Mary Anne VenningRelease date: June 14, 2015 [eBook #49206]Most recently updated: October 24, 2024Language: EnglishCredits: Produced by deaurider, Cosmas and the Online DistributedProofreading Team at http://www.pgdp.net (This file wasproduced from images generously made available by TheInternet Archive)*** START OF THE PROJECT GUTENBERG EBOOK RUDIMENTS OF CONCHOLOGY ***
This ebook is for the use of anyone anywhere in the United States and most other parts of the world at no cost and with almost no restrictions whatsoever. You may copy it, give it away or re-use it under the terms of the Project Gutenberg License included with this ebook or online atwww.gutenberg.org. If you are not located in the United States, you will have to check the laws of the country where you are located before using this eBook.
Title: Rudiments of ConchologyAuthor: Mary Anne VenningRelease date: June 14, 2015 [eBook #49206]Most recently updated: October 24, 2024Language: EnglishCredits: Produced by deaurider, Cosmas and the Online DistributedProofreading Team at http://www.pgdp.net (This file wasproduced from images generously made available by TheInternet Archive)
Title: Rudiments of Conchology
Author: Mary Anne Venning
Author: Mary Anne Venning
Release date: June 14, 2015 [eBook #49206]Most recently updated: October 24, 2024
Language: English
Credits: Produced by deaurider, Cosmas and the Online DistributedProofreading Team at http://www.pgdp.net (This file wasproduced from images generously made available by TheInternet Archive)
*** START OF THE PROJECT GUTENBERG EBOOK RUDIMENTS OF CONCHOLOGY ***
RUDIMENTS
OF
CONCHOLOGY;
WITH
EXPLANATORY PLATES.
Rudiments of Conchology.Click on images to view larger version.
Rudiments of Conchology.
Click on images to view larger version.
RUDIMENTS
OF
CONCHOLOGY:
INTENDED AS A
FAMILIAR INTRODUCTION TO THE SCIENCE.
WITH
EXPLANATORY PLATES,
ANDREFERENCES TO THE COLLECTION OF SHELLS INTHE BRITISH MUSEUM.
BY THE AUTHOR OF"THE GEOGRAPHICAL PRESENT,"&c.
A new and improved Edition.
LONDON:DARTON AND HARVEY,GRACECHURCH STREET.
1837.
LONDON:PRINTED BY JOSEPH RICKERBY,SHERBOURN LANE.
ADVERTISEMENT.
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.
ERRATA.
[Note: Corrections were applied.]
Page 3,forPlate 1,readPlate 2.Page 16, line 8,forsquamosa,read, squamosus.Page 20,forcandidas,readcandida; andforPlate 3,readPlate 2.Page 25,forPlates 4 and 5,readPlates 3 and 5; andforgædaropus,readgæderopus.Page 27,forepiphippiumreadephippium.Page 35, line 12,deletenot.Page 36, line 14,readPlate 2.Page 42,readBruguieres; andforPollicepes,readPollicipes.Page 64, line 3,readParmophorus—line 6,readPlate 3.Page 68, line 5 from bottom,readCarocolla.Page 76, line 6,forValvatareadVoluta.Page 90, line 4,readanglicanum.
Page 3,forPlate 1,readPlate 2.
Page 16, line 8,forsquamosa,read, squamosus.
Page 20,forcandidas,readcandida; andforPlate 3,readPlate 2.
Page 25,forPlates 4 and 5,readPlates 3 and 5; andforgædaropus,readgæderopus.
Page 27,forepiphippiumreadephippium.
Page 35, line 12,deletenot.
Page 36, line 14,readPlate 2.
Page 42,readBruguieres; andforPollicepes,readPollicipes.
Page 64, line 3,readParmophorus—line 6,readPlate 3.
Page 68, line 5 from bottom,readCarocolla.
Page 76, line 6,forValvatareadVoluta.
Page 90, line 4,readanglicanum.
RUDIMENTS
OF
CONCHOLOGY.
CHAPTER I.
INTRODUCTORY.
"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 notquiteignorant 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."
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, andUnivalves."
"You are right, Lucy," replied her father.
"Pray show me some bivalve shells," said Charles; "I want to know their forms. Abivalveis 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 alsoVenus,Tellìna,Donax,Arca, andPinna," observed Mr. Elliot, "all very easy to distinguish."
"'The anchor'd pinna and his cancer friend,'"
repeated Charles. "So thePinnais a bivalve; but what hasVenusto 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?"
THE PINNAAND THECANCER.
"I have heard that thePinnais a shell-fish,attended by acrab, 'his cancer friend;' but why it is calledanchor'dI do not know, butcanceris Latin for crab."
"Here is a species ofPinna," 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, orbyssus. ThePinnais 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; "Pholasis another genus of the same division; it has the appearance of a bivalve. In theChitonare severallamina, 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, "thanthe 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."
LAMARCK'SSYSTEM.
"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?"
Plate 1.To Face Page 4.
Plate 1.To Face Page 4.
Plate 1.
To Face Page 4.
USE OFTHE LATINLANGUAGE.
"But so many works on science are written in Latin," said Lucy. "Linnæus, however, has been translated, I know; and as forBritishbotany, 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."
PLEASURE OFSEARCHINGFOR SHELLS.
"Oh," exclaimed Lucy, "I quite forgot the very pretty snails I have so often admired on theheath 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."
CHAPTER II.
INHABITANTSOF 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 withshell-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.
"A species of cowry is in use for money among some people of Africa; and pearls, so muchvalued as articles of ornament, are obtained from the oyster and mussel genera.
FOSSILSHELLS.
"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.
Plate 2.Page 8.
Plate 2.Page 8.
Plate 2.
Page 8.
TERMS FORPARTS OFMULTIVALVES.
"To begin with the first division,Multivalves. There is a group ofLepades, 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 thepeduncle, (c) and is fastened to other bodies. Thefeelers(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 calledsessile. Thebase(a) is that part of the shell by which it is fixed to other bodies: (a) theoperculumis 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.Valvesare the different pieces that compose a shell. When both the valves are alike in form, the shell is calledequivalve: when the valves are different in the same shell, it is calledinequivalve.Mya,Solen,Tellina, are equivalves:Ostrea,Anomia,Pinna, &c. are inequivalves.
TERMS—BIVALVES.
"Thehingeis 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 thecavitiesof the other valve (Plate 3.,a.) When the teeth are placed in the centre of the hinge they are calledcardinal teeth.Lateral teethare 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 ofArca, furnished with many small teeth. (Plate 3,b.)
"Theligamentis 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, inPecten, or scallop, inTellina, &c.
"Thebeaksare the most pointed parts of the bivalve shell (Plate 3,c.); when the valves are closed, the line where they meet is called theseam. (Plate 3,d.)
"Theanterior slopeis that part of the shell where the ligament is placed, and is also called thearea. (Plate 3,e.) Theposterior slope, orareola, is the other side of the beaks. (f.)
"Thelunulais a crescent-like depression on either the area or areola. The edge of the valve is called themargin; it is often finelycrenulated, or toothed. The interior of the valve is called thecavity. (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 aremuscularimpressions; they are the parts where the muscles of the animal have been affixed, and are termedcicatrix.
Plate 3.Page 10.
Plate 3.Page 10.
Plate 3.
Page 10.
TERMS—UNIVALVES.
"Earsare two processes on each side of the beak; thePecten, or scallop, is an example. (Plate 3,i.)
"Sinus, inbivalveshells, is a small hollow in the hinge.
"Byssus, or beard, is an appendage composed of silky threads, by which the muscle andPinnafasten themselves to the rocks. (Plate 3,f.)
"Cordiformis a term applied to heart-shaped shells.
"Acartilageis the same as a ligament. When the valves of a shell are very nearly flat, they are said to becompressed: when a valve has teeth, it is said to bedentated.
"When the valves of a shell do not shut close, they are said to begaping. (Plate 4,Mya.)
"Amuscleis 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.
"Asutureis a toothed joint, in bivalves.
"A shell with ears is said to beauricled.
"The third division,Univalveshells, have also their several parts. The first section has a regular spire. Here are two shells of this section,VolutaandBuccinum, both sawed asunder, in order to show the interior structure of the shell. (Plate 3.) The aperture, or opening, beingturnedtowards you, the front of a univalve is seen; reverse it, and you see the back.
TERMS—UNIVALVES.
"The top, or highest part, is theapex; (a) the lowest part is thebaseof the shell. (b.)
"Thespire(c) is formed of wreaths, or whorls, (ddd) which terminate in the apex: the lowest whorl is the body of the shell. (e.)
"Theaperture, opening ormouth, (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 theTurbo, or periwincle; some longitudinal, as the cowry; others semi-lunar, as theHelix, or snail genus. (For examples of these apertures seePlates 1and7.)
"Thebeakis the lengthened process (g) at the lower part of the shell.
"Thecanal, orgutter, runs through the beak. (Both these parts are perceptible inMurexandStrombus,Plate 7.)
"Suturesare spiral lines which separate the whorls; they are sometimes crenated, or notched, sometimes sulcated, or furrowed.
"Thecolumella, orpillar, extends through the centre of the shell withinside. TheBuccinumandVolutaboth show the columella. (Plate 3.)
TERMS—UNIVALVES.
"Thepillar-lipof the aperture, or columella margin, is on the left-hand side of the shell; theouterlip on the right-hand. Occasionally this order is reversed, but not commonly.
"Theoperculum, 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.
"Theumbilicusis 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 calledimperforate.
"If the spire is truncated, it isdecollated; if it is surrounded with spires, it iscoronated, or crowned.
"Second section, without a regular spire. Theteethin univalve shells, as the cowry, are ridges upon the aperture. (Plate 1.) InVolutathey are regular folds or plaits upon the columella.
"Afissureis a notch or slit, as inPatella fissura. (Plate 3.)
"Some shells of this section are internally lipped, asPatella equestris; (Calyptræaof 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.
TERMS—UNIVALVES.
"ThevertexinPatellais as the superincumbent part of the shell.
"Theepidermisis the outward skin that covers the surface of some shells.
"Faucesare narrow entrances, as at each end of the cowry.
"Tuberclesare protuberances, or knobs, on the surfaces of shells.
"Striæare raised or flat lines upon the surfaces of shells. When the surface is marked with lines longitudinally and transversely, it isdecussated.
"Sulciare furrows.
"Fornicatedsignifies arched, greatly excavated.
"Umbois the swelling part near the beak of bivalve shells; the same asboss.
"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."
CHAPTER III.
SYSTEM OFLINNÆUS.
"As you both assure me," said Mr. Elliot, "that you do not fail to make yourselves familiar with thenomenclature, or terms, used in conchology, I shall proceed this morning to the arrangement of Linnæus.
"This system is established upon theoutwardappearances, 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; andUnivalves, composed of one part or piece only.
"These divisions contain severalgenera, 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, orappearances on the surface of the shell: there are sometimes many varieties of the same species.
LINNÆANGENERA.
"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. anatiferaandtintinnabulum.*Pholas, stone-piercer, ex.P. candida.
*Chiton, coat of mail, example,C. squamosus.
*Lepas, acorn-shell or barnacle, ex.L. anatiferaandtintinnabulum.
*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.
*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.
LINNÆANGENERA.
Third Division: 2 sections.—1st.Univalveswith 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.
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.
*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.
CHITON.LEPAS.
"Multivalves may be divided into two kinds, thepedunculated, or those fixed to other bodies, as rocks, stones, planks, &c.; orfree, as theChitonandPholas.
"Our first genus isChiton. 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 inC. squamòsus, (Plate 1,) and hairy, or spinous. The species are determined by the margins. Some of theChitongenus are common upon our own coasts; they are frequently found among seaweed and stones, rolled up like a ball.C. fasciculàrisandC. lævisare British; there are some other British species. The animal adheres to rocks, like thePatella, or limpet. The number of species forty.
"Second genus,Lepas. Shell multivalve, fixed at the base; valves erect, orupright.
"Observe how much the situation of the valves differs inChitonandLepas. It is scarcely possible to mistake the one for the other. The feathery tentacula, or feelers, ofLepas anatiferaare 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 sessileLepades. 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, asL. tulipa,L. diadema,L. tintinnabulum,L. balanus,L. anatifera, &c. The Indian, American, and Atlantic oceans afford numerous species.
PHOLAS.
"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 thePholasshell is very unlike those of the multivalve division: I think it should rank with bivalves."
"So many conchologists have judged; nevertheless it possesses more thantwovalves, and, according to the system, it must be forced into the division of multivalves.
"ThePholadesare 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. Theanimal 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.
PHOLAS.
"ThePholashas 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. ThePholasgenus 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 dactylusis larger and coarser, and not at all uncommon.
"We have now finished our first division, and must proceed to the bivalves."
CHAPTER IV.
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 thehingesof bivalve shells."
"Thenapplyyourself to the study of hinges, Charles, and your difficulties will chiefly disappear," answered Mr. Elliot.
MYA.
"The hinge ofMya, 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. TheMyarace burrow in the sand. Here isMya arenaria, a large thick shell, frequent on the shores of Kent: the large tooth is sufficiently plain inthisspecies.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.
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. TheSolenlives 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 genusTellìnais 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, isTellìna Feroensis; the shell is finely striated, and has also radiations. (Plate 4.)
"The generic characters are chiefly these: shell compressed towards the anterior slope, teethof 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 theTellìnagenus are found buried in the sea-sands.