"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.)

"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.

"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.

"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."

"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.

"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—

CHAPTER V.

Third Division.—Univalves.

"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.

"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.

"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.

"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.

"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.

"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.

"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."

"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.

"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.

"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.)

"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.

"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."

CHAPTER VI.

"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.

"To begin with the 3rd Order of the 9th Class:—

Class, Annularia. Order, Sedentaria, Annulated Worms.

"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.

"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.

Genera.

"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.

"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.

"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."

CHAPTER VII.

Eleventh Class.—Conchifera.

Two Orders.—1st. Bimusculosa, two muscular impressions.

2nd. Unimusculosa, one muscular impression.

"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.

"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 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.

"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,

"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.

"Solenacea includes

"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.

"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:

"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.

"The family Corbula contains two genera.

"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.

"Lithophaga includes