The Conchifera differ from the Molluscous animals that bear shells, in a very great degree; for, although the substance of the body is soft, unlike the Mollusca it is inarticulate, always enclosed in a shell of two valves, without head or eyes,—a mouth, if it may be so called, concealed from view, and without any hard parts, and the whole body enveloped in a large mantle, or hood, formed of two thin lobes, generally perfectly free, but at times united in front; these are the principal distinguishing characters of this class.

In earlier systems, when shells were classed without much reference to the animals that inhabited them, the only distinction made was the number of pieces of which the shell was formed, and they were arranged under the heads of univalves, of one piece, bivalves, with two pieces, and multivalves, with more than two pieces. This arrangement was inconvenient, as, in some cases, it separated animals that otherwise agreed with each other. With respect to the bivalve shells, however, this objection does not hold good, as they all contain animals belonging to the class Conchifera.

The individuals of this class appear to be deprived of all the senses except that of feeling. Their powers of motion have been so well described by Dr. Roget, in his Bridgewater Treatise, that we cannot do better than extract a portion from that interesting work.

The two valves of the shell of the Conchifera are united at the back by a hinge-joint, often very artificially constructed, having teeth that lock into each other; and the mechanism of this articulation varies much in different species. The hinge is secured by a substance of great strength.

During the life of the animal, the usual and natural state of its shell is, that of being kept open for a little distance, so as to allow of the ingress and egress of the water necessary for its nourishment and respiration; but, as a security against danger, it was necessary to furnish the animal with the means of rapidly closing the shell, and retaining the valves in a closed state. These actions, being only occasional, yet requiring considerable force, are effected by a muscular power, for which purpose sometimes one, sometimes two, or even a greater number of strong muscles are placed between the valves, their fibres passing directly across from the inner surface of the one to that of the other, and firmly attached to both. They are named, from their office of bringing the valves towards each other, the adductor muscles.

The simple actions of opening and closing the valves, are capable of being converted into a means of retreating from danger, or of removing to a more commodious situation, in the case of those bivalves which are not actually attached to rocks, or other fixed bodies.

Diquemarc long ago observed, that even the Oyster has some power of locomotion, by suddenly closing its shell, and thereby expelling the contained water with a degree of force, which, by the reaction of the fluid in the opposite direction, gives a sensible impulse to the heavy mass. He notices the singular fact, that Oysters which are attached to rocks occasionally left dry by the retreat of the tide, always retain within their shells a quantity of water sufficient for respiration, and that they keep the valves closed till the return of the tide; whereas, those Oysters which are taken from greater depths, where the water never leaves them, and are afterwards removed to situations where they are exposed to these vicissitudes, of which they have had no previous experience, improvidently open their shells after the sea has left them; and, by allowing the water to escape, soon perish.

Many bivalve Mollusca are provided with an instrument shaped like a leg and foot, which they employ extensively for progressive motion. In the Cardium, or cockle, this organ is composed of a mass of muscular fibres, interwoven together in a very complex manner, and which may be compared to the muscular structure of the human tongue; the effect in both is the same, namely, the conferring a power of motion in all possible ways; thus it may be readily protruded, retracted, or inflected at every point.

The Solen, or razor-shell fish, has a foot of a cylindrical shape, tapering at the end, and much more resembling in its form a tongue than a foot. In some bivalves, the dilatation of the foot is effected by a curious hydraulic mechanism; the interior of the organ is formed of a spongy texture, capable of receiving a considerable quantity of water, which the animal has the power of injecting into it, and of thus increasing its dimensions.

The foot of the Mytilus edulis, or common mussel, can be advanced to the distance of two inches from the shell, and applied to any fixed body within that range. By attaching the point to such body, and retracting the foot, this animal drags its shell towards it, and by repeating the operation successively on other points of the fixed object, continues slowly to advance.

This instrument is of great use to such shell-fish as conceal themselves in the mud or sand, which its structure is then peculiarly adapted for scooping out. The cockle continually employs its foot for this purpose: first, elongating it, directing its point downwards, and insinuating it deep into the sand, and next, turning up the end, and forming it into a hook, by which, from the resistance of the sand, it is fixed in its position, and then the muscles, which usually retract it, are thrown into action, and the whole shell is alternately raised and depressed, moving on the foot as on a fulcrum. The effect of these exertions is to drag the shell downwards. When the animal is moderately active, these movements are repeated two or three times in a minute. The apparent progress is at first but small, the shell, which was raised on its edge at the middle of the stroke, falling back on its side at the end of it; but when the shell is buried so far as to be supported on its edge, it advances more rapidly, sinking visibly at every stroke, till nothing but the extremity of the tube can be perceived above the sand.

By a process exactly the inverse of this, that is, by doubling up the foot, and pushing with it downwards against the sand below, the shell may be again made to rise by the same kind of efforts which before protruded the foot. By this process of burrowing, the animal is enabled quickly to retreat when danger presses, and when this is past, it can, with equal facility, emerge from its hiding-place.

The Cardium can also advance at the bottom of the sea, along the surface of the soft earth, pressing backwards with its foot, as a boatman impels his boat onwards by pushing with his pole against the ground in a contrary direction. It is, likewise, by a similar expedient, that the Solen forces its way through the sand, expanding the end of its foot into the form of a club.

The Tellina is remarkable for the quickness and agility with which it can spring to considerable distances, by first folding the foot into a small compass, and then suddenly extending it, while the shell is, at the same time, closed with a loud snap.

The Pinna, or marine mussel, when inhabiting the shores of tempestuous seas, is furnished, in addition, with a singular apparatus for withstanding the fury of the surge, and securing itself from dangerous collisions, which might easily destroy the brittle texture of its shell. The object of this apparatus is, to prepare a great number of threads, which are fastened at various points to the adjacent rocks, and then tightly drawn by the animal, just as a ship is moored in a convenient station, to avoid the buffeting of the storm. The foot of this bivalve is cylindrical, and has, connected with its base, a round tendon, of nearly the same length as itself, the office of which is to retain all the threads in firm adhesion with it, and concentrate their power on one point. The threads themselves are composed of a glutinous matter, prepared by a particular organ. They are not spun by being drawn out of the body, like the threads of the silkworm, or of the spider, but they are cast in a mould, where they harden, and acquire a certain consistence before they are employed. This mould is curiously constructed; there is a deep groove which passes along the foot, from the root of the tendon to its other extremity, and the sides of this groove are formed so as to fold and close over it, thereby converting it into a canal. The glutinous secretion, which is poured into this canal, dries into a solid thread; and, when it has acquired sufficient tenacity, the foot is protruded, and the thread it contains is applied to the object to which it is to be fixed, its extremity being carefully attached to the solid surface of that object. The canal of the foot is then opened along its whole length, and the thread, which adheres by its other extremity to the large tendon at the base of the foot, is disengaged from the canal. Lastly, the foot is retracted, and the same operation is repeated.

Thread after thread is thus formed, and applied in different directions around the shell. Sometimes the attempt fails, in consequence of some imperfection in the thread; but the animal, as if aware of the importance of ascertaining the strength of each thread, on which its safety depends, tries every one of them as soon as it has been fixed, by swinging itself round, so as to put it fully on the stretch; an action which probably also assists in elongating the thread. When once the threads have been fixed, the animal does not appear to have the power of catting or breaking them off. The liquid matter, out of which they are formed, is so exceedingly glutinous as to attach itself firmly to the smoothest bodies. It is but slowly produced, for it appears that no Pinna is capable of forming more than four, or at most five threads, in the course of a day and night. The threads which are formed in haste, when the animal is disturbed in its operations, are more slender than those which are constructed at its leisure. In Sicily, and other parts of the Mediterranean, these threads have been manufactured into gloves, and other articles, which resemble silk.

The number of muscles by which the shells are moved have caused this Class to be divided into two orders: the Bimusculosa, in which there are two pair of muscles to perform this office; and the Unimusculosa, with only one pair.

ORDER UNIMUSCULOSA.

The Conchiferous animals which possess but one pair of muscles, are much more limited in number than those which possess two or more; but they contain in their ranks several well-known and useful species, as, for instance, the oyster, the mussel, and the animal which produces the oriental pearl.

The Horse-Foot Bowl Shell,
(Anomia ephippium.)

The shells of the AnomiÆ are exceedingly irregular in their form; like the oysters, they remain during the whole of their existence attached to one spot, either on a rock, or on the shell of some larger inhabitant of the deep. These shells are more frequently found in the same places as the oyster, and very commonly attached to the shell of the latter; as an article of food, the Anomia is of little or no value. Its organization and manner of living are much the same as those of the oyster. The most singular part of its construction consists in the use made of one of the muscles with which it is furnished, which, instead of being attached to the shell, is fixed to a solid piece of shelly substance, in the form of a cone with the top cut off; this operculum, or lid, closes a singular opening in one of the valves of the shell itself. The animal adheres to the rock, or other substance, by means of this lid, and is detached with great difficulty.

The Oyster, (Ostrea edulis.)

Oysters, like all other creatures that have been destined to become food for man, are found in great abundance in most parts of the globe; they are inhabitants of salt waters only, and are always found in rocky ground, in no great depth from the surface.

Oysters generally cast their spat, or spawn, in the month of May; when first shed it has the appearance of a drop of candle-grease, which the dredgers commonly call cultch. The growth of an Oyster is tolerably rapid; three days after the spawn is deposited, the shell of the young Oyster may be seen, nearly a quarter of an inch in width; in three months it is larger than a shilling, in six months bigger than a half-crown, and in a year it exceeds a crown piece in size.

Oysters have been employed as food almost from time immemorial. The Greeks, but more especially the Romans, held them in high repute, attaching, at the same time, great importance to the places in which they were found. Those from the Dardanelles, from Venice, and from England, were considered the best, and the prices paid for them by the luxurious inhabitants of Rome were enormous. They were transported in large vessels, and deposited in the Lucrine Lake, where they were fattened for the table. The Romans, it seems, gave a preference to those which had the border of their mantle of a dark-brown colour, nearly black.

The English Oyster-fishery is principally carried on at the following places:—Wivenhoe, near Colchester, in Essex, (the beds here are generally supplied from Portsmouth;) at Feversham and Milton, in Kent, the Swales of the Medway, and at Tenby, on the coast of Wales. In Scotland, they are chiefly taken at the island of Inchkeith, and at Preston-pans, both in the Firth of Forth. The fishing for Oysters is permitted by law, from the 1st of September to the last of April inclusive. During the remaining months they are considered unwholesome; it is a common saying that Oysters are in season during all the months that have the letter r in them.

In France, the chief fishing-station for Oysters is in the Bay of CanÇal, between the town of that name and Mount St. Michael, or St. Malo. The fishery is effected by means of an iron net or dredge; this is drawn over the Oyster-bed by hand-labour, or by having the rope which is fixed to it attached to the stem of the fishing-boat, which is then allowed to run before the wind; frequently, in the course of a few minutes, as many as two or three hundred are taken. The Oysters taken are sent from the ports of Granville and CanÇal, to different places, where artificial banks or preserves are established. These banks are not only of use in the preservation of the Oysters, but assist materially in their improvement. In fact, the Oyster, when first taken out of the sea, has frequently a strong muddy taste, and appears in what we should call bad condition.

Some of these preserves are a species of tank dug in the sand, or sometimes even in stone, near the sea-shore, and communicating by a narrow tunnel with the sea-water; the bottom and sides of these tanks are usually strewed with large stones. In France great care is bestowed on the management of these preserves; the Oysters are placed by hand on the stones, with the largest shell downwards, and at times the water is let off, and they are freed from all mud and dirt that may have collected, by having large quantities of water poured over them. A fashion existed formerly in France of preferring those Oysters which had a tinge of green, and great pains were taken to cause this change of colour to take place, by placing the animals where they could obtain a peculiar kind of green food.

The Great Comb Shell, (Pecten maximus.)

This shell, although it has the name of the Great Pecten, is not the largest of the numerous tribe to which it belongs; it is found in all the European seas. The regular nature of the fluting with which it is covered, and the elegance of its markings, have brought it much into use among ladies, who employ it in making pin-cushions and other articles of fancy-work; there are about sixty recent, and thirty fossil species.

The power of locomotion appears to be very considerable in some species of the Pectens; it is said the animal can raise itself up in the water, and even reach the surface, by moving the two valves of its shell; but this is a fact not quite established, as but little is known of its habits. It is sometimes used as an article of food; but to render it tolerably palatable it requires cooking.

In some countries, the shells of the larger species are used by the poorer classes instead of plates. In Paris, the restaurateurs employ them for the same purpose when serving up a certain preparation of mushrooms; in England, they are employed in cooking scalloped oysters, and the shell is consequently known as the Scallop Shell.

The Pearl Oyster, (Meleagrina margaritifera.)

The animal of this shell, although popularly called an oyster, is very different in structure, bearing greater resemblance, in some parts of its formation, to the mussel, particularly in possessing a byssus, or beard; it is the shell in which the famous oriental pearls are found. There are but two known species of the Meleagrina, which are chiefly found in the Persian Gulf, and at Ceylon, or in some of the seas of Australasia.

The cause of the formation of pearl in the shells of this and other inhabitants of the water, has been the occasion of considerable dispute, but it is now pretty well ascertained.

The inner portion of the shell of the Meleagrina is lined with a pearly substance, which is called mother-of-pearl; this is formed by an animal deposit, and is in thin layers. If, by any accident, the inner surface of the shell is injured, so as to cause a fracture of the mother-of-pearl, the deposit, in that place, becomes for the future irregular, and a bump is gradually formed. Accidental circumstances cause this bump to assume various shapes; sometimes it is oval, sometimes globular, and at others pear-shaped. This kind of pearl is always originally found attached to the shell by means of a small neck, or footstalk, and the spot at which this neck was placed can always be traced on the pearl itself.

But pearls are at times found loose in the shell;—in this case, the pearly matter is deposited on some extraneous substance, such, for instance, as a grain of sand, and by dissolving the pearl in an acid, this nucleus can be traced.

Some of these round pearls are supposed to be formed on a centre, consisting of the remains of a diseased ovum, or egg, of the animal.

Every schoolboy knows the story of Cleopatra having dissolved a valuable pearl in vinegar, and afterwards drunk it off, to show her ridiculous disregard of expense. But the account may reasonably be doubted; for had the acid been strong enough to dissolve the pearl, it would have been impossible to drink it, and if it was weak enough to drink, it would not have dissolved the pearl, at least not until the lapse of a very considerable time.

At the island of Ceylon the fishery for pearls is a matter of great moment. The following is an account of the mode in which it is conducted.

The country round Aripo, on the north-western coast of the island of Ceylon, is flat, sandy, and barren, presenting nothing to the eye but low brushwood, chiefly of thorns and prickly pears (which are the plants that nourish the cochineal insect[2]), and here and there some straggling villages with a few cocoa-nut trees. But Condatchy, three miles distant, where, in general, nothing is to be seen but a few miserable huts, and a sandy desert, becomes, during the period of the pearl-fishery, a populous town, several streets of which extend upwards of a mile in length (though, as the houses are only intended as a shelter from the sun and rain, they are very rudely constructed), and the scene, altogether, resembles a crowded fair on the grandest scale. The people most active in erecting huts and speculating in the various branches of merchandise, are Mohammedans, Cingalese (natives of Ceylon), and Hindoos from the opposite coast of the continent of India. Apparently, however, from their natural timidity, none of the Cingalese are divers, and scarcely any of them engage in the other active parts of the fishery; they merely resort hither for the purpose of supplying the markets.

About the end of October, in the year preceding a pearl-fishery, when a short interval of fine weather prevails, an examination of the banks takes place. A certain number of boats, under an English superintendent, repair in a body to each bank, and having, by frequent diving, ascertained its situation, they take from one to two thousand oysters as a specimen. The shells are opened, and if the pearls collected from a thousand oysters be worth three pounds sterling, a good fishery may be expected. The “banks,” or beds of oysters, are scattered over a space in the Gulf of Manaar, extending thirty miles from north to south, and twenty-four from east to west. There are fourteen beds (not all, however, productive), of which the largest is ten miles long, and two broad. The depth of water is from three to fifteen fathoms.

The pearl oysters in these banks are all of one species, and of the same form: in shape not very unlike our common English oyster, but considerably larger, being from eight to ten inches in circumference. The body of the animal is white, fleshy, and glutinous: the inside of the shell (the real “mother-of-pearl,”) is even brighter and more beautiful than the pearl itself: the outside smooth and dark-coloured. The pearls are most commonly contained in the thickest and most fleshy part of the oyster. A single oyster will frequently contain several pearls, and one is on record, as having produced one hundred and fifty.

Sometimes the English government of Ceylon fishes the banks entirely at its own risk; sometimes, the boats are let to many speculators: but, most frequently, the light of fishing is sold to one individual, who sub-lets boats to others. The fishery for the season of the year 1804 was let by government to an individual for no less a sum than 120,000l.

At the beginning of March, the fishery commenced, and upwards of two hundred and fifty boats were employed in the fishery alone. These, with their crews, and divers, and completely equipped with everything necessary to conduct the business of the fishing, come from different parts of the coast of Coromandel. After going through various ablutions and incantations, and other superstitious ceremonies, the occupants of these boats embark at midnight, guided by pilots, and as soon as they reach the banks, they cast anchor, and wait the dawn of day.

At about seven in the morning, when the rays of the sun begin to emit some degree of warmth, the diving commences. A kind of open scaffolding, formed of oars and other pieces of wood, is projected from each side of the boat, and from it the diving-tackle is suspended, with three stones on one side, and two on the other. The diving-stone hangs from an oar by a light rope and slip-knot, and descends about five feet into the water. It is a stone of fifty-six pounds’ weight, of a sugar-loaf shape. The rope passes through a hole in the top of the stone, above which a strong loop is formed, resembling a stirrup-iron, to receive the foot of the diver. The diver wears no clothes, except a slip of calico round his loins,—swimming in the water, he takes hold of the rope, and puts one foot into the loop or stirrup, on the top of the stone.

He remains in this upright position for a little while, supporting himself by the motion of one arm. Then a basket, formed of a wooden hoop and net-work, suspended by a rope, is thrown into the water to him, and in it he places his other foot. Both the ropes of the stone and the basket he holds for a little while in one hand. When he feels himself properly prepared and ready to go down, he grasps his nostrils with one hand, to prevent the water from rushing in; with the other gives a sudden pull to the running-knot suspending the stone, and instantly descends: the remainder of the rope fixed to the basket is thrown into the water after him, at the same moment: the rope attached to the stone is in such a position as to follow him of itself. As soon as he touches the bottom, he disentangles his foot from the stone, which is immediately drawn up, and suspended again to the projecting oar in the same manner as before, to be in readiness for the next diver. The diver, arrived at the bottom of the sea, throws himself as much as possible upon his face, and collects everything he can get hold of into the basket. When he is ready to ascend, he gives a jerk to the rope, and the persons in the boat, who hold the other end of it, haul it up as speedily as possible. The diver, at the same time, free of every incumbrance, warps up by the rope, and always gets above water a considerable time before the basket. He generally comes up at a distance from the boat, and swims about, or takes hold of an oar or a rope, until his turn comes to descend again; but he seldom comes into the boat, until the labour of the day is over. When a young diver is training to the business, he descends in the arms of a man completely experienced in the art, who takes great care of him, and shows him the manner of proceeding, and the pupil at first brings up in his hand a single oyster, a stone, or a little sand, merely to show that he has reached the bottom. The length of time during which the divers remain under water, is rarely much more than a minute and a half; yet, in this short period, in a ground richly clothed with oysters, an expert man will often put as many as one hundred and fifty into his basket. There are two divers attached to each stone, so that they go down alternately. The men, after diving, generally find a small quantity of blood issue from their nose and ears, which they consider as a favourable symptom, and perform the operation with greater comfort after the bleeding has commenced. They seem to enjoy the labour as a pleasant pastime, and never murmur or complain, unless when the banks contain a scarcity of oysters, though their labours are continued for six hours.

When the day is sufficiently advanced, the head pilot makes a signal, and the fleet set sail for the shore. All descriptions of people hasten to the water’s edge to welcome their return, and the crowd, stir, and noise, are then immense. Every boat comes to its own station, and the oysters are carried into certain paved enclosures on the sea-shore, where they are allowed to remain in heaps (of course, well guarded) for ten days, that time being necessary to render them putrid. When the oysters are sufficiently decayed, they are thrown into a large vessel, filled with salt water, and left there for twelve hours to soften their putrid substance. The oysters are then taken up, one by one, the shells broken from one another, and washed in the water. Those shells, which have pearls adhering to them, are thrown on one side, and afterwards handed to clippers, whose business it is to disengage the pearls from the shells, with pincers.

When all the shells are thrown out, the slimy substance of the oysters remains, mixed with sand and broken fragments of shells, at the bottom of the vessel. The dirty water is lifted out in buckets, and poured into a sack, made like a jelly-bag, so that no pearls can be lost. Fresh water being then added from time to time, and the whole substance in the vessel continually agitated, the sand and pearls together, are by degrees allowed to sink to the bottom.

As soon as the sand is dry it is sifted; the large pearls, being conspicuous, are easily gathered; but the separating the small and diminutive (“seed pearls,” as they are called,) is a work of considerable labour. When once separated from the sand, washed with salt water, dried, and rendered perfectly clean, they are sorted into classes, according to their sizes, by being passed through sieves. After this, a hole is drilled through each pearl; they are then arranged on strings, and are fit for the market.

Pearls have been considered as valuable ornaments from the earliest times: they are mentioned in the book of Job (xxviii. 18,) and are often alluded to by the classical writers. There have been various attempts made to imitate them successfully, one of the most singular of which,—known to have been practised early in the Christian era, on the banks of the Red Sea,—is still carried on in China. A hole is bored in the shell of the pearl oyster, a piece of iron-wire inserted, and the oyster restored to its place: the animal, wounded by the point of the wire, deposits a coat of pearly matter round it: this gradually hardens, successive layers are added, till a pearl of the requisite size is formed, and the shell is once more brought to land.

A plan, somewhat similar to this, was employed by LinnÆus, who pierced the shells of the fresh-water mussel, causing thereby a pearl to be formed at the punctured spot; and the Swedish government actually established artificial pearleries,—but these were abandoned after a few years; for, although pearls were formed, they were seldom of sufficient size to be of much value.

False pearls are made of hollow glass globules, the inside of which is covered with a liquid, called pearl-essence, and then filled with white wax. This liquid is composed of the silver-coloured particles which adhere to the scales of the bleak, (ablette,) and was first applied to this purpose, early in the last century, by a Frenchman of the name of Jacquin[3].

The Hammer Oyster, (Malleus albus.)

The singular figure of this shell renders it very remarkable; externally its appearance is very rude and irregular, but, on the other hand, the inner surface is equally beautiful, being covered with the most brilliant mother-of-pearl. The different species of the Malleus are all marine, and found in the seas of hot climates, and the rarity of some causes them to be very valuable, and much sought after. Like the neighbouring genera, the animal is furnished with a byssus, or beard, by which it adheres to the rocks.

The Rough Pinna, (Pinna rudis.)

The Pinna is a marine shell; most of the species are large, and the shells very thin in proportion to their size. That represented in the engraving is found in the American seas, and is sometimes as much as a foot and a half in length; it is by no means rare. There is a species found in the Mediterranean, in about five or six fathoms water, which is much sought after by the inhabitants of Sicily and Calabria, not only as an article of food, but also for the sake of its beard, or byssus, of which, in many places, a kind of cloth is made, very remarkable for its softness and warmth. The fishermen, to obtain the Pinna, make use of a kind of iron rake, called a crampe, with teeth a foot in length; when the shells are drawn up, the beards are found to be torn in some part of their substance. If a sufficient length remains attached to the animal, to render the fibres available for the purpose of spinning, they are cut off close to the shell: they are then dried and spun, and afterwards woven into gloves, stockings, caps, and even garments of much larger size.

The threads of which the byssus is formed are extremely fine, and of equal thickness throughout their whole length, very strong, and of a dark morone colour, which is exceedingly permanent.

This curious kind of cloth was long since known to the ancients; but at present its manufacture is very limited, from the great scarcity of the Pinna, and the number of beards necessary to make even so small an article as a pair of gloves. But it is supposed, that if the shells were placed in more favourable circumstances, in preserves, &c., they would increase much more rapidly.

These shells are found in the seas of all hot climates, but the British shores possess but one species, the Pinna lÆvis of Donovan; this is of a horny colour, clouded with brown, and attains a considerable size.

The Common Mussel, (Mytilus edulis.)

The Mussels are a well-known and very useful genus of the shell-bearing animals: they are generally found attached to rocks between high and low water marks.

They are sought after in most parts of the world as an article of food; and, although not equal to the oyster, make a very palatable dish.

The Mussel, although usually wholesome, is at times the cause of severe, though temporary illness. Different reasons have been assigned for this poisonous property, and many signs have been noted, by which it is said the unwholesome state of this shell-fish can be detected,—a yellowness of colour, an extremely meagre appearance, partial corruption, a diseased state of the animal, a small crab or insect found between the valves of its shell. Other observers have ridiculously attributed the effects to the change in the phases of the moon; but, if we are to believe a French physician, who made many experiments, all these guesses are wrong; according to this author, the ill effects are caused only after the Mussels have been feeding on the spawn of the star-fish; this spawn appears to the eye merely a shapeless lump of jelly, but after a few days it is a living mass of infant star-fish. The time of the year during which this spawn is cast, is from the end of April, or beginning of May, to the end of July, or beginning of August; from this, he says, arises the common observation, that Mussels are only poisonous during those months in which the letter r is not found. This spawn, according to our author, is so venomous and caustic, that it causes great pain, swelling, and inflammation, even to the hand, if handled at this season; rubbing the part with vinegar is recommended as a cure. Small star-fish were rolled up in other food, and given to dogs and cats, when the animals suffered severely, and in the end generally died. In spite, however, of all these experiments, it is still doubtful whether the true cause has been discovered. Thus much appears to be certain, that whenever indigestion occurs after eating Mussels, some ill effects are experienced, but this has seldom, or very rarely, taken place when they have been eaten with vinegar, and they are much more wholesome cooked than otherwise.

When an individual is musselled, the effects are very alarming; the body, head, and face swell to a frightful extent; and, in a few hours, the skin is covered with a bright scarlet eruption; the cure is attempted by means of an emetic, and afterwards some aromatic drink, and vinegar and water; this brings on a profuse perspiration, which soon relieves the patient.

The Mussel is taken by our fishermen for bait, for which purpose it is well adapted.

In some parts of the Mediterranean great attention is paid to the multiplication of this animal. At the port of Tarento, in the kingdom of Naples, they drive into the sand a number of long poles, to which the spawn of the Muscle becomes attached. In the following August, when they have attained the size of almonds, they are taken to the mouth of the brooks and small streams which fall into the gulf; here they are left until October, when they are taken back to the sea, and in the following Spring they are considered fit to eat. This change from the salt to the fresh water and back again, is said to improve their flavour and colour. Near Rochelle they are preserved in tanks, preserves in which the salt water remains at rest.

The Giant Tridacna, (Tridacna gigas.)

The Tridacna gigas is the largest of the bivalve shells; it is very thick and close in texture, and is said to have been found as much as five hundred pounds in weight. In Catholic countries the shells have been sometimes used as the receptacles for the holy water in the churches, and formerly they were considered sufficiently valuable to form a present to a king; those in St. Sulpice, at Paris, were given to Francis the First by the Republic of Venice. They have been found in India, as it is related, of so extreme a size, that more than one hundred persons have made a meal on the flesh of a single Tridacna gigas, but this, no doubt, is an exaggeration. These shells adhere to the rocks by their short and strong byssus with so much tenacity, as to require the assistance of a mallet and chisels, in the task of separating them from the rock.

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ORDER BIMUSCULOSA,
(Shells with Two Pairs of Muscles.)

This Order contains by far the greatest portion of the bivalve shells, all interesting to the naturalist, from the variety and beauty of their structure, but few possessing a claim to notice on account of their use as food for mankind, not but that many are equally wholesome with those belonging to the last order, but as they possess two or more pairs of muscles, they are much more capable of moving from place to place, and, consequently, are seldom found in any great quantities in one spot, and being found, as they generally are, in a considerable depth of water, they are not so easily obtained.

The Fresh-Water Mussel, (Anodonta cygnÆa.)

Although this shell, and several other species which nearly resemble it, are known by the trivial name of Mussel, the only resemblance between them consists in their outward appearance, the animals which inhabit the shells being very distinct, both in organization and in habits. The Mussels, as we have already said, have very little power of moving from place to place, while, on the other hand, the Anodonta is at times far from being a sluggish animal, and, for the purpose of shifting its position, it avails itself of a very strong and broad muscular foot. The shell of the Anodonta is sometimes found to contain pearls, a circumstance which frequently occurs in all shells which are lined with mother-of-pearl.

Some of the Scotch rivers have produced numerous specimens of pearl, very large and beautiful, and which used to bear an extremely high price.

A paper in the Philosophical Transactions for 1693, mentions the collection of pearls from this shell, in the river Omagh, County Tyrone, in Ireland. “The poor people,” he says, “in the Summer months, go into the water, and some with their toes, some with wooden tongs, and some by putting a sharpened stick into the opening of the shell, take them up; and, although, by a common estimate, not above one shell in a hundred may have a pearl, and of these pearls not above one in a hundred be tolerably clear, yet a vast number of fair merchantable pearls, and too good for the apothecary, are offered for sale by those people every Summer assizes. Some gentlemen of the country make good advantage thereof, and myself, whilst there, saw one pearl bought for 50l. that weighed thirty-six carats, and was valued at 40l. A miller took out a pearl, which he sold for 4l. 10s. to a man that sold it for 10l., who sold it to the late Lady Glenanly for 30l., with whom I saw it in a necklace; she refused 80l. for it from the late Dutchess of Ormond.”

The Heart-Shaped Isocardia,
(Isocardia cor.)

This shell, which is very common in the Mediterranean, where it goes by the name of the foolscap-shell, and the bullock’s heart shell, is rare in the British seas, but it is sometimes found on the Irish coast; it is the largest British bivalve shell.

The Wedge-Shaped Donax, (Donax cuneata.)

There are nearly thirty species of Donax, all extremely beautiful; that represented in the engraving is of a whitish colour with red streaks: it is often met with in collections of Indian shells. One of these species is found on the English coasts, of a delicate white colour, and streaked with pink.

Donax cuneata.