Acephalous Mollusks, with Bivalve Shells, is the name given by modern naturalists to the class of animals of which we have now to speak; the only one of these terms which will require explanation is the first; it comes from the Greek, and means headless, so an Acephalan is a molluscous animal without a head, as
THE OYSTER,
Which may be considered as the King of Bivalves; his palace, to be sure, is somewhat rough and rugged outside, but within, its walls are smooth and polished, lustrous and iridescent, and altogether beautiful; of a nacrous or pearly appearance, now flushing into a rose tint, now fading into pure white, and adorned sometimes with goodly pearls of price; truly this monarch of the Conchifers has a habitation worthy of a prince, wherein he lives in right royal state. Our readers may smile perhaps at the idea of the solitary Oyster doing this, down there on his mud bank or rocky anchorage ground, shut up in his dirty-looking shells, and holding, as it seems, commune with no one, not even his fellow mollusks; how can he be said to live in royal state, or indeed any state at all, except in a most weary, stale, flat, and unprofitable one? And this only shews how erroneously those often judge who do so hastily, and from first appearances.
If we take a peep through a microscope, under the direction of a naturalist named Rymer Jones, we shall see that “the shell of an Oyster is a world occupied by an innumerable quantity of animals, compared to which the Oyster itself is a colossus. The liquid enclosed between the shell of the Oyster contains a multitude of embryos, covered with transparent scales, which swim with ease; a hundred and twenty of these embryos, placed side by side, would make an inch in breadth. This liquid contains besides, a great variety of animalculæ, five hundred times less in size, which give out a phosphoric light. Yet these are not the only inhabitants of this dwelling—there are also three distinct species of worms.”
Let us see if there are any hard names here that want explaining before we go any further. The first we stumble upon is Colossus, which comes from the Latin, and means a great image or statue, like that which ancient historians tell us once bestrode the entrance to the harbour of Rhodes. Embryo comes from the Greek, and means something small and unfinished, that is to expand or grow into a more perfect form, as the seed into a plant. Animalculæ, are minute or very small animals, such as cannot be distinguished without the help of a microscope, hence they are sometimes called microscopic animals; this word comes from the Latin animalis, which means having life. Phosphoric signifies luminous, or giving out light. The Greek name of the morning star is Phospha. In Latin, Phosphorus is a term applied to a substance which chemists extract from bones and other animal matter, and which, when exposed to air, burns with a pale blue light, like that emitted by the glow-worm. Many of the oceanic or sea animalculæ are exceedingly phosphorescent, so that by night, the waves appear like billows of flame. Of this luminosity of the ocean, as it is termed, we shall have to speak on another occasion. We will now return to the Oyster, who, it will be seen, is by no means so solitary in his bivalve palace as might be supposed. He has his torch-bearers, and other attendants, quite a host of them, no doubt magnificently dressed, if we could but see them to advantage, and well instructed in the several duties which they have to perform. Oh yes, certainly, as the Irish poet has said,
Shall we continue the quotation? and say
Scarcely will our limited space permit us to do this, but a few of the most remarkable particulars about this common Acephalan, we feel called upon to set before our readers.
First, then, it belongs to the class Conchifera; this is a word which we must stop to examine a little; it seems to come from the Latin concha, which means a shell-fish with two shells, in other words a bivalve mollusk. Second, our Oyster belongs to the class Pectinidæ. Now pecten is the Latin for a comb, and this class includes those bivalve shells whose edges are toothed, or, as it is said, pectinated; in the scallop and the cockle shells this peculiarity is more observable than in those of other members of the class, and these form the typical, or so to speak, pattern genus, pecten. Thirdly, the Common Oyster is a Monomyarian Conchifer. Ah! that’s something like a name for the acephaloid monarch! Look at these two words, mono-myarian, di-myarian, you know of course that mony-syllable means one syllable, and dis-syllable means two. You sometimes hear of a person who leads a monotonous life, and you think perhaps of the Oyster shut up in his shell all alone, one by himself; this notion you now know to be a false one; although it is true that he has but one abductor muscle, and therefore belongs to the division of the Pectinidæ family called Monomyaria, while the Pearl Oyster has two, and therefore belongs to that termed Dimyaria. If, as they say, there is reason in the roasting of eggs, surely there must be in the names given to the classes and divisions of shells. We hope to have succeeded in making the why and the wherefore in this case somewhat plain;—one—two—and away we go out of this maze of hard names. But what about the abductor muscle, above spoken of? well, this must be explained; abduce, coming from the Latin abduco, means to separate, to draw away, hence we have abduction. During the life of an Oyster, the usual and natural state of the shell is that of being kept open for a little distance, to allow the water necessary for its nourishment and respiration to flow in and out; 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 means of a muscular power, for which purpose one or two, or sometimes more strong muscles are placed between the valves, their fibres passing directly across from the inner surface of one to that of the other, and firmly attached to both, and these are called the abductor muscles, because their office is to draw or pull; how strongly they do this those whose business it is to open Oysters can best tell; if the animal within were not alive, the process would not be a difficult one, as in that case the muscles would be relaxed, and the shell would come open of itself, so that actually people who eat Oysters directly they are opened, swallow them “all alive-O!”
If a pair of the shells from which the delicious morsel has been extracted, be taken in the hand, it may be noticed that one is much thinner, smoother, and flatter than the other; this is the side most exposed to the action of the water; the rougher and rounder side is that which is attached to the rock, or other substance to which the animal forms an attachment, that is usually life-long. The two portions of the shell are joined together by a hinge of curious workmanship, which is formed of the inner layer of the shell, and strengthened by a ligament which is wonderfully elastic; when the shell is drawn together by the abductor muscles, the ligament is at full stretch, and as soon as they relax at all, it contracts, and causes the shell to gape. This process is repeated as often as may be necessary for the safety and sustenance of the animal within, whose mouth is situated at the narrowest part of its habitation, namely, near the joint of the hinge, which connects its upper and under shell. The anatomical structure of the Oyster is more perfect than would be supposed, from its apparently low state of organization; it has a heart, liver, and intestinal canal, and a bag near the mouth, which answers the purpose of a stomach. Its breathing organs are gills, closely resembling those of most other fish; it has little vessels which convey the bile from the stomach to the liver, and may perhaps be subject to bilious attacks, as well as those who swallow this curious piece of organization at a mouthful, without thinking at all of the goodly structure they are demolishing. There is the tiny heart with its series of blood-vessels, just as perfect as in the larger animals. There are the nerves in the shape of minute feelers, which appear to be acutely sensible not only of actual contact with foreign bodies, but also of sounds and movements from without. A very nice sense of feeling appears to reside in what is called the beard, in scientific language bissus; this is a kind of double fringe to the two lobes of the mantle, or sac, as it is called, which envelopes the body of the animal, and floats free from the shell, except just at the part nearer the valve where it is attached.
We have just spoken of the beard of the Oyster, and this reminds us of a conundrum which may serve to amuse our readers, and enliven these dry details a little. Why is an Oyster the most anomalous, that is strange, contradictory, creature in existence? Do you give it up? Well then it is because
Again, by this allusion to the “tucking in” of Oysters, a phrase more expressive than polite, we have recalled to memory the saying of a quaint old author, that they are “ungodly, uncharitable, and unprofitable meat; ungodly, because they are eaten without grace; uncharitable, because they leave nothing but shells, and unprofitable because they must swim in wine.” Not, generally, however, are they eaten in this luxurious manner, a little pepper and vinegar is all they commonly get in the way of sauce, and those who swallow them thus accompanied, seem to do so with infinite relish. A very long chapter, if not a whole book, might be written about the historical associations of Oysters, for which our country has been famous, as far back as the time of the first Roman invasion; much, too, might be said about the Oyster beds and fisheries, which give employment to thousands of our industrious population, but all this has so little to do with natural history, that we can find no excuse for dwelling upon it here. It is quite within the range of our subject, however, to state that the “spat” or “spawn” of the Oyster is cast about the beginning of May: at first it resembles a drop of greenish tallow, but by the aid of the microscope it may be seen to consist of a great number of minute particles, each of which is an egg, and will by-and-by become a perfect fish; these increase in size very rapidly, and after floating about for a while, sink to the bottom, and become attached to rock or some other substance, in which position, if not violently detached or removed, they complete their growth, and live out the term of their natural life. Their food is minute animalculæ, and microscopic vegetation, on the nature of which their flavour greatly depends.
They have many enemies besides man; the whelk, and the crab, the sea-star, or “five fingers,” and the large drum-fish, which swallows them almost by the bushel, shells and all; these help to thin the Oyster-beds, and make the dredger’s labours less remunerative than they would otherwise be. Here is a picture of one as he stands in his boat just about to throw his dredge into the sandy bottom, where he knows the delicious testaceans do, or ought to, lie most thickly. The dredge, which is a triangular iron frame with a net over the bottom, will naturally sink, and when the line to which it is attached ceases to run out, the dredger will put his boat in motion, and draw it thus over the Oyster-bed, and then pull it up filled, it may be, with little fat “Miltons,” or large “Colchesters,” or such other kind as the spot is known to yield.
The Latin for Oyster is Ostrea, and that is a name given to a genus of the Pectinidæ family, comprising beside the O. edulis, or Common Oyster, many other species. Edulis means eatable. Home naturalists divide these Ostraceans into two groups, first with simple or undulated, but not plaited valves; second, those which have the borders of their valves distinctly plaited.
To the first group belong the Common Oyster, and between thirty and forty other living species which are found principally in warm and temperate latitudes. In the Polar ocean none have been discovered, and in the hotter climates they are most abundant, being found in large beds or banks near the coast, and often attached to rocks and even to trees which grow by the water, so that the accounts of some old travellers who stated that they saw Oysters growing upon trees, were not so false as many supposed them.
The annexed figure is that of the Cock’s-comb Oyster, Ostrea Crista-Galli, a native of the Indian Seas, and a very remarkable shell, on account of its crooked or deeply indented form; the specific name means cock’s-crest. The Chinese Window Oyster, called Placuna Placenta, which we may, if we like, translate into a pleasant or agreeable cake; the shell, it will be seen, is round like a cake, and its smoothness and regularity of form render it agreeable to look upon; this species too comes from the Indian Seas, where it is taken on sandy bottoms. The American Spiny Oyster, or Spondylus Americanus, brings us into another family, that of the Water Clams, called by naturalists Spondylidæ; with the spines stuck out every way, and no way in particular, it looks like a head of hair greatly in need of the assistance of one of its pectinated relatives. The specific name of this curious shell explains itself; the generic name comes from the Latin Spondylis—a kind of serpent.
Passing over the family Malleidæ, or Hammer Oysters, we come to the Meleagrinidæ, or Pearl Oysters, of which Fig. 1, Plate VIII, is an example, this is the M. Margaritifera of naturalists, the mollusk in whose shells pearls are chiefly found. Here are two long words; Meleagris is the Latin for a Guinea or Turkey Hen, to the markings of whose plumage naturalists might have imagined the shells of this genus bore some resemblance. There was, says the mythology, a celebrated hero of antiquity named Meleaga, but we can hardly suppose that there is any association between his name and that of a genus of Oysters, of which edible we read the ancients were very fond, and they are said to have had a fancy not only for the mollusk itself, but also for the pearls found in its shell, which at their luxurious banquets they dissolved in wine, to make the draughts richer, or at all events more expensive; and this brings us to the specific name of the Pearl Oyster, Margaritifera, which comes from the Latin Margarita—a pearl; the French use this word slightly altered in the spelling, thus Marguerite for both a daisy, and
A PEARL.
This jewel, so highly valued for its chaste beauty, is but a secretion of animal matter, resulting from the efforts of some uneasy mollusk, annoyed by a foreign substance, which has found its way into his habitation, to make the best of an unavoidable evil by enclosing it in a soft smooth covering. Let us imitate the Oyster, and when annoyed or afflicted, by meekness and patience, and christian charity, strive to turn our vexations and troubles into “pearls of great price,” and “goodly pearls,” like those mentioned in scripture.
It is on the north-west coast of the Island of Ceylon, in the Indian Ocean, that the Pearl Oyster most abounds, and there it is that the Pearl fishery is conducted in the most extensive, systematic, and successful manner; this fishing commences at the beginning of March, and upwards of two hundred boats are usually employed in it; in each of these boats are ten divers, who go down to the Oyster-beds, five at a time, and so relieve each other; there are besides thirteen other men who manage the boat, and attend to the divers. Altogether it is computed that from fifty to sixty thousand persons, in some way engaged in the fishery, or preparation, or sale of the pearls, assemble at and near the scene of operations, which must be indeed a busy one. The number of Oysters taken during the period of the fishing, which is about a month, must be prodigious. One boat has been known to bring on shore, in the day, as many as thirty-three thousand; they are placed in heaps, and allowed to remain until they become putrid, when they undergo a very elaborate process of washing and separating from the shells, which are carefully examined and deprived of their pearly treasures. The stench arising from the decomposed animal matter is described as horrible, and the whole process filthy and loathsome in the extreme; yet out of the slime and mud and disgusting effluvia, come every year gems of inestimable value, calculated to adorn the brow of beauty, and form ornaments the most pure and delicate that can be imagined. For the exclusive right of fishing on the banks of Ceylon, for a single season, as much as £120,000 have been paid to the English government by one person, who sublets boats to others. Pearls vary greatly in value according to their colour and size; those which are perfectly white are the most valuable; next to these are those which have a yellowish tinge; the smallest kind, used for various ornamental purposes, are called seed pearls, the refuse is made into a kind of confection called chimum, highly relished by Chinese epicures. A single Oyster will sometimes contain several pearls, which are generally embedded in the body of the animal, but are sometimes fixed to the shell; it is recorded of one rich mollusk, that there were found in his possession no less than one hundred and fifty precious jewels; he must have been a miser, or perhaps he had taken them in pledge from his less provident neighbours.
From the earliest time, pearls have been considered as valuable ornaments; they are mentioned in the book of Job, (see chap. xxviii, verse 18th.,) and are often alluded to by Greek and Roman writers. Various attempts have been made to imitate them, and one mode of producing them, practised, it is said, more than a thousand years ago, is still carried on in China. In the shells of Pearl Oysters, holes are bored, into which pieces of iron are introduced; these wounding and irritating the animal, cause it to deposit coat upon coat of pearly matter over the wounded part, and so the pearl is formed. Artificial pearls are made of hollow glass globules or little globes, covered on the inside with a liquid called pearl-essence, and filled up with white wax. Historians speak of an ancient traffic in native pearls carried on by this country; and in modern times, British pearls of considerable value have been discovered, one not many years since, by a gentleman who was eating oysters at Winchester, was valued at two hundred guineas. Generally, however, the pearls of this country are inferior in the two requisites of colour and size.
Interesting accounts of Pearls and Pearl-fishing, will be found in “the Penny,” and “Saturday Magazines,” and many other works easy of access. There our young readers may learn of the perils and dangers to which the poor divers are exposed from the voracious sharks, which hover about the fishing grounds, and make a dash at their victim, heedless of the written charms, with which the priest or shark-charmer has provided him previous to his descent, and of much more than we can find space here to tell. All we can now do is to give the portrait, as drawn by Thomas Hood, of a lady who takes up her abode in all the pearl-producing bivalves, and who is therefore, perhaps on this account, called
THE MUSSEL AND THE COCKLE.
It is in the Dimyaria division of the Conchifera that we must look for these familiar bivalves, the Mussel, or, as it is sometimes spelled, Muscle, and the Cockle; the former called in scientific language Mytilus, which in Latin means simply a shell-fish, and the latter Cardium, which may have reference to the hinge of this bivalve, or the heart-shape assumed by several of the species; cardo, in Latin, signifying the hinge of a gate, and cardesco, a stone in the shape of a heart.
It is to the Mytilidæ family that we shall first direct our attention, and here we find the Common or Edible Mussel, (M. edule,) and many other species, in all of which the shell is more or less elongated, or lengthened out, and pointed at one end. The members of this family are abundant on most rocky coasts, where facilities are afforded for the mollusks to moor themselves to rocks, stones, and other substances covered at high-water, but left dry by the retreating tide. They are not, however, confined to shores of this description, but are sometimes found in vast numbers on low sandy or pebbly flats, which run far out into the sea; these are called beds of Mussels, and are, like the Oyster grounds, specially cared for and protected. As a ship by its cable, so commonly the Mussel, by its bissus or beard, is made fast to its anchorage-ground, be it pebbly or sandy beach, or jutting rock. Sometimes, however, the mollusk travels, and this is how it manages to do so; it has a stout fleshy foot, in shape something like that of a chubby child, and this it can advance about two inches beyond the edge of the shell, then fixing the point of it to a piece of rock or any other body, and contracting it, the shell is drawn onward, and sure, though slow, progress is made in any desired direction. The Pinna, as the marine Mussel is called, has a foot which is cylindrical in shape, and has at the bottom a round tendon, almost as long as itself, the use of which appears to be to gather in and retain the numerous threads with which, when inhabiting the shores of tempestuous seas, it lashes itself fast to the fixed objects around; these threads are fastened at various points, and then drawn tight by the animal, whose instinct teaches it that its brittle shell would soon be broken in pieces, if suffered to roll hither and thither at the mercy of the waves.
The Mussel has a very curious method of preparing its cable for this service; it is not woven, nor spun, nor drawn out of the body, like the web of the spider, but produced in a liquid form, and cast in a mould which is formed by a groove in the foot, extending from the root of the tendon to the upper extremity; the sides of this groove are formed so as to fold over it and form a canal, into which the glutinous or sticky secretion is poured; there it remains until it has dried into a solid thread, when the end of it is carried out by the foot, and applied to the object to which it is to be attached; the canal is then opened through its whole length to free the thread, and closing again is ready for another casting; as if conscious how much depends upon the security of his lines, the animal tries every one after he has fixed it by swinging itself round so as to put the threads fully on the stretch; when once they are all firmly fixed, it seems to have no power of disengaging itself from them; the liquid matter out of which they are formed, is so very glutinous, or glue-like, as to attach itself firmly to the smoothest bodies. The process of producing it is a slow one, as it does not appear that the Pinna can form more than four or five in the course of twenty-four hours. When the animal is disturbed in its operations, it sometimes forms these threads too hastily; they are then more slender than those produced at leisure, and, of a consequence, weaker. On some parts of the Mediterranean coast, as in Sicily, gloves and other articles have been manufactured from the threads of this mollusk; they resemble very fine silk in appearance.
The foot of the Cockle, of which we here give a figure, is commonly employed in scooping out the mud or sand, beneath which it conceals itself; this useful limb assumes the form of a shovel, hook, or any other instrument necessary for the purpose; it appears to be a mass of muscular fibres, and to possess great power. As a boatman in shallow water sends his vessel along by pushing against the bottom with his boat-hook, precisely so does Mr. Cardium travel; he doubles up his foot into a club, and by an energetic use of it as a propeller, makes considerable headway along the surface of the soft sand beneath the waters. In this way, too, some members of the genus solen force their way through the sand; while those called Tellina spring to a considerable distance, by first folding the foot into a small compass, and then suddenly expanding it, closing the shell at the same time with a loud snap; so that you see these sober-looking mollusks are sometimes frolicksome fellows; this is an enforcement of the lesson, judge not by appearances.
Some of the species, both of the Mussel and Cockle families, have very beautiful shells. We give a representation of one of each, on Plate VIII. Fig. 2 is the Magellanic Mytilus, (M. Magellanicus,) found chiefly in the Straits of Magellan; it is generally four or five inches long, the shells when polished are very brilliant, the deep purple colour changing into rich violet, as they are held in different lights. In most cabinets the large fan-like delicate shells of the genus Pinna may be observed; the largest species is that called Pinna flabellum, taken in the Mediterranean; it sometimes exceeds two feet in length. The first of these names is a Latin word signifying, besides a shell-fish, the fin of a fish, or the wing feathers of a bird—hence the term pinion; it refers to the fin-like or wing-like shape of this shell. Flabellum means a fan, referring probably to the bissus of the mollusk, which is fine and glossy, like silk, and very abundant.
Many pretty specimens for figuring might be selected from the Naidæ, a family of Fresh-water Mussels, so called from the Naiades, fabulous divinities of the streams and rivers. The shells of many of these, which are of considerable thickness, are lined with the most brilliant nacre, and in these, as might be expected, pearls are sometimes found. One species, abundant in some English rivers, called the Mya Margaritifera, or, as some say, Uno elongates, has long been celebrated for this valuable production. It was most likely with pearls from this mollusk that Julius Cæsar adorned a breast-plate, which he dedicated to Venus, and hung up in her temple. The rivers Esk and Conway were formerly celebrated as British pearl-fishing grounds; a Conway pearl was presented by her chamberlain, Sir Richard Wynn, of Gwyder, to Catharine, Queen of Charles the Second; and in the royal crown of Britain this jewel is said still to occupy a place. Sir John Hawkins, the circumnavigator of the globe, held a patent for the pearl-fishery of the River Irt, in Cumberland. The rivers of Tyrone and Donegal, in Ireland, have, or had, their pearl-bearing Mussels; we read of one which weighed thirty-six carats, (a carat is nearly four grains,) but not being of perfect shape and colour, it was only valued at forty pounds. We also read of another purchased by Lady Glenlealy, for £10, and found to be so perfect and admirable, that £80 was afterwards offered for it, and refused.
These Naidæ have not a bissus like the Marine Mussels, they are therefore never attached to one object; they use their foot as a propeller in traversing the muddy floor of the pond or river, and they have a very funny way of getting along indeed; first, they open the valves of the shell, put out the foot, and after some little hard work, manage to set themselves up on edge; they then proceed by a series of jerks, leaving a deepish furrow in the mud behind them.
We will now go to Fig. 3, the Spined Cytherea, the Cytherea or Venus Dione of naturalists; the meaning of the term is the mother of Venus, who was, as you will remember, the goddess of beauty, given to this shell perhaps because it is entitled to occupy a place at the head of the Cytherea, a genus of the Cardiidæ, or Cockle family, of which genus there are about seventy-eight living species; this, as it is the most rare, is also, perhaps, the most beautiful; it is found in the seas of America, and is remarkable for the row of spines on the hinder border of each valve; these vary much in size and number, being in some individuals long and far apart, in others, short, thick, and closely set. The colour of the shell also varies considerably, being sometimes of a delicate rose colour; at others, more of a claret; at others again, bordering on purple. It was for one of the first discovered specimens of this shell, that £1000 is said to have been given. Truly a Venus of value this; it ought to be called the Queen of Cockles!
Our next example, (see Fig. 4,) is the Spotted Tridacna, (T. maculatus,) the latter term signifying spotted. In the Chamidæ or Clam family, is placed the Tridacna genus, the discovered species of which are not numerous; they are chiefly found in the Indian seas. The one above mentioned claims pre-eminence for beauty. We cannot quite see the applicability of the generic name; Tridacnus, in Latin, signifies to be eaten at three bites, but he must be a man of large capacity indeed who could so devour the head of this family, the Giant Tradacna, (T. gigas,) a single specimen of which has been known to weigh as much as five hundred and seventy pounds; from three to four hundred is by no means an uncommon size. The shell of this giant mollusk is of a very picturesque shape, something like its spotted congener, as we call anything of the same kind or genus, only it is somewhat plainer, and more deeply ribbed and indented. The inside is of a glossy whiteness, and it is frequently used as a basin for garden fountains, or the reception of rills or little jets of water, which sparkle in its stainless hollow. In the church of St. Salpice, at Paris, is a shell of this immense Clam, the valves of which are used as receptacles for holy water; it was presented to Francis the First, by the republic of Venice. Fancy the clapping to of such a pair of valves, when the animal closes its shell in alarm, and the strength of the cable required to moor it to the rocks or coral reef. The spotted species here figured has a solid and heavy shell, very elegantly shaped, and beautifully marked, as will be seen; the greatly reduced size of the figure prevents anything like justice being done to the original.
The above is a figure of the Heart Isocardea, (I. cor,) which is also a member of the Clam family, and one of the most elegantly-shaped shells in the whole range of Conchology. It is a native of the Mediterranean and other seas of Europe, and has been taken in deep water on the West coast of Ireland. We complete this group with a representation of the curious Arcadæ family, or Ark shells, as they are commonly called, because one of the species was thought to resemble the ark built by Noah. Mr. Swainson tells us that the animals of these shells affix themselves to other bodies by a particular muscle, which is protruded through the gaping part of the valves; they also adhere, when young, by means of the bissiform epidermis, or bissus-like outer skin: this species is a native of the Atlantic Ocean and the seas of Europe. The Antique Ark, (A. antiqua,) is very like the Common Cockle, being of a white colour, and heart-shaped. We give below a representation of this shell, and also of the shell of the pretty little Pearly Trigonia, (T. margaritacea,) included in the Arcadæ family; this is a rare species, found only in the seas of New Holland.
SCALLOP SHELLS.
Several species of Scallop Shells are found scattered about on our shores; they belong, as before stated, to the family Pectinidæ, the meaning of which term has been already explained. These shells were called by Cuvier “the Butterflies of the Ocean,” on account of the various and beautiful colours which they exhibit. Some of them are exceedingly thin, and brittle as glass; one species found in the Arctic regions, is as transparent as that substance, and is therefore called P. vitreus, from the Latin for glass, which is vitreum. One of the commonest of our native Scallops is the St. James’ Cockle, (P. Jacobœus;) this shell is found in great plenty along our southern coasts; it is often referred to by old writers, on account of having been commonly worn in the hats of pilgrims to Palestine, or the Holy Land, as the scene of our Saviour’s life and death was called. Sir Walter Raleigh, in his poem called “The Pilgrimage,” thus enumerates the different articles considered necessary for a Palmer, as these pilgrims were termed:—
This Mollusk, it may be noticed, like many other bivalves, has a flat, and a concave or hollow shell: in early times when plates and drinking vessels were not so plentiful as they are now, one of these served the former purpose, and the other the latter; thus, in speaking of a feast, a Gaelic or Scottish bard has said—
Sometimes the species termed Pecten opercularis, was used as the pilgrim’s badge; the specific name comes most likely from the Latin operculum, whose meaning has been explained.
This too, is a common British shell, as is also the little speckled Scallop, (P. varia,) which may be found on almost any part of the coast where the water-line is margined with a sandy ridge. The shells are generally about two inches long, of various colours, clouded, speckled, and marked with about twelve ribs. There is a foreign species called the Flounder Scallop, P. pleuronectes, which is remarkable for having the two valves of the shell of different colours, the upper one being of a rich reddish brown, and the lower one white: the specific name has reference to this, being compounded of the Latin pleura—something double, and necto—to join. The fish called the Flounder, is brown above and white beneath, hence the English name of this shell. The preceding engraving of the Common Scallop, viewed from the front, shows the flat and concave form of the two valves of this shell, and also the depth of the indentations or ridges.
LIMPITS.
Among the rocks of the British coast, there are no shells more frequently met with than those of the Common Limpit, Patella vulgata; they lie scattered about like so many little empty cups, each having, on the death of the mollusk, fallen from the rocky cavity in which it was embedded, and which was just large enough to contain it. Here the animal attaches itself so firmly by its fibrous foot, which is hollow in the centre, and acts like a sucker, that it is almost impossible to loosen its hold otherwise than by inserting something thin, like the blade of a knife between it and the stone. By this power of adhesion, the Limpit is protected from the violence of the waves, and also from its numerous enemies, aquatic birds and animals, which have a relish for its flesh. Still vast numbers are used as food, both by man and the inferior creatures, so that the means of defence furnished to the Limpits of the rock, are not always sure. “The peasantry of the western isles of Scotland,” we are told by Miss Pratt, “look to the Periwinkles and Limpits, which abound on the rocks, for their daily meal, often for long seasons, subsisting almost entirely upon this humble food. In the Isle of Skye, the inhabitants are often, at one time of the year, without any other source of provision.” Then comes the Sea-gull, and the Duck, and the Pied Oyster-catcher, to feed on the poor little mollusk, the bill of the latter bird being admirably adapted for loosening its hold on the rock.
Patella in Latin signifies a salad-dish, a knee-pan, and several other domestic utensils, of a broad shallow make, and hence we find the plural form of the word applied to the Limpit family, whose shells are of such a shape. Members of this family are found on all rocky coasts, except those of the Arctic seas; on Tropical rocks they grow to a large size, and form a valuable article of food. A very curious piece of mechanism is the tongue of the Common Limpit, it is from two to three inches long, and has a spoon-like extremity, so that it looks, when extended from the mouth, like a small snake; if examined through a microscope, it is seen to be armed throughout its whole extent with rows, four deep, of sharp hooked teeth, and between each row are placed two others, which have three points, and are set in a slanting position; the use of this arrangement we cannot at present determine, but no doubt it has a perfect adaptation to the wants of the animal.
There are shell-fish called Key-hole Limpits, which belong to the genus Fissurellidæ, from fissura—a cleft or slip, from whence comes also fissure. All the members of this genus are distinguished by the aperture at the top of the shell, shaped like a key-hole, which is situated exactly over the breathing organs, and serves as a channel for the water necessary for respiration.
Frequently upon the fronds of the large olive sea-weeds may be found a tiny shell shaped something like that of the Common Limpit; it is of an olive green colour, with blue streaks, and is called, from its clearness, the Pellucid Limpit, P. pellucida. There is also another much like it in appearance, which naturalists call P. lœvis. To the labours of these little mollusks, according to Dr. Harvey, may be partly attributed the destruction of the gigantic Algæ, (sea-weed.) Eating into the lower part of the stems, and destroying the branches of the roots, they so far weaken the base, that it becomes unable to support the weight of the frond; and thus the plant is detached and driven on shore by the waves.
ROCK-BORERS.
The family Pholadæ comprises a group of mollusks, the boring habits of which have long been known; they penetrate wood, hard clay, chalk, and rocks, and devastate the labours of man; they attack the hulls of ships, the piles which form the foundations of piers and break-waters, and they force themselves upon our attention by the loss of property, as well as of life, which results from their hidden depredations. Of this family, those belonging to the genus Pholus may be more especially likened to the Edomites of Scripture, because they take up their abode in the rock, and hollow out for themselves dwellings therein. With a shell as thin as paper, and brittle as glass, the wonder is how these Rock-borers work their way into and through hard stones. Some naturalists assert that they effect this by means of an acid which decomposes the substance of the rock, and renders it soft; others, that the animal keeps turning round and round like an instrument called an auger, and so gradually rasps away the surface of the stone with the angles of its shell, but we question whether the shell would not be worn out first in such a process. The generic name of these “stone-piercers,” comes from the Greek word Pholeo—to hide, and the rocky chambers which they hollow out for themselves, are as snug hiding-places as can well be imagined; yet, however deep they may go into these gloomy caverns, as we should be apt to suppose them, they need not be in darkness, for it appears that these Pholades emit a most remarkable light, whether phosphorescent or not does not appear to be determined; so strong is it, that it is said to illuminate the mouth of the person who eats the mollusk; and it is remarked by Dr. Priestly, that “contrary to the nature of most fish, which give light when they tend to putrescence, this is more luminous the fresher it is, and when dried its light will revive on being moistened with water.” So that in more respects than one these rock-borers are mysteries. The most common of them, perhaps, is the Prickly Pidduck, or Peckstone, (P. dactylus,) which is much used by the fishermen of our coasts as bait; the specific name is the Latin for a fruit shaped like a finger, which is something like the shape of this mollusk, as will be seen by the annexed engraving.
The genus Pholus is very widely distributed, and all the species have the same boring habits as those of our own coast, which we need not enumerate. Like them too in this respect are the marine worms called Teredo, which make their way into the bottoms of ships, and all submerged timber, but these will be more fully spoken of in another volume. The above figure exhibits the Pholas dactylus as it appears in a section of rock, split open for the purpose of seeing the shelly miner at his work.