§ II Univalves
2. The Admiral
One of the cone-shells, the inhabitant of which is a kind of snail, with a very distinct head. If nature has taken a delight in painting the wings of birds, the skins of quadrupeds, and the scales of fishes, she seems not to have been less pleased in pencilling the shells of these inhabitants of the deep. The variety, brightness, and versatility of the colouring have long been deservedly the object of man’s admiration; and we cannot help being astonished at the richness which a cabinet of well-selected shells presents to the eye.
The Tiger Cowry. (Cypræa Tigris.)
The Cowries or Porcelain shells are amongst the most beautiful of the univalves. The shells are generally of an elegant oval form, with no visible spire; the mouth is a long slit on the middle of the lower surface, with two nearly equal lips toothed along their margins; the surface is most beautifully polished, and generally adorned with rich colours, arranged in varied and elegant patterns. The Tiger Cowry, which is one of the commonest, is rather broad, and very convex; it is of a white colour, covered with numerous dark brown spots. It is usually four or five inches in length, and inhabits the seas of India. The Money Cowry (Cypræa moneta) is a little Indian species, which is used in place of money in some countries, especially the interior of Africa. It is imported into England for exportation to Africa in large quantities; as much as 300 tons having been landed at Liverpool in one year.
The Whelk, (Buccinum Undatum,)
Is a common British shell-fish of considerable size, which is obtained in large quantities by dredging, and used as food. In London it is sold commonly at stalls in the streets, we believe in a pickled state. The mouth of this animal is furnished with a powerful rasping proboscis, by means of which it is able to bore through the shells of other mollusca.
So called on account of the length of a prominency coming out of the shell. It is surrounded with blunt prickles, and the colour of the whole is elegantly variegated.
The Periwinkle, (Littornia Littorea,)
Is too well known to require any description. It is found in incalculable numbers all round the European coasts, and captured in immense quantities as an article of food.
The shape of this shell is pyramidal; it adheres to the rock with such strength, that it can only be removed by means of a knife or a strong blow. The apex of the shell is sometimes sharp, sometimes obtuse, and often surrounded with points and sharp prickles. When thoroughly cleansed the shell is generally of a beautiful purple tint of great brilliancy, though the animal that lives under this magnificent roof is a kind of snail, disagreeable to the eye and insipid to the palate. They are found on the rocks, which are incessantly beaten by the surges and breakers, on the sea-shores of almost every country in the world. It is not by any glutinous liquid, as it has been asserted, that this fish adheres so strongly to the rock; but by the simple process of producing a vacuum between its foot and the rock to which it affixes itself.
The variety which is thrown into the sum of animated beings is so wonderfully great, that naturalists have reckoned more than a hundred and twenty-nine species of Limpets, and nearly allied genera; the difference arising principally out of the diversity of the shells in form and colour.
Is furnished with four tentacula, two of which are smaller than the others; at the end of these tentacula, which the animal pushes out or draws back, like telescopes, are blackish knobs, which are the eyes. The snail lays eggs, which are about the size of small peas, semi-transparent, and of a soft substance. By closely examining with a magnifying lens the eggs which a Water Snail, kept in a bottle of water, had deposited against the glass, the young Snail was seen in the egg, with its embryo shell on its back; two have also been observed in one egg, each of them with the rudiments of the shell.
The Garden Snail is extremely tenacious of life, and remains in a state of torpor during the winter. It is said, indeed, that it can remain in this state for many years, and the following instance is probably without parallel in any other animal:—Mr. S. Simon, a merchant of Dublin, whose father, a Fellow of the Royal Society, and a lover of natural history, left him a small collection of fossils and other curiosities, had, among them, the shells of some Snails. About fifteen years after his father’s death, he gave to his son, a child of ten years old, some of these Snail-shells to play with. The boy placed them in a flower-pot, which he filled with water, and the next day put them into a basin. Having occasion to use this, Mr. Simon observed that the animals had come out of their shells. He examined the child respecting them, and was assured that they were the same which had been in the cabinet. The boy said he had a few more, and brought them. Mr. S. put one of these into water, and, in an hour and a half afterwards, observed that it had put out its horns and body, which it moved but slowly, probably from weakness. Major Vallancy, Dr. Span, and other gentlemen, were afterwards present, and saw one of these Snails crawl out; the rest being dead, probably from their remaining some days in the water. Similar observations have since been so frequently repeated, that there is now no doubt that Snails of various kinds may retain their vitality for years when preserved in a dry state.
The Small Grey Slug, (Limax Cinereus,)
Resembles a Snail in all points except that it has no shell, consequently the brown skin of the back is rougher and stronger than that of the Snail. Its progress on the ground may easily be traced by the slime which it leaves in its track. Few animals are more destructive to vegetation than these.
The Black Slug, (Arion Ater,)
Is a well-known inhabitant of our fields and meadows, during the summer season. The country people consider its appearance as an indication of approaching rain; but this is rather to be accounted for by the moisture of the ground and plants. Indeed, it very seldom appears abroad during dry weather. The Black Slug feeds on the leaves of different kinds of plants.
The structure of these animals is very remarkable. Their body is nearly cylindrical, and, in some of the species, entirely covered with a fleshy sheath; in others the sheath reaches only to the middle of the body. They have eight arms, or rather legs, and in general two feelers, much longer than the arms. Both the feelers and arms are furnished with strong circular cups or suckers. The mouth is hard, strong, and horny, resembling in texture the beak of the parrot. The body is of a jelly-like substance, and usually covered with a coarse skin, having the appearance of leather. This skin contains cells of different colours, which are capable of changing their relative position, so that the Cuttle-fish is able to change the colour of its skin. By means of the numerous circular cups or suckers with which the arms are furnished, they seize their prey, and firmly attach themselves to the rocks. Their adhesive power is so great, that it is generally more easy to tear off the arms than to separate them from the substance to which they are affixed: if the arms happen to be broken off, they are soon reproduced. The size to which this creature grows has been variously stated; and, although evidently exaggerated by some authors, it undoubtedly attains to a very considerable magnitude. When attacked in its own element, it has been known to overcome a large dog. Its jaws are extremely strong and powerful, and with its beak it can crush in pieces the shells of the fish on which it feeds. In the body is a bladder filled with a dark inky fluid, which it emits when alarmed, and which not only tinges the water so as to conceal its retreat, but is so bitter as immediately to drive off its enemies. This inky fluid, when dried, forms a very valuable colour, used by artists, and known as Sepia.
The bone, or calcareous plate of the Sepia Officinalis, a species common on our coasts, is a well-known substance, and is much employed in the manufacture of toothpowder; and by silversmiths for moulds, to cast their small work, such as rings, &c. It is also converted into that useful article of stationery, called pounce.
The Poulpe, (Octopus Vulgaris,)
Has only eight arms, the two long tentacles of the Sepia being absent. It is found on our coasts, and is especially abundant in the Mediterranean, where it is regularly brought to market as an article of food.
Is a kind of Poulpe, in which only six of the arms present the ordinary form, the other pair being expanded into broad, flat organs. It was supposed by the ancients, and, indeed, until very recently, that these expanded arms were used by the animal as sails; it was described as floating at the surface of the sea, with the back of the shell downwards, the six arms sticking into the water like so many oars, and the two broad members elevated to catch the breeze; but it is now known that the so-called sails are used to embrace the shell when the animal is swimming backwards, in the same way as its allies, and it also appears that it is by these arms that the shell is enlarged. The Argonaut is found in the Mediterranean.
Is a very different creature, and instead of the eight arms of the Argonaut has its head surrounded by numerous ringed and sheathed tentacles. It is remarkable for the structure of its shell, the cavity of which is divided into numerous chambers by transverse partitions; these chambers, of which the outermost alone is occupied by the animal, are filled with air, but a narrow tube passes through the whole of them, and communicates with the cavity of the body. By this arrangement the Nautilus is enabled to alter his specific gravity so as either to rise to the surface or sink to the bottom of the water. The few existing species of Nautilus are all found in the Indian and South Pacific Oceans.