Page images
PDF
EPUB
[blocks in formation]

the other species, have each twenty-four claws or tentacula, all joined in pairs near the bottom, and inserted into one common base. The twelve longest stand somewhat erect and arched, and arise from the back part of the animal. They appear like so many yellow curled feathers, clear, horny, and articulated. Every joint is furnished with two rows of hairs on the concave side. They are of use in catching prey, and the animals are continually employed in extending and contracting them for this purpose.

The twelve smallest tentacula are placed, six on each side, in front of these. They are more pliable and more thickly set with hairs than the others, and seem to perform the office of hands. The mouth, formed not unlike a contracted purse, is in front, between the smaller tentacula; and within its folds are situated six or eight horny laminæ or erect teeth. Under this lie the stomach and intestines, and the tendons, by which the animal adheres to the shell.

OF THE TEREDO TRIBE.

a

THERE are not more than four known species of Teredo. Of these, two are found in holes, which they perforate in wood; a third, in the seed vessels of a plant which grows in the East Indies, and called, by Linnæus, Xylocarpum Granatum; and the fourth, (the Gigantic Teredo,) in mud at the bottom of the ocean, on the coast of the island of Battoo, near Sumatra. The shells of the latter are sometimes between five and six feet in length.

These animals were formerly arranged with the more simple of the univalve shells, but their proper place is certainly among the multivalves.

THE SHIP-WORM

Great numbers of these destructive worms, which are supposed to have been introduced from India into Europe, are sometimes found in the sides and bottoms of ships. By means of their hard and cutting jaws, they are able to penetrate into any timber, except such as is of an extremely hard and compact substance. They, however, bore as seldom as possible across the grain; for, after they have penetrated a little way, they turn, and continue with the grain tolerably straight, until they meet with another shell, or knot. Their course ther depends on the nature of the obstruction: if this be considerable, they prefer making a short turn back, in form of a syphon, rather than to continue for any distance across.

OF THE PHOLAS TRIBE.

The animals of this tribe, while very young, perforate clay, spongy stones, and wood; and, as they increase in size, they enlarge their habitation within, and thus become imprisoned. They are always found below high water mark, and a mass of rock may sometimes be seen wholly perforated by them. They have two orifices, or openings, capable of elongation in the manner of a proboscis: one of these is supposed to be the mouth, and has the faculty of spouting water. Most of them contain a phosphorescent liquor, of great brilliancy in the dark, which also illuminates whatever it touches or happens to fall upon.

From the following species, the character of nearly the whole tribe may be collected.

THE DACTYLE PHOLAS.

The very extraordinary powers possessed by these animals

, of penetrating into solid bodies, when compared with their apparent imbecility, have justly excited the astonishment of philosophers and naturalists in all ages.

When divested of their shells they are roundish and soft, and seem destitute of any instrument fitted for boring into stones. They are, indeed, each furnished with two teeth; but these are placed in such a situation as to be incapable of touching the hollow surface of their stony dwellings. They have also two corners to their shells, that open and shut at either end; but these are totally unserviceable to them as miners. The instrument with which they perform all their operations, and by means of which they bury themselves in the hardest rocks, is a broad fleshy substance, somewhat resembling a tongue. With this soft, yielding instrument, while yet young and small, they work their way into the substance of the stone, and enlarge their apartment as their increasing size requires.

Furnished with the bluntest and softest augur imaginable, it effects, by slow successive applications, what other animals are incapable of performing by force, and penetrates the hardest bodies with only its tongue. When, while yet small, it has effected an entrance and buried its body in the stone, it there continues, for life, at its ease; the sea-water that enters at the little aperture, supplying it with luxurious plenty. On this seemingly thin diet it by degrees grows larger, and soon finds itself under the necessity of increasing the dimensions of its habitation and its shell.

The motion of the Pholas is slow, almost beyond conception, its progress keeps pace with the growth of its body; and, in proportion as it becomes larger, it makes its way further into the rock. When it has penetrated to a certain depth, it turns from its former direction and hollows downward; till at last

, when its habitation is completed, the whole apartment resembles the bowl of a tobacco pipe; the hole in the shank being that by which the animal entered.

Thus immured, the Pholas lives in darkness, indolence, and plenty: it never removes from the narrow mansion into which it has penetrated; and seems perfectly content with being enclosed in its own sepulchre. The influx of the sea-water that enters by its little gallery satisfies all its wants. These animals are found in immense numbers at Ancona, in Italy.

BIVALVES.

OF THE MYA TRIBE.

The shell, in most of the species, is gaping at the end. The hinge is furnished with a strong, thick, and broad tooth, not inserted into the opposite valve.

Most of these animals are inhabitants of the ocean, but some of them are found in fresh water. They perforate the sand or mud at the bottom, where many of the species are caught for food, and others for the pearls which are formed within their shells. Some few of the species perforate and live in limestone, in the same manner as the pbolades.

OF THE SOLEN, OR RAZOR-SHELL TRIBE.

THESE animals in general reside in holes, which they form in the sand at the bottom of the ocean. Their position in these holes is always upright. In situations where they are exposed to the air by the ebbing of the tide, their place is easily known to fishermen, by a small dimple which they leave on the surface. Some of the species live in stone. Nearly all of them are used as food.

[graphic]

THE COMMON, AND THE SCABBARD RAZOR-SHELL.

Many of the bivalved shell-fishes have the power of progressive or retrograde motion, by an instrument that has some resemblance to a leg or foot, and called the au Longue. But these ani. mals can, at pleasure, make this tongue assume almost every form which their exigencies require.

Like all the other species of Razor-shells, they are incapable of progressive motion on the surface; but they dig a hole or cell in the sand, sometimes two feet in depth, in which they can ascend or descend at pleasure. The instrument by which their motions are performed, is fleshy, cylindrical, and situated near the centre of their body. When necessary, the animals can make the termination of the tongue assume the form of a ball. The Razor-fish, when lying on the surface of the sand, and about to sink into it, extends its tongue from the inferior end of the shell, and makes the extrenity of it take the form of a shovel, sharp on each -side, and terminating in a point. With this instrument the animal cuts a hole in the sand. After the hole is made, it advances the tongue still further into the sand, makes it assume the form of a hook, ard with this hook, as a fulcrum, it obliges the shell to descend into the hole. In this manner the animal operates until the shell totally disappears. When it chooses to regain the sur. face, it forms the termination of the tongue into the shape of a ball, and makes an effort to extend the whole tongue; but the ball prevents any further descent, and the muscular effort necessarily pushes the shell upward, until it reaches the surface. It is amazing with what quickness and dexterity these seemingly awkward motions are performed.

It is remarkable that the Razor-fish, though it lives in salt water, seems to abhor salt. When a little salt is thrown into the hole, the animal instantly quits its habitation. But it is still more remarkable, that, if the animal be once seized with the hand, and afterwards allowed to retire into its cell, salt will then be strewed in vain, for the fish will never again make its appearance. If it be not handled, the animal, by an application of salt, may be made to come to the surface as often as a person pleases; and fishermen sometimes make use or this stratagem as a means of catching it.

a

OF THE CARDIUM, OR COCKLE TRIBE.

Os sandy shores of almost all the known seas, some of the species

of Cockle are to be observed. Most of them are found im. mersed in the sand, at the depth of a few inches. Their size is various, from five or six inches to half an inch in diameter. In a fossil state these shells are by no means uncommon; and species corresponding with some of them inhabit the Indian Ocean.

The shell is bivalve, equivalve, convex, and in most of the species, longitudinally ribbed. The hinge has two teeth near the beak, and a larger one

placed remote on each side, CARDIUM GLOBAD.

locking into the opposite valve.

[graphic]

THE COMMON COCKLE-OYSTER.

1021

THE COMMON COCKLE.

All the locomotive powers of these well-known animals are concea: Lrated in the triangular yellow foot, which is so conspicuous when we open the shells. This foot is not only capable of great inflection, but also of seizing with its point the glutinous matter which proceeds from it, drawing this into threads, and thereby, in some measure, securing the animals within the sand which they inhabit.

Few of our shell-fish are more common, in inlets and bays near the mouths of rivers, than these. In such situations they are usually found immersed at the depth of two or three inches in the sand, the place of each being marked by a small, circular, depressed spot.

[graphic]

CARDIUM OPENED.

OF THE OYSTER TRIBE.

OYSTERS are bivalve shell fish, having the valves generally unequal. The hinge is without teeth, but furnished with a somewhat oval cav. ity, and mostly with lateral transverse grooves.

There are few tribes of shell-fish more numerous or more generally dispersed over submarine rocks and sands, in all parts of the world, than these. The greater number of them are wholesome and extremely palatable food.

From a similarity in the structure of the hinge, the Oysters and Scallops have been united into one tribe. But they differ very essentially, both in their habits and external appearance. The oysters adhere to rocks, or, as in two or three species, to roots of trees on the shore; while the Scallops are always detached, and usually lurk ir the sand.

THE COMMON OYSTER, AND GREAT SCALLOP

It is the nature of Oysters in general to have their lower valve fix od to rocks or loose stones, and frequently even to each other. Some of them, however, are loose; these have very thin shells, and are more regularly shaped than the others.

« PreviousContinue »