CLASS MOLLUSCA.

In noticing the animal of a univalve shell, the part which more readily attracts the attention is the mantle, which covers the head of the creature, something like a hood; it varies much in form and size in different genera. The eyes, which in the sepia are amazingly large and brilliant, are very minute in most of the other tribes, although they are frequently visible, and would appear, from their formation, to be of little use as organs of sight; indeed, it is supposed, that in the snail they are devoted to the sense of smelling.

The organs of motion in the Mollusca, according to their different form and position, give names to most of the orders; these consist of muscular expansions of the body, by means of which the animal swims or drags itself along the ground. The gills, or breathing apparatus, are situated internally, and communicate with the air or water, by means of a small canal opening outwardly. The mouth is usually concealed from view when the creature is at rest; in some, this organ is furnished with a hard substance, which supplies the place of teeth, while, in others, it is in the form of a projecting tube. The greatest portion ofthese creatures are produced in the water, the tribes that inhabit that element, exceeding by far those that are to be found upon the land.

The Molluscous animals have been separated into the five following Orders:—

The creatures belonging to this order, says Lamarck may be considered as the first vestiges of the appearance of a series of marine animals, intermediate in their formation between the fishes and the Cephalopods; they are all natives of hot climates, and possess a body of a jelly-like substance, and so transparent as to be seen with difficulty when floating in the water. They do not all possess shells, and are less known than they otherwise would be, on account of the great difficulty there is in preserving them.

This singular animal is rarely taken, on account of its delicate and perishable substance; it is found in the Southern Ocean. It will be seen, on referring to the engraving, that the shell which it bearsmerely covers a portion of its body, that in which the most material organs of the animal are found, namely, the heart and the branchiæ, or organs of breathing. These are most curiously placed on the upper part of its body, projecting from it and protected by a delicately white and transparent shell, shaped like a little cap, and of a substance resembling glass. The creature is able to enlarge its body by filling it with water, and in swimming the back is undermost. The shell, which seldom exceeds an inch in length, has been sought after by collectors with great assiduity, and has, at times, fetched as much as ten guineas at a sale; a perfect specimen is very rarely met with. There is a wax model of one of these shells in the British Museum, nearly two inches wide.

THE GLASSY CARINARIA, (Carinaria vitrea.)

The Cephalopods have been so named by Cuvier, from being furnished with a kind of inarticulated arms which surround the head. We find among this class some of the most singular productions of the waters; they differ materially from each other, and have been separated into threegroups; first, those without any external shell, as the Sepia; secondly, the inhabitants of a shell without any divisions, as the Argonaut; and, thirdly, those whose shell is divided into numerous chambers, as the Nautilus.

The Cuttle Fish, of which there are many different species, is a native of all the temperate and tropical seas. Its body is, in general, of an irregular oval shape, and of a jelly-like substance, and usually covered with a coarse skin, having the appearance of leather. Unlike all other inhabitants of the water which are without a backbone, the Sepia possesses two large and brilliant eyes, covered with a hard transparent substance.

TheCuttle Fish, figured in the engraving, is furnished in front with eight arms or feelers, with which it grapples with its enemy, or conveys its prey to its mouth. These arms are most curiously constructed, and afford it ample means of defence; they possess in themselves a strong muscular power, and this is materially assisted by numerous cups or suckers, placed along the whole of their inner surface, with which they fasten themselves to any object they come in contact with. These feelers appear to be also endued with some peculiar power, of a galvanic nature; since the pain which they inflict does not cease for a long time after the removal of the animal, leaving a kind of stinging sensation, like that produced by nettles, which remains for many hours, and is followed by a troublesome irritation and itching.

THE CUTTLE FISH.

BEAK OF ACEPHALOPOD.

The size to which this creature grows has been variously stated; and, although evidently exaggerated by some authors, there can be no doubt that it attains a very considerable magnitude. When attacked in its own element, it has been known, even in the seas of temperate latitudes, capable of overcoming a powerful mastiff. The jaws of all this tribe are, likewise, extremely strong, formed like the beak of a parrot, and very hard. In addition to these means of defence, it possesses within its body a bladder, containing an inky-coloured fluid, which it has the power of throwing out at will, and, by thus discolouring the water, it escapes the pursuit of its enemies. This inky liquid, when dried, forms a very valuable colour, used by artists, and called, after the animal,Sepia. The eggs of the female are of an oval form, and joined to each other in clusters. They are of the size of filberts, of a black colour, and commonly known by the name ofSea Grapes. They are found attached to sea-weed, rocks, and other marine substances.

TheCuttle Fishgenerally remains with its body in some hole in a rock, while its arms are extended in every direction, to seize the wanderer that may chance to pass its place of ambush. Its appetite is voracious, and it seizes as its prey every living thing that it has the power to conquer.

The species figured in the engraving is very common on the English coasts, and the bone which is enclosed in its body is frequently found on the sands; it is a well-known substance, and much employed in the manufacture of tooth-powder. This bone, which, with the exception of the jaws, is the only solid part in the Sepia, differs in shape inthe different species, but is always somewhat oval in its form, though varying considerably in texture.

The tender Nautilus that steers its prow,The sea-born sailor in its light canoe.

He, when the lightning-winged tornadoes sweepThe surge, is safe; his home is in the deep.He triumphs o’er the armadas of mankind,That shake the world, but tremble in the wind.

The curious inhabitant of this elegant shell has, from the earliest ages, excited the admiration of the student in natural history; and, at the same time, its real place in the system has eluded the research of the most acute observers. The animal agrees, in many points, with the sepia, or cuttle fish, which never possesses a shelly covering, so that, had it been found without that beautiful addition, naturalists would have referred it, without hesitation, to that particular division of the dwellers in the deep; it is, however, always met with along with the shell; and, although there appears to be no bond of union between the tenant and its dwelling, still the purposes to which it applies it, imply, at any rate, a long-continued occupancy, if they do not absolutely point out the Nautilus as the original architect of the shell.

The name Argonaut has been applied to this sea-born navigator from its resemblance, when floating on the surface of the waves, to a vessel in full sail, Argo being the name of the ship, which was supposed to have been the first fitted out for commercial adventure.

THE ARGONAUT, OR PAPER NAUTILUS.

In calm Summer days, these beautiful little creatures may be seen, in considerable numbers, steering their little barks on the surface of the waters of the Mediterranean. The words of the ancient Roman naturalist, Pliny, give a pleasing description of its habits. “Among the principal miracles of nature,” says he, “is the animal called Nautilos, or Pompilos: it ascends to the surface of the sea, in a supine posture, and, gradually raising itself up, forces out, by means of its tube, all the water from its shell, in order that it may swim more readily; then, throwing back the two foremost arms, it displays between them a membrane of wonderful tenuity, which acts as a sail, while, with the remaining arms, it rows itself along, the tail in the middle acting asa helm to direct its course, and thus it pursues its voyage; and, if alarmed by any appearance of danger, takes in the water and descends.”

Although the Argonaut has never yet been discovered attached to its shell, some observations which have been recently made on the Pearly Nautilus, which very nearly resembles it, have almost proved that such a connexion does really exist. But whether the shell is formed by itself, or only used to assist the creature in its movements, the instinct displayed is not the less wonderful, or worthy of observation. The Mediterranean, and warmer parts of the Atlantic, abound in these interesting animals, and one species is also found in the Indian Ocean.

The inhabitant of this singular shell had long been sought after with eagerness by naturalists, and it is only within these few years that its true nature has been ascertained. We are indebted for this knowledge to the researches of the late Mr. George Bennet, who, while engaged in a voyage among the Polynesian Islands, captured a specimen containing a living animal, which was brought to England, and is now deposited in the Museum of the Royal College of Surgeons in London.

The shell of the Nautilus, as may be seen by the engraving, is divided into numerous cells. The use of these cells to the animal we are now describing, was formerly not well understood, but they were supposed to be employed, by their inhabitant, for the purpose of rising or sinking in the Water at will. The body of thisCephalopod, it will be seen, only occupies the outer cell of its habitation, its increased sizehaving rendered it too large to remain in that preceding it. If, as the animal deserted its smaller tenements, one after the other, they had been filled, up with solid matter, the shell would have become too cumbersome for its owner; so that we have here another proof of the providing care of the Creator. We shall describe, in Mr. Bennet’s own words, the capture of this interesting object.

THE PEARLY NAUTILUS,Showing the Animal, and a Section of its Shell.

THE PEARLY NAUTILUS,

Showing the Animal, and a Section of its Shell.

“It was on the twenty-fourth of August, 1829, (calm and fine weather, thermometer at noon 79°,) in the evening, when the ship Sophia was lying at anchor, in Marakini Bay, on the south-west side of the island of Erromanga, one of the New Hebrides group, Southern Pacific Ocean, that something was seen floating on the surface of the water, at some distance from the ship; to many it appeared like a small deadtortoise-shell cat, which would have been such an unusual object in this part of the world, that the boat, which was alongside of the ship at the time, was sent for the purpose of ascertaining the nature of the floating object.”

“On approaching near, it was observed to be the shell-fish, commonly known by the name of thePearly Nautilus: it was captured and brought on board; but the shell was shattered from having been struck with the boat-hook, in taking it, as the animal was sinking when the boat approached, and, had it not been so damaged, it would have escaped. I extracted the fish in a perfect state, which was firmly attached to each side of the cavity of the shell.” The hood has been stated by Dr. Shaw, as being “of a pale, reddish-purple colour, with deeper sports and variegations,” the colour, however, as it appeared in this recent specimen, was of a dark reddish-brown.

SHELL OF THE NAUTILUS; AND THE SEA-PEN,OR INTERNAL SHELL OF THE LOLIGO.

Although this is the only instance of the animal itself having been brought to this country, there is but little doubt of its having been frequently taken, but as the shell was the object of the captors, and not its inhabitant the latter has been thrown away as useless. An office in his Majesty’s Navy found a Nautilus in a hole in a reef of rocks, near an island on the Eastern coast of Africa; the mantle of the fish, like a thin membrane, covered the shell, which was drawn in as soon as it was touched, and the elegant shell was then displayed. “I and others,” says the same informant, “when it was first seen did not notice it, regarding the animal, as the membrane enveloped the shell, merely as a piece of blubber; but having touched it by accident, the membranous covering was drawn in, and we soon secured our beautiful prize.”

Rumphius, a German naturalist, appears to have been acquainted with its habits; he says, “When he thus floats upon the water, he puts out his head, and all his barbs, and spreads them on the water, with the poop of the shell above water: but at the bottom he creeps in a reverse position, with his boat above him, and with his head and barbs upon the ground, making a tolerably quick progress. He keeps himself chiefly on the ground, creeping sometimes also into the nets of the fishermen: but after a storm, as the weather becomes calm, they are seen in troops floating on the water, being driven up by the agitation of the waves. This sailing, however, is not of long continuance, for having taken in all their tentacles, they upset their boat, and so return to the bottom.”

The Trachelipodes contain by far the largest portion of the univalve shells, and are mostly inhabitants of the waters. They form two numerous groups, the feeders on animal food, (Zoophagi,) and those that exist on vegetable substances, (Phytophagi.) The animal feeders are well distinguished from the other group, by having a mouth without jaws, being furnished with a tube which they can retract or advance at pleasure, for the purpose of sucking their nutriment from the bodies of other inhabitants of the deep. The animal feeders are also known from the other section by the possession of a projecting tube called asiphon, which conveys the water to the gills. The shell also points out to which section its possessor belonged, from the lower part of its opening being formed either into a sort of canal, or a groove for the reception of its siphon. They are all marine animals, and breathe water. The flesh-eating tribes compose five families.

FamilyCONVOLUTA.

The convoluted shells contain but few genera; but these are very rich in species, and furnish us with some of the most beautiful specimens of this class.

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