366

THE BEAKED SPINDLE-SHELL.

found for the fossils. It must, therefore, suffice in the present instance to remark that the well-known ammonites, rams'-horns, and other similar fossil shells, belonged to the same order as the Chambered Nautilus.

The colour of the shell is very beautiful. The ground is white, over which are drawn, as with single dashes of a painter's brush, sundry bold streaks of reddish chestnut, mostly coalescing above, and reaching nearly to the centre of the spiral. This porcelainlike material is, however, only an outer coat laid on the real pearly substance of the shell, which is seen on looking into the hollow or into any of the chambers. The Chinese avail themselves of this double coating, and, with the untiring perseverance of their laborious nature, take the greatest trouble to spoil the finest shells, by covering them with their grotesquely unperspective carvings of figures and landscapes, cut so as to relieve the deep colour of the raised figures by the white pearly background. Unlike the shell of th argonaut, which is almost as fragile as if made of sugar, that of the Nautilus is firm a strong, and will bear a considerable amount of rough handling before betraying any signs of injury.

WE now take leave of these highly developed molluscs, and pass to another order where the organization is not nearly so perfect, and where the habits are either so commonplace as to be devoid of general interest, or the animals so shy that they never can be seen performing any act which is likely to attract the attention of an unprofessed naturalist.

The last order of molluscs are named cephalopods, because their feet surround their head. The order which now comes before our notice is composed of animals which crawl upon a broad muscular organ, termed, from its use, the foot. It is an enormously large order, containing all the snails, whether terrestrial, aquatic, or marine, the whelks, limpets, and similar animals not so familiarly known. Many species are much used as food, while others are of great service in the arts, furnishing employment to many hundreds of workmen. As the shell of these creatures consists of one piece or valve only, they are sometimes termed univalves, in contradistinction to the oysters, muscles, scallops, and similar shells, which are termed bivalves, in allusion to their double shell.

Passing by, for the present, the mere anatomical peculiarities of these creatures, and leaving them to be mentioned in the Table of Generic Differences at the end of the volume, we will proceed at once to our first example of the gasteropods, the BEAKED SPINDLE-SHELL, so called from the rather distant resemblance which its long and pointed form bears to a spindle, and the elongated beak-like process which is seen pointing downwards to the ground as the animal walks along. The right-hand figure represents the Beaked Spindle. In the family to which this mollusc belongs, the lip of the shell is always extended and deeply notched.

The animal possesses large and well-developed eyes, set on stout and moderately long footstalks, from each of which a small tentacle proceeds. The foot is small, and not well calculated for crawling, but more adapted for the abrupt leaping style in which these animals proceed, their weighty shell swaying from side to side in rather an awkward

manner.

There is a structure belonging to these animals which must be described before proceeding further, inasmuch as its shape and comparative dimensions often afford valuable indications by which a species, or even a genus, may be distinguished. This structure is called the "operculum," and its use, when fully developed, is to close the aperture of the shell, when the animal has withdrawn itself into the recesses of its home. The operculum can be well seen in the water-snails, where it attains its full size, and exactly fits the opening which it is intended to protect. The material of which the operculum is essentially composed is a horny substance, but in some species the horn is strengthened by layers of the same nacreous matter which lines the shell, and becomes so thick and heavy that, when found separate from its owner, it is often mistaken for some species of shell. The operculum is very variable both in its form and comparative dimensions, and even in its presence or absence. Sometimes it is circular, like a flat plate, and composed of concentric circles, while in some species it assumes a regularly spiral form, like a flattened watch-spring.

THE THREE-HORNED STROMB.

367

Whatever be its shape, it is always developed from a well-defined spot, termed the nucleus, which is in many cases, but not in all, the centre of the structure. The forms of this most variable plate are too numerous to be separately described, but in the course of the following pages the reader will often find the operculum represented in its place on the mollusc, and will be able to form a better idea of it than would be gained by mere description. In many instances the operculum is only rudimentary, and in others is so very small in proportion to the dimensions of the shell that it is quite incapable of closing the opening. This is mostly the case with shells which have very wide-spreading mouths. It is a curious fact that the operculum is developed at the same time with the shell, and even within the egg this plate may be detected upon the inclosed mollusc.

On reference to the engraving, the reader will see the animal represented as in the act of walking, a feat which, on account of the small size of the foot, is not achieved with much ease. In front of the foot may be seen the siphon pointing downwards to the ground, and on each side of the siphon are set the footstalks, which carry the eyes at their extremities and a tentacle about the centre. The colour of the Beaked Spindle-shell is a pale brownish chestnut, with a slight wash of yellow. The beak, a long spiny process of the shell, is edged with black, and the inside is pure white. The surface of the shell is smooth, and its length is about five inches in a good specimen.

ON the left-hand of the engraving is another shell belonging to the same family, the THREE-HORNED STROMB, represented empty, and lying on the ground in order to show the curious form of its lip.

The Strombs form a large genus, containing about sixty species, and are found in almost every warm sea. They do not appear to be deep-water lovers, being mostly found on the reefs at low water, and seldom extending their range beyond ten fathoms. The operculum of the Strombs is rather curious in its structure, the nucleus being set at one extremity, and the operculum being made up of a succession of horny plates or scales

368

THE COMMON SPIDER-SHELL.

overlapping each other like the tiles of a house, or the successive steel layers of a carriage-spring.

Some species of Strombs attain a considerable size, and are much used in the arts, as, for example, the GIANT STROMB, or FOUNTAIN SHELL (Strombus gigas), one of the West Indian species, which sometimes attains the weight of four or five pounds, and is imported into Europe in several thousands for the use of engravers, who cut the wellknown cameos from its beautifully tinted substance. Three hundred thousand of these shells were brought to Liverpool alone in a single year. As the animal increases in age, it gradually fills up the hollow apex and spines with solid matter, and thus materially adds to the weight of the shell without improving its value to the engraver. In some parts of the world, such as Barbadoes, the Giant Stromb is eaten, and sold regularly for that purpose. Pearls of a delicate pink colour have sometimes been found in this shell, but their occurrence is not frequent, probably on account of the careless and unobservant habits of the negroes who clean the shells. Pearls are also found in other species belonging to this genus.

The teeth of the Strombs are extremely beautiful and most complicated, but cannot well be described without the aid of illustrations.

The colour of the Three-horned Stromb is brown and yellow of different shades, richly mottled with pale saffron. Its average length is about four inches.

THE two species represented in the illustration derive their popular names from the generally spider-like contour of their form.

When adult, the outer lip is furnished with several horny appendages, always curved, and not precisely of the same shape in the same species, although the general character of their form is sufficiently well marked to distinguish the species. One of these horns is always close to the spine, and is rolled in such a manner as to form a posterior canal. About ten species of these animals are known, and seem to be confined to the Chinese and Indian seas.

The COMMON SPIDER-SHELL is seen on the left of the illustration, the animal being represented in the act of crawling, the foot being applied to the ground, the operculum trailing behind, and the two eyes in their long footstalks projecting in front. The colour of this shell is very handsome, consisting of boldly mottled chestnut, like the hue of old rosewood, variegated with white, and traversed by lines of orange. The interior of the shell is pale brown, with a dash of yellow. The average length is three or four inches.

On the right-hand may be seen the empty shell of the ORANGE-MOUTHED SPIDERSHELL, so disposed as to exhibit the curious projecting horns, with their sharp points and bold curves. It is worthy of notice that in all the Spider-shells these projections are not developed until the creature has attained adult age, the young Spider-shell resembling that of the stromb. From the peculiar shape of some of the species, these creatures are sometimes called SCORPION-SHELLS.

The colour of the Orange-mouthed Spider-shell is creamy white on the exterior, and rich orange within. The curved spines are white and shining, and bear no small resemblance to the poison-teeth of serpents.

THE shells that are included in the family of the Muricida may readily be distinguished by the straight beak or canal in front, and the absence of any such canal behind. The eyes of these animals are not placed on long footstalks, as in the preceding family, but are set directly on the tentacles, without any supporting stalk or projection. All the animals belonging to this family are not only carnivorous, but rapacious, preying on other molluscs, and destroying them with the terrible armature called the tooth-ribbon, and which, when examined with the microscope, proves to be a set of adamantine teeth, sharp-edged and pointed as those of the shark, and cutting their way through the hard shells of their victims as the well-known cordon saw passes through thick blocks of hard wood.

About one hundred and eighty species are known to belong to the typical genus, and there is hardly a portion of the world where a Murex of some kind may not be found.

THE larger of the two specimens represents the shell which is popularly known under the name of THORNY WOODCOCK, the latter title being given to it, in common with several

of its congeners, on account of the long beak, which is thought to bear some resemblance to that of the woodcock, and the former in allusion to the vast number of lengthened spines or thorns which are arranged regularly over its surface. It has also received the equally appropriate and more poetical name of VENUS' COMB.

This shell is found in the Indian Ocean, and varies greatly in dimensions, four or five inches being about the average length. It is evident that as nothing is ever made in vain, or to be wasted, the wonderful array of external spines must play some important part in nature, if not in the economy of the particular species. But what that part may be, and what may be the object of these beautiful structures, is a problem which seems almost insoluble, at all events, with our present means of discovery.

The colour of the shell is very pale brown, each ridge being slightly tuberculated and edged with white. The spines are uniform drab, or very pale brown, with an almost horny translucence.

ANOTHER species is given in the same illustration, in order to show the animal and the position of the eyes, to which reference has already been made. This is the BRITISH WOODCOCK OF HEDGEHOG SHELL, a creature which, as its popular name imports, is a native of our seas. It is very much smaller than the thorny woodcock, and affords a good example of the contrast that can often be effected by different animals which yet belong to the same genus. Its length is hardly more than an inch and a half, and its colour is a pale yellowish brown.

IF the so-called tongue-ribbon be carefully removed from the owner, and mounted on a glass slide for microscopic purposes, it can be examined with the attention it deserves, and by its great beauty will be sure to repay the labours of the observer. This beautiful structure contains a vast series of the teeth already mentioned; and although the general formation of these organs and their arrangement is alike in all the Muricida, the teeth themselves are varied in an almost incredible manner, and are so differently shaped, that the particular species can be recognised by one who is conversant with these structures, merely from a glance at the tooth-ribbon. By means of this curious and complicated apparatus, the carnivorous animal is able to attack other molluscs with unfailing certainty. In vain do they retire into the recesses of their shelly homes, for the rasp-like teeth of their assailants soon bore a hole through the opposing walls, and enable the marauder to kill and devour the victim at its leisure. Perhaps it would be more correct to transpose the two verbs, and say, devour and kill, for in the molluscs the life retains its hold of the body with such tenacity, that the greater part of the substance may be actually eaten by the slayer, while the remainder is still quivering with life, or even endeavouring, with vain instinct, to crawl away from its foe.

The reader has, doubtlessly, while wandering on, the seashore, picked up many shells in which a round hole had been made, as perfectly circular as if cut with a drill. This hole is an unfailing indication that the quondam owner of the shell has fallen a victim to some mollusc such as we have just been describing, and whose task seems to be the continual restoration of the balance of nature, which would be disturbed by the unlimited increase of the vegetable-eating shells.

ONE or two other species belonging to this genus require a passing notice. The WOODCOCK'S HEAD (Murex haustellum), remarkable for its long peak and rounded shell, inhabits the same localities as its more beautiful neighbour, being found in the Indian and Chinese seas. It has but few of the spines which decorate the thorny woodcock in such profusion, and even those which are seen upon the surface are comparatively short. The rounded body of the shell, however, together with its long beaked process, does really bear some resemblance to the head and bill of the bird from which it takes its popular name.

The ROYAL MUREX (Murex regius) is a very fine example of this genus, and is valued, not only for its rarity, but for the extreme beauty of its form and colouring, which render it an ornament to any cabinet. In colour it resembles the thorny woodcock.