CHAPTER XIV.

PULMONARY GASTEROPODS.

The _Pulmonary Gasteropods_ comprehend those molluscs which, as we have said, live in the air and breathe the natural atmosphere. The respiratory organ is a cavity in the walls of which the blood-vessels form a complicated network. The air enters this cavity through an orifice, which the animal opens and shuts at will--a species of lung, in short, which is placed upon the back of the animal. They are both terrestrial and aquatic animals. In the latter case, they must come to the surface of the water in order to breathe, like the phocas and cetacea among the Mammifera.

The Pulmonifera, the second order of Gasteropods, comprehends those animals which live in and breathe the air.

It is divided into four sections; the Operculata, or animals whose shells are closed by an operculum, and the In-Operculata, or animals without operculum.

Operculata is divided into two families; first, Aciculidæ, types, Geomelania and Acicula; and second, Cyclostomidæ, types, Pupina and Cyclostoma. Cyclostoma is perhaps the best known; the mouth is circular, the name being derived from _cyclos_, circle, and _stoma_, mouth.

The second section, In-Opercula, contains five families.

First, Auriculidæ, types, Conovulus and Auricula.

Second, Limnæidæ, types, Planorbis, Physa, and Limnæa.

Third, Oncidiadæ, types, Vaginulus and Oncidium.

Fourth, Limacidæ, types, Testacella and Limax.

Fifth, Helicidæ, types, Clausilia, Pupa, Achatina, Bulimus, Succinea, Vitrina, and Helix.

LIMNÆIDÆ.

The Limnæidæ, _Aquatic Pulmonary Gasteropods_, is the second family of the series. They belong to the group that come to the surface of the water to breathe, as do the cetacea and phocas among the Mammifera. The _Limnæa_, _Planorbis_, and _Physa_ are the principal members of this group.

Limnæa lives in great numbers in the stagnant waters of all countries, particularly of temperate climates. It cannot remain long under water, being compelled frequently to rise to the surface in order to breathe atmospheric air. It is even observed, by a mechanism not very well understood, to turn itself upside down, in such a manner as to present itself feet uppermost, and to move slowly along in this position, creeping, as it were, through the water. It is difficult to comprehend how the movable liquid bed upon which the animal operates can offer resistance enough to permit of its creeping as if it were on a solid resisting body; it seems to produce the movement with the assistance of its foot, which is broad and thick, and shorter than the shell.

Limnæa has a large flat head, from each side of which issues a triangular contractile tentacle, carrying at its base and on the inner side an extremely small dot, or eye. The most considerable part of the body, comprehending the visceral mass, is spiral, and is contained in a thin diaphanous shell (Fig. 188), the turns in the spiral of which are generally elongated, the last turn being larger than all the others. The interior of this is occupied by the respiratory cavity, which communicates outwardly by an opening analogous to that which exists in the snails. This opening dilates and contracts in such a manner as to receive the air in the cavity, and exclude water when the animal feeds itself under the water. The mouth is a transverse slit between two rather thin lips, and is armed with small canine teeth. When the animal sallies from its shell, it has the appearance of a short trumpet. In its interior is a roundish, thick, and fleshy tubercle, not unlike the tongue of a paroquet. The true tongue, however, which lies at the bottom of the slit, is flat, oval-shaped, and supported by a cartilaginous or bony pedicle.

Limnæa, aided by this very complicated buccal apparatus, is enabled to feed itself with vegetable substances, such as the leaves of aquatic plants, which it cuts and bruises with its teeth. They are very active in the season, reproducing towards the end of spring. At this period little oval or semi-cylindrical masses are frequently found adhering to floating bodies, glittering and transparent as crystal. These are agglomerations of the eggs of Limnæa. When winter sets in, the _Limnæa_ of our climate fall into a state of torpor, and sink, more or less deeply, into the mud of the lakes, marshes, rivers, or brooks, which they inhabit.

They are of great utility, both to feed fishes and aquatic birds, and also as scavengers of the decaying vegetation of brooks.

Planorbis has an organization analogous to Limnæa, of which it is the faithful companion in stagnant waters. Their shells (Fig. 189) are thin, light, and disk-like in form, rolled round its plane in such a manner as to render all the turns of the spiral visible from above as well as below; it is concave on both sides, with an oval, oblong-shaped opening, and with an operculum or lid. The animal is conformable to the shell in shape. The visceral mass forms a very elongated cone, which unwinds itself absolutely, according to the spiral turns of the shell. The foot, or abdominal locomotive mass, is short, and very nearly round. The head is sufficiently distinct, and furnished with two very long filiform, contractile tentacles, having at their base, and on the inner side, a small organ, which looks like an egg. The mouth is armed in the upper part with cross-cutting teeth, and in the lower part with a tongue, bristling with a great number of hooked excrescences.

In habits Planorbis resembles Limnæa: it creeps like it on the surface of solid bodies, and swims in the water with the foot upwards and the shell down. It feeds on similar substances, and its eggs are collected in gelatinous masses also. It passes the winter in a state of torpor, buried in the mud of the rivers it inhabits.

The principal species is _Planorbis corneus_ (Fig. 189) which is common in the rivers of England and France.

Another group of molluscs, which occupy our fresh rivers, and swim with the shell down and feet up, is represented by _Physa castanea_ (Fig. 190). The genus _Physa_ have an oval, oblong, or nearly globular shell, very thin, smooth, and fragile, opening longitudinally, narrow above, with the right edge sharp; the last turn of the spiral being largest of all.

The animal appears to be intermediate in form between Planorbis and Limnæa: it is oval in form, and unrolls itself like the Limnæa, but its tentacles, in place of being triangular and thick like the latter, are elongated and narrow, like those of Planorbis. These little inhabitants of fresh water swim with facility, the feet upwards, the shell below, and like Limnæa, they feed on vegetables.

The fourth family, Limacidæ, containing Testacella and Limax, are terrestrial pulmonary molluscs, entirely naked, or having only a very small shell. The Limax varies very considerably in appearance, in consequence of its extreme contractibility. When seen creeping along on the surface of the soil, it has nearly the form of a very elongated ellipse, at one extremity of which is the head; the surface of the body in contact with the earth is flat, the other convex. Towards the anterior extremity, and upon the middle of the back, a portion of the skin projects as if it were detached from the body, and is ornamented with transverse stripes of various convolutions. This part is named the cuirass, or buckler, under which the animal can hide its head.

The mouth is a transverse opening in the front of the head; above are two pairs of tentacles, or horns, immensely retractile, cylindrical, and terminating in a small button; the lower tentacles are the shorter; the upper present at their summit a black point, as in _Helix_, which have sometimes been mistaken for the eyes.

Upon the right side of the cuirass, and hollowed in the thickness of its edge, which is large and contractile, whose function it is to give access to atmospheric air, it abuts on an internal cavity, also large, and is intended to promote respiration. The outer skin, or epidermis, is rayed in brownish furrows, its surface covered with a viscous glutinous substance, which permits of the animal creeping up the smoothest surfaces, locomotion being produced by the successive contraction and extension of the muscular fibres of the feet.

The internal organization of the Limax is analogous to that already described in the snails. The taste and smell in the Limaceans differ only very slightly from those organs in Helix. They are, like the snails, deaf, and nearly blind. They love humid places; they lodge themselves in the holes of old walls, under stones, or half-decomposed leaves, in the crevices of the bark of old trees, and even underground, coming forth only at night and in the morning; especially after soft showers in spring and summer. In the garden, after one of these soft showers, many of these little creatures are sure to be met with in the more shaded alleys.

The Limax is mostly herbivorous. They seek, above all, for young plants, fruits, mushrooms, and half-decayed vegetables. They are very voracious, and cause great ravages in gardens and young plantations, and many are the devices of the watchful gardener to destroy them. Lime and salt are their abomination; ashes and fine sand they avoid. They dislike the noonday sun, and the gardener knows it; he arranges little sheltering tiles, or planks of wood and stone, under which they retire, where they are surprised to their destruction.

There are thirty known species of Limax. Some are remarkable for their very striking colours. _Limax rufus_ (Fig. 191) is common in woods, and well known for its large size and its colour of rich yellowish red; it is known all over Europe, from Norway to Spain.

Among the Limaceans nearly destitute of shells we find _Testacella_ _haliotidea_ (Fig. 192), which is provided with a very small shell placed at its posterior extremity, just over the pulmonary cavity. This shell becomes more important in _Vitrina_, already spoken of as forming the point of transition between Limax and Helix. This passage from Limaceans entirely destitute of shells to those furnished with a very small shell, as in _Testacella_, is very exactly indicated by Nature. _Limax rufus_, spoken of above, presents, under the posterior part of the cuirass, calcareous, unequal, isolated granulations, which are, so to speak, the elements, as yet internal, of a shell which is on the point of being built. Other species in the same genus present under the cuirass a little rough, imperfect scale, which seems to be produced by a great number of these calcareous granulations, which show themselves in an isolated state in _Limax rufus_.

The Helicidæ is the fifth family we shall now consider.

It is only necessary to witness the snail as it creeps along the gravel walks of a garden, or in the damp alleys of a park, in order to see that it is a being of higher organization than the headless molluscs. The common snail (_Helix aspersa_) goes and comes; it roams and saunters after its own peculiar manner, searching for its food or its pleasure; it has a head and two prominent tentacles, which feel and seem to express their sensations; it has nerves, a brain, a strong mouth, and a well-formed stomach.

Without possessing a high order of intelligence, the snail is by no means imbecile; it knows very well how to choose a tree the fruit of which is agreeable to it. A fine cluster of grapes, a succulent pear, which the horticulturist devours with his looks, and hopes to devour otherwise, is sure to be the identical fruit which will be chosen by our enlightened depredator, the snail.

The body of the snail is oval, elongated, convex above, flat below. The convex or upper surface of the body is rugged, in consequence of the existence of numerous tubercles projecting slightly, and separated by irregular furrows; its anterior is terminated by an obtuse head, its posterior more flat and less pointed. All the flat portion, thick, soft, and upon which the animal moves itself by a creeping motion, bears the name of the foot. The head is not really very distinct, especially in the upper part, but the organs with which it is provided are prominent. These organs are in reality tentacles, although they are more popularly known as _horns_, especially among children--those charming ignoramuses--who have been taught to repeat the well-known stanza--

"Snail, snail, come out of your hole, Or else I'll beat you black as a coal"--

which finds its counterpart in all European languages. There are two pair of these tentacles or horns; one pair quite in front and above, and another smaller and less forward. The first are distinguished by their size, and also by a black spot or point at their extremity, which is sometimes erroneously said to be the eye of the snail.

These tentacles differ in many respects from the same organs in other molluscs; they are retractile, and can be drawn altogether within the animal into a sort of sheath, by the contraction of a muscle. At the anterior extremity of the head we find a sort of plaited opening, which is the mouth: it is of moderate extent, closed in front by two lips, and armed with two shear-like organs of horny consistence, one of them being a sort of rasp, which occupies the plate of the buccal cavity, and may be called a tongue; the other is a median jaw, placed transversely in the membranous walls of the palate, terminating in a free edge, armed with small teeth. This cutting blade, however, executes no movement; but the lingual organ, pressing all alimentary matter forcibly against its lower edge, effects their mastication, and enables it to dispose of fruit, tender leaves, mushrooms, and other substances easily divided.

At the bottom of the mouth is an oesophagus, or gullet, to which succeeds a stomach of moderate size. The intestine lies in folds round the liver, which is divided into four lobes, and terminates in a special orifice.

The little lung of the snail is placed in a cavity, vast for its size, just above the general mass of the viscera, and occupies all the last spiral turn of the cavity.

The mechanism of respiration is as follows: The animal inhales the air into its lung by forcibly dilating the pulmonary orifice, which lies in the largest spiral turn of the shell. In order to expel the air respired by the lung, it withdraws its body into the narrower part of the shell, where it gathers itself up completely, even to its head and feet, and by this compression of all its little being it expels the air which fills it. These respiratory movements, however, are not regular, but succeed each other only at certain intervals. Life would be too hard for the poor snail were it passed in such violent efforts as would be necessary if it respired as the larger animals do. In its case the breathing is intermittent and imperfect; it is merely a rough attempt, as it were, at respiration, which becomes perfect in some of the higher branches of the animal kingdom.

The snail has a heart, consisting of a ventricle and auricle, connected with a well-developed arterial vascular system, while the venous system is imperfect. In short, the blood only returns from the various parts of the body to the respiratory apparatus, after traversing lacunæ, or air-cells, existing between the several organs.

The blood of the snail is of a pale rose colour, slightly tinted with blue. It has a rudimentary brain, composed of a pair of thick ganglions, situated above the oesophagus, which are in connection with another pair of ganglions placed below, which, together, form a sort of collar, or ring. From this ring springs a great number of nervous cords, which are distributed to the mouth, the tentacles, the lung, and the heart. The skin, in those parts covered by the shell, exhibits great sensibility; it receives a considerable quantity of nervous filament, so that the sense of touch ought to possess extreme delicacy.

The tentacles, the skin of which is so fine and so sensitive, are the organs of touch. Other functions are sometimes attributed to them; the anterior tentacles are sometimes considered to be the organs of smell. This, at all events, is certain, that the snail is very sensible of strong odours, and is easily attracted by many plants the odour of which pleases it.

The black points which terminate the first pair of tentacles have been considered as eyes: but the existence of a visual organ in the snail is not quite certain. They are quite insensible to sudden changes of light; they always travel in the dark, and never recognize obstacles placed before them. We may add that the snail is destitute of all organs of hearing. No noise appears to affect it, at least till the noise is so near as to agitate the air which immediately surrounds it. Indeed, the snail few has senses; the poor creature is at once blind, deaf, and dumb.

The snails are male and female in the same individual, or hermaphrodite. Their eggs are roundish, heavy, and of a whitish colour. The animal deposits them on the soil in little irregular heaps; at other times it deposits them one after the other, like the grains of a chaplet, in holes which it digs in the soil, or in the natural excavations created by moisture. The eggs are even found in the hollows of old trees; in fissures of walls or rocks.

When the young _Helix_ issues from the egg, it is already provided with an extremely thin membranous shell. The timid and tender youth is conscious of its weakness and full of humility. It rarely trusts itself out of the obscure hole in which it was hatched; when it does, it is only at night, dreading the desiccating air, and, above all, the sun's rays, even with the house it always carries with it for shelter.

This calcareous and velluted house is spiral, which the animal has the inappreciable advantage of transporting without fatigue. It is light, and sometimes quite disproportionate to the body of the animal, which it covers only in that part which contains the viscera and respiratory organs. The form of the shell is generally much variegated. Some are flattened, others are orbicular or globose; in some the spiral is very pointed. The edges of the shell are sometimes simple, sharp, and pointed; others, on the contrary, thick and inverted, presenting an edging of great solidity.

The spire is generally rolled up from right to left. A helix shell, the spiral of which follows the inverse direction, that is, from left to right, is a rarity much sought after by amateurs.

* * * * *

The ancients held snails in especial esteem for the table. The Romans had many species served up at their feasts, which they distinguished in categories according to the delicacy of their flesh. Pliny tells us that the best were imported from Sicily, from the Balearic Isles, and from the Isle of Capri, the last dwelling-place of the aged Tiberius. The largest came from Illyria. Ships proceeded to the Ligurian coast to gather them for the tables of the Roman patricians. The great consumption led to the establishment of parks (_Cochlearia_, Varro; _Cochlearum vivariá_, Pliny), in order to fatten the animals, as is now done with oysters. They were fed for this end upon various plants mixed with soup; when it was desired to improve the flavour a little wine and sometimes laurel leaves were added. These parks were formed in humid shady places surrounded by a foss or a wall. Pliny has even transmitted to us the name of the inventor of the _Cochleariæ_, a certain Fulvius Hispinus. Addison describes with details one of these establishments kept up by the Capuchins at Fribourg in Switzerland, in imitation of the ingenious Roman gourmet we have named.

Among the Romans, snails were served at the funeral repast. Certain heaps of their shells, which are found in the cemetery of Pompeii, are the remains of those funeral festivities with which the inhabitants of the buried city honoured the tombs of their friends and relations.

The practice of eating snails had fallen into disuse in Europe when, in the seventeenth century, John Howard, the philanthropist, began to collect them with the view of reintroducing them as human food. He chose _Helix Varronis_, which was probably the species cultivated by the Romans; it surpasses all those of Europe in size, and was found plentifully in the district of Bagnes, in the Valois. Howard, having procured the species from Bagnes, found their increase so rapid that the crops were likely to be devoured by the swarms of molluscs thus brought together, and steps were at once taken to destroy them. In other parts of Europe the snail continues to be sought for as an article of luxury. They are consumed at Vienna in great numbers during Lent, supplies being brought from the Swiss canton of Appenzell. At Naples a soup made from _Helix nemoralis_ is sold publicly to the strange population with which the streets of that city swarm, for the king's pavement is their bed-chamber, dining-saloon, and work-room. In France, snails are a valuable resource to the poor in the southern departments.

The flesh of all snails is not alike in a culinary point of view. Amateurs class as first in quality _Helix vermicula_, called at Montpelier the Little Hermit, because it buries itself so deeply in its shell. _Helix aspersa_ (Figs. 193, 194, 195) is thought to be more tender and delicate. In Provence a species is called _tapada_, that is, "closed," from the cretaceous deposit with which it closes its shell.

In the north of France, and round Paris, _Helix pomatia_ is the favourite culinary snail (Fig. 196). This is the species which is used as a speaking sign-board over the doors of the wine-shops and small restaurants in the neighbourhood of the Halles, at Paris. Its shell is globose and tun-shaped, very solid, marked with irregular transverse stripes of a brownish rust colour, with bands, often nearly effaced, of a deeper tint, and of the same colour. The animal is large, of a yellowish grey, and covered with elongated irregular tubercles.

Besides _Helix pomatia_, according to Moquin-Tandon, they eat in the north of France _Helix sylvatica_ and _H. nemoralis_; at Montpelier, as we have already said, _H. aspersa_ and _H. rhodostoma_; at Avignon, also, these, along with _H. vermicula_, are favourites. In Provence, _Helix Pisana_, with _H. aspersa_ and _melastoma_, are preferred. At Bonifacio, _Helix aspersa_, _H. vermicula_, and, more rarely, _H. rhodostoma_; and in other localities the smaller species and young individuals of the larger kinds are employed for feeding poultry.

Certain species are also employed for feeding ducks. Thus, in the neighbourhood of Montpelier, ducks are fed upon _Helix variabilis_ and _H. rhodostoma_. Some fishes, especially the young salmon, are very partial to the flesh of snails.

This very important genera is very numerous in species, which are distributed in groups according to the form of the shell; that is, whether it be globulous, as in Fig. 197, tun-bottomed, as in Fig. 198, plain or biform, as in Fig. 199, or truncated, as in Figs. 200 and 201. These figures will give the reader some idea of the multiplied and elegant forms which the shells of _Helix_ sometimes assume.

In connection with the snails (_Helix_), we shall note some kindred genera which our space only permits us to name. Such is the genus _Bulimus_, the European species of which are numerous; some of them very small, others of medium size; of these, _Bulimus sultanus_ (Figs. 204 and 205). In Figs. 206 and 207, the Berry Pupa (_P. uva_), as an example of another genus, is represented.

Yet another typical species may be noted, which is found abundantly amid the grass and shrubs near brooks round Paris and elsewhere. It is _Succinea putris_, presenting a small, thin, diaphanous shell of a pale amber yellow, marked with close and very fine longitudinal stripes (Fig. 208). The _Achatina zebra_ of Chemnitz is a great snail, which devours shrubs and trees in Madagascar (Fig. 209). Finally, _Vitrina_, the shell of which is very small and very thin in some species--so small, indeed, in _Vitrina fasciata_ (Fig. 210), that the animal cannot fully enter the shell--occupies a point of transition between _Helix_ and _Limax_.

In the Pectinibranchial Gasteropods the gills are composed of numerous leaflets cut like the teeth of a comb, and attached, on one or many lines, to the upper part of the respiratory cavity. They constitute the most numerous order of Cephalous Molluscs, comprehending nearly all the univalve spiral shells, and many others which are simply conical. They inhabit the sea, rivers, and lakes, and are of all sizes. The most remarkable genera which we shall describe belong to the family of _Trochoïdæ_ and _Buccinoïdæ_.

The fourth order of Gasteropods, Prosobranchiata, which includes the Pecteni Branchiata, is distinct in the sexes, has the branchiæ pectinated, and the mantle forms a vaulted chamber over the back of the head. It is divided into two sections and twenty-one families. The first section, _Holostomata_, contains the sea-snails. The first family we shall treat of is the _Chitonidæ_, containing _Chitonellus_ and _Chiton_.

The _Chitons_ are very singular creatures, destitute of eyes, of tentacles, and without jaws; they bear upon their back in place of a shell a cuirass composed of imbricated and movable scales. They have the power of elongating and contracting themselves like the snails. They roll themselves up into a ball like the woodlouse. They adhere with great force to the rocks, preferring those places most exposed to the beating waves. _Chiton magnificus_ (Fig. 211) is widely distributed.

The second family, _Dentaliadæ_, affords the curious _Dentalium_, or tooth shell.

The _Patellidæ_, or Limpets, constitute a very numerous family, distinguished at once by the form and structure of the animal, and by that of the shell. Linnæus called it Patella, _i. e._, a deep dish or knee-cap.

The shells of the Patellidæ, our third family, are univalve, oval, or circular, non-spiral, but terminating in an elliptic cone, concave and simple beneath, non-pierced at the summit, entire and inclined anteriorly. They are smooth, or ornamented on the sides with ridges radiating from the summit, and often covered with scales; the edges are frequently dentate. The colours much varied. The interior is very smooth, and remarkable for the brilliancy and lustre of its tints.

The head of the animal is furnished with two pointed tentacles or horns, having an eye at the external base of each. The body is oval and nearly circular, conical, or depressed. The foot is in the form of a thick fleshy disk. Certain lamellar branchiæ are arranged in series all round the body.

The Limpets dwell upon the sea-shore, in the parts alternately covered and uncovered by the waves. They are almost always attached to rocks, or other submerged bodies, to which they adhere with great tenacity. If the common Limpet (_Patella vulgata_) is alarmed before any attempt is made to dislodge it, no human force, pulling in a direct line, can remove it, and it can sustain without being crushed a weight of many pounds. It holds on by the great quantity of vertical fibres of the foot, which in raising the median part forms in the centre a sort of sucker. It is the celebrated experiment of the Magdeburg cups which these little molluscs realise by their vital action.

These animals bury themselves in the chalky rocks to the depth of two or three lines; when they are dispersed, they are observed constantly to return to the same place. Their movements are, besides, extremely slow; the advance of the Limpet being only perceived by watching the slow upheaval of the shell above the plane of its position. It is supposed, from the mouth being armed on its upper edge with a large semi-lunar, horny, cutting tooth, and in its lower part from having a tongue furnished with horny hooks, and from their inhabiting in great numbers places covered with marine plants, that their food is chiefly vegetable.

The poorer inhabitants of the coast eat limpets when they have nothing else, but their flesh is singularly coriaceous and indigestible.

They are found in every sea; but are, however, found to be larger as well as more numerous, and much richer in colour, in Equatorial seas, and especially in the southern hemisphere, than in European seas. They attain, in fact, their maximum of development here; for in the Straits of Magellan species are found as large as a slop-basin, which the natives use for culinary purposes.

The common Limpet is thick, solid, oval, and nearly circular, generally conical, and covered with a great number of very fine stripes. Its colour is of a greenish grey, uniform above, and of a greenish yellow inside. It is abundant in the Channel and on Atlantic coasts.

The Blue Limpet, _Patella cærulea_ (Fig. 212), from St. Helena, has an oval shell, broadest behind, moderately thick, depressed, flattened, covered with angular wrinkles, and dentate on the edge. It is of a spotted green outside and of a fine glossy blue within.

Other very elegant species are _Patella umbella_ (Fig. 213), from the African coast. _Patella granatina_ (Fig. 214), the ruby-eyed Limpet from the Antilles; _Patella barbata_, the bearded Limpet (Fig. 215); and the long spined Limpet, _Patella longicosta_ (Figs. 216 and 217).

The fourth family, _Calyptræidæ_, types _Pileopsis_ and _Calyptræa_, was classed by the older conchologists with _Patella_. _Pileopsis Hungaricus_, the Hungarian bonnet shell, is rather abundant on some parts of the British coast.

The fifth family, _Fissurellidæ_, contains _Parmophorus_, the duck's-bill-limpet of Australia, and _Fissurella_, the key-hole-limpet, which is remarkable for the opening of the apex of the shell.

The sixth family, _Haliotidæ_, contains _Ianthina_, _Scissurella_, and _Haliotis_.

The attention of naturalists has long been directed to a curious mollusc known under the name of _Ianthina communis_ (Fig. 218); its body is globular, and it presents an opening in front without contracting itself in order to form the head, which is long and trumpet-shaped, terminating in a large buccal opening, furnished with horny plates, and covered with little hooks; and two conical tentacles, slightly contracted, but very distinct, each bearing at their external base a long peduncle. The foot is short, oval, divided into two parts: the anterior, concave and cup-shaped; the posterior, flat and fleshy. It is this foot, which bears a vesiculous mass like foam, which gives its peculiar character to the pretty mollusc. The mass consists of a great number of small bladders, which combine to keep the animal on the surface of the water. The shell is light, transparent, violet-coloured, and very much resembles the shell of the Helix. The _Ianthinas_ inhabit the deep sea, and often form bands of very great extent. Messrs. Quoy and Gaimard have seen legions of Ianthinas driven by the current. They have sailed during many days through these wandering tribes, which would be the sport of every gale if they could not, by drawing their heads within their shells and contracting their natatorial vesicles, diminish their volume and increase their weight at will, so as to sink quietly to the bottom of the water till the tempest was over. The _Ianthina_ possesses a liquid of a dark violet colour, which is believed by many naturalists to have been one of the purple dyes known to the ancients, if not the purple of Tyre: it is very common in the Mediterranean.

_Haliotis_, the ear-shell, is remarkable for its brilliant colours, and for a line of singular perforations in many of the species.

The seventh family, _Turbinidæ_, contains _Trochus_, _Turbo_, _Protella_, _Monodonta_, and _Delphinula_.

The genus _Trochus_ are found in all seas, and near to the shore in the clefts of rocks, especially in places where sea-weeds grow luxuriantly. Some of these thick, cone-shaped shells are extremely beautiful, being richly nacred inside, and remarkable for the beauty and diversity of colour exhibited. Generally smooth, the great spiral is, nevertheless, sometimes edged with a series of regular spines. The form is conical, the spiral more or less raised, broad and angular at the base; the opening entire, depressed transversely, and the edge disunited in the upper part.

The animal which inhabits this shell is also spiral; its head is furnished with two conical tentacles, having at their base eyes borne on a peduncle; its foot is short, round at its two extremities, edged or fringed in its circumference, and furnished with a horny operculum, circular and regularly spiral.

The family is divided into many sub-genera. Among the _Trochi_, properly so called, we may notice _Trochus niloticus_ (Fig. 219), _T. virgatus_ (Fig. 220), _T. inermis_ (Fig. 221), and _T. Cookii_ (Fig. 222).

The genus _Turbo_ are very generally diffused, being found on every shore, where they cling to rocks beaten by the waves. About fifty species are known, some of them large shells, others very small. _Turbo margaritaceus_ (Fig. 225) is large, thick, and weighty, round-bellied, and deeply furrowed; in colour it is yellow, or rust-coloured, marked by square brown spots. _Turbo argyrostomus_, the Silver-mouthed Turbo (Fig. 226), is still larger, with protecting spines on the top of its larger spiral. _Turbo marmoratus_ (Linnæus), the Marbled Turbo (Fig. 227), is the largest shell in the group. It is marbled, green, white, and brown, outside, and superbly nacred within. The Gold-mouthed Turbo is so named from its nacre being of a rich golden yellow. The Wavy Turbo (_T. undulatus_), (Fig. 228), vulgarly known as the Australian Serpent's Skin. The shell is white, ornamented with longitudinal waving flexible lines of spots of green, or greenish-violet. _Turbo imperialis_ (Fig. 229), from the Chinese seas, is green without, and brilliantly nacred within; it is vulgarly known as the paroquet.

The _Turbos_ are found in the North seas, in the Channel, and on the Atlantic coast. The animal is eaten in nearly all the sea-ports of the Channel.

_Rotella Zealandica_, from the Indian Ocean, whose shell, represented in Fig. 230, presents the most lively colours, forms one of a genus by no means numerous in species.

Near to the _Trochi_ and _Turbos_ in the system are the _Monodonta_.

The _Monodonta_ are elegantly-marked shells, belonging to the seas of warm countries. _M. Australis_ (Fig. 231) is a native of Australian seas. _M. labia_ (Fig. 232) is a small brown shell, with white spots, which is very common on the shores of the Mediterranean.

The eighth family is _Neritidæ_, of which we give as types, _Pileolus_ and _Nerita_. The hoof-shells, or Nerites, are numerous and pretty, and in external form approach _Turbo_.

Of the _Delphinula_ only a small number of living species are known. They are natives of the Indian Ocean, and remarkable for their numerous spines and the asperity of their shell (Fig. 233).

The ninth family, _Paludinidæ_, contains _Ampullaria_, the idol snail of India, and the widely distributed _Paludina_.

Our tenth family, _Littorinidæ_, contains _Solarium_, and the periwinkles, _Littorina_ and _Phorus_, example, _P. Conchyliophorus_ (Fig. 224).

The genus _Imperator_ belongs to the _Turbinidæ_, and as examples of it we may instance the Spurred Trochus, _Imperator stella_, which is studded with radiating spines (Fig. 234), and _Imperator stellaris_ (Fig. 235); they are natives of the Australian seas. _Imperator imperialis_, vulgarly called the Royal Spur, and _Trochus_ or _Rotella Zealandica_ (Fig. 230), the New Zealand Spur, the spiral turns of which are sculptured in descending furrows, and studded with imbricated scales, which form a projecting edging round the margin of the shell, and give it a radiating form. This species is of a violet brown above and white below, and is still rare in collections.

The Sun-dial (_Solarium_), recognized by its deep umbilicus, wide and funnel-shaped, in the interior of which may be seen the little crenated teeth which follow the edge of every turn of the spiral up to the top. In most collections of these pretty shells we find the Staircase-shell (_Solarium perspecticum_) of Lamarck, from the Indian Ocean (Figs. 236, 237), the diameter of which is sometimes two inches and a half. The Australian Sun-dial (_S. variegatum_, Linnæus, Fig. 238) is another species frequently seen in collections: it is as much variegated above as below, of a white and rusty brown. The minute trellised Sun-dial, which is only ten lines in diameter, comes from the coast of Tranquebar.

The eleventh family, _Turritellidæ_, types _Vermetus_ and _Turritella_, which last is a numerous family, being found in every sea. All these shells, as their name indicates, represent a winding pyramid, terminating in a sharp point, some of them having fluted spirals, others rounded, angular, or flat, and some of them elegantly pencilled. Figs. 239 to 243 represent some of the varied forms they assume.

The twelfth family, _Melaniadæ_, types, _Paludomus_ and _Melania_, fresh-water genera.

The thirteenth family, _Cerithiadæ_, types, _Aporrhais_ and _Cerithium_.

_Cerithium_ is a marine shell, which is found in muddy bottoms, on ships, and more frequently at the mouths of rivers, but rarely beyond the point to which the tide reaches. The genus is numerous in species. Such are _Cerithium fasciatum_ (Fig. 244) and _Cerithium aluco_ (Fig. 245).

The Giant Cerithium, _Cerithium giganteum_ (Fig. 246), is the living analogue of a magnificent fossil species belonging to the tertiary formation. The single known example of this species belongs to the Delessert Museum at Paris. A manuscript note by Lamarck, attached to this specimen, relates that this shell was first brought to Dunkirk in 1810 by an Englishman, one of the crew of an English ship. The English sailor had drawn it up from the bottom of the sea with the sounding-lead from a bed of rocks off the coast of Australia.

The fourteenth family, _Pyramidellidæ_, contains _Chemnitzia_ and _Pyramidella_, extremely pointed shells.

The fifteenth family, _Naticidæ_, contains _Lamellaria_ and _Natica_; the last of which is found in most seas.

The second section of the _Prosobranchiata_ is termed _Siphonostomata_, which are characterized by a spiral imperforate shell, the animal of which has sometimes a horny operculum, and is furnished with an elastic trunk, the margin of the mantle acting as a siphon. They are carnivorous.

The first family is the _Cypræidæ_, containing the well-known _Cypræa_ and _Ovulum_.

The Cowries, or _Cypræa_, are brilliant, smooth, and polished, oval-shaped, or oblong convex, with edges rolling inwards and longitudinal openings, narrow, arched, dentate on both edges, and notched at the extremities. The spiral, placed quite posteriorly, is very small, and often hidden by a calcareous bed of a vitreous appearance.

It is now known that the form and colouring of the shells vary very considerably, according to the age of the animal: so much so, indeed, that the same species examined at various stages of its growth would almost seem to belong to species and even to genera essentially different.

The young cowries are thin, conical, elongated; with conspicuous spiral, and large openings. The right edge soon becomes thicker, and folds itself inwardly; the opening is narrowed; finally, the spiral is unfolded in successive folds from the right edge, and by successive deposits of the vitreous matter we have spoken of the opening is gradually contracted, its extremities hollowed out, its edges disconnected, and the shell, until now only shaded in pale tints, assumes its most brilliant colours, disposed in bands or spots, as exhibited in PL. XXII., in which Figs. I. and II. are the adult shells, and Fig. III. the young shell, of _Cypræa Scottii_.

The animal which inhabits this shell is elongated, and is provided with a well-developed mantle, furnished on the inside with a band of tentacles; it is able to fold itself up in its shell in such a manner as to be enveloped all round. The head is provided with two very long conical tentacles, each having a very large eye, in which a pupil and iris can be distinguished. The foot is oval, elongate, and without operculum, and is well represented in _Cypræa tigris_ (Fig. 247). The cowries are found at a little distance from the shore, generally in clefts of the rocky bottoms; but sometimes they bury themselves in the sand. They are timid, shun the light, and only leave their retreats to creep about in search of food, which appears to be exclusively animal. These magnificent molluscs are natives of every sea. One small creature lives in the British Channel; another and much larger species is found in the Adriatic; but the Indian Ocean is the home of the largest and finest species of these shells.

As objects of curiosity and ornament these shells have been much in request in all ages. The inhabitants of the Asiatic coast make bracelets, collars, amulets, and head-dresses of them, and use them to ornament boxes and harness. In New Zealand the chiefs carry a rare and choice species, suspended from the neck, as a badge of their rank or sign of distinction. This is _Cypræa aurantium_. In some parts of India and Africa a very small species of Cowrie passes as current money. These shells are, indeed, extremely numerous, and we can only find room for very brief descriptions of a few of the best known among them.

The Waving and Zigzag Cowries, whose native country is unknown, are beautifully ornamented with waving and broken lines, as we see them in Figs. 249 to 252.

The New Zealand Cowrie, of which we have spoken above, is nearly globular, of a uniform orange colour above, and white below; the teeth of the opening are of a bright orange. The shell is rare, and much sought after.

The Money Cowrie, _Cypræa moneta_ (Figs. 253 and 254), is a little oval shell, depressed, flat below, with very thick edges and slightly waving. It is of a uniform yellowish white colour, sometimes citron-yellow above and white below. There are usually twelve teeth in the opening. It comes from the Indian Ocean, the Maldivian Isles, and the Atlantic Ocean.

This shell, so common in collections, is gathered by the women on the shore of the Maldivian Isles, three days after the full moons and before the new moons; it is afterwards transported to Bengal, to India, and Africa, where, as we have already said, it is used by the negroes and other natives as money.

The Madagascar Cowrie, _Cypræa Madagascariensis_ (Fig. 255), and the Granular Cowrie, _Cypræa nucleus_ (Figs. 259 and 260), are beautifully marked species, having the general appearance of the Cowrie.

The species most abundant in the Channel is the little _Coccinella_, already mentioned; it is very small, oval, tun-bellied, the opening dilated in front with smooth transverse stripes of greyish, tawny, or rose-colour, with or without spots.

_Cypræa mappa_ (PL. XXII., Fig. IV.) is oval-shaped, swelling below its sides, well-rounded, ornamented with small white spots below, with a dorsal branching line above; the interior is violet colour, with thirty-six teeth on one side, and forty-two on the other. It belongs to the Indian Ocean.

The Harlequin Cowrie, _Cypræa histrio_ (Figs. V. and VI.), from the coast of Madagascar, is ornamented with white spots very closely arranged, and much circumscribed above, with black spots upon the sides. The under side is violet.

A very fine species, which is very common in collections, is found in the Indian Ocean, from Madagascar to the Moluccas--the Tiger Cowrie, already figured with its inhabitant. This shell (Fig. VII.) is large, oval, tun-bellied, thick, and convex, of a bluish white, ornamented with numerous broad, black, round spots, much scattered, and a straight dorsal line, brown above, and very white below. It has generally twenty-three teeth on each edge, quite white. Somewhat resembling the Tiger Cowrie is the _Cypræa pantherina_ (Fig. 261), which is perhaps a variety of the same species. Another remarkable species is _Cypræa argus_, as represented in PL. XXII. (Figs. VIII. and IX.)

The genus _Ovulum_, so called from their egg-shaped form, occupy a place near the cones in some systems. The shell is highly polished, white or rose-coloured, oblong or oval, convex, attenuate, and acuminate at the extremities without apparent spiral, the edges milled within the long, narrow, and curved opening, with teeth upon the left edge, and with a few ripples on the right edge. The Ovula are inhabitants of the Indian Ocean and Chinese Seas. Some few species, however, belong to the Mediterranean and the Black Sea. The three species represented in Figs. 262, 263, and 264, present very singular contrasts of form and size.

The second family, _Volutidæ_, contains _Mitra_ and _Voluta_.

MITRA.

The Mitres are so called from their resemblance to the bishop's mitre. They are natives of warm climates, such as the Indian Ocean, the Australian Seas, and the Moluccas. The shell of the Mitra is long, slender, and spiral, the spire ending in a point at the summit; the opening is small, narrow, and triangular, and notched in front. The inhabitant of the shell has the peculiarity of projecting from its mouth a sort of cylindrical trunk, which is long, very extensible as well as flexible, and probably prehensile, the use of which is only the subject of surmise. _Mitra episcopalis_ (Fig. 265), from the Indian Ocean, is white, ornamented with square spots of a fine red, and capable of high polish.

_Mitra papalis_ (Fig. 266) has dentiform folds round the opening, which also crown each turn of the spiral; the spots are smaller, and much more numerous and varied in form than those of _M. episcopalis_.

In the genus _Voluta_, from _volvere_, to turn, the shell is oval, more or less tun-bellied. A spiral rising, slightly mammelate, the opening large, the edges notched, without channel; the columellar edge is lightly excavated and arranged in oblique folds. The right edge is arched, thick, or cutting, according to the species.

The animal has a large head, provided with two tentacles. The mouth terminates in a thick trunk furnished with hooked teeth. The foot is very large, furrowed in front, and projecting from all parts of the shell, but without operculum. The Volutæ live on the sands near the shore; sometimes they are found high and dry, left by the retreating tide. Their shells, of various forms, are ornamented with the most lively colours, the surface covered with irregular lines, the tint of which is generally in strong contrast with that of the ground.

Among the more remarkable species illustrated in PL. XXIII., we may note: Fig. I., _Voluta undulata_; Fig. II., _Voluta cymbium_; Fig. III., _Voluta delessertii_; Fig. IV., _Voluta musica_; Fig. V., _Voluta imperialis_; Fig. VI., _Voluta scapha_; and Fig. VII., _Voluta vexillum_.

The third family, _Conidæ_, contains _Pleurostoma_ and _Conus_.

The genus _Conus_ is especially rich in species, as well as numerous in many individuals. They are much sought after by collectors, many being rare, and so command high prices. The shells belonging to this group present a very remarkable uniformity of shape, at the same time that the colours are very fine, and much varied in design. The shell is thick, solid, inversely conical, wreathing spirally from the base to the apex, the spiral being generally short, the last turn constituting alone the greater part of the surface of the shell. The opening extends nearly along its whole length, occupying all the height of the last whirl. It is always narrow, its edges quite parallel; the columella presents neither fold nor curvature; the right edge is plain, sharp, and thin, detached from the front of the last spiral by a sloping hollow, more or less deep.

The animal which inhabits the Conus shell creeps upon a foot, elongated, narrow, truncate in front, furnished behind with a horny rudimentary operculum, altogether insufficient to cover the opening. The head, which is large, is elongated into a little snout, or muzzle, at the base of which rises on either side a conical tentacle, having an exterior eye upon its anterior extremity. At the extremity of the muzzle is the mouth, which is armed within with numerous horny hooks, inserted in the tongue. A cylindrical syphon, reversing itself in the shell, serves the purpose of carrying water to the branchiæ or gills. The shells inhabit the seas of warm countries, especially those lying between the Tropics, where they affect sandy coasts, with a depth of ten to twelve fathoms of water.

Among the species bearing a spiral crown, we may mention the rare _Conus cedonulli_, of which several varieties are known, which come from the South American Seas and the Antilles.

_Conus hebraica_, from the shores of Asia, Africa, and America, is a common species. It is white with black spots, which are nearly square, arranged in transverse bands.

In PL. XXI. we have represented some interesting species. _Conus imperialis_ (Fig. I.) is a fine species, of white colour, with bands of a greenish yellow or tawny colour, ornamented with transverse, cord-like, articulated lines of white and brown. One of the largest species is _Conus geographus_ (Fig. II.), which sometimes attains the length of six or seven inches; it is shaded white and brown.

Among the non-crowned species, we have represented in Fig. III. _Conus tessellatus_, common in the Indian Ocean. Its anterior part is violet in the interior. The spots with which it is surrounded are of a fine red or scarlet, or, in short, a red lead colour upon a white ground.

_Conus ammiralis_, of which three varieties, Figs. IV., V., and VI., are natives of the seas which bathe the Moluccas; they are beautifully marked varieties, of a brownish citron colour, marked with white spots nearly triangular, with tawny bands painted in very fine tracery. This species has been, and is still, much sought after by collectors, and presents many varieties besides those represented.

Among the shells, which seem almost ready to become cylindrical, may be noted _Conus nobilis_ (Fig. VII.), a rare shell of yellowish colour approaching citron, ornamented with white spots. The golden drop, _Conus textile_ (Fig. VIII.), is yellow in colour, ornamented with waving longitudinal lines of brown, and white corded spots edged with tawny colour. The glory of the sea, _Conus gloria maris_ (Fig. IX.), is white in colour, banded with orange, and reticulated with numerous triangular white spots edged with brown. This is a native of the East Indies, and one of the most beautiful shells of the whole group.

The fourth family, _Buccinidæ_, contains numerous genera, as examples of which we may instance _Oliva_, _Harpa_, _Cassis_, _Purpura_, _Nassa_, _Terebra_, _Eburna_, and _Buccinum_.

_Oliva_ is so named from their resemblance in form to the olive. Their nearly cylindrical shell is slightly spiral, polished, and brilliant as the Cowries; its opening is still long and narrow, strongly notched in front, its edge columellar, swollen anteriorly into a kind of cushion, and striped obliquely in all its length.

These Molluscs belong to the seas of warm countries, where they frequent the sandy bottoms and clear waters. They creep about with much agility, reversing themselves quickly when they have been overturned; they live upon other animals, and are flesh-eaters. They are, in fact, taken at the Isle of Tranu by using flesh as bait. The colours of the shell are very varied, and sometimes fantastically streaked. _Oliva erythrostoma_ (Fig. 267) is ornamented externally with flexual lines of a yellowish brown, with two brown bands, combined with the fine yellowish tint of gold colour within. _Oliva porphyria_, from the Brazil coast (Fig. 268), presents lines of a reddish brown, regularly interlaced with spotted large brown marks, upon a flesh-coloured ground. _Oliva irisans_ (Fig. 269) is painted in zigzag lines, close and brown, edged with orange-yellow, and with two zones of darker brown, and reticulated. _Oliva Peruviana_ (Fig. 270) is furrowed with regularly spaced bands.

In the casque, _Cassis_, the shell is oval, convex, and the spiral of considerable height. The longitudinal opening narrow, terminating in front in a short channel, which becomes suddenly erect towards the back of the shell, as in _Cassis glauca_ (Fig. 271), a fine shell from the Moluccas. The columella is folded or toothed transversely, as in Fig. 272 (_Cassis rufa_); the right edge thick, furnished with a sort of pad externally, and dentate within. This shell is from the Indian Ocean, and is of a fine purple colour, varied with black above; the edges of the opening being of a coral red colour, the teeth alone being white.

The head of the animal is large and thick, furnished with two conical elongated tentacles, at the base of which are the eyes. The mantle is ranged outside the shell, falling back upon the edges of the opening, and terminating at its anterior extremity in a long cylindrical channel, cloven in front, and passing by a hollow at the base into the bronchial cavity. The foot is large, and furnished with a horny operculum.

These animals keep near the shore, in shallow water. They walk slowly, and often sink themselves into the sand, where they prey upon small bivalves. They are not numerous in species; but specimens from the Indian Ocean are often large and beautifully marked. The shells of the less marked species are frequently used in India as lime; and employed as mortar, under the name of Chunam.

Our space only permits us to mention, among the more curious, _Cassis canaliculata_ (Fig. 273), two varieties of _Cassis Madagascariensis_ (Figs. 274 and 275), and the curious _Cassis undata_ (Martini), _Zebra_ (Lam.), or Zebra-marked Casque (Fig. 276).

PURPURA.

The Purpuras have a classical name and history, having furnished the Greeks and Romans with the brilliant purple colouring matter which was reserved for the mantles of patricians and princes. The Purpura is an oval shell, thick pointed, with short conical spiral, as in _Purpura lapillus_ (Fig. 277). In some it is tubercular or angular, the last turn of the spiral being larger than all the others put together. The opening is dilated, terminating at its lower extremity in an oblique notch. The columellar edge is smooth, often terminating in a point; the right edge often digitate, thick internally, and folded or rippled.

The animal presents a large head, furnished with two swollen conical tentacles, close together, and bearing an eye towards the middle of their external side. Its foot is large, bilobate in front, with a semicircular horny operculum.

The Purpuras inhabit the clefts of rocks in marine regions covered with algæ. On occasions they bury themselves in the sand. They creep about by the help of their foot in pursuit of bivalves, which they open by means of their short snout. They are found in all seas; but the larger species and greatest numbers come from warm regions, more especially from the Australian seas.

The Purpura of the ancients was not, as is generally thought, a vermilion red, but rather a very deep violet, which at a later period came to have various shades of red. The secret of its preparation was only known to the Phoenicians, that being most esteemed which came from Tyre. An English traveller, Mr. Wilde, has discovered on the eastern shores of the Mediterranean, near the ruins of Tyre, a certain number of circular excavations in the solid rock. In these excavations he found a great number of broken shells of _Murex trunculus_. It is probable that they had been bruised in great masses by the Tyrian workmen for the manufacture of the purple dye. Many shells of the same species are found actually living on the same coast at the present time.

Aristotle, in his writings, dwells upon the purple. He says that this dye is taken from two flesh-eating molluscs inhabiting the sea which washes the Phoenician coast. According to the description given by the celebrated Greek philosopher, one of these animals had a very large shell, consisting of seven turns of the spiral, studded with spines, and terminating in a strong beak; the other had a shell much smaller. Aristotle named the last animal _Buccinum_. It is thought that the last species is recognized in the _Purpura lapillus_ (Fig. 277), which abounds in the Channel. Réaumur and Duhamel obtained, in fact, a purple colour from this species, which they applied to some stuffs, and found that it resisted the strongest lye. The genus _Murex_ is supposed to have been the first species indicated by Aristotle.

Up to the present time, the production of the purple remains a mystery. It was long thought this fine dye was furnished by the stomach, liver, and kidneys; but M. Lacaze-Duthiers has demonstrated that the organ which secretes it is found on the lower surface of the mantle, between the intestines and the respiratory organs, where it forms a sort of fascia, or small band. The colouring matter, as it is extracted from the animal, is yellowish; exposed to the light, it becomes golden yellow, then green, taking finally a fine violet tint. While these transformations are in progress a peculiarly pungent odour is disengaged, which strongly reminds one of that of assafoetida. That portion of the matter which has not passed into the violet tint is soluble in water; when it has taken that tint it becomes insoluble. The appearance of the colour seems provoked rather by the influence of the sun's rays than by the action of the air. The matter attains its final colour, in short, in proportion to the power of the sun's rays.

It is a question how far the colour evolved under the solar rays remains indelible. It is known that the contrary is the case with the colouring matter of the cochineal insect, which changes very quickly when exposed to the sun. It is probably the remarkable resistance it opposes to the rays of the sun which recommended it to the ancients. The patricians of Rome, and the rich citizens of Greece and Asia Minor, loved to watch the magical reflections of the sun on the glorious colour which ornamented their mantles.

But to return to our humble shells. _Purpura lapillus_ (Fig. 277) is a thick shell, oval acute, with conical spiral, generally of a faded or yellowish white, zoned with brown, and more or less spotted.

_Purpura patula_ (Fig. 278) is very common in the Philippines, and is one of the handsomest species; its geographical distribution has been a subject of much controversy.

_Purpura consul_ (Fig. 279) is one of the large shells, and of a fine salmon colour, with brown bands and a corona of spines.

The _Buccinums_ resemble the Purpura in many respects. Their shell is oval or conical, much notched in front. They inhabit every sea, especially those of Europe. The animal has a small flat head, furnished with lateral tentacles or horns, bearing the eyes upon an external swelling, situated near their central length. We need only refer to Fig. 280, _Buccinum senticosum_, and _Buccinum undatum_ (Fig. 281), for their general form, the well-known whelk of our markets.

The _Harpas_ are shells of the Indian Ocean, richly enamelled within, and ornamented externally with slightly oblique longitudinal stripes in gay colours, with finely-sculptured forms in the intervals; spiral very small, and opening large. Among the more attractive species are _Harpa ventricosa_ (Fig. 282), _Harpa imperialis_ (Fig. 283), and _Harpa articularis_ (Fig. 284).

The fifth family, _Muricidæ_, contains _Fusus_, _Pyrula_, _Triton_, and _Murex_.

The _Murex_, or Rock Shells, include a large number of species, all remarkable for their bright colours and somewhat fantastical and varied forms. They are found in all seas, but become larger and more branching in the seas of warm regions. The shell is oval, or rather oblong, the spire more or less elevated, its surface generally covered with rows of spines, or tubercular ramifications. The opening, which is oval, is prolonged in a straight canal, often of very considerable length, as in Fig. 286 (_Murex haustellum_); the external edge is often smooth or rippled, the columellar edge sometimes callous.

The head of the animal is furnished with two horns or tentacles, ocular upon their external side, the mouth elongated in the form of a trunk. The foot is large and round, and furnished with a horny operculum.

Among the species with long slender tube, covered with spines, one of the most notable is _Murex tenuispina_ (Fig. 285), which is a native of the Indian Ocean and the Moluccas.

Among the strong-tubed species with long canal and no spines, from the same regions, is _Murex haustellum_ (Fig. 286).

Among the short-tubed species, furnished with foliaceous and jagged fringes, is _Murex scorpio_ (Fig. 287).

One more typical species may be noted, namely, _Murex erinaceus_ (Fig. 288), which is found on all the coasts of Europe, and especially in the Channel. Other species worthy of notice are found in the Mediterranean and the Adriatic, some of them, according to Cuvier and de Blainville, species which furnished the true Tyrian purple of the ancients; but our space prevents us from dwelling on them.

The _Tritons_ are ranged beside the genus _Murex_ in the system. Their shell is irregularly covered with scattered swelling excrescences, not, as in _Murex_, in longitudinal rows, but scattered all over the surface. About one hundred species of Triton are known. They inhabit many seas, but more especially those in warm countries. _Triton variegatum_, vulgarly called the Marine Trumpet (Fig. 289), is a very large shell, which even attains a length of sixteen inches; it is enamelled with great elegance in white, red, and tawny-brown. They come from the Indian Ocean, where they are very common. _Triton lotorium_ (Fig. 290) is of a reddish brown externally and white within. The _Triton anus_ (Fig. 291) is of a whitish colour, spotted with red.

The genus _Fusus_, or spindle shells, is distinguished by the elegance of its form rather than by the brilliancy of its colours. They are spindle-shaped, spire many-whorled, canal long, operculum egg-shaped. Among the more remarkable species may be noted _Fusus proboscidiferus_ (Fig. 292), _Fusus pagodus_ (Fig. 293), and _Fusus colus_ (Fig. 294).

The sixth family is _Strombidæ_, of which we give as types, _Rostellaria_, _Pteroceras_, and _Strombus_. _Strombus_ is a marine shell, belonging to Equatorial seas, of whose habits and manners very little is known. It is probable that they are long-lived, for their shells, when found perfect, have acquired a very considerable thickness and weight. They are even found encrusted in the interior with numerous layers of soft earthy sediment, and covered externally with small corals and other marine productions. _Strombus gigas_ is represented in Figs. 295 and 296.

Some species of _Strombus_ attain great size, and are placed as ornaments in halls and dining-rooms. In some of them the opening is brilliantly shaded, and those are chiefly sought after to decorate grottoes in gardens, or for collections of shells, where, from their size, they necessarily occupy a prominent place.

These shells are tun-bellied, terminating at their base by a short canal, notched or truncated; the right edge gets dilated with age; simple on one wing, lobed or cuneated in the upper part, and presenting in its lower part a groove or cavity separated from the canal or from the notch at the base. But these shells are not merely ornamental, for some of the streets of Vera Cruz are said to be paved with _Strombus gigas_.

The animal which inhabits this shell presents a distinct head, provided with a trunk or snout, and with two tentacles or horns, each bearing a large and vividly-coloured eye. The foot is compressed and divided into two portions, the posterior one, which is the longest, bearing a horny operculum. In the eagle-winged _Strombus_, represented in Figs. 296 and 297, these several peculiarities are well developed. This shell is large, turbinate, distended in the middle, with an acutely-pointed spiral studded with conical tubercles, the right edge very broad, rounded off below. The opening is of a vivid rose purple fading into white. It is a native of the Antilles.

_Strombus gallus_, or the angel-winged (Fig. 297), veined with stripes of white and red, comes from the coasts of Asia and America. _Strombus luhuanus_ (Fig. 298) is fawn-coloured, marked with white, and externally the right edge is red and striped; inside the columella is shaded purple and black.

_Strombus cancellatus_, the trellised Strombus (Fig. 299), is small in size and white in colour. _Strombus thersites_ is also represented (Fig. 300).

PTEROCERAS.

The Pteroceras, from πτερὸν, _wing_, and κέρας, _horn_, in many respects resemble the Strombi. They are distinguished from them chiefly in this, that the right edge developes itself with age in long and slender digital spines more or less numerous, the numbers of which vary according to the species. The Pteroceræ are found in the seas of both hemispheres, their vulgar denomination being sea-spiders or scorpions. A glance at the illustrations (Fig. 301, _Pteroceras scorpio_; Fig. 302, _P. millepeda_; Fig. 303, _P. chiragra_; and Fig. 304, _P. lambis_) will satisfy the reader as to the general correctness of this designation.

The genus Pteroceras, whose remarkable form is so well calculated to excite our admiration, has yet another attraction: the colouring of the shell exhibits many shades, which are particularly varied towards the opening, where it is generally distinguished by great freshness and brilliancy, which, added to its other characters, render it the most interesting of all the Gasteropods.