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 Phœnicians, 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 Phœnician 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 assafœtida. 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.

CHAPTER XV.

These little molluscs may be seen to ascend to the surface very suddenly, turn themselves in a determinate space, or rather swim, without appearing to change their place while sustaining themselves at the same height. If anything alarms them they fold up their flappers, and descend to such a depth in their watery world as will give them the security they seek. They thus pass their lives in the open sea far from any other shelter, except that yielded by the gulf weed and other algæ. In appearance and habits, these small and sometimes microscopic creatures resemble the fry of some other forms of mollusca. They literally swarm both in Tropical and Arctic seas; sometimes so numerous as to colour the ocean for leagues. They are the principal food of whales and sea-birds in high latitudes, rarely approaching the coast. Only one or two species have been accidentally taken on our shores, and those evidently driven thither by currents into which they have been entangled, or by tempests which have stirred the waters with a power beyond theirs. Dr. Leach states that in 1811, during a tour to the Orkneys, he observed on the rocks of the Isle of Staffa several mutilated specimens of Clio borealis. Some days after, having borrowed a large shrimp-net, and rowing along the coast of Mull, when the sea, which had previously been extremely stormy, had become calm, he succeeded in catching one alive, which is now in the British Museum.

"In structure," Mr. Huxley tells us, "the Pteropods are most nearly related to the marine univalves, but much inferior to them. Their numerous ganglia are concentrated into a mass below the œsophagus; they have auditory vesicles containing otolithes, and are sensible of light and heat, and probably of odours, although at most they possess very imperfect eyes and tentacles. The true foot is small or obsolete; in Cleodora lanceolata (Fig. 309) it is combined with the fins; but in Clio it is sufficiently distinct, and consists of two elements or spirals; the superior portion of the foot supports an operculum. The fins are developed from the sides of the mouth or neck, and are the equivalents of the side-lappets (Epipoda) of the sea-snails. The mouth of Pneumodermon is furnished with two supporting miniature suckers; these organs have been compared to the dorsal arms of the cuttle-fishes; but it is doubtful whether their nature is the same. A more certain point of resemblance is the ventral flexure of the alimentary canal, which terminates on the under surface near the right side of the neck. The Pteropods have a muscular gizzard armed with gastric teeth, a liver, a pyloric cæcum, and a contractile renal organ opening into the cavity of the mantle. The heart consists of an auricle and a ventricle, and is essentially opisthobranchiatic, although sometimes affected by the general flexure of the body. The venous system is extremely incomplete. The respiratory organ, which is little more than a ciliated surface, is either situated at the extremity of the body, and unprotected by a mantle, or included in a branchial chamber with an opening in front. The shell when present is symmetrical, glassy, and translucent, consisting of a dorsal and a ventral plate united, with an anterior opening for the head, lateral slits for long filiform processes of the mantle, and terminated behind in one or three points; in other cases it is conical or spirally-coiled, and closed by a spiral operculum. The sexes are united, and the orifices situated on the right side of the neck. According to Vogt, the embryo Pteropod has deciduous vola like the sea-snails, before the proper locomotive organs are developed."

The Pteropods seem to be eminently sociable and gregarious, swarming together in great numbers; they present some analogical resemblances to the Cephalopodæ; but permanently they represent the larval stage of the sea-snails. De Blainville divides the group into two sections, Thecosomata and Gymnosomata, the first including the Hyaleidæ and Limacinidæ; the second contains one family, the Cliidæ. The Hyaleidæ have small horny shells, very thin and transparent, globulous, or elongated, open anteriorly, cloven on the sides, and truncate at the posterior extremity. Their globular body is formed of two parts, the one including the head, bearing two very strong tentacles, and two large fins or flappers in the form of wings, springing from each side of the mouth.

These molluscs are small, and generally of a yellowish-blue or violet colour. They are inhabitants of the deep sea, and rarely seen out of what sailors call "blue water." They plough the waves with great rapidity by the aid of their powerful fins. Certain winds throw them sometimes in great numbers on the shores of the Mediterranean. These little creatures, so inoffensive, and which live together in vast numbers, seem to be an easy and ready-prepared prey, which the great marine animals may swallow by thousands. Twenty species of Hyalea are described as actually living in the Atlantic and Australian seas. Of these Hyalea gibbosa (Figs. 305, 306) and Hyalea longirostris (Figs. 307, 308) are here represented.

The great flappers of Hyalea tridentata are yellow, marked at their base with a fine violet spot. Its shell, plain above, convex beneath, is cloven on the side. The superior part is longer than the inferior, and the transverse line which unites them is furnished with three teeth. This shell is yellow, and nearly translucent. When the animal swims, two expansions of its mantle issue from the lateral clefts in the shell.

Cleodora lanceolata is a delicate and graceful creature; its body, of gelatinous appearance, has a distinct head, with its fins near the neck, notched in the form of a heart (Fig. 309); its posterior part is globulous, transparent, and luminous even in the dark. The animal which inhabits it sometimes shines through the shell like a light placed inside a lantern. This shell is triangular, as in Cleodora cuspidata (Fig. 311), thin, vitreous, and fragile, terminating in a long spine at the base.