Sea-Weeds, Shells and Fossils

SEA-WEEDS, SHELLS and FOSSILS.

BY

PETER GRAY, A.B.S. Edin.;
AND
B. B. WOODWARD,

Of the British Museum (Natural History), South Kensington.

Butler & Tanner,
The Selwood Printing Works
Frome, and London.

SEA-WEEDS.

By PETER GRAY.

Algæ, popularly known as sea-weeds, although many species are inhabitants of fresh water, or grow on moist ground, may be briefly described as cellular, flowerless plants, having no proper roots, but imbibing nutriment by their whole surface from the medium in which they grow. As far as has been ascertained, the total number of species is about 9000 or 10,000. Many of them are microscopic, as the Desmids and Diatoms, others, as Lessonia, and some of the larger Laminariæ (oarweeds), are arborescent, covering the bed of the sea around the coast with a submarine forest; while in the Pacific, off the northwestern shores of America, Nereocystis, a genus allied to Laminaria, has a stem over 300 feet in length, which, although not thicker than whipcord, is stout enough to moor a bladder, barrel-shaped, six or seven feet long, and crowned with a tuft of fifty leaves or more, each from thirty to forty feet in length. This vegetable buoy is a favourite resting place of the sea otter; and where the plant exists in any quantity, the surface of the sea is rendered impassable to boats. The stem of Macrocystis, which "girds the globe in the southern temperate zone," is stated to extend sometimes to the enormous length of 1500 feet. It is no thicker than the finger anywhere, and the upper branches are as slender as pack-thread; but at the base of each leaf there is placed a buoy, in the shape of a vesicle filled with air.

Although the worthlessness of Algæ has been proverbial, as in the "alga inutile" of Horace and Virgil's "projecta vilior alga," they are not without importance in botanical economics. A dozen or more species found in the British seas are made use of, raw or prepared in several ways, as food for man. Of these edible Algæ, Dr. Harvey considers the two species of Porphyra, or laver, the most valuable. Berkeley says, "The best way of preparing this vegetable or condiment, which is extremely wholesome, is to heat it thoroughly with a little strong gravy or broth, adding, before it is served on toast, a small quantity of butter and lemon juice." A species of Nostoc is largely consumed in China as an ingredient in soup. A similar use is made of Enteromorpha intestinalis in Japan. Many species of fish and other animals, turtle included, live upon sea-weed. Fucus vesiculosus is a grateful food for cattle. In Norway, cattle, horses, sheep, and pigs are largely fed upon it, and on our own coasts cattle eagerly browse on that and kindred species at low water. In some northern countries, Fucus serratus sprinkled with meal is used as winter fodder.

Fig. 1. Group of Sea-weeds (chiefly Laminariæ).

All the marine Algæ contain iodine; and even before the value of that substance in glandular complaints had been ascertained, stems of a sea-weed were chewed as a remedy by the inhabitants of certain districts of South America where goître is prevalent. Chondrus crispus and (Gigartina) mamillosa constitute the Irish moss of commerce, which dissolves into a nutritious and delicate jelly, and the restorative value of which in consumption doubtless depends in some degree on the presence of iodine. The freshwater Algæ not only furnish abundant and nourishing food to the fish and other animals living in ponds and streams, but by their action in the decomposition of carburetted hydrogen and other noxious gases purify the element in which they live, thus becoming important sanitary agents. The value of aquatic plants in the aquarium is well known. A Chinese species of Gigartina is much employed as a glue and varnish; and also much used in China in the manufacture of lanterns and transparencies, and in that country and Japan for glazing windows. Handles for table knives and forks, tools, and other implements have been made from the thick stems of oarweeds, and fishing lines from Chorda filum. Tripoli powder, extensively used for polishing, consists mainly of the silicious shells of Diatoms. On various parts of our coast, the coarser species of sea-weed, now used as a valuable manure, were formerly extensively burnt for kelp, an impure carbonate of soda. This industry, when carried on upon a large scale, became a fruitful source of income to some of the poorest districts in the kingdom, bringing, in the last decade of last century, nearly £30,000 per annum into Orkney alone. Since the production of soda from rock salt has become general, kelp is now only burnt for the extraction of iodine, this being the easiest way of obtaining that substance.

Although the vegetable structure and mode of reproduction are essentially the same in all Algæ, as regards the former they vary from the simple cell, through cells arranged in threads, to a stem and leaves simulating the vegetation of higher tribes. And although the simpler kinds are obviously formed of threads, most of the more compound may also be resolved into the same structure by maceration in hot water or diluted muriatic acid. In substance some are mere masses of slime or jelly, others are silky to the feel, horny, cartilaginous or leather-like, and even apparently woody. A few species secrete carbonate of lime from the water, laying it up in their tissues; others cover themselves completely with that mineral, while some coat themselves with silex or flint. Many Algæ are beautifully coloured, even when growing at depths to which very little light penetrates. As in their vegetative organs, so in their reproductive, Algæ exhibit many modifications of structure without much real difference. In the green sea-weeds reproduction is effected by simple cell division in the unicellular species, and by spores resulting from the union of the contents of two cells in the others. The red sea-weeds have a double system of reproduction, a distinctly sexual one, by spores and antheridia, and another by tetraspores, which by some are considered to be of the nature of gemmæ, or buds. The spores are generally situated in distinct hollow conceptacles (favellæ, ceramidium, coccidium). The tetraspore is also sometimes contained in a conceptacle. It consists of a more or less globular, transparent cell, which when mature contains within it four (rarely three) sporules. Reproduction in the olive sea-weeds is also double, by zoospores, generally considered gemmæ, and by spores and antherozoids, which is a sexual process.

Fig. 2. A, Species of Gleocapsa, one of the Palmelleæ, in various stages. A becomes B, C, D, and E by repeated division. Magnified 300 diameters.

Following the classification adopted by Professor Harvey, which is that generally employed in English systematic manuals, we divide the order into three sub-orders, named from the prevailing colour of their spores. 1. Chlorospermeæ, with green spores; 2. Rhodospermeæ, with red spores; and 3. Melanospermeæ, with olive-coloured spores. The entire plant in the first group is usually grass-green, but occasionally olive, purple, blue, and sometimes almost black; in the second it is some shade or other of red, very seldom green; and in the third, while generally olive green, it is occasionally brown olive or yellow.

The Chlorospermeæ are extremely varied in form, often threadlike, and are propagated either by the simple division of the contents of their cells (endochrome), by the transformation of particular joints, or by the change of the contents of the cells into zoospores, which are cells moving freely in water by means of hairlike appendages. In their lower forms they are among the most rudimentary of all plants, and thus of special interest physiologically, as representing the component parts of which higher plants are formed. They are subdivided into twelve groups, as follows:

The first group, Palmelleæ, are unicellular plants, the cells of which are either free or surrounded by a gelatinous mass, and they are propagated by the division of the endochrome. One of the most remarkable of the species of this family is Protococcus cruentus, which is found at the foot of walls having a northern aspect, looking as if blood had been poured out on the ground or on stones. Protococcus nivalis, again, is the cause of the red snow, of which early arctic navigators used to give such marvellous accounts. ([Fig. 2.])

Fig. 3. A, Fragment of a Filament of Zygnema, one of the Conjugateæ;
B, Closterium; C, Euastrium; two desmids.

The Desmideaceæ, together with the plants of the next succeeding group, are favourite subjects of investigation or observation by the possessors of microscopes, an attention they merit from the beauty and variety of their forms. They are minute plants of a green colour, consisting of cells generally independent of each other, but sometimes forming brittle threads or minute fronds, and are reproduced by spores generated by the conjugation of two distinct individuals. The process of conjugation in Desmids and Diatoms consists in the union of the endochrome of two individuals, each of which in these families is composed of a single cell. This ultimately forms a rounded body or resting spore, which afterwards germinates, the resulting plant not however acquiring the normal form until the third generation. ([Fig. 3.])

The Diatomaceæ, closely allied to the preceding group in structure and reproduction, are however distinguished from them by their flinty shells, which are often beautifully sculptured. Their endochrome is a golden brown, instead of green as in the Desmideaceæ. The latter, also, are confined to fresh water, while the Diatomaceæ are found, though not exclusively, in the sea, where their shells sometimes, microscopically minute as they are individually, form banks extending several hundred miles. It is stated that in the collection made by Sir Joseph Hooker in the Himalayas the species closely resemble our own.

In the next group, Confervaceæ, we are introduced to forms more like the general notion of what a plant should be. The individuals of which it consists are composed of threads, jointed, either simple or branched, mostly of a grass-green colour, and propagating either by minute zoospores or by metamorphosed joints. They are found both in fresh and salt water, and in damp situations. The number of species is very great. A considerable number consist of unbranched threads; the branched forms grow sometimes so densely as to assume the form of solid balls. After floods, when the water stands for several days, they sometimes increase to such an extent, as to form on its subsidence a uniform paper-like stratum, which while decomposing is extremely disagreeable. The name Conferva has been almost discontinued as a generic title, the majority of British species being now ranged under Clado- and Chæto-phora. The latter are branched, and require great care and attention in order to distinguish them, on account of their general resemblance to each other. Good characters are however to be found in their mode of branching and the form and comparative size of the terminal joints.

The Batrachospermeæ constitute a small but very beautiful group, consisting of gelatinous threads variously woven into a branched cylindrical frond. The branches are sometimes arranged, as in the British species, so that the plants appear like necklaces. In colour they pass from green, through intermediate shades of olive and purple, to black. In common with some of the higher Algæ, the threads of the superficial branches send joints down the stem, changing it from simple to compound. The native species are all fluviatile.

The Hydrodicteæ are among the most remarkable of Algæ. Hydrodictyon utriculatum, the solitary British species, is found in the large pond at Hampton Court, and in similar situations in various parts of the country, but not very generally. It resembles a green purse or net, from four to six inches in length, with delicate and regular meshes, the reticulations being about four lines long. Its method of reproduction is no less remarkable than its form. Each of the cells forms within itself an enormous mass of small elliptic grains. These become attached by the extremities so as to form a network inside the cell, and, its walls being dissolved, a new plant is set free to grow to the size of the parent Hydrodictyon.

The Nostochineæ grow in fresh water, or attached to moist soil. They consist of slender, beaded threads surrounded by a firm jelly, and often spreading into large, wavy fronds. The larger beads on the inclosed threads are reproductive spores. ([Fig. 4, A.])

Fig. 4. A, Fragment of a Filament of Nostoc. B, End of a Filament of Oscillatoria.

The Oscillatoreæ are another remarkable group, on account of the peculiar animal-like motions they exhibit. They occur both in salt and fresh water, and on almost every kind of site in which there is sufficient moisture. The threads of which they are composed are jointed, and generally unbranched; they are of various tints of blue, red, and green, and, where their fructification has been ascertained, are propagated by cell division. The most curious point about them is, however, the movements of their fronds. According to Dr. Harvey, these are of three kinds—a pendulum-like movement from side to side, performed by one end, whilst the other remains fixed, so as to form a pivot; a movement of flexure of the filament itself, the oscillating extremity bending over from one side to the other, like the head of a worm or caterpillar seeking something on its line of march; and lastly, a simple onward movement of progression, the whole phenomenon being, Dr. Harvey thinks, resolvable into a spiral onward movement of the filament. Whatever is the cause of this motion, it is not, as used to be supposed, of an animal nature; for the individuals of this group are undoubted plants. ([Fig. 4, B.]) Several species of Rivularia, belonging to the Oscillatoreæ, are found both in the sea and in fresh water. They are gelatinous, and have something of the appearance of Nostoc, in aspect as well as in minute structure.

The Conjugatæ are freshwater articulated Algæ, which reproduce themselves by the union of two endochromes. They are very interesting objects under the microscope, owing to the spiral or zigzag arrangement of the endochrome of many of them, and the delicacy of all.

The Bulbochæteæ constitute a small group, some half-a-dozen species being British. They are freshwater plants, composed of articulate branched filaments, with fertile bulbshaped branchlets. The endochrome is believed to be fertilized by bodies developed in antheridia, the contents of each fertilized cell dividing into four ovate zoospores.

The last two groups of green sea-weeds consist chiefly of marine plants. Of these the first, Siphoneæ, is so called because the plant, however complicated, is composed invariably of a single cell. It propagates by minute zoospores, by large quiescent spores, or by large active spores clothed with cilia. It includes the remarkable genus Codium, three species of which inhabit the British seas. In Codium Bursa the filamentous frond is spherical and hollow, presenting more the appearance of a round sponge or puff-ball than a sea-weed, and is somewhat rare. Another species greatly resembles a branched sponge, and the third forms a velvety crust on the surface of rocks. Another genus, Vaucheria, is of a beautiful green colour, forming a velvety surface on moist soil, on mud-covered rocks overflowed by the tide, or parasitic on other sea-weeds. The most attractive plants of this family are however those of the genus Bryopsis, two of which are found on the British shores. The most common one is B. plumosa, the fronds of which grow usually in the shady and sheltered sides of rock pools.

The fronds of the last of the green-weed groups, the Ulvaceæ, are membranous, and either flat or tubular. Two of them, Ulva latissima, the green, and Porphyra laciniata, the purple laver, are among the most common sea-weeds, growing well up from low-water mark. The propagation in all of them is by zoospores. An allied genus, Enteromorpha, is protean in its forms, which have been classed under many species. They may, however, be reduced to half a dozen. Some of them are very slender, so as almost to be mistaken for confervoid plants.

With the Rhodospermeæ we enter a sub-order of Algæ, exclusively marine, the plants in which have always held out great attractions to the collector. In structure they are expanded or filamentous, nearly always rose-coloured or purple in colour. Of the fourteen groups into which they are divided by Harvey, the first is Ceramiaceæ, articulate Algæ, constituting a large proportion of the marine plants of our shores. Of the genus Ceramium, C. rubrum is the most frequent, and it is found in every latitude, almost from pole to pole. It is very variable in aspect, but can always be recognized by its fruit. C. diaphanum is a very handsome species, growing often in rock pools along with the other. There are about fifteen native species altogether, some of them rare, and all very beautiful, both as displayed on paper and seen under the microscope. Crouania attenuata is a beautiful plant, parasitic upon a Cladostephus or Corallina officinalis. It is however extremely rare, being only found in England about Land's End. A more common and conspicuous, but equally handsome plant is Ptilota plumosa ([Fig. 9]), which is mostly confined to our northern coasts; although P. sericea, a smaller species, or variety, is common in the south, and easily distinguished from its congener, which it otherwise greatly resembles, by its jointed branchlets and pinnules. Callithamnion, Halurus and Griffithsia, articulate like Ceramium, furnish also several handsome species. ([Fig. 5.])

Fig. 5. Species of Callithamnion.

Fig. 6. Chondrus crispus.

The group Spyridiaceæ contains only one English plant, Spyridia filamentosa, which is curiously and irregularly branched, the branches being articulate and of a pinky red. One of its kinds of fruit, consisting of crimson spores, is contained in a transparent network basket, formed by the favellæ, or short branches, whence its name.

The Cryptonemiaceæ are very numerous in genera and species. They all have inarticulate branches, some are thread-like. Grateloupia filicina is a neat little plant, met with rarely on the south and west coasts. Gigartina mamillosa, a common plant everywhere, is the plant sold, along with Chondrus crispus, as Irish or Carrageen moss. A handsome little plant, Stenogramme interrupta, is very rare, but it has been gathered both on the Irish and English coasts. The Phyllophoræ, one species of which is frequent on all our shores, may be recognised by the way in which the points and surfaces of their fronds throw out proliferous leaves. Gymnogongrus has two British species, one much resembling Chondrus crispus, already named, of which it was formerly considered a congener. Their fructification is however very different. Ahnfeltia plicata is a curious wiry, entangled plant, almost black in colour, and like horsehair when dry, and can scarcely be mistaken. Cystoclonium purpurascens is very commonly cast up by the tide on most of our coasts. It varies in colour, but is easily distinguished by the spore-bearing tubercles imbedded in its slender branches. Callophyllis laciniata is a handsome species, of a rich crimson colour, and sometimes a foot square. It can scarcely have escaped the notice of the sea-side visitor, for it is widely distributed and often thrown out in great abundance; one writer describes the shore near Tynemouth as having been red for upwards of a mile with this superb sea-weed. Kalymenia reniformis is another of the broad, flat Algæ, but it is scarcer, and of a colour not so conspicuous. Among the most frequent of our sea-weeds, both as growing in the rock pools and cast ashore, is Chondrus crispus, already twice referred to in connexion with its officinal uses. It is very variable in form, one author figuring as many as thirty-six different varieties. ([Fig. 6.]) Chylocladia clavellosa, which is sometimes cast ashore a foot and a half long, is closely set with branches, and these again clothed with branchlets in one or two series. The whole plant is fleshy, of a rose-red or brilliant pink colour, turning to golden yellow in decay. There is another small species, confined to the extreme north of Britain. Halymenia ligulata is another flat red weed, but sometimes very narrow in its ramifications. Furcellaria fastigiata has a round, branched, taper stem, swollen at the summit, which contains the fruit, consisting of masses of tetraspores in a pod-like receptacle. Schizymenia edulis, better known perhaps by its old name Iridea, is a flat, inversely egg-shaped leaf with scarcely any stem. It is one of the edible Algæ, and pretty frequent in shady rock pools. Gloiosiphonia capillaris is a remarkably beautiful plant, and not common, being confined to certain parts of the southern coasts. The stem is very soft and gelatinous; the spores are produced in red globular masses imbedded in the marginal filaments, which have a fine appearance under the microscope when fresh.

Fig. 7. Rhodomenia palmata.

Fig. 8. Wormskioldia sanguinea.

The Rhodomeniaceæ are purplish or blood-red sea-weeds, inarticulate, membranaceous, and cellular. Among the dark-coloured is Rhodomenia palmata, better known as dulse, a common and edible species. ([Fig. 7.]) Wormskioldia sanguinea is not only the most beautiful sea-weed, but the finest of all leaves or fronds. It is usually about six inches long, but sometimes nearly double that length and six inches broad, with a distinct midrib and branching veins, and a delicate wavy lamina, pink or deep red. The fruit is produced in winter from small leaflets growing upon the bare midrib. ([Fig. 8.]) The commonest of all red sea-weeds on our coast, one of the most elegant, and much sought after by sea-weed picture makers, Plocamium coccineum, belongs to this group. Calliblepharis ciliata and jubata are coarser plants, the latter being the more frequent. They were formerly included in the genus Rhodymenia, from which they were removed when their fruit was better understood.

Fig. 9. Ptilota plumosa.

Wrangelia and Naccaria are the only British genera in Wrangeliaceæ. There is only one native species in each, both being rare, the latter especially.

The Helminthocladiæ are also a limited group, of a gelatinous structure; so much so that on being gathered they feel like a bunch of slimy worms, whence the name of the family. Helminthora purpurea and divaricata with Nemaleon multifidum and Scinaia furcellata represent them in Britain. They are nearly all very rare, pretty plants, and very effective as microscopic objects.

The Squamariæ, formerly included in the Corallinaceæ, are a small group of inconspicuous plants resembling lichens, of a leathery texture, and growing on rocks and shells attached by their lower surface.

A single genus only, Polyides, represents the Spongiocarpeæ. Polyides rotundus resembles Furcellaria fastigiata very closely, but differs widely in the fruit, which consists of spongy warts surrounding the frond, composed of spores and articulated threads.

Of the next group represented in Britain, Gelidiaceæ, we have only one plant, Gelidium corneum, very common on our shores, and perhaps the most variable of all vegetable species.

The Sphærococcidæ include both membranaceous and cartilaginous species. Of the latter is Sphærococcus coronopifolius, which cannot easily be mistaken, owing to the numerous berry-like fruits that tip its branchlets. It is rather rare on the northern, but often thrown ashore in large quantities on the southern coasts. The genus Delesseria has four British species, the largest being the well-known D. sinuosa, the fronds of which resemble an oak leaf in outline. The handsomest are D. ruscifolia and D. hypoglossum, which are more delicate and of a finer colour than sinuosa. There are three British species of Gracillaria, in two of which the branches are cylindrical, and in the other flat. G. compressa makes an excellent preserve and pickle, but unfortunately it is the rarest of the three. Nitophyllum is one of the greatest ornaments of this tribe. There are six British species, which are amongst the most delicate and beautiful of our native Algæ.

The Corallinaceæ are remarkable for the property they possess of absorbing carbonate of lime into their tissues, so that they appear as a succession of chalky articulations or incrustations. The most common is Corallina officinalis. There are two British species of Corallina, and two also of the nearly allied genus, Jania. Of the foliaceous group there are likewise two British genera, Melobesia and Hildenbrantia.

The next group, the Laurenciaceæ, are cartilaginous and cylindrical or compressed, the frond in the greater portion of them being inarticulate and solid. They contain several species valued by collectors, although some of them are amongst our commonest plants. Their colour is, when perfect, a dull purple or brownish red, but they change under the influence of light and air, while fresh water is rapidly destructive to their tints. ([Fig. 10.])

Fig. 10. Laurencia pinnatifida.

The Chylocladiæ are curiously jointed plants, removed by Agardh to a new genus, Lomentaria, and a new order Chondriæ. Bonnemaisonia asparagoides is the most rare and beautiful of the tribe.

The last tribe of red weeds, Rhodomelaceæ, varies greatly in the structure of the frond, but the fruit is more uniform. Polysiphonia and Dasya contain the finest of the filiform division; the leafy one, Odonthalia, a northern form, is a very beautiful sea-weed both as respects form and colour. Well-grown specimens are not unlike a hawthorn twig, and of a blood red colour.

The plants of the sub-order Melanospermeæ, are, like the red sea-weeds, exclusively marine. They are usually large and coarse, and confined mostly to comparatively shallow water. In the Laminariaceæ we find the gigantic oarweeds already briefly referred to. Lessonia, which encircles in submarine forests the antarctic coasts, is an erect, tree-like plant, with a trunk from five to ten feet high, forked branches, and drooping leaves, one to three feet in length, and has been compared to a weeping willow. Sir Joseph Hooker says, that from a boat there may on a calm day be witnessed in the antarctic regions, over these submarine groves, "as busy a scene as is presented by the coral reefs of the tropics. The leaves of the Lessoniæ are crowded with Sertulariæ and Mollusca, or encircled with Flustra; on the trunks parasitic Algæ abound, together with chitons, limpets, and other shells; at the base and among the tangled roots swarm thousands of Crustaceæ and Radiata, while fish of several species dart among the leaves and branches." Of these and other gigantic melanosperms, flung ashore by the waves, a belt of decaying vegetable matter is formed, miles in extent, some yards broad, and three feet in depth; and Sir J. Hooker adds that the trunks of Lessonia so much resemble driftwood that no persuasion could prevent an ignorant shipmaster from employing his crew, during two bitterly cold days, in collecting this incombustible material for fuel. Macrocystis and Nereocystis are also giant members of this sub-order. Some of the Laminariæ which form a belt around our own coasts not seldom attain a length of from eight to twelve feet. The common bladder-wrack (Fucus vesiculosus) sometimes grows in Jutland to a height of ten feet, and in clusters several feet in diameter. The colour of most of the plants in this sub-order is some shade of olive, but several of them turn to green in drying.

The first group, Ectocarpeæ, is composed of thread-like jointed plants, the fructification of which consists of external spores, sometimes formed by the swelling of a branchlet. The typical genus, Ectocarpus, abounds in species, a dozen or so of which, very nearly allied plants, being found around our own shores. One or two of them are very handsome. There are also some very beautiful plants in the genus Sphacelaria, belonging to this group, several of them resembling miniature ferns. All the Sphacelariæ are easily recognized by the withered appearance of the tips of the fruiting branches. Myriotrichia is a genus of small parasitical plants, the two British species of which grow chiefly on the sea thongs (Chorda).

The Chordariæ are sometimes gelatinous in structure, in other cases cartilaginous. The fruit is contained in the substance of the frond. The genus Chordaria consists of plants which have the appearance of dark coloured twine. There are two British species, one being rather common. Chorda filum, sea-rope, another string-like sea-weed, grows in tufts from a few inches to many feet in length, and tapering at the roots to about the thickness of a pig's bristle. In quiet land-locked bays with a sandy or muddy bottom, it sometimes extends to forty feet in length, forming extensive meadows, obstructing the passage of boats, and endangering the lives of swimmers entangled in its slimy cords, whence probably its other name of "dead men's lines."

Fig. 11. Padina pavonia.

The Mesogloieæ in a fresh state resemble bundles of green, slimy worms. There are three British species, two of which are not uncommon. Although so unattractive in external aspect, they, like many others of the same description, prove very interesting under the microscope. One of the cartilaginous species, Leathsia tuberiformis, has the appearance, when growing, of a mass of distorted tubers.

The species of Elachista, composed of minute parasites, are, as well as unattractive like the Mesogloieæ, inconspicuous, but are beautiful objects when placed under the microscope. Myrionemæ are also parasitic, and even smaller than the plants of the preceding genus.

In the Dictyoteæ the frond is mostly flat, with a reticulated surface, which is sprinkled when in fruit with groups of naked spores or spore cysts. This tribe includes not a few of the most elegant among the Algæ. In structure they are coriaceous, and include plants both with broad and narrow, branched and unbranched fronds. In Haliseris there is a distinct midrib. The largest of the British Dictyoteæ is Cutleria multifida, sometimes found a foot and a half long; and the best known is doubtless Padina pavonia, much sought after by seaside visitors where it grows. Its segments are fan-shaped, variegated with lighter curved lines, and fringed with golden tinted filaments. ([Fig. 11.]) Owing to its power of decomposing light, its fronds, when growing under water, suggest the train of the peacock, whence its specific name. Taonia atomaria somewhat resembles Cutleria, but exhibits also the wavy lines of Padina. The plant of this group most often cast ashore is Dictyota dichotoma. It makes a handsome specimen when well dried, and is interesting on account of the manner in which it varies in the breadth of its divisions. The variety intricata is curiously curled and entangled. Dictyosiphon fœniculaceus, the solitary British example of its genus, is a bushy filiform plant, remarkable for the beautiful net-like markings of its surface. The Punctariæ have flattened fronds, marked with dots, which sufficiently distinguish them from all the others. A small form is often found parasitic on Chorda filum, spreading out horizontally like the hairs of a bottle brush. Asperococcus derives its name from its roughened surface, occasioned by the thickly scattered spots of fructification.

The Laminariaceæ are inarticulate, mostly flat, often strap-shaped. Their spores occur in superficial patches, or covering the whole frond. The plants of this order, as we have already seen, include the giants of submarine vegetation. In point of mass they constitute the larger part of our native Algæ, although they number only a few species. They are popularly known as tangle or oarweeds, and the stems of Laminaria saccharina and the midrib of Alaria esculenta are used as food.

The Sporochnaceæ are a small but beautiful tribe, inarticulate, and producing their spores in jointed filaments or knob-like masses, and remarkable for their property of turning from olive brown to a verdigris green when exposed to the atmosphere.

Fig. 12. Fucus serratus, showing a transverse section of the Conceptacle, and Antheridium with Antherozoids escaping.

They are deep sea plants, or at least grow about low water mark. The largest of the group is Desmarestia ligulata, which, with the other British species, D. aculeata, is often cast ashore. The latter species, at an early period of its existence, is clothed with tufts of slender hairs, springing from the margin of the frond. Desmarestia viridis is the most delicate and also the rarest of the three. Nothing like fruit has been discovered on any of them. Arthocladia villosa and Sporochnus pedunculatus are branched sea-weeds, covered also with tufts of closely set hairs. Carpomitra Cabreræ, a rare species, bears, in common with the two preceding species, its spores in a special receptacle. In the first the receptacle is pod-like; in the second knotted; and in the last mitriform.

The concluding group of Algæ is the Fucaceæ, including the universally known sea wrack (Fucus). The frond in all of them is jointless. They are reproduced by means of antheridia and oogonia developed in conceptacles, clustered together at the apex of the branches. Both from their bulk and their decided sexual distinctions, they deserve to rank at the head of the order. Of all sea-weeds they are also perhaps of the greatest use to man. One of the most interesting among them is the Gulfweed (Sargassum bacciferum), occupying a tract of the Atlantic extending over many degrees of latitude. Pieces of it, and of its congener, S. vulgare, are occasionally drifted to our shores, and they consequently find a place in works on British Algæ, although they have no claim to be considered native plants. On rocky coasts the various species of Fucus occupy the greater part of the space between tide-marks, the most plentiful being Fucus vesiculosus. F. serratus ([Fig. 12]) is the handsomest of the genus, the other species being F. nodosus, said to be the most useful for making kelp, and F. canaliculatus. Halidrys siliquosa is remarkable for its spore receptacles, which have quite the appearance of the seed vessel of a flowering plant. The species of Cystoseira, chiefly confined to the southern coasts, are also very interesting. Their submerged fronds are beautifully iridescent, and the stems, of the largest species at least, are generally covered with a great variety of parasites, animal and vegetable, the former consisting of Hydrozoa and Polyzoa, and other curious forms. Himanthalia lorea is another remarkable plant. It has conspicuous forked fruit-bearing receptacles; but the real plants are the small cones at the base of these, and from which they are shed when ripe.

As to conditions of site and geographical distribution, Algæ do not differ from land plants. Latitude, depth of water, and currents influence them in the same way as latitude, elevation, and station operate on the latter; and the analogy is maintained in the almost cosmopolitan range of some, and the restricted habitat of others. Not many extra-European species of Desmids are known, but those of Diatoms are far more widely diffused, and extend beyond the limits of all other vegetation, existing wherever there is water sufficient to allow of their production; and they are found not only in water, but also on the moist surface of the ground and on other plants, in hot springs and amid polar ice. They are said to occur in such countless myriads in the South Polar Sea as to stain the berg and pack ice wherever these are washed by the surge. A deposit of mud, chiefly consisting of the shells of Diatoms, 400 miles long, 120 miles broad, and of unknown thickness, was found at a depth of between 200 and 400 feet on the flanks of Victoria Land in 70° south latitude. Such is their abundance in some rivers and estuaries that Professor Ehrenberg goes the length of affirming that they have exercised an important influence in blocking up harbours and diminishing the depth of channels. The trade and other winds distribute large quantities over the earth, which may account for the universality of their specific distribution; for Sir Joseph Hooker found the Himalayan species to closely resemble our own. Common British species also occur in Ceylon, Italy, Virginia, and Peru. The typical species of the Confervaceæ are also distributed over the whole surface of the globe. They inhabit both fresh and salt water, and are found alike in the polar seas and in the boiling springs of Iceland, in mineral waters and in chemical solutions. Some of the tropical ones are exceedingly large and dense. Batrachospermum vagum, in the next tribe, a native of England, is also found in New Zealand. An edible species of Nostochineæ, produced on the boggy slopes bordering the Arctic Ocean, is blown about by the winds sometimes ten miles from land, where it is found lying in small depressions in the snow upon the ice. The common Nostoc of moist ground in England occurs also in Kerguelen's Land, high in the southern hemisphere. Floating masses of Monormia are often the cause of the green hue assumed by the water of ponds and lakes. Certain species of Oscillatoria of a deep red colour live in hot springs in India, and the Red Sea is supposed to have derived its name from a species of this tribe, which covers it with a scum for many miles, according to the direction of the wind. The lake of Glaslough in County Monaghan, Ireland, owes its colour and its name to Oscillatoria ærugescens, and large masses of water in Scotland and Switzerland are tinted green or purple by a similar agency. A few species of Siphoneæ have a very wide range, two British species of Codium occurring in New Zealand. The Ulvaceæ abound principally in the colder latitudes. Enteromorpha intestinalis, a common British species, is as frequent in Japan, where it is used, when dried, in soup. The Rhodosperms are found in every sea, although the geographical boundaries of genera are often well-marked. Gloiosiphonia, one of our rarest and most beautiful Algæ, is widely diffused. Of Melanosperms the Laminariæ affect the higher northern latitudes, Sargassa abound in the warmer seas, while Durvillæa, Lessonia, and Macrocystis characterize the marine flora of the Southern Ocean. The Fucaceæ are most abundant towards the poles, where they attain their greatest size. The marine meadows of Sargassum, conceived by some naturalists to mark the site of the lost Atlantis, and which give its name to the Sargasso Sea, extending between 20° and 25° north latitude, in 40° west longitude, occupy now the same position as when the early navigators, with considerable trepidation, forced through their masses on the way to the New World. Sargassum is drifted into this tract of ocean by currents, the plants being all detached; and they do not produce fruit in that state, being propagated by buds, which originate new branches and leaves. ([Fig. 13.])

Fig. 13. The Gulf-weed (Sargassum bacciforum).

Owing to their soft, cellular structure, Algæ are not likely to be preserved in a fossil state; but what have been considered such have been found as low down as the Silurian formation, although their identity has been disputed, and several of them, it is more than probable, belong to other orders, and some even to the animal kingdom. Freshwater forms, all of existing genera and species, are believed to have been detected in the carboniferous rocks of Britain and France; others also of the green-coloured division are said to occur from the Silurian to the Eocene, and the Florideæ to be represented from the Lias to the Miocene. The indestructible nature of the shells of the Diatomaceæ has enabled them to survive where the less protected species may have perished. Tripoli stone, a Tertiary rock, is entirely composed of the remains of microscopic plants of this tribe. It is from their silicious shells that mineral acquires its use in the arts, as powder for polishing stones and metals. Ehrenberg estimates that in every cubic inch of the tripoli of Bilin, in Bohemia, there are 41,000,000 of Gaillonella distans. Districts recovered from the sea frequently contain myriads of Diatoms, forming strata of considerable thickness; and similar deposits occur in the ancient sites of lakes in this and other countries.

Before setting out in search of Algæ the collector ought to provide himself with a pair of stout boots to guard his feet from the sharp-pointed rocks, as well as a staff or pole to balance himself in rock-climbing, which ought to have a hook for drawing floating weed ashore. A stout table-knife tied to the other end will be found very useful. A basket—a fishing-basket does very well—or a waterproof bag, for stowing away his plants, is also necessary. It is advisable to carry a few bottles for the very small and delicate plants, and care should be taken to keep apart, and in sea-water, any specimens of the Sporochnaceæ; for they are not only apt to decay themselves but to become a cause of corruption in the other weeds with which they come in contact. These bottles should always be carried in the bag or pocket, never in the hand.

Sea-weeds, as every visitor to the coast knows, are torn up in great numbers by the waves, especially during storms, and afterwards left on the shore by the retiring tide. Many shallow-growing species are also to be found attached to the rocks, and in the rock pools, between high and low water mark. There are three points on the beach where the greatest accumulations of floating Algæ are found: high water mark, mid-tide level, and low water mark. Low water occurs about five or five and a half hours after high water. The best time for the collector to commence is half an hour or so before dead low water. He can then work to the lowest point safely, and, retiring before the approaching tide, examine the higher part of the beach up to high water mark. If the coarse weeds in the rock pools and chinks are turned back, many rare and delicate Algæ will be found growing under them, especially at the lowest level. The most effective method of collecting the plants of deeper water is by dredging, or going round with a boat at the extreme ebb, and taking them from the rocks and from the Laminaria stems, on which a great number have their station. Stems of Laminaria thrown out by the waves should also be carefully examined. In all cases the weed should be well rinsed in a clear rock pool before being put away in the bag or other receptacle.

The next thing to be considered is the laying out and preserving of the specimens selected for the herbarium. Wherever possible these should be laid out on paper, and put under pressure as soon as gathered, or on the same day at all events. When this is impracticable, they may be spread between the folds of soft and thick towels and rolled up. Thus treated the most delicate plants will keep fresh until next day. Another way is to pack the plants in layers of salt, like herrings; but the most usual method of roughly preserving sea-weeds collected during an unprepared visit to the shore is by moderately drying them in an airy room out of the direct rays of the sun. They are then to be placed lightly in bags, and afterwards relaxed by immersion and prepared in the usual way. The finer plants, however, suffer more or less by this delay. If carried directly home from the sea the plants should be emptied into a vessel of sea-water. A flat dish, about fourteen inches square and three deep, is then to be filled with clean water. For most plants this may be fresh, for some it is essential that it should be salt. Some of the Polysiphonias and others begin to decompose at once if placed in fresh water. The Griffithsias burst and let out their colouring matter, and a good many change their colour. The appliances required are some fine white paper—good printing demy, thirty-six pounds or so in weight per ream, does very well,—an ample supply of smooth blotting paper, the coarse paper used by grocers and called "sugar royal," or, best of all, Bentall's botanical drying paper, pieces of well-washed book muslin, a camel's hair brush, a bodkin for assisting to spread out the plants, a pair of scissors, and a pair of forceps. The mounting paper may be cut in three sizes: 5 in. by 4 in., 7½ in. by 5¼ in., and 10 in. by 7½ in. Then having selected a specimen, place it in the flat dish referred to above, and prune it if necessary. Next take a piece of the mounting paper of suitable size, and slip it into the water underneath the plant, keeping hold of it with the thumb of the left hand. Having arranged the plant in a natural manner on the paper, brush it gently with the camel's hair brush, to remove any dirt or fragments, draw out paper and plant gently and carefully in an oblique direction, and set them on end for a short time to drain. Having in this way transferred as many specimens as will cover a sheet of drying paper, lay them upon it neatly side by side, and cover them with a piece of old muslin. Four sheets of drying paper are then to be placed upon this, then another layer of plants and muslin and four more sheets of drying paper, until a heap, it may be six or eight inches thick, is built up. Place this between two flat boards, weighted with stones, bricks, or other weights; but the pressure should be moderate at first, otherwise the texture of the muslin may be stamped on both paper and plant. The papers must be changed in about three hours' time, and afterwards every twelve hours. In three or four days, according to the state of the weather, the muslin may be removed, the plants again transferred to dry paper, and subjected to rather severe pressure for several days.

The very gelatinous plants require particular treatment. One way is to put them in drying paper and under a board but to apply no other pressure, change the drying paper at least twice during the first half hour, and after the second change of dryers apply very gentle pressure, increasing it until the specimens are fully dry. A safer and less troublesome way, for the efficacy of which we can vouch, is to lay down the plants and dry them without any pressure, afterwards damping the back of the mounting papers and placing them in the drying press. Some Algæ will scarcely adhere to paper. These should be pressed until tolerably dry, then be immersed in skim-milk for a quarter of an hour, and pressed and dried as before. A slight application of isinglass, dissolved in alcohol, to the under side of the specimen is sometimes necessary. Before mounting, or at all events before transference to the herbarium, care should be taken to write in pencil on the back of the paper the name of the plant, if known, the place where gathered, and the date. The coarse olive weeds, such as the bladder-wrack, Halidrys, and the like, may in the case of a short visit to the coast be allowed to dry in an airy place, and taken home in the rough. Before pressing, in any case, they should be steeped in boiling water for about half an hour to extract the salt, then washed in clean fresh water, dried between coarse towels, and pressed and dried in the same way as flowering plants. A collection of Algæ may be fastened on sheets of paper of the usual herbarium size and kept in a cabinet or portfolios, or attached to the leaves of an album. For scientific purposes, however, the latter is the least convenient way.

There are few objects more beautiful than many of the sea-weeds when well preserved; but the filiform species, especially those of the first sub-order, do not retain their distinguishing characters when pressed as has been described. Portions of these, however, as well as sections of stems and fruit, may be usefully dried on small squares of thin mica, for subsequent microscopic examination, or they may be mounted on the ordinary microscope slides. This is the only course possible with Desmids and Diatoms. The former are to be sought in shallow pools, especially in open boggy moors. The larger species commonly lie in a thin gelatinous stratum at the bottom of the pools, and by gently passing the fingers under them they will be caused to rise towards the surface, when they can be lifted with a scoop. Other species form a greenish or dirty cloud on the stems and leaves of other aquatic plants, and by stripping the plant between the fingers these also may be similarly detached and secured. If they are much diffused through the water, they may be separated by straining through linen; and this is a very common way of procuring them. Living Diatoms are found on aquatic plants, on rocks and stones, under water or on mud, presenting themselves as coloured fringes, cushion-like tufts, or filmy strata. In colour the masses vary from a yellowish brown to almost black. They are difficult, both when living and dead, to separate from foreign matter; but repeated washings are effectual in both cases, and, for the living ones, their tendency to move towards the light may also be taken advantage of. When only the shells are wanted for mounting, the cell contents are removed by means of hydrochloric and nitric acid. The most satisfactory medium for preserving fresh Desmids and Diatoms is distilled water, and if the water is saturated with camphor, or has dissolved in it a grain of alum and a grain of bay salt to an ounce of water, confervoid growths will be prevented. For larger preparations of Algæ, Thwaites' fluid is strongly recommended. This is made by adding to one part of rectified spirit as many drops of creasote as will saturate it, and then gradually mixing with it in a pestle and mortar some prepared chalk, with sixteen parts of water; an equal quantity of water saturated with camphor is then to be added, and the mixture, after standing for a few days, to be carefully filtered.

For authorities on the morphology and classification of the Algæ, students may be referred to Sachs' "Text Book" and Le Maout's "System of Botany," of which there are good translations, and the "Introduction to Cryptogamic Botany," by the Rev. M. J. Berkeley; for descriptions and the identification of species, to the text and figures of Harvey's "Phycologia Britannica," and "Nature-Printed Sea-weeds." Both of these are however costly. Among the cheaper works are "British Sea-weeds," by S. O. Gray (Lovell, Reeve & Co.), "Harvey's Manual" and an abridgment by Mrs. A. Gatty, with reduced but well executed copies of the figures, of the Phycologia. This synopsis can often be picked up cheap at second-hand bookstalls; and there is a very excellent low-priced work suitable for amateurs, Grattann's "British Marine Algæ," containing recognizable figures of nearly all our native species. Landsborough's "Popular History of British Sea-weeds," and Mrs. Lane Clarke's "Common Sea-weeds," are also cheap and useful manuals on the subject.

SHELLS.

BY

B. B. WOODWARD.

SHELLS.

INTRODUCTORY.

In the very earliest times, long before there was any attempt at the scientific classification and arrangement of shells, they appear to have been objects of admiration, and to have been valued on account of their beauty, for we find that the pre-historic men, who, in company with the mammoth, or hairy elephant, and other animals now extinct, inhabited Southern France in days long gone by, used to bore holes in them, and, like the savage of to-day, wear them as ornaments. The Greek physician and philosopher, Aristotle, is said to have been the first to study the formation of shells, and to raise the knowledge thus acquired into the position of a science; by him shells were divided into three orders—an arrangement preserved, with some small changes, by Linnæus. It is possible that the world-wide renown of the Swedish naturalist during the last century, and the ardour with which he pursued his investigations, may have given an impetus to the study of natural objects, for we find that at that period large sums were often given by collectors for choice specimens of shells. Nor is this to be wondered at, for few things look nicer, or better repay trouble expended on them, than does a well-arranged and carefully mounted and named collection of shells. Certainly nothing looks worse than a number of shells of all descriptions, of every kind, shape, and colour, thrown promiscuously into a box, like the unfortunate animals in a toy Noah's ark, to the great detriment of their value and beauty; for, as the inevitable result of shaking against each other, the natural polish is taken off some, the delicate points and ornaments are broken off others, the whole collection becoming in time unsightly and disappointing, and all for want of a little care at the outset.

In this, as in every other undertaking, "how to set about it" is the chief difficulty with beginners; and here, perhaps, a few hints gathered from experience may not be without value. One thing a young collector should always bear in mind, however, is, that no instructions can be of any avail to him uhis part, he is prepared to bring patience, neatness, and attention to detail, to bear upon his work.

Since it is important to know the best way of storing specimens already acquired, we will, in the first place, devote a few words to this point, and then proceed to describe the best means of collecting specimens, and of naming, mounting, and arranging the same.

HOW TO MAKE A CABINET.

It is a common mistake, both with old and young, to imagine that a handsome cabinet is, in the first instance, a necessity; but no greater blunder can be made: the cabinet should be considered merely an accessory, the collection itself being just as valuable, and generally more useful, when kept in a series of plain wooden or cardboard boxes. We intend, therefore, to describe the simplest possible means of keeping a collection of shells, leaving elaborate and costly methods to those who value the case more than its contents.

The first thing required is some method of keeping the different species of shells apart, so that they may not get mixed, or be difficult to find when wanted. The simplest plan of doing this is to collect all the empty chip match-boxes you can find, throw away the cases in which they slide, and keep the trays, trying to get as many of a size as possible. (The ordinary Bryant & May's, or Bell & Black's, are the most useful, and with them the trays of the small Swedish match-boxes, two of which, placed side by side, occupy nearly exactly the same space as one and a half of the larger size, and so fit in with them nicely.) In these trays your shells should be placed, one kind in each tray; but although very convenient for most specimens, they will of course be too small for very many, and so the larger trays must be made. This may easily be done as follows: cut a rectangular piece of cardboard two inches longer one way than the length of the match-tray, and two inches more the other way

Fig. 1. How to cut
a cardboard tray. than twice the width of the match-tray; then with a pencil rule lines one inch from the edges and parallel with them ([Fig. 1]); next cut out the little squares (a a, a a) these lines form in the corners of the piece of cardboard, and then with a penknife cut half through the card, exactly on the remaining pencil-lines, and bend up the pieces, which will then form sides for your tray; and by binding it round with a piece of blue paper, you will have one that will look neat, uniform with the others, and yet be just twice their size. If required, you can make in the same way any size, only take care that they are all multiples of one standard size, as loss of space will thereby be avoided when you come to the next process in your cabinet. This is, to get a large box or tray in which to hold your smaller ones.

The simplest plan is to get some half-dozen cardboard boxes (such as may be obtained for the asking or for a very trifling cost at any draper's), having a depth of from one to two inches (according to the size of your shells); in these your trays may be arranged in columns, and the boxes can be kept one above the other in a cupboard or in a larger box. More boxes and trays can, from time to time, be added as occasion requires, and thus the whole collection may be kept in good working order at a trifling cost. A more durable form of cheap cabinet may be made by collecting the wooden boxes so common in grocers' shops, cleaning them with sand-paper, staining and varnishing them outside, and lining them inside with paper; or, if handy at carpentering, you may make all your boxes, or even a real cabinet, for yourself.

HOW TO COLLECT SHELLS.

Provision being thus made for the comfortable accommodation of your treasures, the next consideration is, how to set about collecting them. Mollusca are to be found all over the globe, from the frozen north to the sun-baked tropics, on the land or in lakes, rivers, or seas—wherever, in fact, they can find the food and other conditions suitable for their growth and development; but the collector who is not also a great traveller, must of course rely for his foreign specimens upon the generosity of friends, or else procure them from dealers. In most districts of our own country, there are, however, to be found large numbers of shells whose variety and beauty will astonish and reward the efforts of any patient seeker. Begin with your own garden,—search in the out-of-the-way, and especially damp, corners; turn over the flower-pots and stones which have lain longest in one place, search amongst the roots of the grass growing under walls, and in the moss round the roots of the trees, and you will be surprised at the number of different shells you may find in a very short space of time. When the resources of the garden have been exhausted, go into the nearest lanes and again search the grass and at the roots of plants, especially the nettles which grow beside ditches and in damp places; hunt amongst the dead leaves in plantations, and literally leave no stone unturned. All the apparatus it is necessary to take on these excursions consists of a few small match or pill-boxes in which to carry home the specimens; a pair of forceps to pick up the smaller ones, or to get them out of cracks; a hooked stick to beat down and pull away the nettles; and, above all, sharp eyes trained to powers of observation. The best time to go out, is just after a warm shower, when all the grass and leaves are still wet, for the land-snails are very fond of moisture, and the shower entices them out of their lurking-places. Where the ground is made of chalk or limestone, they will be found most abundant; for as the snail's shell is composed of layers of animal tissue, strengthened by depositions of calcareous earthy-matter which the creature gets from the plants on which it feeds, and these in their turn obtain from the soil—it naturally follows that the snail prefers to dwell where that article is most abundant, as an hour's hunt on any chalk-down will soon show.

When garden and lanes are both exhausted, you may then turn to the ponds and streams in the neighbourhood, where you will find several new kinds. Some will be crawling up the rushes near the margin of the water, others will be found in the water near the bank, while others may be obtained by pulling on shore pieces of wood and branches that may be floating in the water; but the best are sure to be beyond the reach of arm or stick, and it will be necessary to employ a net, which may be easily made by bending a piece of wire into a circle of about four inches in diameter, and sewing to it a small gauze bag; it may be mounted either on a long bamboo, or, better still, on one of those ingenious Japanese walking-stick fishing-rods. For heavier work, however, such as getting fresh-water mussels and other mollusca from the bottom, you will require a net something like the accompanying figure ([Fig. 2]), about one foot in diameter. This, when attached to a long rope, may be thrown out some distance and dragged through the water-weeds to the shore, or if made with a square instead of a circular mouth, it may be so weighted that it will sink to the bottom, and be used as a dredge for catching the mussels which live half-buried in the mud. To carry the water-snails home, you will find it necessary to have tin boxes (empty mustard-tins are the best), as match-boxes come to pieces when wetted.

Fig. 2. Net for taking water-snails.

The finest collections of shells, however, are to be made at the sea-side, for the marine mollusca are both more varied in kind and more abundant than the land and fresh-water ones, and quite an extensive collection may be made in the course of an afternoon's ramble along the shore; it is necessary, however, to carefully reject such specimens as are worn by having been rolled by the waves upon the beach, as they are not of any great value in a collection; it is better, in fact, if possible, to go down to the rocks at low water and collect the living specimens. Search well about and under the sea-weeds, and in the rock-pools, and, when boating, throw your dredge-net out and tow it behind, hauling it in occasionally to see what you have caught, and to empty the stones and rubbish out.

At low tide also, look out for rocks with a number of round holes in them, all close together, for in these holes the Pholas ([Fig. 22]) dwells, having bored a burrow in the solid rock, though how he does it we do not yet quite know.

The Razor-shells and Cockles live in the sand, their presence being indicated by a small round hole; but they bury themselves so fast that you will find it difficult to get at them. Some good specimens, too, of the deeper water forms are sure to be found near the spots where fishermen drag their boats ashore, as they are often thrown away in clearing out the nets; moreover, if you can make friends with any of the said fishermen, they will be able to find and bring you many nice specimens from time to time.

The reason that so much has been said about collecting living specimens, is not only because in them the shell is more likely to be perfect, but also because in its living state the shell is coated with a layer of animal matter, sometimes thin and transparent, at others thick and opaque, called the periostracum (or epidermis), which serves to protect the shell from the weather, but which perishes with the animal, so that dead shells which have lain for some time tenantless on the ground, or at the bottom of the water, exposed to the destructive agencies that are constantly at work in nature, have almost invariably lost both their natural polish and their varied hues, and are besides only too often broken as well. Since, however, even a damaged specimen is better than none at all, such should always be kept until a more perfect example can be obtained.

HOW TO PREPARE THE SHELLS FOR THE CABINET.

The question with which we have next to deal is, after collecting a number of living mollusks, how, in the quickest and most painless manner possible, to kill the animals in order to obtain possession of their shells. There is but one way we know of in which this may be accomplished, and that is by placing the creatures in an earthen jar and pouring boiling water on them. With land, or fresh-water snails, the addition of a large spoonful of table-salt is advisable, as it acts upon them chemically, and not only puts them sooner out of pain, but also renders their subsequent extraction far easier. Death by this process is instantaneous, and consequently painless; but to leave snails in cold salt water is to inflict on them the tortures of a lingering death; while for the brutality of gardeners and other thoughtless persons who seek to destroy the poor snail they find eating their plants by crushing it under foot on the gravel path, no words of condemnation are too strong, since it must always be borne in mind that snails have not, like us, one nervous centre, but three, and are far more tenacious of life; hence, unless all the nerves are destroyed at once, a great deal of suffering is entailed on the poor creature; and if merely crushed under foot, the mangled portions will live for hours. Hot water has also the advantage of tending to remove the dirt which is almost sure to have gathered on the shells, and so helping to prepare them better for the cabinet. As soon as the water is cool enough, fish out the shells one by one and proceed to extract the dead animals. This, if the mollusk is univalve (i.e., whose shell is composed of a single piece), such as an ordinary garden snail, can easily be done by picking them out with a pin; you will find, probably, that some of the smaller ones have shrunk back so far into their shells as to be beyond the reach of a straight pin, so it will be necessary to bend the pin with a pair of pliers, or, if none are at hand, a key will answer the purpose if the pin be put into one of the notches and bent over the edge until sufficiently curved to reach up the shell. You will find it convenient to keep a set of pins bent to different curves, to which you may fit handles by cutting off the heads and sticking them into match stems. It is a good plan to soak some of the smaller snails in clean cold water before killing them, as they swell out with the water, and do not, when dead, retreat so far into their shells. If you have a microscope, and wish to keep the animals till you have time to get the tongues out, drop the bodies into small bottles of methylated spirit and water, when they will keep till required, otherwise they should of course be thrown away at once. The now empty shells should be washed in clean warm water, and, if very dirty, gently scrubbed with a soft nail or tooth brush, and then carefully dried.

In such shells as the Periwinkle, Whelk, etc., whose inhabitants close the entrance of their dwelling with a trap-door, or operculum as it is called, you should be careful to preserve each with its proper shell.

If you are cleaning bivalves, or shells composed of two pieces, like the common mussel, you will have to remove the animal with a penknife, and while leaving the inside quite clean, be very careful not to break the ligament which serves as a hinge; then wash as before, and tie them together to prevent their gaping open when dry.

Sometimes the fresh-water or marine shells are so coated over with a vegetable growth that no scrubbing with water alone will remove it, and in these cases a weak solution of caustic soda may be used, but very carefully, since, if too strong a solution be employed, the surface of the shell will be removed with the dirt, and

Fig. 3. (a) Helix sericea and (b) Helix hispida. the specimen spoilt. In some shells the periostracum is very thick and coarse, and must be removed before the shell itself can be seen; but it is always well to keep at least one specimen in its rough state as an example. In other shells the periostracum is covered over with very fine, delicate hairs (Helix sericea and Helix hispida, [Fig. 3]), and great care must then be taken not to brush these off.

HOW TO MOUNT THE SHELLS FOR THE CABINET.

When the specimens are thoroughly cleaned, the next process is to sort out the different kinds, placing each description in a different tray, and then to get them ready for mounting, for no collection will look well unless each kind is so arranged that it may be seen to the best advantage, and is also carefully named. Where you have a good number, pick out first the largest specimens of their kind, then the smallest, then a series, as you have room for them, of the most perfect; and finally those which show any peculiarity of structure or marking. Try, too, to get young forms as well as adult, for the young are often very different in appearance from the full-grown shell. Mark on them, especially on such as you have found yourself, the locality they came from, as it is very important to the shell collector to know this, since specimens common enough in one district are often rare in another. Either write the name of the place in ink on a corner of the shell itself, or gum a small label just inside it, or simply number it, and write the name of the place with a corresponding number against it in a book kept for the purpose. Next select a tray large enough to hold all you have of this kind; place a piece of cotton wool at the bottom, and lay your shells upon it. For small shells, however, this method is not suitable, as the cotton wool acts on them like a spring mattress, and they are liable on the least shock to be jerked out of their trays and lost. This difficulty may be met by cutting a piece of cardboard so that it just fits into your tray, and then gumming the shells on to it in rows; but remember that, in this plan of mounting, it is impossible to take the shells up and examine them on all sides as you do the loose ones, and so you must mount a good many, and place them in many different positions, so that they may be seen from as many points of view as possible. The gum used should always have nearly one-sixth of its bulk of pure glycerine added to it; this prevents it from becoming brittle when dry, otherwise your specimens would be liable after a time to break away from the card and get lost. If the shells will not stay in the position you require, wedge them up with little pieces of cork until the gum is dry.

When the shells are mounted, you must try, if you have not already done so, to get the proper names for them; it is as important to be able to call shells by their right names as it is to know people by theirs. The commoner sorts you will be able to name from the figures of them given in text-books, such as those quoted in the list at the end of this little work; but some you will find it very difficult to name, and it will then be necessary to ask friends who have collections to help you, or to take them to some museum and compare them with the named specimens there exhibited. When the right name is discovered, your label must then be written in a very small, neat hand, and gummed to the edge of the tray or on the card if your specimens are mounted. At the top you put the Latin name, ruling a line underneath it, and then, if you like, add the English name; next, put the name of the place and the date at which it was found, thus:—

A double red ink line ruled at the top and bottom will add a finished appearance to it.

HOW TO CLASSIFY THE SHELLS FOR THE CABINET.

All the foregoing processes, except the naming of your specimens, are more or less mechanical, and are only the means to the end—a properly arranged collection. For, however well a collection may be mounted, it is practically useless if the different shells composing it be not properly classified. By classification is meant the bringing together those kinds that most resemble each other, first of all into large groups having special characteristics in common, and then by subdividing these into other smaller groups, and so on. Thus the animal kingdom is divided, first of all, into Sub-kingdoms, then each Sub-kingdom into so many Classes containing those which have further characteristics in common, the Classes into Orders, the Orders into Families, the Families into Genera, and these again into species or kinds.

The Mollusca, or soft-bodied animals, of whose protecting shells your collection consists, form a sub-kingdom, and are subdivided into four classes:—

1. Cephalopoda.
2. Gasteropoda.
3. Pteropoda.
4. Lamellibranchiata (or Conchifera).

And these again into Families, Genera, and Species.

The space at our disposal being limited, it is impossible to do more than furnish some general outlines of the different forms. For further details it will be necessary to refer to one of the larger works, a list of which will be found on the last page.

Fig. 4. Argonauta Argo.

Fig. 5. "Bone" of Sepia officinalis.

CLASS I.—The CEPHALOPODA (Head-footed) contains those mollusca that, like the common Octopus, have a number of feet (or arms) set round the mouth, and is divided into those having two gills. (Order I. Dibranchiata); and those with four (Order II. Tetrabranchiata). Order I. is again divided into: (a.) Those with eight feet like the Argonaut (or Paper-nautilus, [Fig. 4]), which fable has so long endowed with the power of sailing on the surface of the ocean, (it is even represented in one book as propelling itself through the air!) and the common Octopus. (b.) Those with ten feet, such as the Loligo (or Squid, [Fig. 6]), whose delicate internal shell so much resembles a pen in shape; the Cuttle-fish (Sepia, Figs. [5] & [7]), whose so-called "bone" (once largely used as an ink eraser) is frequently found on our southern coasts; and the pretty little Spirula ([Fig. 8]).

The only representative of the four-gilled order now living is the well-known Pearly Nautilus; but in former times the Tetrabranchiata were extremely numerous, especially the Ammonites.

Fig. 8. Spirula.

CLASS II.—GASTEROPODA (Belly-footed) comprises those mollusca which, like the common snail, creep on the under-surface of the body, and with one exception (Chiton, [Fig. 20]) their shells are univalve (i.e., composed of one piece). But before we go further, it may be well to point out the names given to different parts of a univalve shell. The aperture whence the animal issues is called the mouth, and its outer edge the lip; each turn of the shell is a whorl; the last and biggest, the body-whorl, the whorls, from the point at the top, or apex, down to the mouth form the spire; and the line where the whorls join each other is called the suture. The axis of the shell around which the whorls are coiled is sometimes open or hollow, and the shell is then said to be umbilicated (as in Fig. 3b); when closely coiled, a pillar of shell, or columella, is left (as in [Fig. 9]). Sometimes the corner of the mouth farthest from the spire and next the columella, is produced into a channel, the anterior canal (as in [Fig. 9]); whilst where the mouth meets the base of the spire there may be a kind of notch which is termed the posterior canal. Most Gasteropods are dextral, that is to say, the mouth is to the right of the axis as you look at it; a few, however, are sinistral, or wound to the left (like Physa); whilst reversed varieties of both kinds are met with.

Gasteropods of the first order have comb-like gills placed in advance of the heart, and are hence termed Prosobranchiata. They are divided into two groups: (a) Siphonostomata (Tube-mouthed), in which the animal has a long proboscis, and a tube, or siphon, from the breathing-chamber that passes along the anterior canal of the shell, which in this group is well developed. They have a horny operculum, or lid, with which to close the aperture. (b) Holostomata (or Whole-mouthed). In these the siphon is not so produced, and does not want to be protected; accordingly the mouth of the shell is entire, i.e. has no canal. The operculum is horny or shelly. The former (group a) includes several families:

1. Strombidæ, comprising shells, like the huge Strombus, or "Fountain-shell," which is so often used to adorn the mantelpiece or rockery, and from which cameos are cut.

2. The Muricidæ, of which the Murex (an extraordinary form of this is the "Venus' comb," Murex tenuispina, [Fig. 9]), the Mitre-shells, and the Red-Whelks (Fusus) are examples.

3. The Buccinidæ, taking its name from its type, the Common Whelk (Buccinum undatum), and including such other forms as the Dog-Whelk (Nassa), the Purpura, the strange Magilus, and the lovely Harp-Shells and Olives ([Fig. 10]).

Fig. 9. Murex tenuispina.

4. The Cassididæ, or "Helmet-Shells." Cassis rufa, from West Africa, is noted as the best species of shell for cameo engraving; with it are classed the "Tun" (Dolium) and the great "Triton" (Triton tritonis), such as the sea-gods of mythology are represented blowing into by way of trumpet, and which are used by the Polynesian Islanders to this day instead of horns.

Fig. 10. Oliva tessellata.

5. The Conidæ, whose type, the "Cone-shell" ([Fig. 11]), is at once distinctive and handsome, but which in the living state is covered by a dull yellowish-brown periostracum that has to be carefully removed before the full beauties of the shell are displayed.

6. The Volutidæ, embracing the Volutes and "Boat-shells" (Cymba).

7. The Cypræidæ, or Cowries ([Fig. 12]), which owe their high polish to the size of the shell-secreting organ (mantle), whose edges meet over the back of the shell, concealing it within its folds. With these is classed the "China-shell" (Ovulum).

Fig. 11. Conus vermiculatus.

The second group, or Holostomata, is divided into nineteen families, beginning with—

1. The Naticidæ, whose type, the genus Natica, is well known to all shell-collectors through the common Natica monilifera of our coasts.

2. The Cancellariadæ, in which the shells are cancellated or cross-barred by a double series of lines running, one set with the whorls, and the other across them.

3. The Pyramidellidæ, which are high-spired, elongated, and slender shells, with the exception of the genus Stylina, which lives attached to the spines of sea-urchins or buried in living star-fishes and corals.

Fig. 12. Cypræa oniscus.

4. The Solaridæ or "Staircase-shells," whose umbilicus is so wide that, as you look down it, the projecting edges of the whorls appear like a winding staircase. It is a very short-spired shell.

5. The Scalaridæ, "Wentle-traps" or "Ladder-shells," which may be readily recognised from their white and lustrous appearance and the strong rib-like markings of the periodic mouths that encircle the whorls.

6. The Cerithiadæ, or "Horn-shells," which are very high-spired, and whose columella and anterior canal are produced in the form of an impudent little tail, the effect of which, however, in the genus Aporrhais, or "Spout-shells," is taken away by the expanded and thickened lip.

7. In the next family, the Turritellidæ, or "Tower-shells," the type Turritella is spiral; but in the allied form Vermetus, though the spire begins in the natural manner, it goes off into a twisted tube resembling somewhat an ill-made corkscrew. The mouth in this family is often nearly round.

8. The Melaniadæ, and 9. The Paludinidæ, are fresh-water shells. The former are turreted, and the latter conical or globular. Both are furnished with opercula, but the mouth in the first is more or less oval and frequently notched in front, while in the latter it is rounded and entire.

10. The Litorinidæ, or Periwinkles, need no word from us.

11. The Calyptræidæ comprise the "Bonnet-limpet," or Pileopsis, and "Cup-and-saucer-limpets" (Calyptræa). They may be described briefly as limpets with traces of a spire left. The genus Phorus, however, is spiral, and resembles a Trochus. They have been called "Carriers" from their strange habit of building any stray fragments of shell or stone into their house, thus rendering themselves almost indistinguishable from the ground on which they crawl.

12. The Turbinidæ, or "Top-shells," are next in order, and of these the great Turbo marmoreus is a well-known example, being prepared as an ornament for the whatnot or mantelpiece by removing the external layer of the shell in order to display the brilliant pearly nacre below. These mollusca close their mouths with a horny operculum, coated on its exterior by a thick layer of porcelain-like shelly matter. With them are classed the familiar Trochus and other closely allied genera.

13. The Haliotidæ offer in the representative genus Haliotis, or the "Ear-shell," another familiar mantelpiece ornament.

14. The Ianthinidæ, or "Violet-snails," that float about in mid-Atlantic upon the gulf-weed, and at certain seasons secrete a curious float or raft, to which their eggs are attached, are next in order, and are followed by—

15. The Fissurellidæ, or "Key-hole" and "Notched limpets," whose name sufficiently describes them. To these succeed—

16. The Neritidæ, an unmistakable group of globular shells, having next to no spire and a very glossy exterior, generally ornamented with a great variety of spots and bands.

17. The Patellidæ, or true Limpets, are well known to every sea-side visitor: large species, as much as two inches across, are to be found on the coast of Devon, but these are pigmies compared with a South American variety which attains a foot in diameter.

18. The Dentaliadæ, represented by the genus Dentalium, or "Tooth-shell," are simply slightly curved tubes, open at both ends and tapering from the mouth downwards, and cannot be mistaken.

19. Lastly, we have the Chitonidæ, whose single genus Chiton possesses shells differing from all other mollusca in being composed of eight plates overlapping each other, and in appearance reminding one of the wood-louse. This animal is not only like the limpet in form but also in habits, being found adhering to the rocks and stones at low-water.

Order II.—Pulmonifera. Contains the air-breathing Gasteropods, and to it consequently belong all the terrestrial mollusca, though some few aquatic genera are also included. The members of this order have an air-chamber instead of gills, and are divided into two groups, (a) those without an operculum, and (b) those having an operculum. Foremost in the first group stands the great family—

1. Helicidæ, named after its chief representative, the genus Helix. It also includes the "Glass-shell" (Vitrina), the "Amber-shell" (Succinea), and such genera as Bulimus, Achatina, Pupa, Clausilia ([Fig. 13]), etc., which differ from the typical Helix in appearance, possessing as they do comparatively high spires.

Fig. 13. Clausilia biplicata.

2. The Limacidæ, or "slugs," follow next; of these only one, the genus Testacella, has an external shell stuck on the end of its tail; the rest have either a more or less imperfect shell concealed underneath the mantle, or else none at all.

3. The Oncidiadæ are slug-like, and devoid of shell.

4. The Limnæidæ embrace the "Pond-snails," chief of whom is the well-known, high-spired Limnæa stagnalis. Other shells of this family associated with Limnæa are, however, very different in shape; for instance, Physa has its whorls turning to the left instead of to the right; Ancylus ([Fig. 24]), or the freshwater limpet, is of course limpet-like; while Planorbis, or the "Coil-shell," is wound like a watch-spring.

5. The Auriculidæ includes both spiral shells, such as Auricula and Charychium, and a limpet-like one Siphonaria.

At the head of group b stands 1, Cyclostomidæ. Cyclostoma elegans is a common shell on our chalk-downs, and well illustrates its family, in which the mouth is nearly circular. Foreign examples of this genus are much esteemed by collectors. The other two families are, (2) Helicinidæ and (3) Aciculidæ.

Fig. 14. Bulla ampulla.

Order III.—Opisthobranchiata. These animals carry their gills exposed on the back and sides, towards the rear of the body. Only a few have any shell. 1. The Tornatellidæ, which have a stout little spiral shell. 2. The Bullidæ, in which the spire is concealed ([Fig. 14]). 3. The Aplysiadæ, where the shell is flat and oblong or triangular in shape. The remaining families are slug-like and shell-less.

Order IV.—Nucleobranchiata. Derives its name from the fact that the animals constituting it have their respiratory and digestive organs in a sort of nucleus on the posterior part of the back, and covered by a minute shell. As they are pelagic, the shells are not readily to be obtained. They are divided into two families, Firolidæ and Atlantidæ.

CLASS III.—PTEROPODA. Like the last, these pretty little mollusca are ocean-swimmers. The members of one division of them, to which the Cleodora belongs, is furnished with iridescent external shells.

CLASS IV.—The LAMELLIBRANCHIATA (Plate-gilled), or Conchifera (Shell-bearing), includes the mollusca commonly known as "bivalves," the animal being snugly hidden between two more or less closely fitting shelly valves. The oysters, cockles, etc., are examples of this class. The two valves are fastened together near their points, or beaks (technically called umbones), by a tough elastic ligament, sometimes supplemented by an internal cartilage. If this be severed and the valves parted, it will be found that in most cases they are further articulated by projecting ridges or points called the teeth, which, when the valves are together, interlock and form a hinge; the margin of the shell on which the teeth and ligament are situated is termed the hinge-line. A bivalve is said to be equivalve when the two shells composing it are of the same size, inequivalve when they are not. If the umbones are in the middle, the shell is equilateral ([Fig. 15]); but inequilateral when they are nearer one side than the other ([Fig. 16]). If the shell be an oyster or a scallop, you will find on the inside a single circular scar-like mark near the

Fig. 15. Petunculus guerangeri.

Fig. 16. Venus plicata. centre; this is the point to which the muscles that close the valves and hold them so tightly together are attached. In the majority of bivalves, however, there are two such muscular impressions, or scars, one on either side of each valve of the shell. The former group on this account are often called Monomyaria (having one shell-muscle), and the latter Dimyaria (having two shell-muscles). In the last named the two muscular impressions are united by a fine groove (or pallial-line), which in some runs parallel to the margin of the shell ([Fig. 15]), whilst in others it makes a bend in (pallial-sinus) on one side of the valve towards the centre ([Fig. 16]). In Monomyaria it will be found running parallel to the margin of the shell. It marks the line of attachment of the mantle or shell-secreting organ of the animal to the shell which grows by the addition of fresh matter along its edges, so that the concentric curved markings so often seen on the exterior correspond in their origin with the periodic mouths of the Gasteropods. The bivalves are all aquatic, and many bury themselves in the sand or mud by means of a fleshy, muscular foot. These are furnished with two siphons, or fleshy tubes, sometimes united, sometimes separate, through which they respire, drawing the water in through one and expelling it by the other. Those kinds whose habit it is to bury themselves below the surface of the mud or sand are furnished with long retractile siphons, and to admit of their withdrawal into the shell, the mantle is at this point attached farther back, giving rise to the pallial-sinus above described; this sinus is deeper as the siphons are proportionately longer, and in many cases, too, the valves do not meet at this point when the shell is closed.

Attention to these particulars is necessary when arranging your bivalves, as on them their classification depends, the class being divided into—

a. Asiphonida (Siphonless).

b. Siphonida Integro-pallialia (with Siphons).—Pallial-line entire.

c. Siphonida Sinu-pallialia (with Siphons).—Sinus in pallial-line.

Fig. 18. Trigonia margaritacea.

Fig. 17. Hinge-teeth of Arca barbata.

Division a.—Asiphonida—is next subdivided into—

1. The Ostreidæ, or oysters, which are deservedly a distinct family in themselves.

2. The Anomiadæ, comprising the multiform and curiously constructed Anomia, with the "Window-shells" (Placuna).

3. The Pectinidæ, taking its name from the genus Pecten, or "Scallop-shells," of which one kind (P. maximus) is frequently to be seen at the fishmongers' shops. The "Thorney oysters" (Spondylus) take rank here, and are highly esteemed by collectors, one specimen indeed having been valued at £25!

4. The Aviculidæ, or "Wing-shells," among which are numbered the "Pearl-oyster" of commerce (Meleagrina margaritifera). The strange T-shaped "Hammer oyster" belongs to this family, as does also the Pinna. The Pinnas, like the mussels and some other bivalves, moor themselves to rocks by means of a number of threads spun by the foot of the mollusc, and termed the byssus, which in this genus is finer, more silky, than in any other, and has been woven into articles of dress.

5. The Mytilidæ, or mussels, including the Lithodomus, or "Date-shell," which bores into corals and even hard limestone rocks.

6. The Arcadæ, or "Noah's-ark-shells," characterized by their long straight hinge-line set with numerous very fine teeth ([Fig. 17]). The "Nut-shell" (Nucula) belongs to this family.

7. The Trigoniadæ, whose single living genus, the handsome Trigonia ([Fig. 18]), is confined to the Australian coast-line, whereas in times now long past they had a world-wide distribution.

8. The Unionidæ, comprising the fresh-water mussels.

Fig. 19. Hinge of Cardita sinuata.

Division b.—Siphonida Integropallialia.

1. The Chamidæ, represented by the reef-dwelling Chama.

2. The Tridacnidæ, whose sole genus Tridacna contains the largest specimen of the whole class of bivalves, the shells sometimes measuring two feet and more across.

3. The Cardiadæ, or cockles.

4. The Lucinidæ, in which the valves are nearly circular, and as a rule not very attractive in appearance, though the "Basket-shell" (Corbis) has an elegantly sculptured exterior.

5. The Cycladidæ, whose typical genus Cyclas, with its round form and thin horny shell, is to be found in most of our ponds and streams.

6. The Astartidæ, a family of shells having very strongly developed teeth, and the surface of whose valves is often concentrically ribbed.

7. The Cyprinidæ, which have very solid oval or elongated shells and conspicuous teeth ([Fig. 19]). The "Heart-cockle" (Isocardia) belongs to this family.

Fig. 22. Pholas dactylus.

Fig. 20. Hinge of Cytherea crycina.

Division c.—Siphonida Sinu-pallialia.

Fig. 21. Hinge of Lutraria elliptica

1. The Veneridæ. The hard, solid shells of this family are for elegance of form and beauty of colour amongst the most attractive a collector can posses. Their shells are more or less oval and have three teeth in each valve ([Fig. 20]).

2. The Mactridæ are somewhat triangular in shape, and may be at once recognised by the pit for the hinge-ligament, which also assumes that form, as seen in the accompanying figure of Lutraria elliptica ([Fig. 21]).

3. The Tellinidæ comprise some of the most delicately tinted, both externally and internally, of all shells. In some, coloured bands radiate from the umbones, and well bear out the fanciful name of "Sunset shells" bestowed upon them. Their valves are generally much compressed.

4. The Solenidæ, or "Razor-shells," rank next, and are readily recognised by the extreme length of the valves in proportion to their width, and also by their gaping at both ends.

5. The Myacidæ or "Gapers," have the siphonal ends wide apart (in the genus Mya both ends gape), and are further characterized by the triangular process for the cartilage, which projects into the interior of the shell. One valve (the left) is generally smaller than the other.

6. The Anatinidæ have thin, often inequivalve pearly shells. The genus Pandora is the form most frequently met with in collections.

7. The Gastrochænidæ embraces two genera (Gastrochæna and Saxicava) of boring mollusca, which perforate shells and rocks, and also, the remarkable tube-like "Watering-pot-shell" (Aspergillum) which is hardly recognisable as a bivalve at all.

8. The Pholadidæ concludes the list of bivalves, and comprises the common rock-boring Pholas ([Fig. 22]) of our coasts and the wood-boring shipworm "Teredo" ([Fig. 23]).

Although the Brachiopoda, or "Lamp-shells," are not true mollusca, they are not very far removed from them, and are so often to be found in cabinets that it will not do to pass them over, especially since in past times they were very abundant, an enormous number occurring in the fossil state. Only eight genera are now living. Shells belonging to this class are readily recognised by the fact of one valve being larger than the other, and possessing a distinct peak, the apex of which is perforated. The Terebratulidæ are the most extensive family of this class.

Fig. 23. Teredo navalis.

HOW TO ARRANGE THE SHELLS IN THE CABINET.

When you have arranged your specimens in the order above indicated, proceed to place them in your boxes, arranging and labelling them after the manner shown in the accompanying diagram.

+----------+----------+----------+----------+----------+
| Class. | | | | |
+----------+ Species. | Species. | Species. | Species. |
| Order. | | | | |
+----------+----------+----------+----------+----------+
| Family | | | | |
| Name. | | | | |
+----------+ Species. | Species. | Species. | Species. |
| Generic | | | | |
| Name. | | +----------+ |
+----------+----------+----------+ Family +----------+
| | | | Name. | |
| Species. | Species. | Species. +----------+ Species. |
| | | | Generic | |
+----------+----------+----------+ Name. +----------+
| | | +----------+ |
| | Generic | | | |
| Species. | Name. | Species. | Species. | Species. |
| | | | | |
+----------+----------+----------+----------+----------+
| | | | | Generic |
| Species. | Species. | Species. | Species. | Name. |
| | | | | |
+----------+----------+----------+----------+----------+
| | | Generic | | |
| Species. | Species. | Name. | Species. | Species. |
| | | | | |
+----------+----------+----------+----------+----------+
| | | | | |
| Species. | Species. | Species. | Species. | Species. |
| | | | | |
+----------+----------+----------+----------+----------+

On the lid, or on a slip of paper or card placed at the head of your columns of trays, write the class and order, with its proper number (I., II., etc., as the case may be); then at the top of your left-hand column place the family and its number, and under it the name of the first genus. The species (one in each tray) come next, then the name of the next genus following it, succeeded by its species, and so on.