VENERUPIS PERFORANS.PSAMMOBIA.
"These genera consist mostly of small shells, inhabiting stones, into which they bore holes.S. rugosais British.Venerupis perforansis found on our coasts in stones. The valves of these shells have no accessory pieces likePholas.
"Nymphaceais the next family, containing, in the first section,
"In the genusPsammobiawe find ourTellina Feroensis. (Plate 4.) The shells of this and the preceding genus resemble the solens in a trifling degree, being a little open at the sides. In form they are nearTellina, but have not the fold on the anterior valve, but an angle oneachvalve. The ligament is exterior.
"In the second section are—
CORBIS.LUCINA.CAPSA.CYCLAS.
"There is but one species ofTellinidesfrom the island of Timor. The genusCorbisis fossil, with one exception,Corbis fimbriata, from the Indian Ocean.Lucinais a pretty genus of shells.L. carnariais frequently found in collections. The interior of the valves is of a deep red colour: the muscular impressions are very distant from each other; one is greatly lengthened out; the valves delicately striated.Capsais taken, you perceive, fromDonax.
"Tellinais found fossil on the borders of the Red Sea, also in the county of York. OfDonaxandMactrathe fossil species are few.
"In the third section of this order we find six families. 1st.Conchæ, which are of two kinds, fluviatic, living in fresh-waters; and marine, or living in the sea. Of the first are,
Cyclas, taken fromTellina.Cyrene, partly fromTellinaandVenus.Galathea,Venus paradoxa, (one species.)
"Cyclas rivicola(Plate 9.) will give you an idea of this genus: it isTellina corneaof Linnæus. The species are very common in lakes, rivers, and ponds: it abounds in river-sand, from which you may often procure perfect specimens. Lamarck observes that it is rare in France; but appears common in the Thames.
Plate 9.Page 50.
Plate 9.Page 50.
Plate 9.
Page 50.
POTAMOPHILA.ASTARTE.PULLASTRA.
"Cyreneis a foreign genus.
"In theConchæ marìnæthe genera are very numerous. They are all assembled under theVenusof Linnæus. Lamarck reduced the genus; but it has been yet further divided by later writers.
"Pullastrawas the name of a species, and includesV. pullastra,V. papilionacea,V. decussata,V. litterata,V. virginea.
"Astarteincludes some British species,V. Scotica, &c.
VENUS.CYTHEREA.ISOCARDIA.
"Potamophilais a scarce river-shell from Ceylon. Some species have also been brought from Congo by African travellers. The form is triangular, very thick, covered with an olive-green epidermis. Lamarck's two genera have been still further reduced; but I shall refer you to the Museum for their new names. Observe, inVenusthere are three cardinal teeth, close together, on each valve, with divergent lateral teeth.V. lamellatais rare and beautiful, from the seas of New Holland. There are many species ofVenusin a fossil state. InCythereawe find four cardinal teeth on therightvalve, three of them near together, the fourth quite apart. Theleftvalve has three cardinal teeth.C. Dionè, the thorny Venus, is a pretty shell with spines. You may easily procure it.
"Astartehas some fossil species in the crag and green sand:A. obliquatais one species.
"Venericardiais wholly a fossil genus: one species is found in the crag,V. senilis.
"The familyCardiaceacontains
"Isocardia coris British. (Plate 9.) There is a beautiful species,Isocardia moltkianafrom the East Indies, which is much valued by collectors.
"In the familyArcaceawe find,
ARCA.PECTUNCULUS.NUCULA.NAYADA.
"The hinge ofArcain this arrangement is alwaysstraight, furnished with a number of teeth; the ligament is external. The shells are open at one end, for the animal throws out at the aperture a number of threads, by which it fastens itself to the rocks. The species are thirty-seven, and also several fossil.
"The orbicular form ofPectunculus, and its arched hinge, distinguish this genus from the preceding one. They are allied to the Pectens by their form, and their crenulated internal margin.
"The hinge ofNuculais set with little teeth on each side, like a comb. It is pearly within, and sometimes small pearls are found in the shell.Pectunculus costatusis found in London clay.
"Trigonianais a small family containingTrigoniaandCastalia. The first is a fossil genus chiefly. Some species are found in the Portland stone, or oölite beds.
"The next family contains theNayada, chiefly composed of fluviatic, or fresh-water shells. They are covered with an olive-brown epidermis, which is constantly found eroded, or destroyed at the beaks. The muscular impressions are lateral and much separated; one ofthem is formed of two or three distinct irregular impressions.
UNIO.ANODON.DICERAS.
"Uniohas two teeth on each valve; one is cardinal, the other lengthened out. The ligament is exterior—the shell pearly.Unio pictorumis common in rivers. The shell is used to hold small masses of gold or silver for artists, under the name ofshell-gold.
"Anodonis also to be met with in our rivers.
"A. anatinais eaten by ducks and crows. The latter, when the shell proves too hard to penetrate, mount with it into the air, and letting it fall, pick out the fish from the broken shell.
"Chamaceahas only three genera.
Etheria, a rare genus, from the Indies and Madagascar.
"Dicerasis a fossil genus—only two species known according to Lamarck.
CHAMA.
"Linnæus had assembled in his genus,Chama, shells with equal and with unequal valves, shells fixed to other marine bodies, with those that are free; some withone, others withtwomuscular impressions. In the present genus,Chama, the shells are irregular, thick, scaly, or spinous. The hinge has one thick tooth, often notched: the beaks are bent inwards. They are found in the Indian, American, and Mediterranean seas. There are several fossil species.
"The first order,Bimusculosa, is finished. In our next lesson we shall proceed to the families and genera contained in the second,Unimusculosa."
CHAPTER VIII.
Class.—Conchifera.
Second Order.—Unimusculosa.
"1st family,Tridacnacea.
UNIMUSCULOSA.TRIDACNA.MODIOLA.
"In the first genus we find the greatTridacna gigas, the largest and heaviest shell yet known. It sometimes weighs five hundred pounds. The hinge has two teeth, the lunula is open, the valves equal, the ligament exterior.
"Mytilacea.
"The greater part of these genera attach themselves to marine substances by a byssus. TheModiolagenus are rarely found fixed. The ligament internal, lodged in a marginal gutter. Beaksnearly lateral; hinge without teeth. The genusPinnais unaltered. Small crustaceous bodies, resembling the crab, are sometimes found in the shells of thePinna.
PINNA.PERNA.AVICULA.
"Malleacea.
"The first genus is found in the seas of warm climates. The shells are thin and foliated. The hinge ofPernadiffers widely from that of the oyster. It is linear, formed of sulcated teeth. There is a sinus under the extremity of the hinge, for the passage of the byssus. CompareP. isognomonwith the common oyster, and you will find few points of resemblance between them. (Plate 5.)Perna ephippiumis also a curious species, very pearly within. Thehammersare rugged and singular in form. They are all foreign, from the oriental seas.
"Avicula, or Swallow, so called from the resemblance of the shells to a bird flying, was considered as a single species by Linnæus. Lamarck makes eighteen species in his new genera.Meleagrinahas two species. The pearl-bearingmuscle, as it is called, is found in the Persian Gulf, the Gulf of Mexico, &c. The interior of the shell is coated with thick pearl, and within it are formed those globular substances known by the name of pearls.
MELEAGRINA.LIMA.PECTEN.
"Family,Pectenida: genera—
"The genusLimais longitudinal, auricled, or eared; hinge without teeth, with a hollow receiving the ligament. These are very pretty shells, generally white, almost transparent, resembling thePecten.Limacomes from the American seas, and is a species easily obtained. There are also several fossil species.
"Plagiostomais wholly a fossil genus, of which several species are found in this country, in lias, &c.
"The pectens are so easily known that I need only mention some fine species, such asP. pallium, a splendid shell, from the Indian seas:P. pleuronectesis a finely polished, smooth species from the Indian Ocean.
"The genus is divided into sections, viz. ears equal, ears unequal. You may find some common species on our own shores, and you may procure fossil species: they are numerous.
PLICATULA.OSTREA.
"Plicatulais a genus taken fromSpondylus.Spondylus gæderopus, from the Mediterranean, is a common shell in collections.
"Podopsisis a fossil genus.
"Ostracea.
"The oysters and pectens differ so widely that they do not even rank in the same family.
"In theOstraceaare,
"There is but one recent species of the first genus; but many fossil.
"The oyster is said to possess the most limited faculties of all shelly tribes. Immovable upon the rock or marine substance to which it is fastened, it receives no other nourishment than what the waves contribute, and indicates no other sign of life than opening and closing the valve of the shell. This genus still retains a great number of species: one section has the margin of the shelleithersimple, orwaved, the otherfolded.O. edulis, common oyster, belongs to the first division.
"O. foliumis of the second; a curious species, from the Indian and American seas: the shell is fixed to wood and to the roots of trees on the sea-shores.
"Vulsellais a foreign genus, from the Indian and other seas.
PLACUNA.ANOMIA.
"Placunadoes not adhere to any marine substance. The valves are flat, thin, and transparent; the very small space between them shows that the animal must be extremely flattened: there are two singular ribs at the hinge in the form of a V.
"P. placenta, Chinese window-glass, is so transparent when young, that it serves instead of that material in China.
"Anomia.The shells of this genus are fixed, like the oyster, to marine bodies. They live and perish on the spot where they are at first produced. I have noticed the muscle by which they attach themselves. Lamarck informs us that a hard, small operculum is to be seen at the extremity of this muscle, and fills up thehole in the flat valvewhen the muscle is contracted. (Plate 5.)
"The familyRudistacontains only a few genera, which will be quite uninteresting to you at present.
"The next,Brachiopoda, has
Lucy could not forbear interrupting her father upon hearing the name ofPatella. "How can that genus be mixed with theConchifera?" she inquired.
"The shell isbivalve," he replied; "raised upon a fleshy peduncle, and fixed to marine substances; the hinge is without teeth, having the form of a duck's beak; the colour a greenish tint. It is found near the Molucca isles.
HIPPONYX MITRATA.
"Yet more remarkable is theHipponyx mitrata, a common shell, known asPatella mitrata, long supposed to be a univalve, the upper valve only being known. A French naturalist discovered the lower valve, andbothhave one muscular impression in the form of a horse-shoe.
"I think that it will be best to pause a little before we enter upon the study of the twelfth class,Mollusca, which contains most of the univalves of Linnæus."
CHAPTER IX.
MOLLUSCA.CLEODORA.
Twelfth Class—Mollusca.
"As I have observed that you have been very diligent in studying Lamarck since our last lesson," said Mr. Elliot, "I propose to make you acquainted with the variations in the univalve genera.
"The animals of theMolluscaare soft, without joints, generally possessing a head, eyes, and tentacula, or feelers. They have also a fleshy membrane, called a foot, which they use for climbing. The orders, excepting the first, are named from the position of this foot. They are five in number. The first order contains very few genera. One genus, namedCleodora, contains a species brought from Africa. The shell is curious, transparent, and shaped like the head of a halberd.
"The animals of the second order,Gasteropoda, have a muscular foot, or disk, on which they rest. The families are seven. The first,Tritonia, I shall pass over.
"Phyllidianaincludes the genera—
CHITON.PATELLA.
"TheChitonmoves like thePatella, upon a disk, or foot.
"The body ofPatellais entirely covered by the shell. You may have many opportunities of examining the British species.P. pellucidais very transparent, with blue lines.
"The familySemi-phyllidianacontains
"TheUmbellashell is flat and white, and is sometimes four inches in diameter. It is common in the Isle of France: there is another from the Mediterranean.
"Calyptraceais a larger family: it has many genera taken fromPatella:
FISSURELLA.PILEOPSIS.BULLA.
Parmophorusis found in the seas of New Holland and New Zealand. The margin of the next genus is distinguished by a slit: the shell is conic. (Plate 3.)Fissurellahas the top of the shell perforated; it is called thekey-holelimpet, from the shape of the aperture.Pileopsisis obliquely conic. It was with this division that the curiousHipponyxranked.
"Calyptræais very thin and brittle, with an internal lip. (SeeFrontispiece.)
"Crepidulahas the shell partly covered, or arched: it looks like a little slipper.
"Ancylus spina-rosais a pretty species from the south of France: the genus is fluviatic.A. lacustrisandfluviatilisare both natives of our fresh-waters.
"The next family,Bullæana, has
"Aceraand the following genus have each but one species,Bulla carnosaandB. apertaof Linnæus. The original genusBullawas composed of an assemblage of shells of various characters,having little resemblance except in their gibbous form.Bulla naucumis an example of the genus of Lamarck's system; so isB. lignaria. (SeeFrontispiece.)B. ampullaandB. striataare common in collections.
APLYSIA.DOLABELLA.
"Aplysianais a small family, containing
"One species ofAplysiais found on the Devonshire coast: the name Sea-hare marks the singularity of the two tentacula, which resemble the ears of the hare. The body is folded up in a loose skin, or mantle: upon the middle of the back it carries a circular shield, thin, transparent, and yellowish, in which it resembles the slug. These animals swim with ease.
"Dolabellaresembles theAplysiain some degree; the genus is foreign, and one species is known to inhabit the bays of the Isle of France, where it covers itself with a portion of mud."
"I cannot understand why animals related to the slugs should find a place here," said Charles.
"Have not slugs the characteristics of theMolluscaclass?" asked his father. "And are you quite sure that they are without a shell?
ONCHIDIUM.LIMAX.
"Our next family, theLimacina, has
"Onchidiumis a genus from the shores of the Indian seas. The animals have a shield: they live near the sea, and some are known to swim, often coming to the surface to breathe the air.
"Parmacellawas found by an English traveller in Mesopotamia. It has a shell covered by a shield. But you have not answered my question respecting theLimax, or slug."
"I do not recollect," replied Charles; "yet how often we see slugs!"
"If I may be allowed to answer," said Lucy, "I think that the slug has what I now understand to be ashield. I have often watched the animal contract itself, and seen a broad, flat piece upon the back, which I thought was a kind of shelter for it."
"TheLimax, or slug," continued Mr. Elliot, "is, in fact, provided with a coriaceous escutcheon, or shield, beneath which the animal partly conceals itself. TheLimax agrestis, or spinning-slug, has the power of suspending itself bya kind of thread, formed of the viscid substance that covers the body.
TESTACELLUS.COLIMACEA.
"Testacellusis a very interesting genus, lately found in England: the animal has a resemblance to the common slug: it carries the shield on the hinder part of the body.
"Testacellus scutellumfeeds on earth-worms, and can so much lengthen the body that it follows them under-ground.
"Our next order will show great alterations in the very large genusHelix. I shall name to you those of Lamarck.
"The third order ofMollusca,Trachelipoda, begins with a well-known genus, the snail,Helix. The term signifies that thefootis situated under the neck, or anterior part of the body. The families in this order are numerous: they are divided into two sections; the first includes those that breathe only in the air; the second those that can exist only in the water, and are furnished with a syphon.
HELIX.CUROCOLLA.ANOSTOMA.
"First section: familyColimacea; genera numerous; animals live upon land only; tentacula generally four; during winter they enclose themselves in their shells, with a false operculum.
"What a number of new genera!" said Lucy. "I see the forms of the shells vary very much; and how beautiful these little transparent shells are!"
"They will find a place shortly. Here is a well-known species,H. aspersa, in most of its varieties;H. pomatia, the apple-snail, now naturalized in the county of Surrey;H. ericetorum, white with brown bands, very frequent on chalky soils;H. citrina, transparent, pale yellow, sometimes with one dark band;H. muralis, from the walls of Rome;H. bidentalis, from Teneriffe; and the littleHelix hispida, which you may search for in your own garden; it is small, dark brown, and rough.
"Carocollahas the shells more flattened thanHelix.
"Anostoma depressais a rare and curious shell.
"Helicinais a West Indian genus. Yousaw them just now. We shall find Helix in two other families.
PUPA.BULIMUS.AURICULA.
"Pupais a curious genus. The shells resemble a chrysalis. A few minute species are found in Britain.P. muscorumI have found buried among damp moss. The larger species are natives of tropical regions. These shells are often founddecollated.
"Clausilia papillarisis a pretty shell. (Plate 9.)
"Clausilia rugosais found in some parts of Britain, under old hedges, at the foot of old trees, and similar places. It is a tapering shell, with the aperture reversed, or left-handed, and bi-dentated: the colour red-brown. It is to be found in the vicinity of Dorking, in Surrey.
"Bulimusis a large genus. A common small species is theGaudaloupe Bulimus.
"The largest land-shells are found in the genusAchatina. The greater number are African.
"Succineacontains a few species. One of them,S. amphibia, is common near fresh-water.
"Auriculahas some resemblance to aVoluta. The aperture is longitudinal: the columella has one or more folds.
"The forms of the species inCyclostomaare variable; but the aperture is circular, and the margin revolute, or rolled back.C. elegansisoften to be found on hedge-banks or chalk soils. It is a pretty shell, sometimes white, often tinted with purple.
"In the familyLymænana, the species are amphibious; inhabiting fresh-water; but rising to the surface to breathe the air. They have but two tentacula.
"As several species are British, you may have the satisfaction of examining them for yourselves.
PLANORBIS.
"The genera are,
"Planorbisis a discoid shell, and one peculiarity of the genus is, that they are all reverse shells. In a discoid shell the spire is depressed; when held up, the whorls turn from right to left, and the aperture is left-handed. The largest species isP. cornu-arietis,[B]which is a native of Brazil.P. corneusis common in ponds and ditches. Empty shells are to be found at the edge of the water. (Plate 9.) If you take the animal to examine, and study its habits, remember that you have no right to injure it, and that you have already promised me that no kind of cruelty shall take place.
[B]Ram's-horn.
[B]Ram's-horn.
"P. vortexis a smaller species. The outer valve is carinated.
"Physais found in fresh-water upon aquatic plants. They are small shells.
LYMNÆA.MELANOPSIS.VALVATA.
"The animal of theLymnæagenus has two flat tentacula.L. stagnalisis a very pretty spiral shell, common in ponds.
"L. auriculariais also frequent. It is much smaller than the first species. The last whorl is swelling, and the aperture very wide. They are both thin and brittle.
"The familyMelanianaare chiefly foreign. The shells are covered with a dark-coloured epidermis. They are operculated.
"A species ofMelanopsisinhabits the river Orontes, in Syria.
"There is yet another family connected withHelix, thePeristomata, containing
PALUDINA.
"Some of theValvatagenus are found in fresh-water in Britain and other European countries. The shells are small; they are discoid or conoid, and have an operculum. In the shells of this family the margin of the aperture is carried completely round. InPaludinathe whorls are convex. They generally inhabit fresh-waters.
"P. viviparais found in rivers. Quantities of empty shells may be taken from the sand of the Thames.
"Fossil species abound—Petworth marble is full of them."
CHAPTER X.
NERITACEA.NERITINA.
"The family of theNeritacea," said Mr. Elliot, as he renewed his lessons to Charles and Lucy, "are remarkable in their form. Their left-margin is truncated, without any appearance of a columella. They possess an operculum, and are either marine or fluviatic. The genera are,
"You will recollect that the orderTrachelipodais still continued.
"Navicellais a foreign genus from the Indian rivers.
NERITINA.NERITA.
"Neritìnais a pretty genus of shells, from the European, the East and West Indian rivers. They resemble theNerìtagenus, but are all fresh-water shells; thin, smooth, and variously marked; without any tooth or notch on the right-margin of the aperture.
"N. virgineais common in collections; it is marked with various lines and dots.
"N. fluviatilisis common in our rivers: you may find plenty in river-sand, of red and brown colours, and various sizes.
"N. zebraandN. meleagrisare also pretty shells. The littleNeritìna viridis, from the West Indian streams, is one of the smallest species, of a pale pellucid green.
"Nerìtais a marine genus. The shells are solid and semi-globose; the left-margin is truncated, the right-margin toothed, or crenulated. This genus is never umbilicated.
"N. polìtais a handsome shell: it is thick, polished, and variously marked; the base of the aperture is yellowish.
"N. peloronta, the bleeding-Nerite, is marked with a crimson spot.
"N. tessellatais sulcated, or furrowed, chequered with black and white.
"Natìcadiffers from the former genera in these particulars: the shell is umbilicated; the left-margin oblique, not toothed, callous, the callosity sometimes covering the umbilicus. The species are numerous, and several are common in collections. "N. aurantiusandN. millepunctataare good shells.
IANTHINA.SIGARETUS.STOMATELLA.
"Ianthinais the last of the snail-like genera. Its beautiful purple colour renders the shell afavourite. They are marine, though so fragile and transparent. The animal floats upon the surface of the sea, by means of a vesicular appendage to the foot, which, it is said, may be inflated or contracted at pleasure.Ianthinashines by night.I. communisis found in abundance in the Atlantic and in the Mediterranean.
"The familyMacrostomacontains,
"These genera form a beautiful family, and all bear a resemblance to the human ear.
"Sigaretusis white and pearly; the shell is enveloped in the folds of the mantle belonging to the animal. There are several species, one or two of which were ranked among theHelixrace.
"Stomatellais also very pretty; the shells are pearly.S. auricula, from New Holland, has the appearance of a littleHaliòtis.
"Stomatiais a small genus.