Fig. 24.
The length is measured from the apex, to that part of the aperturea(fig. 24), at the greatest distance from it. Thebreadthis in the opposite direction. Theanterior, or front part of the aperture, is markeda, where the head of the animal protrudes.
Spire of non-symmetrical Univalves.
Figs. 25-32.Fig. 25,obtuse; 26,acute; 27, 28,decollated; 29,concave; 30,papillary; 31,mammellated; 32,discoidal.
Fig. 25,obtuse; 26,acute; 27, 28,decollated; 29,concave; 30,papillary; 31,mammellated; 32,discoidal.
In counting the whorls of which the spire consists, we commence at the apex, and reckon downwards to the last, or body whorl. The spire is described as being long or short in relation to the aperture: in which case, all that is above the aperture is measured with the spire. Its apex requires particular notice, as the character of the whole shell frequently depends upon the particulars observable in this part. It is sometimesobtuse, or blunt; sometimesacute, or sharp. In the Cones it is frequently flat, and in Planorbis it is concave. It is sometimes of a different structure from the rest of the shell, retaining the horny and transparent appearance which characterized it when the animal was first hatched. The Tritons present an instance of this, although it is not always observable, owing to the tenderness of the substances which causes it to break or fall away in many specimens. A very remarkable instance also occurs in Bulinus decollatus (cut, fig. 27, 28), so named, because the apex, to the depth of several whorls, falls off, and the shell isdecollated. In this, and many more instances, among Pupæform land shells, the occurrence of this circumstance seems to be by no means rare or accidental, a provision having been made for filling up the opening by a septum. Apapillary apexis one which is swelled at the extremity into a little rounded nob, or nipple; and amammellatedapex is one which is rounded out more fully into the shape of a teat.
Whorls.
The spire is described as consisting ofnumerousorfewwhorls, and sometimes the number of them is particularly stated. A whorl consists of one turn of the spiral cone. The whorls are described asflattened, when the sides are not bulged out so as to cause the outline of the spire to deviate considerably from straightness: when the contrary is the case, the whorls are said to beventricose, and eitherroundedorangulated. The degree of rapidity with which the whorls become enlarged presents an important source of distinction. Thesuture, or seam, which separates one whorl from another is also noticed as beingdistinctor otherwise;canaliculated, or grooved; or covered by an enamel, which in some instances is swelled into a ridge ortumid.
Figs. 33-37.Fig. 33,few; 34,numerous; 35,rounded,ventricose; 36,angular,ventricose; 37,flattened.
Fig. 33,few; 34,numerous; 35,rounded,ventricose; 36,angular,ventricose; 37,flattened.
Suture.
Figs. 38-39.Fig. 38,canaliculated; 39,enamelled.
Fig. 38,canaliculated; 39,enamelled.
Varices.
Varices are caused by periodical rests or stoppages in the growth of the shell, when the edge of the aperture thickens, and renders the shell as complete as when full grown. Again, after an interval, another check takes place, and another thickened edge is formed, and so on in succession, until the animal arrives at maturity, and the shell is full-grown. The thickened edges successively forming the aperture, remain visible on the outside, through all the subsequent stages. When these rests take place at frequent periods, the varices will of course be numerous as in Harpa and Scalaria. They occur at regular or irregular distances, varying in shape and other characters. When the varices occur at regular intervals, and form a connected ridge from whorl to whorl up the spire, they are said to becontinuous, as in Ranella; when on the contrary, the varix on one whorl does not come in contact with that on the other, they are described asdiscontinuous. In order to distinguish a regular varix from a mere external ridge, it will be sufficient to notice whether its edge overlaps the external surface, and whether it resembles the open edge of the aperture, which true varices do.
Figs. 40-42.Fig. 40,numerous; 41,few, continuous; 42,few, discontinuous.
Fig. 40,numerous; 41,few, continuous; 42,few, discontinuous.
Aperture.
The aperture or opening of the spiral tube, was formerly described as the mouth; a term calculated to convey an erroneous impression, when applied to a part of the shell which has no correspondence with the mouth of the animal. The wordapertureis used by modern writers in a general sense, including the cavity, its edge, and the canals. The cavity itself is distinguished in various shells as to its shape, which depends much upon the degree of modification produced by the last whorl. In some cases, as in Cyclostoma, where the aperture stands apart from the last whorl, the shape is round, or nearly so. The Scalaria presents a good example of this. In others, where the inner edge or lip, wrapping over the body whorl is nearly straight, the aperture issemi-lunar, or half-moon shaped: this is remarkable in the "Neritacea" of Lamarck, named, on that account, "hemi-cyclostomata" by De Blainville. In a great number of instances, the lower part of the body whorl enters obliquely into the upper part of the aperture, the result being apyriform, or pear-shaped opening. The aperture is described aslongwhen it is largest in the direction of the axis, andwide, in the contrary case. Theanterioris the part at the greatest distance from the apex, and the body whorl; theposterior, the part nearest to the apex. Thus some apertures are described asposteriorly contractedandanteriorly widened, or the reverse. Alinearaperture is one contracted in its whole length, as in Cypræa. When the whorls are angulated, atrigonalaperture is the result, as in many species of Trochus. Some aretransversely oval, that is in an opposite direction to the axis, and otherslongitudinally oval. When the whorls are formed with two outer angles, a somewhat quadrated aperture is formed. There are other variations too numerous to mention.
Apertures.
Figs. 43-50.Fig. 43, Helicina,semilunar; 44, Pirena,pyriform; 45, Cypræa,linear; 46, Trochus,trigonal; 47, Cyclostoma,rounded; 48, Chilina,posteriorly contracted; 49, Stomatia,transversely oval; 50, Murex,longitudinally oval.
Fig. 43, Helicina,semilunar; 44, Pirena,pyriform; 45, Cypræa,linear; 46, Trochus,trigonal; 47, Cyclostoma,rounded; 48, Chilina,posteriorly contracted; 49, Stomatia,transversely oval; 50, Murex,longitudinally oval.
The entire edge of the aperture described generally, is named the Peritrême, but this term can only be conveniently applied in cases where, in some at least of its characters, it is the same all round, so that one descriptive term is applicable to the whole. As, however, this is of rare occurrence, it is found convenient in descriptions to separate the rim from the outer lip. In a great number of instances, this is done naturally, by a canal, or notch at the anterior or lower extremity, and by the posterior union of that part which overlays the body whorl with the other portion. At these two points the outer and inner lips separate from each other: we therefore describe the
Canals of the Aperture.
When there is neither notch nor canal, anteriorly or posteriorly, interrupting the edge of the aperture, it is described as entire. When there is a notch or sinus at the anterior extremity, it is said to beemarginated. When the edge of this notch is expanded, and drawn out in the form of a beak, it is said to becanaliferous, or to have acanal. When, in addition to this, the lips are thickened and contracted posteriorly near their junction, and drawn out so as to form a groove, it is said to bebi-canaliculated, or to have two canals. Theanterior canalis said to be long or short, according to the proportion which it may bear to the rest of the shell. Thus the canal of Ranella ranina (fig. 393 in the plates), may be described asshort; while that of Murex haustellum, (fig. 396, pl.) islong. When it is wide near the aperture, and becomes gradually contracted towards its termination, it is said to betapering, as in Pyrula (fig. 388, pl.); when the termination is sudden, it is described astruncated. If, on placing the shell upon a plane, with the aperture downwards, the canal is seen to rise upwards, it isrecurved. In Buccinum and Nassa it is turned suddenly over the back, and forms a short, curved elevation; it is then described asrecurvedandvaricose. If the edges meet, so as to form a tube, it is said to be closed, as in some species of Murex and Typhis. The posterior canal is, in some cases,free, or standing out from the spire, as in some species of Ranellæ; while in others it isdecumbent, running up the sides of the spire, as in Rostellaria (fig. 402, pl.).
Canals.
Figs. 51-54.Fig. 51, Fasciolaria,truncated; 52, Nassa,recurved,varicose; 53, Cerithium,recurved; 54, Typhis,closed.
Fig. 51, Fasciolaria,truncated; 52, Nassa,recurved,varicose; 53, Cerithium,recurved; 54, Typhis,closed.
Lips, or edges of the Aperture.
The part of the edge of the aperture next to the body whorl is named theinner, orcolumellarlip. Posteriorly it commences at the point of union with the outer lip, where that touches the body whorl, the junction being generally marked by an angle, and sometimes by a canal. Anteriorly it terminates where there is generally seen a notch or canal, or sudden angle, from which the outer lip proceeds. The part which setting out from the body whorl, and proceeds outwards at a distance from the axis, till it reaches the anterior canal or notch (or its place in case of absence) is named theouter lip. In many cases the edges are united in such a manner, that it is difficult to distinguish where the inner lip terminates, and the outer lip commences: when this is the case, it is usual to describe the margin or peritrême, as a whole, without distinguishing the parts. Theouterlip, sometimes called the right lip, orlabrumof continental writers, is sometimes acute, not being of thicker substance than the remainder of the shell. In other cases it isobtuse, or thickened and rounded at the edge. When thickened and turned backwards it is described asreflected; when, on the other hand, it is turned inwards towards the axis, as in the Cyprædæ, it isinflected, or involute. When it istoothed, a distinction must be observed as to whether the dentations are external or internal. If the teeth are small and numerous, it isdenticulated; if larger, it isdentated; when expanded into a kind of wing, as in some species of Strombus and Rostellaria, it is described asalated; and a family in Lamarck's system is named "Alatæ," from this very circumstance. In some of those which are expanded, the expansion is divided into separate, attenuated portions, they are then said to be digitated.
Outer Lips.
Figs. 55-59.Fig. 55, Helix,reflected; 56, Cypræa,involute,denticulated; 57, Sera,alated; 58, Murex,digitated; 59, Rostellaria,dentated.
Fig. 55, Helix,reflected; 56, Cypræa,involute,denticulated; 57, Sera,alated; 58, Murex,digitated; 59, Rostellaria,dentated.
Theinnerlip, sometimes named thecolumellarlip, or "labium," is subject to similar variations as to thickness, dentition, &c. That portion of it which lies upon the body-whorl is frequently distinguished from that which intervenes between it and the notch or canal. De Blainville, restricting the termlip"bord gauche" to the former portion, applies the term "columella" to the latter; and in some instances this may be the more convenient method of describing the part in question. The columellar lip is sometimesdetachedentirely from the body of the shell, as in Murex haustellum; in others it isdecumbent, or lying over the last whorl, although quite distinct, and in some cases,thickened,callous, ortumid.
At the lower or anterior part, sometimes called thecolumella, there are in many instances flattened, laminated folds; these are particularly conspicuous in the genera Cymba and Melo, where, being obliquely spiral and laminar, they are extremely elegant, presenting to the eye graduated repetitions of the line of beauty. In other cases, as in the Turbinellæ, they are more horizontal and thickened.
In some cases the columella is swelled into a varicose mass; as in Oliva, Ancillaria, &c.; it is then described astumidor varicose. It is sometimestortuous, and sometimes straight, and is susceptible of many variations, too minute and particular to be described in this part of the work.
Columellar Lips.
Figs. 60-63.Fig. 60, Melo,obliquely plaited; 61, Turbinellus,horizontally plaited; 62, Ancillaria,varicose,tortuous; 63, Natica,straight.
Fig. 60, Melo,obliquely plaited; 61, Turbinellus,horizontally plaited; 62, Ancillaria,varicose,tortuous; 63, Natica,straight.
OPERCULUM.
The aperture of many species of shells remains constantly open; but in a great number of species it is occasionally closed, whenever the animal is retracted within the shell, by a calcareous or horny piece called the operculum. This must be distinguished in the first instance from another kind of calcareous covering, which in some univalve shells serves to close the aperture during a certain portion of the year. This piece, named theepiphragm, although hardened and shelly in appearance, is no real part of the animal or of the shell; being only a secretion temporarily hardened, for the purpose of defending the animal from external influences during thehibernatingortorpidseason, to be dissolved when that season is at an end. On examining this piece, it will be observed that it is not formed in regular layers like the rest of the shell; while the true operculum is of a regularly laminated structure, having a nucleus and receiving obliquely deposited additions, either in a lateral spiral or concentric direction. It is attached to the posterior part of the foot on the upper surface; and when the animal retires within its shell, that part of the foot enters last, drawing the operculum after it, and thus closing the aperture.
The opercula of various shells differ in the first place as to their chemical composition. They arecalcareouswhen formed principally of calcareous matter, like the rest of the shell, as in Neritina, Nerita, and some others. They arecorneo-calcareous, when upon an internal lamina of horny consistency there is a thickened layer of shelly matter. This is the case with shells of the genus Turbo and Phasianella, which are on this account distinguished from those of the genus Trochus; the opercula of the latter being horny orcorneus.
The size of the operculum is distinguished by comparison with the rest of the shell; thus, those of Strombus, Cassis, &c. are small; while those of Cyclostoma and others are large, filling up the cavity at its outer edge.
The direction in which the successive layers are deposited, forms another ground of distinction. The disc is formed in some instances of a series of whorls, the apex or nucleus being more or less central; if these whorls are numerous, the operculum is described asmultispiral, as in shells of the genus Trochus; if few, as in Cyclostoma, it ispaucispiral. In some instances the flattened spire consists of but one whorl, it is thenunispiral; and when scarcely one turn is completed, it is described assubspiral. When the layers are applied upon each other in such a manner that the nucleus is central, and the edges of the subsequent layers are extended beyond each other all around, so as to form rims, the operculum is described asconcentric; if the nucleus is lateral, or at one side without being spiral, it islammellated; and when it forms a terminal point, enlarging in the form of a finger-nail or claw, it isunguiculated. In the operculum of a Neritina, there is a lateral process, by means of which it is locked into the columella, the termarticulatedis then applied. In that of Navicella, there is also a process which appears to radiate from the nucleus, it has therefore been described as aradiatedoperculum.
Opercula of Spiral Univalves.
Figs. 64-70.Fig. 64,multispiral; 65,paucispiral; 66,concentric; 67,articulated; 68,radiated; 69,lammellated; 70,unguiculated.
Fig. 64,multispiral; 65,paucispiral; 66,concentric; 67,articulated; 68,radiated; 69,lammellated; 70,unguiculated.
BIVALVE SHELLS.
Bivalve shells, named Conchacea by Lamarck, are those which consist of two principal portions united to and folded upon each other by means of a hinge. The pieces united compose the shell, while each piece separately is called a valve. Considering the bivalve shell as a whole, it will be necessary, in the first instance, to describe the position in which it is to be observed, in order to give the student a clearly defined notion of what is intended, when terms expressive of height, depth, length, breadth, &c. are used, as well as when the anterior and posterior extremities are spoken of. For this purpose, we must suppose the animal to be living and creeping along the bed of the sea by means of its foot; where this foot protrudes, will be theventral margin, and the opposite part thedorsal marginof the shell. There will then be a valve on each side; and if we further suppose the animal to be walking forward with its back to the observer, therightandleftvalves will correspond with his right and left sides.
Measurements.
Figs. 71-72.
Thelengthwill be measured fromanterior(a) toposterior(p), and the lines of growth running in the same direction will consequently belongitudinalorconcentric;transverseof some authors. The height will be from the umbones (u), to theventral margin, and lines or bands in that direction are termedradiating; longitudinal, according to some authors.
The points from which the growth of the shell commences, are called theumbones; these usually turn towards the anterior part of the shell: if this circumstance fails to point out the anterior, it may in many cases be distinguished by the muscular impressions of the mantle. If this has a sinus or winding, it is always near the posterior muscular impression; and in all cases where there is an external ligament, it is on the posterior side.
There is sometimes an impression near the front of the umbones, which forms a semicircle on each valve; the space within this semicircle is called thelunule(wood-cut, fig. 71 and 72,l. l. l.); a corresponding depression, when it exists on the posterior margin near the umbones, is named the escutcheon.
Hinge.
Fig. 73.Fig. 73,l t, lateral teeth;c t, cardinal teeth;c, cartilage under the ligament;l, ligament;f, fulcrum of the ligament.
Fig. 73,l t, lateral teeth;c t, cardinal teeth;c, cartilage under the ligament;l, ligament;f, fulcrum of the ligament.
Thehingeof the shell is on thedorsalmargin, and is composed of the various apparatus by which the two valves act upon each other in opening and shutting. It consists of aligament, which is placed on the dorsal margin, just at the back of the umbones, and unites the two valves together; thecartilageor thick gristly elastic substance, sometimes found close to theligament, to which it then forms an inner coating, and sometimes received into a pit within the shell. It serves the purpose of keeping the shell open when not forcibly closed by the adductor muscles. An inner layer of shelly matter upon which are placed teeth, and pits to receive them on the two valves reciprocally. Each of these it will be necessary to treat of more at large; observing, at the same time, that in some species of Bivalves these parts may be wholly or partially wanting. Thus we meet with some shells, such as the Muscle, without teeth; and there is the group containing Pholas, &c. the hinge of which is destitute of teeth and ligament, the two valves being kept together by loose cartilages, and by the contracted space in which they are confined.
Ligament and Ligamentary Cartilage of the Hinge.
These two distinct substances have been described by many writers as though, composing the same mass, they were of one substance; but the difference may very easily be explained. Thetrue ligamentis external, being fixed on the edge of one valve behind the umbones, and passing over in an arch to the corresponding edge of the other, very correctly retaining the name ofligament, because it serves the purpose of binding the two together. The thick, elastic substance, which Mr. Gray names thecartilage, is sometimes found in connexion with the ligament, so as to form one mass with it, although it is always separable and placed within it: it is sometimes placed quite within the shell, and separated from the ligament, in a pit or hollow formed for its reception in the hinge lamina, near the centre. It is found in both valves, and being elastic, the portion in one valve presses against that in the other, so as to keep the valves apart, unless voluntarily closed by the adductor muscles of the animal. The ligament is sometimes spread over an external area, as in Arca, while the cartilage is placed in several grooves of the same area, beneath the outer covering.
Hinge lamina, Teeth and Fulcrum of the Ligament.
In a great variety of cases, there is a thickening of the substance of the shell within, under the dorsal margin; this is named the hinge lamina. It is sometimes merely callous; but in many cases it has raisedteethin both valves, those in one valve entering into corresponding cavities in the other. Those which are placed immediately below the umbones, and seem to take their rise from beneath them, are calledcardinal teeth; those at a distance from the umbones, which are seen to lie along the upper margin of the shell are namedlateral teeth.
When the cardinal teeth terminate in a double point, which is not unfrequently the case, they are said to bebifid. The lateral teeth, in various species, are distinguished as terminatingnearto, or at adistancefrom the umbones. In the Nuculæ and Arcæ there is a row of teeth placed across the hinge lamina. In which case, the lateral cannot be distinguished from the cardinal teeth.
Muscular Impression.
Fig. 74.Fig. 74.a, anterior; p, posterior; m i, muscular impressions.
Fig. 74.a, anterior; p, posterior; m i, muscular impressions.
Lamarck divides the Bivalve shells into two general orders; the first is named "Dimyaria," having two adductor muscles; and the second, "Monomyaria," having but one. These adductor muscles are used for the purpose of drawing the valves together, being composed of contractile fibrous gristle, fastened firmly to the inner surface of each valve. The place where they are thus fixed may be seen when the animal is removed, by depressed areas, which are generally pretty well defined, and are namedmuscular impressions. Where there is but one adductor muscle, there will be but one of these impressions near the centre of each valve, but in the Dimyaria, where there are two, the impressions are seen, one on the anterior, and one on the posterior of each valve, just below thehingelamina. They are sometimescomplex, that is composed of several portions in a group; but in general, they are simple and well defined.
They are also described as large or small, in proportion to the size of the shell; regular or irregular in form. The animal is attached to the inner surface by the fibrous portions of the mantle, which creates a linear impression orcicatrix, commonly described as thepalleal impression, or muscular impression of the mantle. It runs near the ventral margin from one muscular impression to the other, sometimes in a smoothcontinuousline or band, and sometimes in an interrupted series of small impressions. Near the point of union with the posterior muscular impression, there is sometimes a more or less considerable winding inwards towards the centre of the shell, and back again towards the point of union. This is named thesinus, and is distinguished as beingangularorrounded, large or small, according to the species. When it enters towards the centre of the shell in a tongue-shaped outline it is said to beligulate. Where it exists it affords a certain index to the posterior side of the shell; as it is the region through which the excretory tubes pass.
Umbones.
These are the prominent points of the dorsal edge, where the growth of the shell commenced, and are called beaks, by some English writers. In some instances they are close to each other; in others they are rendered distant from each other by the intervention of areas in the hinge, as in Spondyli, &c. In Pectunculus they arestraight; in Venuscurvedtowards the anterior margin; in Isocardia,spiral; in Chama,decumbent; in Diceras,free. In shells subject to external corrosion, the process commences at the umbones.
Figs. 75-81.Fig. 75,distant; 76,straight; 77,curved; 78,spiral; 79,decumbent; 80,free; 81,close.
Fig. 75,distant; 76,straight; 77,curved; 78,spiral; 79,decumbent; 80,free; 81,close.
GENERAL CHARACTER OF BIVALVES.
When thebreadthis spoken of, the distance between the most convex parts of both valves, when closed, is intended; but when an expression implyingthicknessis used, it refers to the substance of each valve: it is important to bear this in mind, as many persons have been misled by descriptions in which the distinction has not been attended to. Glycimeris (fig. 67 in the plates) is athickshell, but Anatina (fig. 69 in the plates) is abroadone.
Regularity.
A great number of Bivalves are extremely regular in their form. These are generally locomotive, and consequently free from those obstructions in growth occurring to stationary shells, which being confined in a particular position, or to a particular spot, modify their shape according to the substance with which they come in contact, and thus become irregular. This is generally the case with shells which are attached to submarine substances, such as Spondyli, Oysters, &c.; and the degree of irregularity will depend upon the extent of surface involved in the attachment. In the case of fixed shells, the attached valve is usually termed the under valve, and the other which moves freely upon the hinge, is termed the upper valve.
Form and Proportions.
Bivalves are said to beequivalvewhen the two valves correspond in extent, breadth, and thickness; and of courseinequivalvein the contrary case. They areequilateralwhen a line drawn from the umbones to the ventral margin would divide the shell into two nearly equal parts; and of courseinequilateralin the opposite case, which occurs in the great majority of instances.
A Bivalve is said to becompressed, when the distance is small from the most prominent part of one valve to that of the other. It iscylindricalwhen lengthened, and more or less rounded in its breadth, as in Lithodomus (fig. 161 in the plates). It iscordiformwhen the shape presents a resemblance to an imaginary heart, as in Cardium cardissa (fig. 122 in the plates), and in the Isocardia (fig. 126 in the plates). It islinguiformwhen it resembles a tongue in shape, as in Vulsella (fig. 185 in the plates);rostratedwhen it protrudes at either extremity, and terminates in a kind of point, as in Sanguinolaria Diphos (fig. 99 in the plates);truncatedwhen it ends in a square or angle, as if cut off; an example of which may be seen in Solen (fig. 60 in the plates).
Other Bivalves are distinguished as beingauriculated, having processes flattened and expanded on either side of the umbones, as in Pecten (cut, fig. 82). When there is one of these on each side of the umbones, it isbi-auriculated; when only on one side, it isuni-auriculated. When the expansion is very broad, as in Unio alatus (fig. 142 in the plates), and in the Hammer Oyster (cut, fig. 83), the termalatedis used.
Figs. 82-83.Fig. 82,auriculated; 83,auriculated,alated.
Fig. 82,auriculated; 83,auriculated,alated.
With regard to these alated species ofUniones, it is necessary to observe that they are also "adnate," as it is termed; the two valves being joined to each other by the dorsal edge of the expanded parts, and united so completely in substance with each other, that they cannot be separated without being broken. Many other terms are used to express difference in Bivalves, but being generally applicable to Univalves and Multivalves, as well as to them, they will be found explained at large in the alphabetical part of the work.
MULTIVALVE SHELLS.
These are of three different kinds; first, the "dorsal," as they are termed by Linnæus, because they form a ridge in the back of the animal. They are composed of eight pieces, or separate valves, placed in a longitudinal series, being joined to each other by inserted lamina, and namedArticulataby De Blainville, on that account. The genus Chiton is the only example of this kind of Multivalves.
Figs. 84-85.Fig. 84, 85, Chiton.a, anterior;p, posterior;d, dorsal ridge;l l, lateral areas of the valves;c c, central areas;i i, inserted lamina;m, margin.
Fig. 84, 85, Chiton.a, anterior;p, posterior;d, dorsal ridge;l l, lateral areas of the valves;c c, central areas;i i, inserted lamina;m, margin.
The second kind, M. De Blainville terms thelateralbivalves, the pieces being placed in pairs on each side of the animal; these compose the "Pedunculated Cirripedes."
Fig. 86.Fig. 86, Anatina.
Fig. 86, Anatina.
They differ considerably in the number and arrangement of the valves; the small ones, which are found near the peduncle in some species, are sometimes termed accessary valves; those which form the edge through which the bunch of Cilia protrude, are termedventral, and those on the opposite sidedorsal. The extremity joining the peduncle is the basal, or anterior; and the upper extremity is the apsiral, or posterior. The peduncle is the medium of attachment to submarine substances, to which this well known tribe of shells adhere.
The third kind are termedcoronularby De Blainville, and compose the order Sessile Cirripedes of Lamarck; they consist of a number of valves placed against each other side by side in a circle, supported on a plate, or tube, or cup, and closed by an operculum composed of two or more valves.
Thebasal supportis sometimes thick and flat, sometimes forming an elongated tube, and sometimes hollowed out into a cup. In other species it is altogether wanting. The operculum always consists of more than one piece, generally of two pairs: they are either articulated to each other by serrated edges, and placed against each other conically, as in Balanus, or they lie flat in two pairs against each other. Through the ventral pair thecirrhiprotrude.
Theparietalvalves, composing the principal part of the shell, vary in number, form and position. Theanteriorvalves are placed on the same side with the cirrhi; theposterior, those on the opposite side; and those which remain between on each side are the lateral valves. In many cases, particularly in Balanus, each valve is separated into theprominentanddepressedareas, and the inserted lamina. In some instances, the parietal portion is formed by a single rounded piece.
Figs. 87-90.
In the accompanying cut (87), the prominent areas are distinguished by the letterspr, and the depressed areas byr; the posterior valves of the operculum are markedp. o., and the anteriora. o.The basal valve (fig. 88) belongs to a Balanus. Fig. 89 is an Acasta, the cup-shaped base of which is represented at fig. 90.
In the foregoing explanations we have omitted many of those general terms which, relating to external characters, are applicable to shells in almost every division of the system. It may be as well, however, to enumerate a few of them in this place, although they are explained under their respective letters in the alphabetical part of the work.
When bars or ribs, or large striæ are crossed by others radiating from the umbones, shells are said to becancellated, as represented in cut, fig. 91. When there is a series of nodules or spines on the upper part of the whorls, they arecoronated, as shewn in cut, fig. 92. When a series of projecting parts overlay each other, in the manner of tiles, as in the cut, fig. 93, the wordimbricatedis applied. When marked by a regular series of ridges, radiating from the apex, they arepectinated; the species of Chiton, a single valve of which is represented in cut, fig. 94, has received the specific name ofpectinatus, in consequence of this character. Shells are said to beplicatedwhen characterized by angular bendings or foldings in their surface, as shewn in cut, fig. 95. A strong instance of this is seen in the Ostræa Crista-Galli. When the margin of any shell has a series of minute notches, resembling the teeth of a saw, it is said to beserrated; when covered with raised points or spines it isaculeated; and when striated in both directions, it isdecussated; when covered with a number of raised rounded points, it isgranulated; and having a series of these points placed in a row, near or upon the edge, it isdenticulated, as already explained in reference to the outer lips of Spiral Univalves. When the external surface is rendered uneven by raised knobs, it is said to betuberculated; and if rendered rough and prickly by sharp points it ismuricated, as in the cut, fig. 97. The termreticulatedis applied to fine raised lines, crossing each other, and resembling fine net-work.
Figs. 91-98.External surface. Fig. 91,cancellated; 92,coronated; 93,imbricated; 94,pectinated; 95,plicated; 96,decussated; 97,muricated; 98,foliated.
External surface. Fig. 91,cancellated; 92,coronated; 93,imbricated; 94,pectinated; 95,plicated; 96,decussated; 97,muricated; 98,foliated.
By the foregoing general observations and explanations, it is trusted that the reader will be prepared for the following exposition of the general arrangement of Lamarck, and the principles upon which it is founded.
GENERAL ARRANGEMENT
ACCORDING TO LAMARCK.
In Lamarck's "Histoire Naturelle des Animaux sans Vertebres," he divides the invertebrata into classes, the 9th, 10th, and 11th of which include animals possessed of shells properly so called. These are theAnnelides, theCirripedes, theConchifera, and theMollusca.
The classAnnelidesconstitutes the 9th, and is divided into three orders, namely, the "Apodes," "Antennees," and "Sedentaires"; the last of which,Sedentaria, alone contains testaceous animals. This order includes tubular shells, which, with the exception of Dentalium, are irregularly twisted, and attached to each other, or to extraneous substances. The first familyDorsalia, contains the genus Siliquaria (plates, fig. 1), known from the Serpulæ, by the slit which passes through the whole length of the shell on the upper surface of the tube. The second family,Maldania, has the genus Dentalium (plates, fig. 2), a species of which are commonly known by the name of "tooth shells"; these are regularly formed, curved conical tubes, open at both extremities. The third family,Serpulacea, includes the genera Serpula, Spirorbis, Galeolaria, Vermilia, Spiroglyphus, and Magilus. The only shell that a learner would be likely to place among these incorrectly, according to the system, is the Vermetus (plates, fig. 345), which being regularly spiral at the apicial extremity, has been placed among the Mollusca; to which situation the whole of the shells under consideration have a better title than is generally supposed. It should be mentioned that the Serpulacea are provided with opercula.
ClassCirripedes.
This class constitutes the tenth of invertebrated animals, and receives its name from the jointed and ciliated branchia which protrude between the opercular valves. They are Multivalve shells, and were all included in the single genus Lepas in the system of Linnæus, and are commonly known by the name "Barnacles." Lamarck has, however, divided them into two distinct orders. First, theSessileCirripedes or those which being composed of several valves, joined to each other, side by side in a circle, are attached to each other, or to submarine bodies by the basal portion of their own substance, and form a hollow, irregular cone, with the aperture above closed by an operculum consisting of two or more valves. Secondly, thePedunculated Cirripedes, which are composed of valves placed in pairs against each other, so as to form a flattened disc attached by means of a tendinous tube called a peduncle. The first of these orders includes the genera Tubicinella, Coronula, Platylepas, Clitia, Conia, Elmineus, Catophragmus, Octomeris, Balanus, Creusia, Nobia, Savignium, Pyrgoma, Adna, Megatréma. The second contains the genera Pentelasmis, Scalpellum, Smilium, Pollicipes, Bisnæus, Lithotrya, Ibla, Octolasmis, Cineras, Otion.
Conchological writers are not agreed as to the propriety of allowing the above to enter into the present science.
ClassConchifera.
The shell of a conchiferous animal is always bivalve, composed of two pieces placed opposite to each other, joined at the dorsal margins by an elastic hinge. All true bivalve shells belong to animals of this class; and the correspondence between the shell and the animal is so true that on examining an empty bivalve shell we can not only determine that its inhabitant belonged to this class, but also decide on the particular order and family in which it should be placed, without seeing the soft parts.
The first general division of Conchifera is that which results from observing the muscular impressions, or marks made on the inner surface of the valve by the insertion of the adductor muscles. All Conchifera are divided into two orders, as follows:
First Order,Conchifera Dimyaria.
Having two adductor muscles, and consequently two impressions in each valve. They are separated into the following families:
1.Tubicolæ(plates, fig. 44 to 54), having shelly tubes besides the valves. This family contains the genera Aspergillum, Clavagella, Teredina, Teredo, Xylophaga, Fistulana, and Gastrochæna.2.Pholadaria(plates, fig. 55 to 59), cylindrical, living in holes in rocks pierced by the animals. Lamarck places in this family the genera Pholas and Gastrochæna, the last of which belongs more properly to the family Tubicolæ, as placed above.3.Solenacea(plates, fig. 60 to 68), longitudinally (transversely, Lam.) elongated, open at the anterior and posterior extremities. This family contains the genera Solen, Pholadomya, Panopæa, Glycimeris (Solecurtus) and Solenimya.4.Myaria(plates, fig. 69 to 76), ligament internal. A spoon-shaped ligamentary pit in one or both valves. Shell generally gaping at one or both extremities. This family includes the genera Anatina, Mya, Anatinella, Lyonsia, Myochama, Cleidotherus.5.Mactracea(plates, fig. 77 to 88), the cartilage placed in a trigonal pit, with a small external ligament. The genera Lutraria, Mactra, Crassatella, Erycina, Ungulina, Amphidesma, and Solenimya belong to this family, the last of which ought to have been placed among the Solenacea, as above.6.Corbulacea(plates, fig. 89, 90), inequivalve, with an internal ligament resembling the Mactracea, but differing in having one valve deeper than the other, although regular shells. This small family contains only the genera Corbula and Pandora.7.Lithophagidæ(plates, fig. 91 to 97), irregular, terebrating, living in holes of rocks. The genera are Saxicava, Petricola, and Venerirupis.8.Nymphacea(plates, fig. 98 to 110), ligament external, generally placed upon a prominent fulcrum, which passes from the inside to the outside of the hinge; valves generally gaping at the extremities. This family contains the genera Sanguinolaria, Psammobia, Psammotæa, Tellinides, Corbis, Lucina, Donax, Capsa, and Crassina.9.Conchacea(plates, fig. 111 to 121), regular, having several cardinal teeth and sometimes lateral teeth. The Conchacea constitute one of the most beautiful and numerous families of the class; they present equivalve shells, which are always regular, unattached, and in general closed, especially at the sides; they are always more or less inequilateral. They are divided into thefluviatileandmarine Conchacea, the first containing the genera Cyclas, Cyrena, and Galathæa, found in rivers; and the second, Cyprina, Cytherea, Venus, and Venericardia.10.Cardiacea(plates, fig. 122 to 130). This family, which resembles the last in some general characters, are also regular and equivalve, and are generally provided with radiating ribs, which are seldom seen in the Conchacea. The genera enumerated in this family are Cardium, Cardita, Cypricardia, Hiatella, and Isocardia.11.Arcacea(plates, fig. 131 to 138). These are known by having a row of numerous small teeth on the cardinal hinge in each valve. The genera included are, Cucullæa, Arca, Pectunculus, Nucula.12.Trigonacea(plates, fig. 139 and 140). It is doubtful whether this family should remain distinct. As of the two genera placed in it, the first, Trigonia, is thought by some naturalists to have strong affinities with Nucula, in the family of Arcacea; and the latter, Castalia, certainly belongs to the Nayades.13.Nayades(plates, fig. 141 to 152). These are fresh-water shells, covered on the outside by a thick horny epidermis, and pearly within. They include the genera Unio, Hyria, Anodon, Iridina.14.Chamacea(plates, fig. 153 to 155), inequivalve, irregular, foliaceous, attached; containing the genera Diceras, Chama, and Etheria.
1.Tubicolæ(plates, fig. 44 to 54), having shelly tubes besides the valves. This family contains the genera Aspergillum, Clavagella, Teredina, Teredo, Xylophaga, Fistulana, and Gastrochæna.
2.Pholadaria(plates, fig. 55 to 59), cylindrical, living in holes in rocks pierced by the animals. Lamarck places in this family the genera Pholas and Gastrochæna, the last of which belongs more properly to the family Tubicolæ, as placed above.
3.Solenacea(plates, fig. 60 to 68), longitudinally (transversely, Lam.) elongated, open at the anterior and posterior extremities. This family contains the genera Solen, Pholadomya, Panopæa, Glycimeris (Solecurtus) and Solenimya.
4.Myaria(plates, fig. 69 to 76), ligament internal. A spoon-shaped ligamentary pit in one or both valves. Shell generally gaping at one or both extremities. This family includes the genera Anatina, Mya, Anatinella, Lyonsia, Myochama, Cleidotherus.
5.Mactracea(plates, fig. 77 to 88), the cartilage placed in a trigonal pit, with a small external ligament. The genera Lutraria, Mactra, Crassatella, Erycina, Ungulina, Amphidesma, and Solenimya belong to this family, the last of which ought to have been placed among the Solenacea, as above.
6.Corbulacea(plates, fig. 89, 90), inequivalve, with an internal ligament resembling the Mactracea, but differing in having one valve deeper than the other, although regular shells. This small family contains only the genera Corbula and Pandora.
7.Lithophagidæ(plates, fig. 91 to 97), irregular, terebrating, living in holes of rocks. The genera are Saxicava, Petricola, and Venerirupis.
8.Nymphacea(plates, fig. 98 to 110), ligament external, generally placed upon a prominent fulcrum, which passes from the inside to the outside of the hinge; valves generally gaping at the extremities. This family contains the genera Sanguinolaria, Psammobia, Psammotæa, Tellinides, Corbis, Lucina, Donax, Capsa, and Crassina.
9.Conchacea(plates, fig. 111 to 121), regular, having several cardinal teeth and sometimes lateral teeth. The Conchacea constitute one of the most beautiful and numerous families of the class; they present equivalve shells, which are always regular, unattached, and in general closed, especially at the sides; they are always more or less inequilateral. They are divided into thefluviatileandmarine Conchacea, the first containing the genera Cyclas, Cyrena, and Galathæa, found in rivers; and the second, Cyprina, Cytherea, Venus, and Venericardia.
10.Cardiacea(plates, fig. 122 to 130). This family, which resembles the last in some general characters, are also regular and equivalve, and are generally provided with radiating ribs, which are seldom seen in the Conchacea. The genera enumerated in this family are Cardium, Cardita, Cypricardia, Hiatella, and Isocardia.
11.Arcacea(plates, fig. 131 to 138). These are known by having a row of numerous small teeth on the cardinal hinge in each valve. The genera included are, Cucullæa, Arca, Pectunculus, Nucula.
12.Trigonacea(plates, fig. 139 and 140). It is doubtful whether this family should remain distinct. As of the two genera placed in it, the first, Trigonia, is thought by some naturalists to have strong affinities with Nucula, in the family of Arcacea; and the latter, Castalia, certainly belongs to the Nayades.
13.Nayades(plates, fig. 141 to 152). These are fresh-water shells, covered on the outside by a thick horny epidermis, and pearly within. They include the genera Unio, Hyria, Anodon, Iridina.
14.Chamacea(plates, fig. 153 to 155), inequivalve, irregular, foliaceous, attached; containing the genera Diceras, Chama, and Etheria.
Second Order,Conchifera Monomyaria.
Having one adductor muscle, and therefore only one impression in each valve. They are separated into the following families:—
1.Tridacnacea(plates, fig. 156 & 157), transverse, equivalve, with an elongated muscular impression, near the centre of the ventral margin; margin undulated at the termination of the radiated large ribs. The genera Tridacna and Hippopus are included.2.Mytilacea(plates, fig. 158 to 162), generally regular, with the hinge linear, without teeth, occupying the greater part of the dorsal margin. This family includes the genera Modiola, Mytilus, Pinna.3.Malleacea(plates, fig. 163 to 170), shell generally thin, inequivalve, irregular, foliaceous, with the hinge linear. This family contains the genera Crenatula, Perna, Malleus, Avicula, Meleagrina.4.Pectinides(plates, fig. 171 to 178). The Pectinides are generally regular or nearly so, with the shell solid; the greater part of them are auriculated at the dorsal margin, and generally characterized by ribs radiating from the umbones. The genera are Pedum, Lima, Plagiostoma, Pecten, Plicatula, Spondylus, Podopsis.5.Ostracea(plates, fig. 180 to 192). The shells of this family are irregular, generally attached and foliaceous. They compose the genera Gryphæa, Ostræa, Vulsella, Placuna, Anomia.6.Rudistes(plates 193 to 200). This family is composed of a particular association of shells, which appear on one side to be connected with the Ostracea; and on the other to approach the Brachiopoda. They differ from Ostracea in having no hinge or ligament, and only resemble them in their irregularity and foliaceous structure. The following six genera are placed by Lamarck in this family:—Sphærulites, Radiolites, Calceola, Birostrites, Discina, Crania. Of these, Calceola, Discina, and Crania are shewn to belong to the Brachiopoda.7.Brachiopoda(plates, fig. 201 to 219). The shells of this family are inequivalve, equilateral, and attached to marine bodies by a tendon passing through one of the valves. The animals have, near their mouth, two elongated, ciliated arms, which are spirally rolled when at rest. The following genera are enumerated by Lamarck, Orbicula, Terebratula, Lingula.
1.Tridacnacea(plates, fig. 156 & 157), transverse, equivalve, with an elongated muscular impression, near the centre of the ventral margin; margin undulated at the termination of the radiated large ribs. The genera Tridacna and Hippopus are included.
2.Mytilacea(plates, fig. 158 to 162), generally regular, with the hinge linear, without teeth, occupying the greater part of the dorsal margin. This family includes the genera Modiola, Mytilus, Pinna.
3.Malleacea(plates, fig. 163 to 170), shell generally thin, inequivalve, irregular, foliaceous, with the hinge linear. This family contains the genera Crenatula, Perna, Malleus, Avicula, Meleagrina.
4.Pectinides(plates, fig. 171 to 178). The Pectinides are generally regular or nearly so, with the shell solid; the greater part of them are auriculated at the dorsal margin, and generally characterized by ribs radiating from the umbones. The genera are Pedum, Lima, Plagiostoma, Pecten, Plicatula, Spondylus, Podopsis.
5.Ostracea(plates, fig. 180 to 192). The shells of this family are irregular, generally attached and foliaceous. They compose the genera Gryphæa, Ostræa, Vulsella, Placuna, Anomia.
6.Rudistes(plates 193 to 200). This family is composed of a particular association of shells, which appear on one side to be connected with the Ostracea; and on the other to approach the Brachiopoda. They differ from Ostracea in having no hinge or ligament, and only resemble them in their irregularity and foliaceous structure. The following six genera are placed by Lamarck in this family:—Sphærulites, Radiolites, Calceola, Birostrites, Discina, Crania. Of these, Calceola, Discina, and Crania are shewn to belong to the Brachiopoda.
7.Brachiopoda(plates, fig. 201 to 219). The shells of this family are inequivalve, equilateral, and attached to marine bodies by a tendon passing through one of the valves. The animals have, near their mouth, two elongated, ciliated arms, which are spirally rolled when at rest. The following genera are enumerated by Lamarck, Orbicula, Terebratula, Lingula.
MOLLUSCA.
Lamarck applies, or rather restricts, this name to those invertebrated animals, which while they are inarticulate in all their parts, have the head sufficiently advanced at the anterior part of the body to be distinguished; which is not the case with the Conchifera. All the shells are univalve, and are divided into six orders, namely, thePteropoda, which have wing-shaped natatory organs or fins, and havelight,thin transparent,nearly symmetricalshells; theGasteropoda, with the foot not distinguishable from the rest of the body, havepatelliform,open, andscarcely spiralshells; theTrachelipodawith the foot distinct and attached to the neck of the animal, havespiral,non-symmetricalshells. TheCephalopoda, with arms covered by suckers surrounding the head of the animal, have generallysymmetrical convoluteshells. The Cephalopoda are divided intoC. polythalamia, which have the internal cavity divided into chambers by septa, as in the Nautilus; and theC. Monothalamia, which are not so divided, as the Argonauta. The orderHeteropodacontains the genus Carinaria alone.
OrderPteropoda.
This order, containing hyaline, symmetrical, non-spiral shells, as above described, is not divided into families, but contains the following genera, Hyalæa, Cleodora, Limacina, Cymbulia; the first of which, although composed of a single piece, resembles a bivalve so nearly, that Linnæus actually placed it in his genus Anomia.
OrderGasteropoda.
With the exception of the genus Bulla and Vitrina, the last of which forms a passage into the next order, the shells contained in this order arepatelliform,open,and scarcely spiral. They are divided into the following families:—
1.Phyllidiana(plates, fig. 227 to 231), containing the genera Chiton, Chitonellus, and Patella, the two former of which present the only exception to the statement above made, that all the shells of Mollusca were univalve.2.Semiphyllidiana(plates, fig. 232 and 233). Of the two genera contained in this family, Pleurobranchus is broad, thin, and slightly spiral at the apex, and Umbrella is flat, circular, with a central apex.3.Calyptracea(plates, fig. 234 to 246). The patelliform shells of this family, although united by no other general characters, are brought together by the characters of the animals which produce them. The genera are Parmophorus, Emarginula, Siphonaria, Fissurella, Pileopsis, Calyptræa, Crepidula, Ancylus.4.Bulleana(plates, fig. 247 to 253), contains the genera Bulla and Bullæa.5.Aplysiacea(plates, fig. 254 and 255). The genera Aplysia and Dolabella are both expanded, somewhat flattened shells, with the apex placed at one extremity, and slightly spiral.6.Limacinea(fig. 256 to 263). Many of the animals (slugs) are without shells; some, as the Limax, or common garden slug, have a slightly developed calcareous piece, hidden beneath the mantle, and of others the shells are scarcely spiral. The genera included in this family are, Parmacella, Limax, Testacella, Vitrina.
1.Phyllidiana(plates, fig. 227 to 231), containing the genera Chiton, Chitonellus, and Patella, the two former of which present the only exception to the statement above made, that all the shells of Mollusca were univalve.
2.Semiphyllidiana(plates, fig. 232 and 233). Of the two genera contained in this family, Pleurobranchus is broad, thin, and slightly spiral at the apex, and Umbrella is flat, circular, with a central apex.
3.Calyptracea(plates, fig. 234 to 246). The patelliform shells of this family, although united by no other general characters, are brought together by the characters of the animals which produce them. The genera are Parmophorus, Emarginula, Siphonaria, Fissurella, Pileopsis, Calyptræa, Crepidula, Ancylus.
4.Bulleana(plates, fig. 247 to 253), contains the genera Bulla and Bullæa.
5.Aplysiacea(plates, fig. 254 and 255). The genera Aplysia and Dolabella are both expanded, somewhat flattened shells, with the apex placed at one extremity, and slightly spiral.
6.Limacinea(fig. 256 to 263). Many of the animals (slugs) are without shells; some, as the Limax, or common garden slug, have a slightly developed calcareous piece, hidden beneath the mantle, and of others the shells are scarcely spiral. The genera included in this family are, Parmacella, Limax, Testacella, Vitrina.
OrderTrachelipoda.
All the remaining spiral non-symmetrical shells are arranged in this order, which is divided into the following families:—
1.Colimacea(plates, fig. 264 to 307). With the exception of the few contained in the family of Limacina, which ought not to be separated from this order, the whole of the land-shells are contained in this family, and although it is difficult to notice any one character by which terrestrial shells may be distinguished from others, few at all conversant with the subject are liable to mistake them. There is a general lightness and simplicity of form, which, though not clearly definable, is generally understood. The following distribution of genera by Lamarck, is generally acknowledged to require numerous modifications; the genera are Helix, Carocolla, Anostoma, Helicina, Pupa, Clausilia, Bulinus, Achatina, Succinea, Auricula, Cyclostoma.2.Lymneana(plates, fig. 308 to 312). The shells of this family are found in fresh water, wells, ditches, and ponds. They are of a light horny structure, and simple form. The genera Planorbis, Physa, and Lymnea are placed in this family by Lamarck.3.Melaniana(plates, fig. 313 to 317). These are also found in fresh water, principally in rivers; they are thicker than those of the last family; and the greater part of them have elevated spires composed of numerous whorls. This family contains the genera Melania, Melanopsis, Pirena.4.Peristomata(plates, fig. 318 to 322). These are also fresh-water shells, having opercula, and covered by a smooth green, or greenish-brown epidermis. They differ from the last family in having the peritreme entire. The genera are Valvata, Paludina, and Ampullaria.5.Neritacea(plates, fig. 323 to 333). The peculiarity of the shells of this family consists in the inner lip being flattened and rather straight at the inner edge. The genera are Navicella, Neritina, Nerita, Natica, and Janthina, the last of which forms an exception to the general character, and is placed by De Blainville in a family by itself.6.Macrostomata(plates, fig. 334 to 341), so named, on account of the large open aperture which they present in comparison to the spire. The shells of this family, which contains the genera Stomatia, Stomatella, and Haliotis, are pearly within.7.Plicacea(plates, fig. 342 to 344), contains the genera Tornatella and Pyramidella.8.Scalariana(plates, fig. 345 to 352). The genera Vermetus, Scalaria and Delphinula, seem to have been placed in this family by Lamarck, on account of the whorls being distinct from each other.9.Turbinacea(plates, 353 to 371). The shells contained in this family are all more or less globose, or angular, thickened and pearly within. The following genera are included in this division by Lamarck, Solarium, Rotella, Trochus, Monodonta, Turbo, Planaxis, Phasianella, and Turritella.10.Canalifera(plates, fig. 372 to 401). The numerous genera of which this family is formed, namely, Cerithium, Pleurotoma, Turbinella, Cancellaria, Fasciolaria, Fusus, Pyrula, Ranella, Murex, Triton, are distinguished by having at the anterior termination of the aperture, a more or less elongated canal.11.Alatæ(plates, fig. 402 to 406). These are known by having the outer lip more or less expanded and generally a posterior canal leaning towards the spire. The genera are Rostellaria, Strombus, and Pteroceras.12.Purpurifera(plates, fig. 407 to 429). In these, the canal, if such it may be called, is extremely short, and turning abruptly backwards, produces a kind of varix at the lower part of the whorl. The genera enumerated in this family are Cassidaria, Cassis, Ricinula, Purpura, Monoceras, Concholepas, Harpa, Dolium, Buccinum, Eburna, Terebra.13.Columellata(plates, fig. 430 to 433). The shells of this family are emarginated at the anterior extremity of the aperture, and the inner lip is characterized by plates or folds, which, with the exception of those on Columbella, are distinct. The genera are Mitra, Voluta, Marginella, Volvaria, Columbella, the latter of which would be better placed among the Purpurifera.14. Convolutæ (plates, fig. 444 to 462). The well-known shells contained in this family are distinguished for the small proportion of the spire, if any, which remains uncovered by the last whorl. They might be well divided into two groups, the first containing the genera Ovulum and Cypræa, under the name of Cypræadæ, which are truly convolute, having the spire entirely hidden; and the second containing the genera Oliva. Ancillaria, and Conus.
1.Colimacea(plates, fig. 264 to 307). With the exception of the few contained in the family of Limacina, which ought not to be separated from this order, the whole of the land-shells are contained in this family, and although it is difficult to notice any one character by which terrestrial shells may be distinguished from others, few at all conversant with the subject are liable to mistake them. There is a general lightness and simplicity of form, which, though not clearly definable, is generally understood. The following distribution of genera by Lamarck, is generally acknowledged to require numerous modifications; the genera are Helix, Carocolla, Anostoma, Helicina, Pupa, Clausilia, Bulinus, Achatina, Succinea, Auricula, Cyclostoma.
2.Lymneana(plates, fig. 308 to 312). The shells of this family are found in fresh water, wells, ditches, and ponds. They are of a light horny structure, and simple form. The genera Planorbis, Physa, and Lymnea are placed in this family by Lamarck.
3.Melaniana(plates, fig. 313 to 317). These are also found in fresh water, principally in rivers; they are thicker than those of the last family; and the greater part of them have elevated spires composed of numerous whorls. This family contains the genera Melania, Melanopsis, Pirena.
4.Peristomata(plates, fig. 318 to 322). These are also fresh-water shells, having opercula, and covered by a smooth green, or greenish-brown epidermis. They differ from the last family in having the peritreme entire. The genera are Valvata, Paludina, and Ampullaria.
5.Neritacea(plates, fig. 323 to 333). The peculiarity of the shells of this family consists in the inner lip being flattened and rather straight at the inner edge. The genera are Navicella, Neritina, Nerita, Natica, and Janthina, the last of which forms an exception to the general character, and is placed by De Blainville in a family by itself.
6.Macrostomata(plates, fig. 334 to 341), so named, on account of the large open aperture which they present in comparison to the spire. The shells of this family, which contains the genera Stomatia, Stomatella, and Haliotis, are pearly within.
7.Plicacea(plates, fig. 342 to 344), contains the genera Tornatella and Pyramidella.
8.Scalariana(plates, fig. 345 to 352). The genera Vermetus, Scalaria and Delphinula, seem to have been placed in this family by Lamarck, on account of the whorls being distinct from each other.
9.Turbinacea(plates, 353 to 371). The shells contained in this family are all more or less globose, or angular, thickened and pearly within. The following genera are included in this division by Lamarck, Solarium, Rotella, Trochus, Monodonta, Turbo, Planaxis, Phasianella, and Turritella.
10.Canalifera(plates, fig. 372 to 401). The numerous genera of which this family is formed, namely, Cerithium, Pleurotoma, Turbinella, Cancellaria, Fasciolaria, Fusus, Pyrula, Ranella, Murex, Triton, are distinguished by having at the anterior termination of the aperture, a more or less elongated canal.
11.Alatæ(plates, fig. 402 to 406). These are known by having the outer lip more or less expanded and generally a posterior canal leaning towards the spire. The genera are Rostellaria, Strombus, and Pteroceras.
12.Purpurifera(plates, fig. 407 to 429). In these, the canal, if such it may be called, is extremely short, and turning abruptly backwards, produces a kind of varix at the lower part of the whorl. The genera enumerated in this family are Cassidaria, Cassis, Ricinula, Purpura, Monoceras, Concholepas, Harpa, Dolium, Buccinum, Eburna, Terebra.
13.Columellata(plates, fig. 430 to 433). The shells of this family are emarginated at the anterior extremity of the aperture, and the inner lip is characterized by plates or folds, which, with the exception of those on Columbella, are distinct. The genera are Mitra, Voluta, Marginella, Volvaria, Columbella, the latter of which would be better placed among the Purpurifera.
14. Convolutæ (plates, fig. 444 to 462). The well-known shells contained in this family are distinguished for the small proportion of the spire, if any, which remains uncovered by the last whorl. They might be well divided into two groups, the first containing the genera Ovulum and Cypræa, under the name of Cypræadæ, which are truly convolute, having the spire entirely hidden; and the second containing the genera Oliva. Ancillaria, and Conus.
OrderPolythalamous, or Chambered Cephalopoda.
The greater part of the shells belonging to this order are symmetrical, and the internal cavity is divided into separate compartments, by plates calledSepta. It is divided into the following families:—
1.Orthocerata(plates, fig. 463 to 470), containing the genera Belemnites, Orthoceras, Nodosaria, Hippurites, and Conilites. Hippurites certainly has no affinity with the Cephalopoda, but is ascertained to be a bivalve shell, properly belonging to the family Rudistes; the other genera are straight, elongated, and conical.2.Lituacea(plates, fig. 471), containing the genera Spirula, Spirulina, and Lituola, the two latter of which are microscopic.3.Cristacea, containing the microscopic genera Renulina, Orbiculina, and Cristellaria.4.Spherulacea, containing the microscopic genera Miliola, Gyrogona, and Melonia.5.Radiolacea, containing the microscopic genera Rotalites, Lenticulina, Placentula.6.Nautilacea(plates, fig. 472 to 476). This family contains the following genera—Discorbites, Siderolites, Polystomella, Vorticialis, Nummulites, and Nautilus; the two latter of which alone are now received in cabinets of shells, the four former belonging to that class of microscopic fossils, now termed Foraminifera; the genus Nummulites, although large, may probably belong to the same class, and perhaps it would have been better to have included the remaining genus, Nautilus, in the next family, from which it differs in having the septa which divides the chambers simple at their edges.7.Ammonacea(plates, fig. 477 to 484). The edges of the septa of these are all more or less sinuous and complicated. This family contains the following genera, Ammonites, Ammonoceras, Baculites, and Turrilites, the latter of which presents a singular anomaly in having an oblique spire, like that of the order Trachelipoda, while it is divided into chambers by sinuous septa.
1.Orthocerata(plates, fig. 463 to 470), containing the genera Belemnites, Orthoceras, Nodosaria, Hippurites, and Conilites. Hippurites certainly has no affinity with the Cephalopoda, but is ascertained to be a bivalve shell, properly belonging to the family Rudistes; the other genera are straight, elongated, and conical.
2.Lituacea(plates, fig. 471), containing the genera Spirula, Spirulina, and Lituola, the two latter of which are microscopic.
3.Cristacea, containing the microscopic genera Renulina, Orbiculina, and Cristellaria.
4.Spherulacea, containing the microscopic genera Miliola, Gyrogona, and Melonia.
5.Radiolacea, containing the microscopic genera Rotalites, Lenticulina, Placentula.
6.Nautilacea(plates, fig. 472 to 476). This family contains the following genera—Discorbites, Siderolites, Polystomella, Vorticialis, Nummulites, and Nautilus; the two latter of which alone are now received in cabinets of shells, the four former belonging to that class of microscopic fossils, now termed Foraminifera; the genus Nummulites, although large, may probably belong to the same class, and perhaps it would have been better to have included the remaining genus, Nautilus, in the next family, from which it differs in having the septa which divides the chambers simple at their edges.
7.Ammonacea(plates, fig. 477 to 484). The edges of the septa of these are all more or less sinuous and complicated. This family contains the following genera, Ammonites, Ammonoceras, Baculites, and Turrilites, the latter of which presents a singular anomaly in having an oblique spire, like that of the order Trachelipoda, while it is divided into chambers by sinuous septa.
OrderMonothalamous Cephalopoda.
The only shells included in this order belong to the genera Argonauta (plates, fig. 485), placed here by Lamarck, and Bellerophon (plates, fig. 486 and 487), a fossil genus subsequently added.
OrderHeteropoda.
The singular and beautiful transparent shell contained in this order, under the generic name Carinaria, forms a covering to a small portion of an animal, equally remarkable and equally distinct from those of all other orders.
The above arrangement, although far from perfect, and requiring numerous modifications, is perhaps liable to as few objections as any other yet proposed, and will certainly be more easily understood by those who have not the opportunity of studying the soft parts of the animal.
CONCHOLOGICAL MANUAL.
ABIDA. Leach. A genus founded on a species ofPupa, which has the peristome slightly reflected, and numerous plaits in the aperture. Pupa Juniperi, Pupa secale, Draparnaud. Great Britain; also Central and Southern Europe.ABRA. Leach. A genus composed ofAmphidesmatenue, prismaticum, and other small thin species. British Channel and Mediterranean.Fam.Mactracea.ABSIA. Leach.Lithotrya, Sowerby.Fam.Pedunculated Cirripedes.ACAMAS. Montfort.Belemnitesmultiforatus, Blainville. A species described as being perforated at the apex, by a stellated perforation. No species of Belemnite at present known agreeing with the description; it is supposed to have been taken from a broken specimen.ACANTHOCHETES. A name given to a species of Chiton having bunches of bristles at the sides of the valves.ACARDO. Commerçon. Described from a pair of bony plates, taken from the vertebræ of the Whale, and mistaken for a bivalve shell, destitute of a hinge.ACARDO. Swainson. A generic term applied by Swainson to the nearly toothless species of Cardium, named C. edentulum by some authors; C. Greenlandicum by others: fig. 123*.ACASTA. Leach.Order, Sessile Cirripedes,Lamarck.BalanusMontagui, Sowerby. A small genus separated from Balanus, on account of the cup-shaped base, but re-united by Sowerby, who shews, in his Genera of Shells, that this is a merely accidental circumstance, resulting from the situations in which the shells acquire their growth. If, for instance, the Balanus be attached to a flat surface, in an open situation, the base will be short and flat; if it be placed in a hollow among other growing substances, it will be lengthened out in order that the aperture of the shell may be even with the outer surface of the surrounding mass; and if, as in the Acastæ, it be imbedded in a soft and loose substance, the base, being left to itself, will take a regular form. The Acastæ are found imbedded in sponges.Ex.Balanus Montagui, of Great Britain, fig. 26. Also found in the Pacific ocean and Philippines.ACAVUS. Montfort.Fam.Limacinea, Blainville; Colimacea, Lamarck. A division of the genus Helix, which may be considered synonymous with De Ferrusac's sub-genus Helicogena. De Montfort has given H. Hæmastoma, as an example. Fig. 267.ACCESSARY VALVES, are the smaller or less important testaceous plates, found on the hinge or dorsal margins of the true valves of some shells. Example, the small plates on the hinge of Pholas, fig. 55,a. The Pholades were placed by Linnæus and Bruguière among multivalve shells.ACEPHALOPHORA. Blainville. (a, without;κεφαλε, head.) The third class of the type Malacozoaria, Bl. including all bivalve shells, the animals of which have no distinct head. This class corresponds with the Conchifera of Lamarck, and is divided into the orders Palliobranchiata, Rudistes, Lamellibranchiata, and Heterobranchiata, the last of which contains no genera of testaceous Mollusca.ACHATINA, Auctorum.Fam.Colimacea, Lam. (from Achates, an agate.)Fam.Limacineæ, Bl.Gen.Polyphemus, Montf.—Descr.Shell oval or oblong, sub-turrited, light, thin; aperture oval, or pyriform; outer lip sharp; columella smooth, tortuous, truncated, so as to form a notch at its union with the outer lip.—Obs.It is from this notch that we are enabled to distinguish Achatinæ from Bulini, which, moreover, generally have a reflected outer lip. The Polyphemi of Montfort have an undulation in the centre of the outer lip. Achatina Virginea, fig. 286. Polyphemus Glans, fig. 288. These land shells are found in various parts of the globe, but attain the greatest size and richness of colouring in tropical climates; particularly in the West India Islands.ACHATINELLA.Sow.A small group of shells, differing from Achatina in having the inner edge of the outer lip thickened, and a slight groove near the suture of the spire. Fig. 287. Sandwich Islands.ACHELOIS. Montf.ConilitesAchelois. Knorr. Supp. T. 4, fig. 1.ACICULA. Nilson.AchatinaAcicula, Auct.Cionella, Jeffreys.ACIONA. Leach. A genus described by De Blainville as consisting of those species of Scalaria, the whorls of which do not touch each other. If this account be correct, the genus proposed by Leach will include the typical species of Scalaria, such as S. pretiosa.ACME. Hartmann. A genus formed ofTurbofuscus, Walker.Auriculalineata, Drap. thus described—"Shell sub-cylindrical, with a blunt tip; mouth ovate, simple, thin, slightly reflected over the pillar, forming a slight perforation." The animal is said to resemble a Cyclostoma, but has no operculum. Auricula lineata, Drap. Hist. 57, t. 3, fig. 20, 21. Southern Europe.ACTEON. Montf.Tornatella, Lam.ACTINOCAMAX. Stokes. A genus of Belemnitiform Fossils.ACULEATED. Beset with sharp spines, as the margin of Chiton aculeatus, fig. 227.ACUMINATED. Terminating in a point, as the apex of Melania subulata, fig. 313.ACUS. Humphrey.Terebraof Lamarck.ACUTE. Sharp, pointed, or sharp-edged.ADDUCTOR MUSCLE. That which draws the two valves of a shell together, and leaves a mark on the inner surface of each, called theMuscular Impression.ADELOSINA. D'Orb. A genus of microscopic Foraminifera.ADESMACEA. Bl. (a, without;Δεσμα,desma, ligament.) The 10th family of the orderLamellibranchiata, Bl. composed of Mollusca which either bore tubular dwellings in rocks, wood, &c. or live in testaceous tubes, their shells being consequently destitute of the hinge ligament. The action of opening and shutting the valves being limited to the narrow space to which they are confined, or else the valves themselves being soldered into the tube, renders it unnecessary for them to have a ligament to keep them in their places. The genera Pholas, Teredina, Fistulana, and Septaria, belong to this family, which corresponds in part with the families Tubicolaria and Pholadaria, of Lamarck.ADNA. Leach. One of the genera separated by Leach fromPyrgoma, and characterized as consisting of an upper valve, supported on a funnel-shaped base, which is not buried in the coral to which it is attached, like Pyrgoma, but is seen externally. The operculum consists of four valves. Adna, fig. 32. British Channel and Mediterranean.ADNATE. A term applied by some authors to those shells belonging to the family of Unionidæ, which have the valves joined together at the dorsal margin, not like other bivalves, by a distinct ligament, but by the substance of the shell itself, the valves appearing to grow together in such a manner that they cannot be separated without one of them being broken as will be seen in our figure of Dipsas plicatus, fig. 142. This circumstance has been made the foundation of specific and even generic distinctions, for which however it is insufficient, because many species which when young are "adnate," when fully grown have their valves joined together only by a ligament.ÆGLIA. Say. A division of "Unionidæ," described as having the "shell cuneate; bosses prominent; cardinal teeth much compressed, placed on one side of the bosses. Æglia ovata,Say. OccidensLea. Am. Tr. iii. pl. 10." Lardner's Encyclopedia of Malacology.AGANIDES. Montf.Orbulites, Lam.AGATHIRSES. Montf.Siliquaria, Auct.AGINA ——? Belongs toSaxicava, Auct.AKERA. Bl. The fourth family of the order Monopleurobranchiata, Bl. containing the genera Bulla, Bullæa and Bellerophon, which, excepting the last, constitutes the family Bullæana, Lam.AKERA. A genus of extremely light, horny shells, resemblingBulla, from which it differs, in the outer lip being separated from the body whorl, which is elastic.Ex.Bulla fragilis, fig. 247.ALÆA. Jeffrey's. A genus of minute land shells, resemblingVertigo, but separated because they are dextral, while Vertigo is sinistral.Ex.fig. 292. A. marginata, Pupa marginata, Drap. found in marshy ground, roots of trees, moss, &c. Britain and Southern and Central Europe.ALASMODON. Say. A division of the genusUnio, Auct. consisting of those species which have cardinal, but no lateral teeth.Ex.A. complanatus, fig. 141. North America and Europe.ALATÆ. Lam. A family of the order Trachelipoda, Lam. containing the following genera which may be thus distinguished.
ABIDA. Leach. A genus founded on a species ofPupa, which has the peristome slightly reflected, and numerous plaits in the aperture. Pupa Juniperi, Pupa secale, Draparnaud. Great Britain; also Central and Southern Europe.
ABRA. Leach. A genus composed ofAmphidesmatenue, prismaticum, and other small thin species. British Channel and Mediterranean.Fam.Mactracea.
ABSIA. Leach.Lithotrya, Sowerby.Fam.Pedunculated Cirripedes.
ACAMAS. Montfort.Belemnitesmultiforatus, Blainville. A species described as being perforated at the apex, by a stellated perforation. No species of Belemnite at present known agreeing with the description; it is supposed to have been taken from a broken specimen.
ACANTHOCHETES. A name given to a species of Chiton having bunches of bristles at the sides of the valves.
ACARDO. Commerçon. Described from a pair of bony plates, taken from the vertebræ of the Whale, and mistaken for a bivalve shell, destitute of a hinge.
ACARDO. Swainson. A generic term applied by Swainson to the nearly toothless species of Cardium, named C. edentulum by some authors; C. Greenlandicum by others: fig. 123*.
ACASTA. Leach.Order, Sessile Cirripedes,Lamarck.BalanusMontagui, Sowerby. A small genus separated from Balanus, on account of the cup-shaped base, but re-united by Sowerby, who shews, in his Genera of Shells, that this is a merely accidental circumstance, resulting from the situations in which the shells acquire their growth. If, for instance, the Balanus be attached to a flat surface, in an open situation, the base will be short and flat; if it be placed in a hollow among other growing substances, it will be lengthened out in order that the aperture of the shell may be even with the outer surface of the surrounding mass; and if, as in the Acastæ, it be imbedded in a soft and loose substance, the base, being left to itself, will take a regular form. The Acastæ are found imbedded in sponges.Ex.Balanus Montagui, of Great Britain, fig. 26. Also found in the Pacific ocean and Philippines.
ACAVUS. Montfort.Fam.Limacinea, Blainville; Colimacea, Lamarck. A division of the genus Helix, which may be considered synonymous with De Ferrusac's sub-genus Helicogena. De Montfort has given H. Hæmastoma, as an example. Fig. 267.
ACCESSARY VALVES, are the smaller or less important testaceous plates, found on the hinge or dorsal margins of the true valves of some shells. Example, the small plates on the hinge of Pholas, fig. 55,a. The Pholades were placed by Linnæus and Bruguière among multivalve shells.
ACEPHALOPHORA. Blainville. (a, without;κεφαλε, head.) The third class of the type Malacozoaria, Bl. including all bivalve shells, the animals of which have no distinct head. This class corresponds with the Conchifera of Lamarck, and is divided into the orders Palliobranchiata, Rudistes, Lamellibranchiata, and Heterobranchiata, the last of which contains no genera of testaceous Mollusca.
ACHATINA, Auctorum.Fam.Colimacea, Lam. (from Achates, an agate.)Fam.Limacineæ, Bl.Gen.Polyphemus, Montf.—Descr.Shell oval or oblong, sub-turrited, light, thin; aperture oval, or pyriform; outer lip sharp; columella smooth, tortuous, truncated, so as to form a notch at its union with the outer lip.—Obs.It is from this notch that we are enabled to distinguish Achatinæ from Bulini, which, moreover, generally have a reflected outer lip. The Polyphemi of Montfort have an undulation in the centre of the outer lip. Achatina Virginea, fig. 286. Polyphemus Glans, fig. 288. These land shells are found in various parts of the globe, but attain the greatest size and richness of colouring in tropical climates; particularly in the West India Islands.
ACHATINELLA.Sow.A small group of shells, differing from Achatina in having the inner edge of the outer lip thickened, and a slight groove near the suture of the spire. Fig. 287. Sandwich Islands.
ACHELOIS. Montf.ConilitesAchelois. Knorr. Supp. T. 4, fig. 1.
ACICULA. Nilson.AchatinaAcicula, Auct.Cionella, Jeffreys.
ACIONA. Leach. A genus described by De Blainville as consisting of those species of Scalaria, the whorls of which do not touch each other. If this account be correct, the genus proposed by Leach will include the typical species of Scalaria, such as S. pretiosa.
ACME. Hartmann. A genus formed ofTurbofuscus, Walker.Auriculalineata, Drap. thus described—"Shell sub-cylindrical, with a blunt tip; mouth ovate, simple, thin, slightly reflected over the pillar, forming a slight perforation." The animal is said to resemble a Cyclostoma, but has no operculum. Auricula lineata, Drap. Hist. 57, t. 3, fig. 20, 21. Southern Europe.
ACTEON. Montf.Tornatella, Lam.
ACTINOCAMAX. Stokes. A genus of Belemnitiform Fossils.
ACULEATED. Beset with sharp spines, as the margin of Chiton aculeatus, fig. 227.
ACUMINATED. Terminating in a point, as the apex of Melania subulata, fig. 313.
ACUS. Humphrey.Terebraof Lamarck.
ACUTE. Sharp, pointed, or sharp-edged.
ADDUCTOR MUSCLE. That which draws the two valves of a shell together, and leaves a mark on the inner surface of each, called theMuscular Impression.
ADELOSINA. D'Orb. A genus of microscopic Foraminifera.
ADESMACEA. Bl. (a, without;Δεσμα,desma, ligament.) The 10th family of the orderLamellibranchiata, Bl. composed of Mollusca which either bore tubular dwellings in rocks, wood, &c. or live in testaceous tubes, their shells being consequently destitute of the hinge ligament. The action of opening and shutting the valves being limited to the narrow space to which they are confined, or else the valves themselves being soldered into the tube, renders it unnecessary for them to have a ligament to keep them in their places. The genera Pholas, Teredina, Fistulana, and Septaria, belong to this family, which corresponds in part with the families Tubicolaria and Pholadaria, of Lamarck.
ADNA. Leach. One of the genera separated by Leach fromPyrgoma, and characterized as consisting of an upper valve, supported on a funnel-shaped base, which is not buried in the coral to which it is attached, like Pyrgoma, but is seen externally. The operculum consists of four valves. Adna, fig. 32. British Channel and Mediterranean.
ADNATE. A term applied by some authors to those shells belonging to the family of Unionidæ, which have the valves joined together at the dorsal margin, not like other bivalves, by a distinct ligament, but by the substance of the shell itself, the valves appearing to grow together in such a manner that they cannot be separated without one of them being broken as will be seen in our figure of Dipsas plicatus, fig. 142. This circumstance has been made the foundation of specific and even generic distinctions, for which however it is insufficient, because many species which when young are "adnate," when fully grown have their valves joined together only by a ligament.
ÆGLIA. Say. A division of "Unionidæ," described as having the "shell cuneate; bosses prominent; cardinal teeth much compressed, placed on one side of the bosses. Æglia ovata,Say. OccidensLea. Am. Tr. iii. pl. 10." Lardner's Encyclopedia of Malacology.
AGANIDES. Montf.Orbulites, Lam.
AGATHIRSES. Montf.Siliquaria, Auct.
AGINA ——? Belongs toSaxicava, Auct.
AKERA. Bl. The fourth family of the order Monopleurobranchiata, Bl. containing the genera Bulla, Bullæa and Bellerophon, which, excepting the last, constitutes the family Bullæana, Lam.
AKERA. A genus of extremely light, horny shells, resemblingBulla, from which it differs, in the outer lip being separated from the body whorl, which is elastic.Ex.Bulla fragilis, fig. 247.
ALÆA. Jeffrey's. A genus of minute land shells, resemblingVertigo, but separated because they are dextral, while Vertigo is sinistral.Ex.fig. 292. A. marginata, Pupa marginata, Drap. found in marshy ground, roots of trees, moss, &c. Britain and Southern and Central Europe.
ALASMODON. Say. A division of the genusUnio, Auct. consisting of those species which have cardinal, but no lateral teeth.Ex.A. complanatus, fig. 141. North America and Europe.
ALATÆ. Lam. A family of the order Trachelipoda, Lam. containing the following genera which may be thus distinguished.
1.Rostellaria.Sinus close to the canal; includingHippochrenes, andAporrhais, Fig. 402 to 404.2.Strombus.Sinus not close to the canal. Fig. 406.3.Pteroceras.Same, digitated. Fig. 405.
1.Rostellaria.Sinus close to the canal; includingHippochrenes, andAporrhais, Fig. 402 to 404.
2.Strombus.Sinus not close to the canal. Fig. 406.
3.Pteroceras.Same, digitated. Fig. 405.