A Conchological Manual

Front matter

| 1. Spondylus Americanus. (Young.)

| 2. Nautilus pompilius. (Young.)

| G. B. S. Junr. fecit.

The Conchological System of De Blainville

TABLE OF THE CONCHOLOGICAL SYSTEM OF DE BLAINVILLE.

| Classes. | | Orders. | | Families. | | Genera.

TYPE MALACOZOARIA | Univalves | CEPHALOPHORA | Cellulacea | Planulacea | Renulina, Peneroplis.

Sphærulacea | Miliola, Pollontes, Melonia, Saracenaria, Textularia.

Nummulacea | Nummulites, Orbiculina, Helicites, Placentula, Vorticialis, Siderolites.

Polyphalamacea | Orthocerata | Belemnites, Conularia, Conilites, Orthoceras, Baculites.

Lituacea | Icthysarcolites, Lituola, Spirula, Spirolina, Hamites, Ammonoceras.

Cristacea | Crepidulina, Oreas, Linthuris.

Ammonacea | Discorbis, Scaphites, Ammonites, Simplegas.

Nautilacea | Polystomelle, Nautilus, Lenticulina.

Turbinacea | Cibicides, Rotalia.

Turriculacea | Turrilites.

PARACEPHOLOPHORA DIOICA | Siphonobranchiata | Siphonostomata | Pleurotoma, Rostellaria, Fusus, Pyrula, Fasciolaria.

Turbinella, Columbella, Triton, Struthiolaria, Ranella, Murex.

Entomostomata | Cerithium, Pyrena, Melanopsis, Planaxis, Subula, Terebra.

Eburna, Buccinum, Harpa, Dolium, Cassis, Cassidaria, Ricinula.

Cancellaria, Purpura, Concholepas, Terebra, Mitra.

Angyostomata | Strombus, Conus, Terebellum, Oliva, Ancillaria.

Voluta, Mitra, Marginella, Volvaria, Cypræa, Ovulum.

Asiphonibranchiata | Goniostomata | Solarium, Trochus.

Cricostomata | Monodonta, Turbo, Pleurotomaria, Littorina, Delphinula, Cyclostoma.

Paludina, Valvata, Scalaria, Proto, Turitella, Vermetus.

Siliquaria, Magilus.

Hemicyclostomata | Nerita, Neritina, Clithon, Velates, Pileolus, Navicella, Natica.

Ellipsostomata | Helicina, Ampullaria, Melania, Rissoa, Phasianella, Pleurocerus.

Oxystomata | Janthina.

PARACEPHOLOPHORA MONOICA | Pulmobranchiata | Limnacea | Limnæa, Physa, Planorbis.

Auriculacea | Auricula, Pedipes, Tornatella, Tomogerus, Pyramidella.

Limacinea | Succinea, Bulinus, Achatina, Clausilia.

Pupa, Partula, Helix, Vitrina, Testacella, Parmacella, Limacella, Limax.

Chismobranchiata | Sigaretus, Cryptostomata, Stomatella, Velutina.

Monopleurobranchiata | Sub-aplysiaca | Pleurobranchus.

Aplysiaca | Aplysia, Dolabella.

Patelloidea | Umbrella, Siphonaria.

Akera | Bulla, Bellerophon, Sormetus.

Aporobranchiata | Thecosomata | Hyalæa, Cleodora, Cymbulia.

Nucleobranchiata | Nectopoda | Carinaria.

Pteropoda | Atlanta, Spiratella, Argonauta.

PARACEPHOLOPHORA HERMAPHRODITA | Cirrobranchiata | Dentalium.

Cervicobranchiata | Retifera | Patella.

Branchifera | Fissurella, Emarginula, Parmophorus.

Scutibranchiata | Otides | Haliotis, Ancylus.

Calyptracea | Crepidula, Calyptræa, Capulus, Hipponyx, Notrema.

Bivalves | ACEPHALOPHORA | Palliobranchiata | Lingula, Terebratula, Strophomena, Dianchora.

Thecidium, Plagiostoma, Podopsis, Orbicula, Crania.

Rudistes | Sphærulites, Hippurites, Radiolites, Birostrites, Calceola.

Lamellibranchiata | Ostracea | Anomia, Placuna, Ostræa, Gryphæ.

Sub-ostracea | Spondylus, Plicatula, Hinnites, Pecten, Pedum, Lima.

Margaritacea | Vulsella, Malleus, Avicula, Perna, Crenatula.

Inoceramus, Catillus, Pulvinites, Gervillia.

Mytilacea | Pinna, Mytilus.

Arcacea | Arca, Pectunculus, Nucula.

Sub-mytilacea | Anodon, Unio, Cardita.

Chamacea | Chama, Diceras, Etheria, Tridacna, Hippopus, Isocardium, Trigonia.

Conchacea | Cardium, Donax, Tellina, Lucina, Cyclas.

Cyprina, Mactra, Erycina, Crassatella.

Venerirupis, Venus, Coralliophaga.

Clotho, Corbula, Sphænia, Ungulina.

Pylorides | Pandora, Anatina, Thracia, Mya, Lutricola.

Psammocola, Soletellina, Sanguinolaria, Solenocurtus.

Solen, Solemya, Panopæa, Glycimeris, Saxicava, Byssomya.

Rhomboides, Gastrochæna, Clavagella, Aspergillum.

Adesmacea | Pholas, Teredina, Teredo, Fristulana, Septaria.

SUB-TYPE MALENTOZOARIA | Multivalves | NEMATOPODA | Lepadicea | Gymnolepas, Pentalepas, Polylepas, Litholepas.

Balanidea | Balanus, Acasta, Octhosia, Conia, Creusia, Pyrgoma, Chthalamis.

Coronula, Chelnobia, Cetopirus, Diadema, Tubicinella.

POLYPLAXIPHORA | Seriales | Chiton, Chitonellus.

General Arrangement

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 the Annelides, the Cirripedes, the Conchifera, and the Mollusca.

The class Annelides constitutes 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 family Dorsalia, 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.

Class Cirripedes.

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, the Sessile Cirripedes 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, the Pedunculated 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.

Class Conchifera.

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 the fluviatile and marine 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.

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, the Pteropoda, which have wing-shaped natatory organs or fins, and have light, thin transparent, nearly symmetrical shells; the Gasteropoda, with the foot not distinguishable from the rest of the body, have patelliform, open, and scarcely spiral shells; the Trachelipoda with the foot distinct and attached to the neck of the animal, have spiral, non-symmetrical shells. The Cephalopoda, with arms covered by suckers surrounding the head of the animal, have generally symmetrical convolute shells. The Cephalopoda are divided into C. polythalamia, which have the internal cavity divided into chambers by septa, as in the Nautilus; and the C. Monothalamia, which are not so divided, as the Argonauta. The order Heteropoda contains the genus Carinaria alone.

Order Pteropoda.

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.

Order Gasteropoda.

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 are patelliform, 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.

Order Trachelipoda.

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.

Order Polythalamous, 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 called Septa. 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.

Order Monothalamous 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.

Order Heteropoda.

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.

Introduction

INTRODUCTION.

The Science of Conchology affords a very delightful and instructive amusement for the leisure hours of those who, retiring occasionally from the gaieties of fashionable life, seek pleasure in the quiet contemplation of some of the smaller, but not less wonderful operations of creative wisdom. And, although the study of shells would be more complete, and rank higher in the scale of philosophical pursuits, were it always accompanied by that of the animal inhabiting them, it nevertheless presents means of intellectual gratification, to many who cannot follow it beyond the cabinet and the boudoir. These may examine with admiration and mental improvement, the beautiful colouring and architecture of these wonders of the deep, they may exercise their taste and judgment in the selection and arrangement of specimens, and their discrimination in detecting and appreciating the distinctions upon which the arrangement is founded.

It is but little that can be known of the subject without forming a collection of greater or less extent; for, as it would be uninstructive merely to delight the eye with the bright colours and elegant form of shells, without possessing correct information respecting them, so it would be insipid and useless to learn technicalities without being acquainted by personal observation with the subjects to which they are applied. The first endeavour should, therefore, be to obtain a few shells as examples of the larger divisions, and, when these are understood, to proceed with the smaller groups, until a collection be formed to represent as many generic forms as possible. It may be as well here to advise those who are forming a collection to be very particular in every practicable instance to have the shells properly named at the time of purchasing; as it will save much trouble, and materially assist in the attainment of the desired object. To this end, recourse should be had to those naturalist tradesmen, who unite the attainment and diffusion of real scientific knowledge with their commercial pursuits.

Supposing, however, that the person who desires to learn the science, possesses a small parcel of unarranged and unnamed shells, without any previous acquaintance with the subject, the following introductory explanations, are drawn up with the view of enabling him, without further assistance, to obtain a general insight into its principles, equal to that of those who have studied it long and laboriously. To effect this, he must read them, carefully comparing the descriptions with the figures referred to, and with the specimens which he may have at command.

After describing the nature of the science and defining its objects, we shall proceed to explain the structure of those objects, and the manner of their growth. We shall then enter somewhat minutely into the principles of classification, the distinctions upon which they are founded, and some of the technical terms used to express them. After which we shall pass through the arrangement of Lamarck, defining the general divisions adopted under the terms of "Classes, Orders, and Families," as far as they are capable of definition. The subdivision of the latter into genera will only be entered into so far as to enumerate the principal of them, the more minute descriptions being reserved for the alphabetical part of the work.

Let none be discouraged by the number of generic distinctions proposed and adopted in modern times; for if well defined, they will be found to facilitate rather than encumber the science. The knowledge of species must be the foundation of every system, and the greater their number, the more necessary it becomes to subdivide them; if, for instance, all the species now known were to have been included in the 50 genera of Linnæus, a single genus would have contained many hundreds of incongruous species, in which case it would be much more difficult to remember them, than if they were to be divided into a far greater number of genera. Every well marked division, however arbitrary its limits, tends to simplify the subject, and to facilitate the researches of the student.

NATURE OF THE SCIENCE.

Conchology is the study of shells, viewed and described as to what they are either in themselves, or in relation to the soft, inarticulate animals which produce them, and of which they form a part. These animals are called Mollusca, and perhaps the best general description of them will be found in De Blainville's "Manuel de Malacologie et de Conchyliologie." The following is a translation, "Animal in pairs, the body and its appendages soft, inarticulate (not jointed), enveloped in a muscular skin, commonly called the mantle, which is extremely variable in form, and has developed either within or upon it a calcareous portion, consisting of one or several pieces, commonly called a SHELL."

The term Mollusca was formerly restricted to those soft animals which were destitute of shells, although possessing in other particulars, the characters described above, and it was used in order to distinguish them from the Testacea, which were covered or internally supported by calcareous parts. In the system of Linnæus, the soft portions are first arranged under the general designation of "Vermes Mollusca," and described without regard to the presence, absence, or character of the shells; and then the shells are separately characterized under the appellation of "Vermes Testacea," without any further notice of the animal, than an indication of the genus to which it belongs; thus the animal of Cypræa is said to be a Limax, and that of Tellina a Tethys.

The nearest approach to correctness, and the most philosophical method of study will be found in the modern system, adopted by Lamarck and his followers, of observing these animals as a whole, and arranging them according to the assemblage of characters which they present; of course taking into consideration the existence or non-existence, form and structure of the shell, on the same principle, which, in arranging the vertebrated animals would lead us to study the hair, hoof, nails, claws, &c. as well as the other parts.

At the same time, it must be admitted that there are many private collectors of Shells who would find it a difficult, if not impossible task to study minutely and successfully the soft parts of the Mollusca. Ladies, for instance, could not be expected to handle with pleasure and perseverance, these fleshy substances, which in order to be preserved from putrefaction, must be kept in spirits; and yet such persons may, with improvement and advantage to their own minds, enjoy the interesting and scientific amusement of studying and arranging the clean and beautiful natural objects which are so easily preserved, and so exquisitely curious in their structure. Let it also be remembered, that if shells had not been rendered commercially valuable, by the zeal and emulation manifested by mere Conchologists for the possession of rare specimens, few travelling merchants and sea captains would have thought them worthy of a corner in their cabins. In this case, few specimens being brought to the country, the more Philosophical Naturalist would have been left without the means of obtaining materials to work upon, or of attracting public attention to his favourite pursuit.

On account of these and other considerations, it has been thought advisable that the present undertaking should bear a purely conchological character. The peculiarities of the shells alone being detailed for the assistance of those who collect and study them, while at the same time, in deciding upon their affinities and places, in the arrangement, it will be necessary to take advantage of the conclusion to which those have arrived, who have studied the animal in all its parts. And the conviction must be expressed, that if ever a complete Natural System shall be formed it will result from the labours of the last mentioned class of naturalists.

DEFINITION OF A SHELL.

Before entering minutely into the description of shells, it will be necessary to distinguish from the true testaceous Mollusca two kinds of animals which have formerly been associated with them. Of these, the first is the class of Crustacea, consisting of crabs, crayfish, &c. These differ from shell-fish, not only in structure and chemical composition, but also in the fact that the animal has jointed limbs, and that the substance of the flesh is inseparable from the hard external covering, which invests each particular joint as with a sheath; whereas the Molluscous animal is but partially attached to its shell, from which it possesses the power of partly withdrawing and returning. The second class is that to which the sea-urchin, or Echinus, belongs, of which there are many genera and species. The testaceous covering of Echini is composed of a number of small pieces, placed edge to edge, forming a more or less globular external covering to the flesh, which is supported in the centre by a number of bones leaning upon each other in a pyramidal form. The test is of a fibrous texture, guarded on the outside with moveable spines, which turn on ball and socket joints.