name given by the ancients to a species of marble dug near Megara, and remarkable for containing a great number of sea-shells, and other marine bodies immersed in it.

Conchoïd, in Geometry, the name of a curve, given to it by its inventor Nicomedes. See Fluxions.

Conchology,

Is that department of natural history which treats of testaceous animals. In the Linnean arrangement it constitutes the third order of the class of Vermes. This is the order testacea, of which we propose to lay before our readers a pretty full view in the present treatise. The peculiarity and extent of this order of animals have induced us to consider it in a separate treatise, by which means we shall avoid swelling out to an inconvenient magnitude; the class of Verme, which will be treated of in its proper place in the course of the work.

The fine polish, splendid colours, and elegant form of shells, have been long admired, and have procured for them a conspicuous place in the cabinets of the curious. Indeed in this respect, mankind have discovered no small degree of folly and extravagance, in the high price which has been given for rare and beautiful shells, and often only on account of their rarity. But the study of conchology acquires a higher degree of importance and utility in another view. In many parts of the world, different kinds of testaceous animals are employed as an excellent and nutritious food; and some tribes supply the table with a delicate luxury. Different shells furnish employment to ingenuity and art, in the manufacture of mother-of-pearl for various purposes; and the pearl itself, so much sought after as an ornament of dress, and often the rival of the richest gems, in the estimation of mankind, is the production of testaceous animals. Its nature and mode of formation, therefore, cannot fail to be objects of curious investigation. But testaceous animals and their productions, are not only beneficial and ornamental; some are found to be highly pernicious. The snail ravages the garden and the field, and marks its progress with the destruction of some of the fairest of the vegetable tribes; while the ship-worm is justly the dread of the mariner; secure, as it were, in its insignificance, it humbles the glory and pride of man; and labouring in secret, demolishes the noblest efforts of ingenuity. In these views, then, the economy and habits of testaceous animals, which at first sight might appear a barren and useless pursuit, become an important and beneficial subject of investigation. The following chapters, therefore, shall be occupied in the classification and natural history of this tribe of animals.

CHAP. I. HISTORY OF CONCHOLOGY.

THE few scattered fragments concerning the natural history of shells, or testaceous animals, which are to be found in the writings of the ancients, when compared with the more extended and systematic labours of the moderns, are so unimportant and inaccurate, that it would be altogether superfluous to trouble our readers with an account of the information which they contain. It appears, however, from the works of Aristotle and Pliny, the great naturalists of Greece and Rome, that the study of conchology was not entirely neglected in their time. It appears too, that admirers and collectors of shells were not then wanting. Scipio and Laelius, we are informed, found a relaxation from the toils and cares of war and government, by indulging in this elegant amusement (a).

Nor will it be attended with much advantage to give a particular account of the works of the earlier writers on this subject, among the moderns. These are Gesner, Johnston, Rondeletius, Aldrovandus, Belonius, Wormius, and some other authors, who cultivated this department of natural history, and accompanied their descriptions with figures, illustrative of the objects which they described.

The first author who attempted a systematic division of shells, according to their external form and character, was John Daniel Major, professor of medicine in the university of Kiel in Holstein. His method is published at the end of his curious and interesting remarks on the treatise concerning the purpura of Fabius Columna, printed at Kiel in 1675. The system of the German naturalist was followed by that of our countryman Dr Lister, on a more extended and improved plan, which was published ten years after. Succeeding naturalists turned their attention to the study of conchology, and to the improvement of the classification of the numerous objects of this department of natural history. Such were Buonanni, Rumfius, Langius, Breynius, Tournefort, Guallieri, D'Argenville, Klein, Linnaeus, Adanson, Geoffroy, and Muller.

We shall here exhibit some of the most celebrated systems of conchology which have been proposed by writers on this subject. This, we trust, will not be unacceptable to our readers, and particularly as the works of these authors are in few hands, and therefore become less accessible.

I. The first general arrangement of shells is that published by Dr Lister in a work with the following title. Martini Lister, M.D. Historiae sive Synopsis methodicae Conchyliorum libri quattuor, continentes 1057 figuras are nitidissime inscriptas, a Susanna et Anna Lister depictas. Londini, 1685—1688, folio. A second edition of the same work was published at Oxford in 1770, with additional figures.

SYSTEM OF LISTER.

Lib. I. De Cochleis Terrestribus.

Pars I. De Buccinis et Turbinibus terrestribus.

Sect. 1. De Buccinis terrestribus a sinistra dextrorum tortilibus, laevibus, edentulis. Sect. 2. De Buccinis terrestribus a sinistra dextrorum tortilibus, edentulis, striatis. Sect. 3. De Buccinis terrestribus a sinistra dextrorum tortilibus, apertura dentata. Sect. 4. De Buccinis terrestribus a dextra sinistrorum tortilibus, apertura plana. Sect. 5. De Buccinis terrestribus a dextra sinistrorum tortilibus, apertura dentata. Sect. 6. De Turbinibus terrestribus cochleiformibus, id est compactiore figura.

(a) Laelium et Scipionem conchas et umbilicos ad Cajetam et ad Laurentum legere consuesse, et ad ommem animi remissionem ludumque descendere. Cic. de Orat. lib. ii. Lib. II. De Turbinibus et Bivalvibus aquae dulcis.

Pars I. De Turbinibus.

Sect. 1. De Buccinis fluviatilibus. Sect. 2. De Cochleis fluviatilibus. Sect. 3. De Cochleis fluviatilibus compressis.

Pars II. De Testaceis bivalvibus fluviatilibus.

Sect. 1. De Musculis fluviatilibus, cardine dentato. Sect. 2. De Musculis fluviatilibus, cardine levii. Sect. 3. De Pectunculis fluviatilibus.

Lib. III. De Testaceis bivalvibus marinis.

Pars I. De Testaceis bivalvibus, paribus testis.

Sect. 1. Cap. 1. De Pectinibus ex utraque parte sequaliter auritis, striatis. Cap. 2. De Pectinibus sequaliter auritis, levibus. Cap. 3. De Pectinibus insequaliter auritis, non dentatis. Cap. 4. De Pectinibus insequaliter auritis dentatis.

Sect. 2. Cap. 1. De Ostreis apophysi plana longa recurva, angulo acuto desinente. Cap. 2. De Ostreis apophysi brevi, subter et quasi in occulo positae. Sect. 3. De Spondylis.

Pars II. De Testaceis bivalvibus, paribus testis.

Sect. 1. Cap. 1. De Pectinibus margariferis. Cap. 2. De Pectinibus, binis apophysibus longis conjunctis. Cap. 3. De Pectinibus margariferis polyleptoglymis.

Sect. 2. Cap. 1. De Pectunculis polyleptoglymis, margine ex altera parte productiore. Cap. 2. De Pectunculis polyleptoglymis, margine rotundis, striatis. Cap. 3. De Pectunculis polyleptoglymis, margine rotunda, levibus.

Sect. 3. Cap. 1. De Pectunculis levibus, triquetris fere, cervice angustiore. Cap. 2. De Pectunculis levibus, triquetris, cervice latiore. Cap. 3. De Pectunculis levibus, rostro recurvo.

Sect. 4. Cap. 1. De Pectunculis fasciatis, lunula notatis, margine striata. Cap. 2. De Pectunculis fasciatis, lunula quadam notatis, margine levii. Cap. 3. De Pectunculis fasciatis, ad rostrum integris.

Sect. 5. Cap. 1. De Pectunculis striatis productioribus, striis a rostro ad medium usque dorsum concurrentibus. Cap. 2. De Pectunculis striatis diversimode exaratus, sive dissimilibus. Cap. 3. De Pectunculis striatis, striis similibus, dorso ad altum latus paululum eminente. Cap. 4. De Pectunculis striatis, dorso in aciem compresso. Cap. 5. De Pectunculis striatis, muricatis asperis. Cap. 6. De Pectunculis striatis, striis a rostro tantum deductis levibus. Cap. 7. De Pectunculis cancellatis.

Cap. 8. De Pectunculis striatis, ex latere multo magis diffusis, latioribus. Cap. 9. De Pectunculis striatis, ex latere diffusis angustioribus. Cap. 10. De Pectunculis striatis imbricatis.

Sect. 6. Cap. 1. De Musculis marinis, cardine levii minimeque dentato. Cap. 2. De Musculis marinis polyleptoglymis.

Sect. 7. Cap. 1. De Pinnis, margine velut praecisa obsoavse. Cap. 2. De Pinnis, margine producta et auctore.

Sect. 8. Cap. 1. De Tellinis, id est conchis fere conciformibus, ambitu serrata. Cap. 2. De Tellinis quibus ambitus ex interna parte levius est.

Sect. 9. De Solenis, id est conchis tenuibus longissimisque ab utraque parte naturaliter hiantibus.

Sect. 10. Cap. 1. De Chamis, ab altero tantum latere fere naturaliter hiantibus. Cap. 2. De Chamis pholadibus.

Pars II. De Testaceis multivalvibus.

Sect. 1. Cap. 1. De Pholadibus triumve testarum conchis, cardinibus locuis quibusdam quasi perforatis. Cap. 1. De Pholadibus, cardine integro.

Sect. 2. De Conchis quinque testarum anatiferis pleurisque dictis.

Sect. 3. De Balanis, id est, duodecim testarum conchis prater operculum mitratum.

Sect. 4. Sive appendix ad librum tertium de conchitis hiave lapidibus, qui quondam similitudinem cum conchis marinis habeant.

Lib. IV. De Buccinis marinis, quibus etiam vermiculi dentalia et patellae, numerantur.

Sect. 1. Cap. 1. De Patellis, vertice perforato. Cap. 2. De Patellis, vertice integro, levibus. Cap. 3. De Patellis, vertice integro, striatis, margine quasi radiata. Cap. 4. De Patellis, vertice adunco margine æquali. Cap. 5. De Patellis, vertice adunco, margine obliqua. Cap. 6. De Patellis, vertice adunco, quibus ex interna parte cavitas quaedam quasi arcuata, longis compressis. Cap. 7. De Patellis, vertice acuto, stilo quodam interno donatis.

Sect. 2. De Dentalibus.

Sect. 3. De Vermiculis.

Sect. 4. Cap. 1. De Nautilis caudatis, sive e plurimis tabulatis confectis. Cap. 2. De Nautilis vacois, sive non tabulatis.

Sect. 5. Cap. 1. De Cochleis marinis, apice brevi, umbilicatis, sinu aurito. Cap. 2. De Cochleis marinis, apice brevi, umbilico simplici. Cap. 3. De Cochleis marinis, apice brevi, centro minime sinuato. Cap. 4. De Cochleis marinis, basi brevi, apice ad oris initium parum elato. Cap. 5. De Cochleis marinis, apice mediocriter producto, ore dentato. Cap. 6. De Cochleis marinis, apice mediocriter producto, ore edentulo, levibus. Cap. 7. De Cochleis marinis, apice mediocriter producto, striatis. Cap. 8. De Cochleis marinis, clavícula tenui et longissima, striatis. Cap. 9. De Cochleis marinis, clavícula tenui et longissima, levibus.

Sect. 6. Cap. 1. De Neritis dentatis, clavícula paululum prominente. Cap. 2. De Neritis dentatis, clavícula compressa, striatis. Cap. 3. De Neritis dentatis, clavícula compressa, levibus. Cap. 4. De Neritis ad columellam dentatis, labio productiore edentulo.