Un manuel de la mollusques, ou, UN traité rudimentaire de coquilles récentes et fossiles. Na. Neoc, France. Sutures non foliées.la craie de Normandie a reçu le nom de calcaire baculite, à partir de l'abondance de ce fossile. CLASSE II GASTEROPODA. Les gastéropodes, y compris les escargots terrestres, les escargots de mer, les buccins, les limettes et les thèces, sont les types de mollusque; c'est-à-dire qu'ils présentent toutes les caractéristiques de l'organisation mollusque dans le degré le plus important, et l'approche sans fortune de l'apparence et de l'état des poissons que les céphalopodes, et moins aux crustacés et aux zophytes que

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A manual of the Mollusca, or, A rudimentary treatise of recent and fossil shells . na. Neoc, France. Sutures not foliated.The chalk of Normandy has received the name of baculite limestone, fromthe abundance of this fossil. CLASS II. GASTEROPODA. The gasteropods, including land-snails, sea-snails, whelks, limpets, and thelike, are the types of the mollusca; that is to say, they present all the leadingfeatures of molluscous organization in the most prominent degree, and makeless approach to the appearance and condition of fishes than the cephalopods, and less to the crustaceans and zoophytes than the bivalves. Their ordinary and characteristic mode of locomotion is exemplified by thecommon garden-snail, which creeps by the successive expansion and contractionof its broad muscidar foot. These muscular movements may be seen foUownigeach other in rapid waves when a snail is climbing a pane of glass. The nucleohranches are aberrant gasteropods, having the foot thin andvertical; they swim near the sm-face of the sea, in a reversed position, oradhere to floating sea-weed. -^. A nucleobrmiche.*•e nearly all nns^Tiimetrical, the body being coiled up The, gasteropodsspirally, and the respiratory organs of the left side being usuaUy atrophied.In c/ilton and dentalium the Iranchue and reproductive organs are repeatedon each side. * Fig. 5!). Carinaria cymbium, boscis; /, tentacles, b, branchise; . L. sp. (after Blainville), Mediterranean; p, pro-.?, shell; /, foot; d, disk. 98 MANUAL OF THE MOLLUSCA. A few species of cymha, litorina, paludina, and helit, are viviparous; therest are oviparous. When fii-st hatched the young are always provided -nath a shell, though inmany families it becomes concealed by a fold of the mantle, or it is speedilyand wholly lost.* The gasteropods form two natural groups; one breathing air {puhnonifera), the other water {brancfiifera). The air-breathers undergo no apparent meta-morphosis ; when born, they differ from their parents in size only. Thewater

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• bookcentury1800
• bookdecade1850
• booksubjectmollusks
• bookyear185