A manual of the Mollusca, or, A rudimentary treatise of recent and fossil shells . thegenera.* Their teeth are amber-coloured, glossy, and trans-lucent ; and being silicious (they are insoluble in acid), they canbe used like a file, for the abrasion of very hard them the Umpet rasps the stony nullipore, the whelk boresholes in other shells, and the cuttle-fish doubtless uses its tonguein the same manner as the cat. The tongue, or lingual ribbon,usually forms a triple band, of which the central part is calledthe rachis, and the lateral tracts pleurce, the rachidian teeth ^ The p
A manual of the Mollusca, or, A rudimentary treatise of recent and fossil shells . thegenera.* Their teeth are amber-coloured, glossy, and trans-lucent ; and being silicious (they are insoluble in acid), they canbe used like a file, for the abrasion of very hard them the Umpet rasps the stony nullipore, the whelk boresholes in other shells, and the cuttle-fish doubtless uses its tonguein the same manner as the cat. The tongue, or lingual ribbon,usually forms a triple band, of which the central part is calledthe rachis, and the lateral tracts pleurce, the rachidian teeth ^ The preparation of tte lingual ribbon as a permanent microscopic object,requires some nicety of manipulation, but the arrangement of the teeth maybe seen by merely compressing part of the animal between two pieces ofglass. C 2 28 MANUAL OP THE MOLLUSCA. sometimes form a single series, overlapping each other, or thereare lateral teeth on each side of a median series. The teeth onthe pleurae are termed wicini; they are extremely numerous inthe plant-eating gasteropods. (Pig, 15. A.)*. Fig. 15. Lingual Teeth of Mollusca. Sometimes the tongue forms a short semi-ciicular ridge,contained between the jaws ; at others, it is extremely elongated,and when withdiawn, its folds extend backwards to the lingual ribbon of the limpet is longer than the whole ani-mal; the tongue of the whelk has 100 rows of teeth; andthe great slug has 160 rows, with 180 teeth in each row.
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Keywords: ., bookcentury1800, bookdecade1850, booksubjectmollusks, bookyear185
