The Cambridge natural history . Fki. 132.—Two rows ofthe radula of Ptero-trachea mutica Les.,Naples, X 60. Pectinoclonta, (1 + 0-f 1). in Collisellina (both Acmaei-dae), to (1 -f 0 + 1).2.::5 in Patindla, and (2 + Q + 2). Patella proper. In the Lepetidae there is an absolutelycentral tooth, which appears to be made up of the coalescence ofseveral teeth, ikj laterals, and about two marginals; formula, 228 RADULA OF IIETEROrODA AND AMPHINEURA The radula, of the HcUrojiioda is quite characteristic, andsliows no sign of aiHuity with any other Prosohranchiate. Thecentr
The Cambridge natural history . Fki. 132.—Two rows ofthe radula of Ptero-trachea mutica Les.,Naples, X 60. Pectinoclonta, (1 + 0-f 1). in Collisellina (both Acmaei-dae), to (1 -f 0 + 1).2.::5 in Patindla, and (2 + Q + 2). Patella proper. In the Lepetidae there is an absolutelycentral tooth, which appears to be made up of the coalescence ofseveral teeth, ikj laterals, and about two marginals; formula, 228 RADULA OF IIETEROrODA AND AMPHINEURA The radula, of the HcUrojiioda is quite characteristic, andsliows no sign of aiHuity with any other Prosohranchiate. Thecentral tooth is large, l)road, tricuspid, and denticulated on abroad base; tlie single lateral is strong, often Ijicuspid; thetwo marginals simple, long, falciform; formula, (Pig. 132). Amphineura. — (cO Polyplacophora.—The radula of theChitonidae is quite mucpie. It resembles tliat of the Docof/lossain being very long, and composed of thick and dark horn-coloured teeth. The nund)er of teeth, however, is considerably. rJG, 133.—A, Portion of the radula of tliUon [Acanthopleura) spiniger Sowb., Anda-raans, x 30 ; B, portion of tlic radula of Dentalium entalis L., Clyde, x 50. greater, amounting almost invarial)ly to seventeen in eacli ar(^ three rather small central teeth, tlie two outer of thesebeing sindlar ; next comes a A^ery large lateral (the major lateral),usually tricuspid, which is fulltnved by two much smaller laterals,which are scarcely more than accessory plates; then a very largeand arched marginal (the major uncinus), at the outer side ofwinch are three accessory plates. Some consider there is onlyone central tooth, and count tlie two small teeth on eacli side ofit as laterals. Thus the fornmla, is citlier (.5 + 1) - (2 + 1) .3. (1 + 2). (1 + 3)or (3 + 1). (2 + 1 + 1) .1. (1 + 1 + 2). (1 + 3). (^) Aplauyphora.—Of tins rather obscure order, Cliactodcrmalias a single strong central tooth, Keomenia has no radida. RADULA OF OPISTIIOBRANCHIATA 2
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1895
