| 1. | The posterior extremity is caducous, and destitute of an operculum.
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| 2. | The operculum serves some of the same functions as an epiphragm.
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| 3. | The entire operculum is paucispiral, and has an eccentric nucleus.
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| 4. | The operculum is circular, multispiral, with a central nucleus.
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| 5. | The operculum is yellowish, ovate and has an apical nucleus.
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| 6. | The interior of the operculum is ovate, withan apical nucleus.
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| 7. | The operculum is castaneous within, with four rapidly increasing whorls.
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| 8. | Gills are tissues which consist of threadlike protein structures called operculum.
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| 9. | The operculum and preopercle may or may not have spines.
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| 10. | The adult animal has a very large, solid and heavy operculum.
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