| 31. | The conoid spire is canaliculated, composed of six operculum is thin.
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| 32. | Within the orifice beneath the operculum there is a tongue-like lingula.
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| 33. | Operculum powder is also an important ingredient in Chinese and Japanese incense making.
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| 34. | It has a thick shell with a calcified operculum.
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| 35. | Aberrations in the shape of operculum have been observed.
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| 36. | They can retract into their shell and close it off with an operculum.
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| 37. | A minority however belong to much more ancient operculum.
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| 38. | The upper operculum has a small diffuse dark spot.
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| 39. | Most species have an operculum ( a small lid-like organ ).
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| 40. | A black blotch is also present on the operculum.
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