| 21. | The bivalve's two siphons are situated at the posterior edge of the mantle cavity.
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| 22. | There are no gills; the entire surface of the mantle cavity absorbs oxygen from the water.
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| 23. | The cilia of the lophophore generate a feeding and respiratory current through the lophophore and mantle cavity.
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| 24. | The outer palps send this rejected material into the mantle cavity as a mucus-bound mass.
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| 25. | Inside the mantle cavity the animal has a highly vascularized area of tissue that functions as a lung.
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| 26. | The mantle cavity acts as a lung cavity . The taenioglossan radula has seven elements per transverse row.
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| 27. | The mantle cavity is divided into two chambers by ctenidia that circulate water and waste through the chiton.
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| 28. | However, the ink is not released, instead it is retained inside the now spherical mantle cavity.
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| 29. | Water enters the mantle cavity through the apical aperture, and is wafted along the body surface by cilia.
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| 30. | Air enters through the pneumostome into the animal's single lung, the air-filled mantle cavity.
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