Page:Natural History, Mollusca.djvu/22

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MOLLUSCA.

liantly-painted shells, which throng the damp woods in tropical countries, likewise belong to this group, and furnish the most highly prized treasures of our conchological cabinets. In these the air is

PEROPHORA.

inhaled into an ample chamber, the interior of which is lined with cilia. After parting with its oxygen, it is again expelled; the common orifice for both processes being situated on the side of the