What is (a) A genus of air-breathing mollusks mostly found near the sea, where the water is brackish (b) One of the five arched processes of the shell around the jaws of a sea urchin called?

auricula — (Zoöl.) (a) A genus of air-breathing mollusks mostly found near the sea, where the water is brackish (b) One of the five arched processes of the shell around the jaws of a sea urchin. (Webster's 1913.)

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