What is (a) Having the front edge of the aperture of the shell prolonged in the shape of a channel for the protection of the siphon; -- said of certain gastropods. (b) Pertaining to the Siphonostomata called?

siphonostomatous — (a) Having the front edge of the aperture of the shell prolonged in the shape of a channel for the protection of the siphon; -- said of certain gastropods. (b) Pertaining to the Siphonostomata. (Webster's 1913.)

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