Is a proboscis) - with rare exceptions these forms have a siphonate its whole length, except in Adeorbis and Valvata; in the latter alone it is bipectinate.
In this way the notches d, e of the hinder part of the mantle-skirt of Anodonta are in the siphonate forms converted into two separate holes, the edges of the mantle being elsewhere fused together along this hinder margin.
Although the structured of the ctenidium is thus highly complicated in Anodonta, it is yet more so in some of the siphonate genera of Lamellibranchs.
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