Berthella plumula - Illustration from <i>Natural History: Mollusca</i> (1854), p. 129 - "Gill-plume of Pleurobranchus". Taking this to be <i>P. plumula</i> (as on page 131), the modern name (2012) is <i>Berthella plumula</i> © Philip Henry Gosse - Public domain - Wikimedia Commons
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