demibranchs
From ZooTerms (Dictionary of Invertebrate Zoology)
Mollusca: Bivalvia) A pair of ciliated gill filaments composed of two flat lamellae (inner demibranch and outer demibranch) in which there are blood vessels that facilitate respiration and mucociliary feeding.
demibranchs (noun, plural; Greek demi, half; branchia, gills): (