From ZooTerms (Dictionary of Invertebrate Zoology)
Mollusca: Bivalvia) Fibers or small bundles of silky threads by which they anchor themselves to the substratum; beard.byssus (noun; plural byssi, byssuses; Latin byssos, fine flax): 1. (
2. (NEMATA: Adenophorea) A series of elaborately branched projections at the poles of mermithid eggs, by which they attach to plants.