The velum, derived from Latin ''velum,'' meaning a "sail", "curtain," "awning" or "veil," has several quite separate meanings in Biology :
the locomotory and feeding organ provided with Cilia found in the Larva l stage called the Veliger or "velum-bearing" stage of Bivalve s, such as Mussel s and Oyster s; or a delicate membrane found on certain Protist s.
the circular membrane round the cap of a Sea Jelly , or Medusa .
the veil-like membrane of immature mushrooms extending from the margin of the cap to the stem and is torn by growth, revealing the gills of a mature Sporophore ; in a mature mushroom the remains of the velum may form an ''annulus'' or ring around the stem, familiar from common button Mushrooms , and sometimes on the margin of the cap.
Velum is also a common misspelling of Vellum , pigs skin once used to cover books with. Now it is too expensive to do so we use leatherette, leather, cloth or paper instead.
