The term, 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 larval stage called the veliger or "velum-bearing" stage of bivalves, such as mussels and oysters; also a delicate membrane found on certain Protists. the circular membrane around the cap of a sea jelly or medusa, of class Hydrozoa, which helps with propulsion the veil-like membrane of im… (More on Velum)