Very small enlongated snails found on the shells of snails and clams, usually near the shell openings.On tridacnids they may congregate near the hinge or byssal opening

These snails bore holes in the shells of their prey and use a probosics to feed on their preys fluids slowly killing the snail/clam, they lay jelly like masses of eggs on the shells of thier prey,

Close inspection of any new snails or clams, repeated scrubbing shells to remove egg masses, freshwater dips for tridacnids and biocontrols like wrasses specifically melenarus wrasses can be helpful.