Trichospaherium is a marine amoeba that can occur in a spicule-covered form or as a naked form - as is illustrated here. the cone-shaped pseudopodia with terminal filaments are distinctive.
Marine amoeba, exists as a spicule-covered form and as a naked form. the second is illustrated here. The naked form used to be called Pontifex maximum before it became clear that the two forms are of the same species.