Cell wall of the following protistans looks like a soap box.

In diatoms, the cell wall is embedded with silica and in the form of overlapping halves which looks like a soap box. It is indestructible and form diatomaceous earth over billions of years on the ocean floor. Dinoflagellates have cellulosic cell wall in the form of plates. Euglenoids and Slime moulds do not have cell wall in their vegetative body.