Select the wrong statement.

The cell walls of diatoms are embedded with silica and thus the walls are indestructible. A unique feature of diatom cells is that they are enclosed within a cell wall made of hydrated silicon dioxide called a frustule. These frustules show a wide diversity in form but are usually almost bilaterally symmetrical, hence the group name diatom. The symmetry is not perfect since one of the valves is slightly larger than the other, allowing one valve to fit inside the edge of the other.