By adjusting the basicity of the reaction mixture in the cationic surfactant templating route, a systematic change from 2D-hexagonal chiral to 2D-rectangular p2gg to a lamellar silica mesostructure is precisely controlled. Detailed characterization shows that the novel 2D-rectangular p2gg silica mesoporous crystal exhibits elliptical mesopores peculiarly stacked with varying anisotropy on a 2D-hexagonal lattice, as shown in the figure.