Having the shape of a cross. Usually applied to describe the valve outline of some diatoms.

S Leptostauron Cruciform
Image Credit: Eduardo Morales
A scanning electron micrograph showing the intricate sculpturing of the outside of a valve of Staurosirella leptostauron. Spines project from the costae, lineolate areolae make up the striae, and minute structures compose the apical pore fields.
S Leptostauron Cruciform2
Image Credit: Eduardo Morales
Light micrograph of Staurosirella leptostauron, a species with a cruciform valve outline.