Fascia

A hyaline area of thickened silica extending from the central area of some pennate diatoms. A transverse fascia is formed by secondary deposition of silica into depressions on the valve. Examples of genera having a transverse fascia include Luticola and Staurophora. Plural form is fasciae.

See also stauros for a similar structure.

Staurophora Midvalve  Sem Copy
Image Credit: Loren Bahls
The fascia of Staurophora is the thickened, unornamented area near the central nodule. SEM images such as this one only show the surface features of the silica, so it is difficult to discern that the unornamented area is greater in thickness.
Caloneis Silicula 001 Copy
Image Credit: Pat Kociolek
Caloneis silicula has a fascia that often includes lunate markings.