Vola

A flap of silica projecting from the side of a pore or from a bar crossing an areola. A type of velum. Plural form is volae.

A Crassipunctata Areola
Image Credit: Marina Potapova
SEM image of volae extending from the sides of an areola of Aulacoseira crassipunctata. Scale bar = 0.5 µm.