The silica plate forming one wall of a loculate areola. The velum is perforated with pores. Located on the external or internal wall of the areola, depending on species, opposite the foramen. Plural form is vela.
Round, F.E., Crawford, R.M. and Mann, D.G. (1990). The Diatoms. Biology and Morphology of the Genera. Cambridge University Press, Cambridge, 747 pp.