Foramen

1. The passage through the constriction at the surface opposite the velum (Hasle & Syvertsen, 1996).
2. The opening of an areola on the side opposite to the velum. The foramen may be open, partially occluded by T- or L-shaped radial threads, or, more rarely, occluded by many fine radial threads (Nikolaev, 1993).
   

References

• Hasle, G.R. & Syvertsen, E.E., 1996. Marine Diatoms. In C.R. Tomas (ed), Identifying Marine Diatoms and Dinoflagellates. Academic Press, Inc., California. pp. 5-385.

• Nikolaev, V. 1993. The "pore" apparatus of centric diatoms: a description of terms. Nova Hedwigia, Beiheft 106. p. 33-42.

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