Costa - primary, secondary and tertiary



An internal valve occurring in species in the genus Craticula. This craticular valve consists of a raphe-sternum and robust transverse bars. Frustules with normal morphology produce the craticular valve under conditions of high solute concentration. The formation of these internal valves is not linked to mitosis.


Anonymous. (1975). Proposals for standardization of diatom terminology and diagnoses. Nova Hedwigia, Beihefte 53: 323-354.